LAPAROSCOPY

Laparoscopic management in stone disease. Simforoosh N, Aminsharifi A, Department of Urology, Shahid Labbafinejad Hospital, Urology and Nephrology Research Center, Shahid Beheshti University of Medical Sciences, Tehran Department of Urology, Shahid Faghihi Hospital, Laparoscopy Research Center, Shiraz University of Medical Sciences, Shiraz, Iran.

Curr Opin Urol 2013;23:169-74.

Purpose of Review: While most renal and ureteral stones can be efficiently managed using endourologic techniques, the use of laparoscopy for the management of urolithiasis is increasing. The application of laparoscopy for stone removal will further reduce the need for open stone surgery.

Recent Findings: Laparoscopic ureterolithotomy, pyelolithotomy, and anatrophic nephrolithotomy are highly successful techniques with regard to their one-session, high stone-free rates. These procedures could be considered as the preferred approaches when endourologic procedures are not available or have failed. Laparoscopic stone surgery (LSS) in patients with urinary tract anomalies offers a reliable minimally invasive procedure as an alternative to a complex endourologic technique.

Summary: Although laparoscopy still has a limited role in the urologist's armamentarium for the surgical management of urolithiasis, it can further reduce the need for open stone surgery in complex circumstances. LSS duplicates its open counterpart and offers a high one-session, stone-free rate in most patients with a lower morbidity and quicker convalescence. More comparative studies are needed to define the role and indications of LSS in relation to endourologic and open techniques, especially in complex circumstances.

DOI: 10.1097/MOU.0b013e32835d307f

The emerging role of robotics and laparoscopy in stone disease. Humphreys MR, Department of Urology, Mayo Clinic, Phoenix, AZ.

Urol Clin North Am 2013;40:115-28.

The surgical management of urolithiasis has undergone a remarkable clinical evolution over the past three decades. The once common practice of open stone surgery has nearly been relegated to historical interest by modern technology. The introduction of minimally invasive techniques, laparoscopy and robot-assisted surgery, have emerged to complete the urologist's armamentarium. The benefits to patients when other endourologic procedures have failed include less pain, shorter hospitalization and convalescence, and improved cosmesis. This chapter explores the historical shift from open to minimally invasive management for stone disease and the unique risks and outcomes associated with these procedures in modern urology.

Copyright © 2013 Elsevier Inc. All rights reserved.

DOI: 10.1016/j.ucl.2012.09.005

Commentary

As one gets more senior in one's urologic practice we hopefully can remember back to the earlier stone techniques that we learned during training. As residents we did often “cut for the stone” if it was too large to pass spontaneously. What joy it was to be a junior resident and get to do an open ureterolithotomy or pyelolithotomy. We all know about the tremendous revolution in stone management that occurred in the 1980s, with the advent of percutaneous surgery and ESWL. In the 1990s, laparoscopic surgery allowed us access to the urinary tract and essentially wiped out the need for open stone surgery. It has been estimated that today only 1–5.4% of stone cases will require open surgical intervention. In more affluent countries it is probably even less.

The articles by Humphreys and Simforoosh et al demonstrate that laparoscopic surgery is a very viable alternative to open surgery if the stone cannot be accessed with the less minimally invasive approaches. In countries where medical funding is limited, a “one operation laparoscopic approach” makes sense rather than multiple endoscopic or ESWL procedures.

The technique of coagulum pyelolithotomy is somewhat historical, but I can say from experience that it was very successful, especially in cases where there were multiple small calyceal stones distributed throughout the kidney. In the presence of a fresh ureteropelvic junction repair the surgeon wants, at all costs, to prevent a calyceal or renal pelvic calculi from dropping into the area of anastomosis in the early postoperative period.¹

Finally, we have found the laparoscopic approach ideal for managing large calyceal diverticulum harboring stone debris. Excision of the thinned-out overlying parenchyma and extensive fulguration of the diverticulum interior and neck results in excellent long-term results. Laparoscopic surgery has also been found to be useful in stone cases of anomalous kidney anatomy such as pelvic or horseshoe kidneys.

As a urologist it is highly satisfying to access a kidney laparoscopically, enter the collecting system through the renal pelvis with a flexible nephroscope or ureteropyeloscope, and remove stone material from anywhere in the upper urinary tract. This is a far cry from open surgery where large muscle and fascial layers are violated, leading to long convalescence and concern about postoperative flank or abdominal hernia.

Is robot-assistance needed for managing upper urinary tract stones? Probably not, if one is fascile with the laparoscope and suturing techniques. Certainly, in areas with less medical resources it will only add to the overall cost of the procedure.

Reference

1. Borges R, Azinhais P, Retroz E, et al. Coagulum pyelolithotomy “revisited” by laparoscopy: technique modification. Urology 2012;79:1412.e5–8.

Howard N. Winfield, MD

URETEROSCOPY

How much is a kidney worth? Cost-effectiveness of routine imaging after ureteroscopy for prevention of silent obstruction. Sutherland TN, Pearle MS, Lotan Y, Department of Urology, University of Texas Southwestern Medical Center, Dallas, TX.

J Urol 2012; Dec. 28 [epub ahead of print].

Purpose: The 2012 American Urological Association Clinical Effectiveness Protocol for the Management of Ureteral Calculous Disease recommends routine post-operative imaging after ureteroscopy. We evaluated the cost-effectiveness of routine post-operative imaging after ureteroscopy (URS).

Materials and Methods: A literature search was conducted to determine the risk of complications after routine URS for stones, including incidence of post-operative pain, stricture and silent obstruction. Sequela of renal loss due to undiagnosed silent obstruction may include chronic kidney disease, end-stage renal disease and cardiovascular disease. Imaging and procedure costs were obtained from Medicare reimbursement rates and the literature. Costs and prevalence of lifetime complications associated with silent loss of one kidney were obtained from the renal donor transplant literature. A decision tree was constructed using TreeAge PRO HEALTHCARE software to calculate the cost of a strategy of routinely imaging all patients after URS versus selective imaging based on post-operative pain. One and two-way sensitivity analyses were performed.

Results: The average cost per patient of a strategy of routine post-URS imaging for all patients is $5,326 versus $5,196 for a strategy of selective imaging based on post-operative pain. Assuming a 2% rate of silent obstruction, the cost per kidney saved is $6,262.

Conclusion: While routine post-operative imaging carries a $130 per patient incrementally higher cost over a strategy of selective imaging in patients with post-operative pain, prevention of renal loss and its attendant morbidity justify the additional modest cost.

Copyright © 2012 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

DOI: 10.1016/j.juro.2012.12.059

Commentary

This is a cost-effectiveness study analyzing the routine use of postoperative imaging after ureteroscopy for stones. The investigators have done a fine job of addressing what proves to be a complicated question. The primary question the investigators chose to address was whether imaging (consisting of plain abdominal film and renal ultrasonography) should be performed routinely, or only in symptomatic patients. Under these two scenarios, the investigators attempted to determine the risk of renal loss due to upper urinary tract obstruction. The essence of this comparison boils down to the incidence of silent obstruction, whether by stone or stricture, after ureteroscopy. Based upon their literature review, the authors estimate a 2% rate of postoperative stricture formation, and a 10% rate of residual stones, resulting in an estimated 1.9% rate of postoperative silent obstruction. Certainly, the rates of postoperative stricture formation and residual stones will depend upon stone-related factors such as stone size, the presence of impaction, and stone location, among others. To stratify their model based upon these other factors would further complicate the already challenging analysis.

However, in several large series the risk of ureteral stricture formation after ureteroscopy is 0.5% or less.^1–3 Clearly, stone size and impaction will change this risk. It may be that using these factors rather than the presence of symptoms may be a better determinant of who might require imaging for obstruction after ureteroscopy. Most of my patients receive imaging after ureteroscopy, primarily to determine their stone-free status. While I don't avoid imaging in patients at low risk of ureteral stricture formation or residual stones, I make certain that those patients who I feel are at high risk of ureteral stricture formation (i.e. following treatment of an impacted stone) receive imaging to rule out obstruction. In the end, as the authors demonstrate, varying the rates for these parameters will change the cost per kidney saved. As alluded to in the paper's title, the choice becomes based upon how much we value a kidney. How much is it worth to the patient, society, and the urologist, to avoid this complication, avoid renal replacement therapy, and potential litigation? Based on their analysis, the investigators recommend routine imaging following ureteroscopy to prevent these problems.

References

1. Harmon WJ, Sershon PD, Blute ML, et al. Ureteroscopy: current practice and long-term complications. J Urol 1997;157:28–32.

2. Chow GK, Patterson DE, Blute ML, et al. Ureteroscopy: effect of technology and technique on clinical practice. J Urol 2003;170:99–102.

3. Krambeck AE, Murat FJ, Gettman MT, et al. The evolution of ureteroscopy: a modern single-institution series. Mayo Clin Proc 2006;81:468–73.

Michael Conlin, MD

Safety and efficacy of ureteroscopy after obstructive pyelonephritis treatment. Kanno T, Matsuda A, Sakamoto H, Higashi Y, Yamada H, Department of Urology, Ijinkai Takeda General Hospital, Kyoto, Japan.

Int J Urol 2013; Jan. 24 [epub ahead of print].

Objectives: An obstructed, infected kidney combined with ureteral stones can be lethal, and requires urgent drainage and complete stone removal. However, the optimal method of stone removal, and its safety and efficacy have yet to be conclusively established. The aim of this study was to determine the safety and efficacy of carrying out ureteroscopy after kidney drainage for septic patients with obstructing stones.

Methods: From January 2004 to September 2011, 88 patients underwent stone removal by either ureteroscopy (n = 48) or extracorporeal shock wave lithotripsy (n = 40) after drainage of obstructive pyelonephritis. Patients' characteristics were analyzed, and treatment outcomes between the ureteroscopy and extracorporeal shock wave lithotripsy groups were compared. The outcomes of ureteroscopy carried out during the same period between patients with preoperative obstructive pyelonephritis and those without were also compared.

Results: Obstructed, infected kidneys were decompressed with retrograde ureteral stenting, except for two and three cases treated with nephrostomy in the ureteroscopy and extracorporeal shock wave lithotripsy groups, respectively. The severity of preoperative pyelonephritis was similar in both groups. Importantly, the success rate was 67.5% for extracorporeal shock wave lithotripsy and 98% for ureteroscopy (P < 0.001). Likewise, the retreatment and auxiliary procedure rates were significantly greater in the extracorporeal shock wave lithotripsy group than in the ureteroscopy group (90% vs 0% and 32.5% vs 2%, respectively). Furthermore, patients treated by ureteroscopy with or without preoperative pyelonephritis had similar stone-free and ureteroscopy complication rates (97% vs 93%, and 10% vs 12%).

Conclusions: Ureteroscopy after drainage of an obstructed infected kidney can be a safe and effective option, as it seems to not be associated with an increased risk of complications.

© 2013 The Japanese Urological Association.

DOI: 10.1111/iju.12060

Commentary

This is a nice review of the investigators' experience treating ureteral calculi in patients with obstructive pyelonephritis after initial decompression. By comparing ureteroscopy to shockwave lithotripsy in these patients, the authors sought to determine if ureteroscopy after obstructive pyelonephritis is safe. This is a retrospective cohort study; thus, the patients were not randomized to the different treatments. Most of these patients were decompressed with ureteral stents, and were treated with antibiotics lasting until 4 days' defervescence. The authors found no differences in complications between those patients treated ureteroscopically compared to those treated with shockwave lithotripsy. In particular, the risk of fever or urosepsis was equivalent in both the ureteroscopy and shockwave lithotripsy groups (6% and 8%, respectively). As expected, the success rate for ureteroscopy (98%) was significantly greater than that for shockwave lithotripsy (67.5%). Ureteroscopy appears to be very safe and effective in patients who have been decompressed and treated with antibiotics for obstructive pyelonephritis. What has not yet been determined is how soon we can treat these patients. With efforts to decrease the intrarenal pressure during ureteroscopy, such as limiting irrigation and the use of a ureteral access sheath, can we treat these patients during the same initial hospitalization, perhaps even before they have defervesced? Although this has been done, the risks of this approach probably outweigh any benefit.¹

References

1. Hsu JM, Chen M, Lin WC, et al. Ureteroscopic management of sepsis associated with ureteral stone impaction: is it still contraindicated? Urol Int 2005;74:319–22.

Michael Conlin, MD

PERCUTANEOUS SURGERY

Effect of age on the clinical presentation of incident symptomatic urolithiasis in the general population. Krambeck AE, Lieske JC, Li X, Bergstralh EJ, Melton LJ 3^rd, Rule AD, Department of Urology, School of Medicine, Mayo Clinic, Rochester, MN.

J Urol 2013;189:158–64.

Purpose: We characterized variation in the clinical presentation between older and younger first time symptomatic stone formers in the general population.

Materials and Methods: We studied a random sample of Olmsted County, Minnesota residents with their first diagnostic code for urolithiasis between 1984 and 2003. Chart validated symptomatic stone formers had a confirmed stone by imaging or stone passage. Clinical presentation characteristics were compared between age groups.

Results: Among the 3,473 charts reviewed there were 1,590 validated incident symptomatic stone formers (mean age 43 years, range 18 to 96). Older individuals were more likely to present with atypical or no pain, fever, diarrhea, pyuria, urinary tract infections and bacteremia (p<0.001). Stone size and location did not differ by patient age. Calcium phosphate stone disease was associated with younger age, while uric acid stone and atypical stone composition was associated with older age (p<0.001). Older individuals were less likely to pass the stone spontaneously and were more likely to require surgical intervention (p<0.001). Surgical intervention was required in 516 (32.5%) individuals. Younger individuals were more likely to undergo ureteroscopy while older individuals were more likely to undergo shock wave lithotripsy, temporizing stent placement and percutaneous nephrolithotomy.

Conclusions: The detection of stone disease in older individuals can be challenging due to atypical pain or absence of pain, as well as the presence of other comorbid conditions such as urinary tract infections and diarrhea. A higher index of suspicion for urolithiasis may be needed in the elderly for a more timely diagnosis and intervention to prevent morbidity.

Copyright © 2013 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

DOI: 10.1016/j.juro.2012.09.023

Commentary

This article focuses on the initial presentation of stone formers over a 19-year period (1984 to 2003) based on their age. It is a community-based study and, along with another recent article,¹ highlights several take-home messages. First, typical renal colic symptoms are significantly higher in the younger age group while atypical pain or no pain is more likely in the older age group. This led to a delay in diagnosis and treatment in older individuals resulting in higher morbidity associated with bacteraemia and a higher chance of hospitalization. Furthermore, mortality from stone disease has only been reported in patients aged 70 and older. An increase in concomitant UTI at the time of presentation is also noted in older patients, similar to another study,² although there was no reported increase in struvite stones. In analyzing stone composition in this study group, calcium phosphates were more common in the younger age group while uric acid stones were more commonly seen in the older age group. The authors suggested a drop in pH with increasing age as a contributing factor³ to the increase in uric acid stones and decreased calcium phosphate stones, while the increase in brushite stones in older patients are related to aging kidney processes.

Surgical intervention increased with age, as a result of associated fever, UTI, bacteremia and need for hospitalization. Surgical modalities such as PCNL and URS are shown to be safe and effective when dealing with stones in the elderly. In an earlier report, PCNL in patients over 70 years yielded similar stone-free rates as in the younger age group, with a slightly higher complication rate.³ The authors explained an increase in URS as a treatment modality with increased age as being possibly due to smaller stones at the time of presentation.

The limitations of the current study include a predominantly white population, the retrospective nature with non-standardized follow-up and treatment, and results may not be applicable to recurrent stone formers. Nonetheless, it is an important report showing the need to be more aware of diagnosis and treatment of stones in the elderly.

References

1. Okeke Z, Smith AD, Labate G, et al. Prospective comparison of outcomes of percutaneous nephrolithotomy in elderly patients versus younger patients. J Endourol 2012;26:996–1001.

2. Usui Y, Matsuzaki S, Matsushita K, et al. Urolithiasis in geriatric patients. Tokai J Exp Clin Med 2003:28:81–7.

3. Goldfarb DS, Parks JH, Coe FL. Renal stone disease in older adults. Clini Geriatr Med 1998:14:367–81.

Michael Y.C. Wong, MBBS

EXTRACORPOREAL SHOCK WAVE

Urgent shock wave lithotripsy as first-line treatment for ureteral stones: a meta-analysis of 570 patients. Picozzi SC, Ricci C, Gaeta M, Casellato S, Stubinski R, Ratti D, Bozzini G, Carmignani L, Urology Department, IRCCS Policlinico San Donato, San Donato Milanese, MI, Italy.

Urol Res 2012;40:725-31.

The rationale for the use of immediate shock wave lithotripsy (SWL) after a renal colic episode is to obtain maximum stone clearance in the shortest possible time with associated early detection of lithotripsy failures which can be treated with auxiliary procedures. The aim of this meta-analysis is to understand the role of this treatment option in the emergency setting as first-line treatment and to compare such an immediate procedure to a delayed one in terms of stone-free and complication rates. A bibliographic search covering the period from January 1995 to September 2010 was conducted in PubMed, MEDLINE and EMBASE. Database searches yielded 48 references. This analysis is based on the seven studies that fulfilled the predefined inclusion criteria. A total of 570 participants were included. The number of participants in each survey ranged from 16 to 200 (mean 81.42). Six studies were published after 2000 and one in the 1990s. All studies reported participants' age with mean of 40.9 years, and range between 11 and 88 years. All patients presented with unilateral lithiasis, as such the number of total stones treated was 570. Mean stone diameter ranged between 6.38 and 8.45 mm. According to the logistic regression applied stone-free rates were 79% (61–95) for the proximal ureter, 78% (69–88) for the mid ureter, 79% (74–84) for the distal ureter and 78% (75–82) for overall. Stone-free rates do not evidence a statistically significant difference compared to those described in the AUA and EAU guidelines for elective management. SWL management of ureteral stones in an emergency setting is completely lacking in the international guidelines and they results disperse in the literature in few works. According to our meta-analysis, immediate SWL for a stone-induced acute renal colic seems to be a safe treatment with high success rate. This evidence will be validated by further randomized studies, with a larger series of patients.

DOI: 10.1007/s00240-012-0484-0

Commentary

There is an ongoing discussion on the preferred treatment modality, SWL or URS, for ureteral stones. According to the Joint AUA/EAU Guidelines both SWL and URS are considered treatments of choice for the active management of ureteral stones.¹ Based solely on stone-free rates (SFR), URS is considered superior to SWL only for distal ureteral stones larger than 10 mm. In this current meta-analysis, no differences in SFR were seen among distal, proximal and middle ureteral stones treated with emergency SWL. An overall SFR of 78% with one single session of SWL in an emergency setting is quite a very good result.

There proved to be no statistically significant correlation between SFR and stone diameters. However, in a different study the same group of authors observed that SFR was affected by stone diameter in ureteral stones treated with urgent URS. They noted that every 1 mm diameter increase greater than 8 mm resulted in a reduction of SFR of 5% and 8.5%, respectively, for distal and proximal ureters.²

According to different studies in the meta-analysis, emergency SWL within a short interval after a first episode of colic offers improved fragmentation, a shorter time to achieve complete stone clearance, increase in SFR, a reduced need for repeat SWL sessions and, last but not least, a treatment of the renal colic in itself.^3–5

Although the first objective of any ureteral stone treatment is, of course, to render the patient stone-free as fast as possible and with minimal morbidity, other parameters do play a role in the choice of management. As the authors clearly state, the least invasive form of treatment is spontaneous passage enhanced by medical expulsive therapy (MET). Although minimally invasive, URS still needs to be performed under anesthesia and the complication rate is potentially higher.

In the management of ureteral stones, Tiselius calculated a Treatment Index (TI) and found that the lower retreatment rate in URS is counterbalanced by a much higher need for anesthesia.⁶ Although very difficult to evaluate in different settings, cost-effectiveness may also be an issue. Tiselius also found that, although the principles of reimbursement obviously favor URS over SWL in some regions, SWL remains economically the most favorable method even at a retreatment rate of up to 60–70%. He also stated that “the choice for a more invasive treatment option for economic reasons seems a step backwards from the very useful and versatile procedure that the ESWL technology provides.” Patient preference also plays an important role.

According to Karlsen et al, URS tends to make patients stone-free faster, but SWL is preferred by most patients because there is less discomfort after treatment.⁷ In a matched-pair analysis of outcomes for upper ureteral calculi Stewart et al observed comparable results for SWL and URS.⁸ They concluded that the choice of treatment should be based on such parameters as availability of equipment, waiting times and patient preference.

In conclusion, for more than one reason emergency SWL within a short interval after a first period of renal colic proves to be a safe procedure—it is minimally invasive, with minimal morbidity and an excellent success rate. It seems therefore reasonable to offer it to patients whenever possible.

References

1. Preminger GM, Tiselius HG, Assimos DG, et al. 2007 guideline for the management of ureteral calculi. J Urol 2007;178:2418–34.

2. Picozzi SC, Ricci C, Gaeta M, et al. Urgent ureteroscopy as first-line treatment for ureteral stones: a meta-analysis of 681 patients. Urol Res 2012;40:581–6.

3. Seitz C, Fajković H, Remzi M, et al. Rapid extracorporeal shock wave lithotripsy treatment after a first colic episode correlates with accelerated ureteral stone clearance. Eur Urol 2006;49:1099–1105.

4. Tombal B, Mawlawi H, Feyaerts A, et al. Prospective randomized evaluation of emergency extracorporeal shock wave lithotripsy (ESWL) on the short-time outcome of symptomatic ureteral stones. Eur Urol 2005;47:855–9.

5. Kravchick S, Bunkin I, Stepnov E, et al. Emergency extracorporeal shockwave lithotripsy for acute renal colic caused by upper urinary-tract stones. J Endourol 2005;19:1–4.

6. Tiselius HG. Removal of ureteral stones with extracorporeal shock wave lithotripsy and ureteric procedures. What can we learn from the literature in terms of results and treatment efforts? Urol Res 2005;33:185–90.

7. Karlsen SJ, Renkel J, Tahir AR, et al. Extracorporeal shockwave lithotripsy versus ureteroscopy for 5- to 10-mm stones in the proximal ureter: prospective effectiveness patient-preference trial. J Endourol 2007;21:28–33.

8. Stewart GD, Bariol SV, Moussa SA, et al. Matched pair analysis of ureteroscopy vs. shock wave lithotripsy for the treatment of upper ureteric calculi. Int J Clin Pract 2007;61:784–8.

Geert G. Tailly, MD

Comparison of extracorporeal shock wave lithotripsy for inferior caliceal calculus between children and adults: a retrospective analysis–why do results vary? Mandal S, Sankhwar SN, Singh MK, Kathpalia R, Singh V, Goel A, Singh BP, Dalela D, Department of Urology, Chhatrapati Shahuji Maharaj Medical University, formerly King George Medical College, Lucknow, India.

Urology 2012;80:1209-13.

Objective: To retrospectively evaluate the effectiveness of extracorporeal shock wave lithotripsy (ESWL) for inferior caliceal calculi ≤20 mm in size and compare the results between children and adults.

Materials and Methods: From January 2004 to January 2012, ESWL was performed for inferior caliceal calculi in 230 children and 1006 adults. The Dornier compact alpha-K1025163 (Dornier Med Tech) was used. The success rates, number of ESWL sessions required, and auxiliary procedures used were evaluated in a comparative manner.

Results: The overall stone-free rate (for both stone sizes) was 82.2% for children and 40% for the adults. Of the children, 17% had a residual stone compared with 47.8% of the adults. ESWL was unsuccessful in 0.8% of children and 12.2% of adults. The mean number of ESWL sessions required in children and adults was 1.43 (range 1–4) and 2.13 (range 1–4), respectively. Repeat treatment was required in 31% of the children and 65% of the adults. Auxiliary procedures were required in 5.2% of the children and 16.2% of the adults. Complications were seen in 5.6% of the children and 15% of the adults.

Conclusion: The results of ESWL for inferior caliceal calculi ≤20 mm in adults remains poor but not so in children. Children can achieve high stone-free rates, require a fewer number of ESWL sessions than adults to be stone free, and have a lower need for repeat treatment and auxiliary procedures, and have fewer complications.

Copyright © 2012 Elsevier Inc. All rights reserved.

DOI: 10.1016/j.urology.2012.08.032

Commentary

Following ESWL of lower pole calyx (LPC) stones, clearance of fragments is poorer than from locations in the renal pelvis or other calyces. The problem is not the fragmentation of the stones per se, but the evacuation of the fragments. Apart from the gravity-dependent position of the LPC and the stone size¹ the architecture of the lower pole calyx² seems to play a role in this poorer clearance, at least in adults. In adults, stone size probably is the main predictive factor of success.³

Alternative treatment modalities for the treatment of LPC stones in adults are therefore often proposed. For stones smaller than 10 mm, there proves to be no difference in outcome between ESWL and PNL. For stones larger than 10 mm, the Lower Pole Study Group of the AUA favors PNL. In stones smaller than 20 mm, ESWL is more cost-effective; in stones larger than 20 mm, PNL is more cost-effective. Limiting factors for RIRS are stone burden and the anatomy of the LPC. Both PNL and RIRS are more invasive and associated with higher morbidity. The story is completely different in the pediatric population, however.

In this current study the authors observed a statistically significant difference in ESWL outcomes between children and adults for all parameters and irrespective of stone size. In children, SFR after 1 session and overall SFR were better than in adults, whereas adults were more likely to have residual fragments and unsuccessful outcome. In a study by McAdams et al, stone size proved to be the only independently predictive parameter of success following SWL in children.⁴ In this pediatric population, stone location proved not predictive of success.

Various reasons may be responsible for the significantly better results of ESWL for LPC stones in children. An important factor is likely the smaller SSD (skin-to-stone distance) in children. Attenuation of the travelling shock wave by interposed body fat reduces the energy delivered in the focus and hence impairs fragmentation. This would also explain why less energy is needed to fragment a stone in children than in adults. Total energy delivered in the focus (accumulated energy) is a product of the number of shock waves and the output energy. Another factor proposed by the authors and supported by Goktas et al is the anatomy of the child's ureter.⁵ Shorter and more elastic and distensible than the adult's, it permits easier passage of larger fragments.

Whatever the reasons may be, results for ESWL of LPC-stones ≤20 mm prove to be significantly better in children than in adults. As extracorporeal shockwave lithotripsy is also safe in the pediatric population, ESWL should be considered the treatment of choice for calculi ≤20 mm at any location in the pediatric kidney.

References

1. Sorensen CM, Chandhoke PS. Is lower pole caliceal anatomy predictive of extracorporeal shock wave lithotripsy success for primary lower pole kidney stones? J Urol 2002;168:2377–82.

2. Sahinkanat T, Ekerbicer H, Onal B, et al. Evaluation of the effects of relationships between main spatial lower pole calyceal anatomic factors on the success of shock-wave lithotripsy in patients with lower pole kidney stones. Urology 2008;71:801–5.

3. Al-Ansari A, As-Sadiq K, Al-Said S, et al. Prognostic factors of success of extracorporeal shock wave lithotripsy (ESWL) in the treatment of renal stones. Int Urol Nephrol 2006;38:63–7.

4. McAdams S, Kim N, Ravish IR, et al. Stone size is only independent predictor of shock wave lithotripsy success in children: a community experience. J Urol 2010;184:659–64.

5. Goktas C, Akca O, Horuz R, et al. SWL in lower calyceal calculi: evaluation of the treatment results in children and adults. Urology 2011;78:1402–6.

Geert G. Tailly, MD

TRANSURETHRAL PROCEDURES

In this set of reviews, we focus on technology and techniques involved in a transurethral prostatectomy. With the advent of so many ways to basically accomplish the same surgical end result, we need to revisit and reemphasize some basic tenets common to all current transurethral prostatectomy procedures. These include a basic goal to debulk tissue from the prostatic urethra to provide unobstructed flow, to minimize complications related to the techniques involved in resection such as bleeding, dysuria, incontinence, sexual dysfunction, and to be able to consistently get good results on a wide range of transurethral anatomical variations such as size and intravesical lobes.

In all these procedures, we need to be reminded that various techniques and technologies require the surgeon to be facile with transurethral anatomy because all these techniques require skill, knowledge, and dexterity to maneuver a surgical resecting instrument at the end of a transurethral scope in a technique basically guided by a free hand. As such, all these studies are influenced by the skill of the surgeon or surgeons. Comparative studies not only reflect the safety and efficacy of the various technologies but also the skill and experience of the surgeon using the technologies. One could say that any studies by a single surgeon, while still reflecting the capabilities of the technology, is biased by the skill of the surgeon.

As such, the best studies are, in fact, multicenter studies with multiple surgeons, and preferably, randomized comparative studies. Another analysis that is useful is national registries looking at safety data of various procedures because they reflect a real world expectation for safety. However, it is very difficult to assess efficacy since follow-up data of efficacy is not always well collected because patients who do well do not require close monitoring of their efficacy parameter are usually lost to follow-up because they are doing well. Bearing these thoughts in mind, the reasonably accepted and still current comparative standard is the monopolar TURP. In the hands of a trained resectionist, it can be reasonably expected that a 50 ml gland should take less than 45 minutes to resect, and have less than a 1% rate of dilutional hyponatremia and transfusion rate.

Alexis Te, MD

Complications and early postoperative outcome in 1080 patients after thulium vapoenucleation of the prostate: results at a single institution. Gross AJ, Netsch C, Knipper S, Hölzel J, Bach T, Asklepios Hospital Barmbek, Department of Urology, Hamburg, Germany.

Eur Urol 2012; Dec. 1 [epub ahead of print].

Background: Thulium vapoenucleation of the prostate (ThuVEP) has been introduced as a minimally invasive treatment for benign prostatic obstruction (BPO).

Objective: To analyze immediate outcomes and the institutional learning curve of ThuVEP, and to report its standardized complication rates, using the modified Clavien classification system (CCS) to grade perioperative complication rates.

Design, Setting, and Participants: A prospective evaluation of 1080 patients undergoing ThuVEP from January 2007 until May 2012 at our institution.

Intervention: ThuVEP was performed using the 2-μm, continuous-wave, thulium:yttrium-aluminum-garnet laser.

Outcome Measurements and Statistical Analysis: Preoperative status, surgical details, and immediate outcome were recorded for each patient. Perioperative complications were classified according to the modified CCS.

Results and Limitations: Median prostate size was 51ml (interquartile range [IQR]: 36-78.7). Median operation time was 56min (IQR: 40-80), and median enucleation time was 32.5min (IQR: 22-50). Median catheterization time was 2 d (IQR: 2-2); median length of hospital stay was 4 d (IQR: 3-5). Median resected tissue weight was 30g (IQR: 16.00-51.25). Incidental carcinoma of the prostate was detected in 59 (5.5%) patients. Median maximum urinary flow rate (8.9 vs 18.4ml/s) and postvoid residual urine volume (120 vs 20ml) changed significantly (p<0.001). Minor complications occurred in 24.6% of the patients (Clavien 1: 20.8%; Clavien 2: 3.8%). Early reinterventions were necessary in 6.6% of the patients (Clavien 3a: 0.6%; Clavien 3b: 6%). One Clavien 4 complication occurred (0.09%). The overall complication rates decreased significantly over time due to decreasing Clavien 1, 2, and 3b events. The major limitations of the study are the prospective, unicentric study design, the lack of a control group, and that only short-term data were documented on morbidity and efficacy of the ThuVEP procedure.

Conclusions: ThuVEP is a safe and effective procedure for the treatment of symptomatic BPO, with low perioperative morbidity.

Copyright © 2012 European Association of Urology. Published by Elsevier B.V. All rights reserved.

DOI: 10.1016/j.eururo.2012.11.048

Commentary

Thulium laser is a technology that is very similar to holmium whose main chromophore is water. As such, its main mechanism of action is a thermo-mechanical vaporization of tissue in a precise and superficial manner, as a cutting tool. Holmium is intermittent while thulium is quasi-continuous with more power. Both are best suited in cutting tissue in a hemostatic fashion, and are effective enucleators requiring the use of a morcelator. Often, these technique are best suited to relatively large glands. This series represents the largest published thulium series to date, and while long-term efficacy data is limited, the study reflects an acceptable, comparable, but not superior safety profile compared to TURP. It should be noted that the prostate size in this study is relatively small for an enucleation technique. At these prostate sizes, standard monopolar TURP is equivalent or at least competitive to this technique in terms of safety and outcome.

Alexis Te, MD

A comparative study of thulium laser resection of the prostate and bipolar transurethral plasmakinetic prostatectomy for treating benign prostatic hyperplasia. Peng B, Wang GC, Zheng JH, Xia SQ, Geng J, Che JP, Yan Y, Huang JH, Xu YF, Yang B, Department of Urology, Shanghai Tenth People's Hospital of Tongji University, Shanghai, P.R. China.

BJU Int 2012; Oct. 29 [epub ahead of print].

What's known on the subject? and What does the study add? Thulium laser is a new generation of surgical laser. It is a minimally invasive technology with several advantages, including rapid vaporization and minimal tissue damage and bleeding. However, details regarding the safety and efficacy of thulium laser in treating BPH remains unknown. We performed a comparative study in 100 patients with BPH of the safety and efficacy of thulium laser resection of the prostate (TMLRP, n=50) and bipolar transurethral plasmakinetic prostatectomy (TUPKP, n=50). We found that the efficacy and indications were the same in TMLRP and TUPKP. In TUPKP, the morbidity of urethrostenosis was low, and was nearly bloodless in surgery and had higher safety. Nevertheless, TUPKP is more suitable for patients with larger prostate volume.

Objective: To compare the safety and short-term efficacy of thulium laser resection of the prostate (TMLRP) and bipolar transurethral plasmakinetic prostatectomy (TUPKP) for the treatment of patients with benign prostatic hyperplasia (BPH).

Methods: A total of l00 patients diagnosed with BPH were randomly divided into two groups, treated with either TMLRP (50, group 1) or TUPKP (50, group 2). There was no significant difference in preoperative variables such as age, prostate volume, prostate-specific antigen (PSA) level, International Prostate Symptom Score (IPSS), maximum urinary flow rate (Qmax) and postvoid residual urine volume (PVR) between the two groups. The perioperative parameters and therapeutic effects were recorded and compared between the two groups.

Results: There were significant differences in the following parameters between the two groups (TMLRP vs TUPKP [mean±SD]): operation duration, 61.2±24.2 vs 30.14±15.9 min; catheterization time, 1.8±0.4 vs 3.2±0.6 d; postoperative hospital stay, 3.3±0.8 vs 4.1±1.3 d. The volume of blood loss and postoperative bladder irrigation were significantly lower in TMLRP group than in the TUPKP group. At 1 month after the operation, there were four cases of urethral stricture in the TUPKP group. At 3 months after the operation, IPSS, quality of life (QoL), (Qmax) and PVR were significantly improved, with no significant difference between the two groups.

Conclusions: TMLRP is superior to TUPKP in terms of safety, blood loss, recovery time and complication rate, and is as efficacious as TUPKP for treating BPH. Operation duration was significantly longer in the TMLRP group than in the TUPKP group.

© 2012 BJU International.

DOI: 10.1111/j.1464-410X.2012.11610.x

Commentary

In this study, the same surgical group has employed similar surgical techniques with two different energy modalities to vaporize/resect tissue in a randomized study. The two technique are a thulium resection technique vs. a bipolar resection technique. Efficacy seems similar and comparative, but the safety profile is superior in the laser group. This suggests the laser vaporizing/resecting modality confers an increased hemostatic effect through its laser tissue interaction mechanism of action, and appears to take longer to achieve a similar end result of debulking to achieve a similar efficacy compared to bipolar electrosurgical techniques. Of note, prostate size in this study was also consistent with those generally selected for monopolar TURP.

Alexis Te, MD

Electrosurgical enucleation versus bipolar transurethral resection for prostates larger than 70 ml: a prospective, randomized trial with 5-year followup. Zhu L, Chen S, Yang S, Wu M, Ge R, Wu W, Liao L, Tan J, Department of Urology, Fuzhou General Hospital, Xiamen University, Fujian Medical University, Fuzhou, Fujian.

J Urol 2012; Oct. 31 [epub ahead of print].

Purpose: We compared the perioperative and postoperative characteristics of prostate PlasmaKinetic™ enucleation and bipolar transurethral resection for large volume benign prostatic hyperplasia.

Materials and Methods: In this prospective, randomized, controlled trial 80 patients with benign prostatic hyperplasia and a prostate of larger than 70 ml were randomly assigned to prostate bipolar transurethral resection or PlasmaKinetic enucleation. Operative time, resected adenoma weight, changes in hemoglobin, catheterization time and postoperative hospital stay were recorded and compared. Patients were followed 1, 6, 12, 24, 36, 48 and 60 months after surgery.

Results: Greater resected prostate weight (mean±SD 64.2±19.0 vs 50.6±20.0 gm, p=0.03), less blood loss (mean 0.87±0.42 vs 1.74±0.63 gm, p<0.01), and shorter catheterization time (mean 35.5±5.8 vs 60.1±5.8 hours, p<0.01) and postoperative hospital stay (mean 3.2±0.9 vs 4.4±1.1 days, p<0.01) were recorded in the enucleation group than in the resection group. The postoperative improvement in International Prostate Symptom Score, quality of life, maximal flow rate and post-void residual urine volume was similar in the 2 groups at 1, 6, 12 and 24 months but significantly better in the enucleation group at 36, 48 and 60 months. During the 5-year followup no patient in the enucleation group but 2 in the resection group experienced recurrence.

Conclusions: For large volume benign prostatic hyperplasia PlasmaKinetic enucleation of the prostate is associated with less blood loss, shorter hospital stay and catheterization time than bipolar transurethral resection of the prostate. Moreover, PlasmaKinetic enucleation seems to be superior at long-term followup with fewer reoperations necessary.

Copyright © 2013 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

DOI: 10.1016/j.juro.2012.10.117

Commentary

Monopolar TURP and bipolar TURP are essentially the same in technique, and the same energy source modality is utilized. However, the main advantage, due to the limited current path of electrosurgical current of the bipolar TURP, is the utilization of saline instead of a hyponatremic irrigating solution. This essentially eliminates the risk of dilutional hyponatremia. However, in delivering a larger heat vaporization source similar to other energy modalities like the laser, a bipolar electrosurgical vaporizing tip is utilized to enucleate the prostate in a similar fashion to that of holmium. Thulium and even 532 nm PVP enucleation techniques have been reported in the literature. Consequently, it seems that an improved safety profile is attained concurrent with an improved efficacy profile in large glands with bipolar electrosurgical enucleation compared to TURPs. The main advantage is improved debulking with improved hemostasis in large glands in this study. A well known limitation of electrosurgical TURPs is the increased risk of bleeding requiring transfusion when operative times exceed 45 minutes, and this risk is greater in large glands as a result. By combining the advantages of better debulking with enucleation and better hemostasis with vaporization technology, it is not surprising that safety and efficacy are improved.

Alexis Te, MD

Bipolar versus monopolar transurethral resection of the prostate: results of a comparative, prospective bicenter study - perioperative outcome and long-term efficacy. Neyer M, Reissigl A, Schwab C, Pointner J, Abt D, Bachmayer C, Schmid HP, Engeler DS, State Hospital Bregenz, Bregenz, Austria.

Urol Int 2013;90:62-7.

Objectives: To compare bipolar and monopolar transurethral resection of the prostate (TURP) in a comparative prospective study at two urology centers.

Methods: Of 212 patients with symptomatic benign prostatic hyperplasia entered prospectively into the study, 111 underwent bipolar and 101 monopolar TURP. Patients were treated in two consecutive series with each surgical method at both centers. Improvement in peak flow rate, postvoid residual, International Prostate Symptom Score, and quality of life score postoperatively and at 3, 12, 24 and 36 months, as well as long-term adverse events were compared. Regarding safety, duration of surgery, postoperative catheterization and hospitalization time, amount of fluid absorption, frequency of transurethral resection (TUR) syndrome, and risk of hemorrhage were evaluated.

Results: Patient characteristics of the two series were comparable. The risk of developing TUR syndrome (p=0.32) and bleeding tendency (p=0.52) did not differ significantly between groups. Significant differences were seen for duration of surgery and resection speed. All functional parameters improved significantly during follow-up, with no relevant differences between surgical groups.

Conclusions: Since no major differences in efficacy and safety were seen between the surgical groups, we feel that the monopolar technique still has a valuable place in TURP.

Copyright © 2012 S. Karger AG, Basel.

DOI: 10.1159/000343688

Commentary

This study does not make sense at face value. While it is not surprising that efficacy and hemostasis should be similar, dilutional hyponatremia should not occur with bipolar TURP unless a hyponatremic solution is utilized, removing its advantage over monopolar TURP. Additionally, if the incidence of dilutional hyponatremia is low in the monopolar TURP cohort, due to careful technique, short resection times and small glands, it will not be statistically significant. In this study, the latter is the explanation. Average resection time was 41.8 minutes for monopolar vs 50.03 for bipolar and was statistically significant. Gland size was about 50 ml for both and resection weight similar, at about 22 ml. The adage that any technology will be safe and efficacious in small gland resections holds true, even with monopolar TURP. What cannot be removed is the potential risk of dilutional hyponatremia with monopolar TURP when using a hyponatremic solution, especially with large glands. As the authors conclude, monopolar TURP still has a place in TURP with the caveat that it certainly holds a less valuable place given the plethora of documented safer alternatives.

Alexis Te, MD

MEDICAL ASPECTS OF ENDOUROLOGY

Ascorbic acid supplements and kidney stone incidence among men: a prospective study. Thomas LD, Elinder CG, Tiselius HG, Wolk A, Akesson A.

JAMA Intern Med 2013;173:386–8.

(No abstract provided.)

doi: 10.1001/jamainternmed.2013.2296

Commentary

This cohort study of 48,850 men aged 45 to 79 years at baseline demonstrated that an intake of vitamin C supplements (1000 mg) was associated with a two-fold increase in the risk of an incident kidney stone. The relative risk was 1.66 for those taking 1-6 such tablets and 2.23 for those ingesting 7 or more per week. Similar relationships have been reported in the Health Professional Follow-up Study, another large male epidemiologic cohort.¹ The reason for this association may be the non-enzymatic metabolism of vitamin C to oxalate, which could increase oxalate excretion.

Reference

1. Taylor EN, Stampfer MJ, Curhan GC. Dietary factors and the risk of incident kidney stones in men: new insights after 14 years of follow-up. J Am Soc Nephrol 2004;15:3225–32.

Dean G. Assimos, MD

Urinary stone differentiation in patients with large body size using dual-energy dual-source computed tomography. Qu M, Jaramillo-Alvarez G, Ramirez-Giraldo JC, Liu Y, Duan X, Wang J, Vrtiska TJ, Krambeck AE, Lieske J, McCollough CH, Department of Radiology, Mayo Clinic, Rochester, MN.

Eur Radiol 2012; Dec. 21 [epub ahead of print].

Objective: To evaluate the ability of 100/Sn140 kV (Sn, tin filter) dual-energy computed tomography (CT) to differentiate urinary stone types in a patient cohort with a wide range of body sizes.

Methods: Eighty human urinary stones were categorised into four groups (uric acid; cystine; struvite, oxalate and brushite together; and apatite) and imaged in 30-50-cm-wide water tanks using clinical 100/Sn140 kV protocols. The CT number ratio (CTR) between the low- and high-energy images was calculated. Thresholds for differentiating between stone groups were determined using receiver operating characteristics (ROC) analysis. Additionally, 86 stones from 66 patients were characterised using the size-adaptive CTR thresholds determined in the phantom study.

Results: In phantoms, the area under the ROC curve for differentiating between stone groups ranged from 0.71 to 1.00, depending on phantom size. In patients, body width ranged from 28.5 to 50.0 cm, and 79.1% of stones were correctly characterised. Sensitivity and specificity for correctly identifying the stone category were 100% and 100% (group 1), 100% and 95.3% (group 2), 85.7% and 60.9% (group 3), and 52.6% and 92.5% (group 4).

Conclusion: Dual-energy CT can provide in vivo urinary stone characterisation for patients over a wide range of body sizes.

Key Points: • Dual-energy CT helps assessment of urinary stone composition in vivo. • 100/Sn140 kV DECT differentiates among four stone types with 79.1% accuracy. • In vivo diagnostic test achievable in patients with many body sizes.

DOI: 10.1007/s00330-012-2727-4

Commentary

Dual-energy CT has been demonstrated to discriminate different stone compositions in in vitro studies. These investigators demonstrated that in patients with varying body sizes, this approach correctly identified stone composition in 79.1%. It worked best for identification of uric acid and cysteine stones. Further refinements may improve results with the various types of calcium and struvite stones. Such information may help guide stone prevention strategies.

Dean G. Assimos, MD

INVESTIGATIVE ENDOUROLOGY

Protective effects of reducing renal ischemia-reperfusion injury during renal hilar clamping: use of allopurinol as a nephroprotective agent. Keel CE, Wang Z, Colli J, Grossman L, Majid D, Lee BR, Department of Urology, Tulane University School of Medicine, New Orleans, LA.

Urology 2013;81:210.e5-10.

Objective: To investigate the relationship between renal ischemia injury and concentrations of 8-isoprostane in a rat kidney model during renal hilar clamping and their correlation with the administration of allopurinol before clamping.

Materials and Methods: Reperfusion injury occurs after the reintroduction of blood flow after a prolonged period of ischemia. Thought to be due to oxygen free radicals released by the endothelial, mitochondrial, and parenchymal cells, this process leads to a cascade of events whereby infiltrative leukocytes generate cytokines and reactive oxygen species. The present study was performed in 2 parts. Our primary objective was to first develop a method of quantitating the renal damage using a prostaglandin compound formed in vivo, specifically isoprostane. After the development of this animal model of quantitating renal injury, our second objective was to apply this model and investigate allopurinol's nephroprotective abilities. A microdialysis probe was inserted into the renal parenchyma of rats to allow continuous dialysis and collection of the effluent for isoprostane levels. After clamping of the renal vessels to induce ischemia, the interstitial effluent from the probe was collected and subsequently analyzed for 8-isoprostane levels with and without allopurinol pretreatment.

Results: Clamping of the renal hilum in this rat model significantly increased 8-isoprostane levels. After 60 minutes of clamp time, the largest absolute increase in 8-isoprostane levels resulted, representing a 3.2-fold increase from baseline. However, the rats that had been pretreated with allopurinol demonstrated significantly less isoprostane levels, to baseline levels.

Conclusion: Allopurinol has demonstrated significant benefits by reducing reperfusion injury in rat kidneys, as demonstrated by the use of 8-isoprostane as a tool for the real-time measurement of ischemic injury.

Copyright © 2013 Elsevier Inc. All rights reserved.

DOI: 10.1016/j.urology.2012.08.016

Commentary

As partial nephrectomy becomes the standard treatment for small renal masses, more and more emphasis continues to be placed on maximal nephron-sparing during these surgeries. The most obvious areas in which to concentrate on altering nephron injury are in both minimizing warm ischemia time and reducing the amount of reperfusion injury. Warm ischemia time is influenced by the case complexity which can be driven by a number of factors to include: surgeon experience, location of tumor, blood supply to tumor, tumor size, and patient body habitus. Therefore, if we could discover methods to prevent the reperfusion injury, then we may be able to more effectively prevent renal damage in all partial nephrectomy cases.

Keel et al developed a rat model of renal ischemia injury to study the potential benefit of using allopurinol as a nephroprotective agent. The rationale behind allopurinol as a nephroprotective agent is the inhibition of free radical production through the xanthine oxidase pathway. Previous studies have suggested that a source of oxygen-derived free radicals during ischemic-reperfusion injury is the xanthine oxidase pathway.¹

The study was divided into two parts. First, the authors set to confirm that a marker of renal damage, 8-isoprostane, could be quantified to renal ischemia and reperfusion injury. Next, they tried to determine if the xanthine oxidase inhibitor, allopurinol, may prevent renal reperfusion injury.

The authors were able to show that 8-isoprostane, a unique prostaglandin-like compound formed in vivo from free radical-catalyzed peroxidation of arachidonic acid (independent of the cyclooxygenase enzyme), could reliably measure oxidative stress in the rat model of renal ischemia. The measurement does require a microdialysis catheter placed in the renal parenchyma throughout the experiment. Next, they proved that allopurinol administration by itself did not inhibit the formation of 8-isoprostane in a control setting; in other words, it works through different mechanisms. The authors then demonstrated that allopurinol could decrease oxidative stress and reperfusion injury in all warm ischemia time groups in a rat model, but it only reached statistical significance at 60 minutes of warm ischemia. The administration of allopurinol did not seem to affect the initial ischemic injury levels of 8-isoprostane, but it significantly reduced the reperfusion injury levels of 8-isoprostane.

I congratulate the authors on their meticulous work in this subject. However, the dose of allopurinol needed to prevent injury in the rat model was 100mg/kg. This would be a toxic dose in humans, as high-dose administration in the clinical setting is generally considered to be 5mg/kg. The nephroprotective effect was also only significant at greatly prolonged warm ischemia times of over 60 minutes and did not show statistically significant differences at 30 or 45 minutes of clamp time. Therefore, I don't see allopurinol as being the main nephroprotective drug in the future, but these studies open up the door to examine other potential nephroprotective agents.

Reference

1. Hopson S, Lust R, Chitwood R. Allopurinol improves myocardial reperfusion injury in a xanthine oxidase-free model. J Natl Med Assoc 1995;87:480–4.

David A. Duchene, MD

In vivo evaluation of the third generation biodegradable stent: a novel approach to avoiding the forgotten stent syndrome. Chew BH, Paterson RF, Clinkscales KW, Levine BS, Shalaby SW, Lange D, The Stone Centre, Vancouver General Hospital, Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia, Canada.

J Urol 2013;189:719-25.

Purpose: Ureteral stents are prone to irritation, encrustation and infection, and they require additional procedures for removal. Furthermore, indwelling polymer stents are often forgotten with devastating consequences to the patient. We describe the degradation time, and physiological and histological responses elicited by a novel biodegradable ureteral stent in a porcine model.

Materials and Methods: A total of 16 female Yorkshire pigs were used in the study. Ten biodegradable Uriprene™ stents and 6 biostable Polaris™ stents were cystoscopically inserted unilaterally in 2 groups of animals. Excretory urogram, and blood and urine tests were performed on different days until day 28. Biostable stents were removed on day 21. On day 28 all pigs underwent necropsy for microscopic and histological evaluation.

Results: Nine of the 10 biodegradable stents (90%) degraded completely by 4 weeks, while 1 pig had 3 fragments smaller than 1.5 cm in the bladder. Excretory urogram showed equivalent drainage and significantly less hydronephrosis in biodegradable stented kidneys. Blood and urine parameters were similar in the 2 groups. A transient increase in serum creatinine on day 7 in 40% of the pigs with a degradable stent resolved by day 10. There were significantly fewer abnormal histological findings in the degradable stent group. We evaluated drainage characteristics in an unobstructed ureter and results may not be representative of what develops in obstructed ureters.

Conclusions: The third generation biodegradable stent is a safe, effective alternative to conventional polymer stents, resulting in equivalent drainage and less hydronephrosis.

Copyright © 2013 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

DOI: 10.1016/j.juro.2012.08.202

Commentary

No single ureteral stent exists for all urological indications. We want some stents to last longer, we want others to drain better, some need to be more comfortable for the patient, and others we don't want to have to remember to remove. The authors of this manuscript are in search of a biodegradable stent for temporary placement. The main indication would be in ureteral stent placement after stone therapy. It would ideally eliminate the need for an additional procedure for stent removal and also be associated with fewer stent irritation symptoms.

Chew et al are on their “third generation” of biodegradable stent. The first attempts did not result in satisfactory degradation parameters. The current “Uriprene” stent is a combination of various biodegradable polymers to include L-glycolic acid, polyethylene glycol and barium sulfate. This new generation of biodegradable stent was compared with traditional biostable stents in a porcine model over a 4-week period.

The authors were able to demonstrate that 9 of 10 of the biodegradable stents in a porcine model were completely degraded by 4 weeks, with the remaining animal having 3 fragments, approximately 1.5 cm each, remaining in the bladder. The intravenous pyelogram findings showed equivalent drainage of the biodegradable stent compared to the biostable stent with actually less hydronephrosis in the biodegradable stent on day 14. The biodegradable stents, however, did show a transient increase in creatinine on day 7 of unclear etiology. At sacrifice, significantly fewer abnormal histological findings were noted in the biodegradable stent animals. The authors felt that the biodegradable stent was an effective alternative to conventional biostable stents.

The results of this study are promising. It is important to remember, however, that these results are in an unobstructed ureter animal model. We do not know how the stents would behave in the presence of obstruction or edema. Interestingly, the stents are designed to degrade distal (bladder) to proximal (kidney). This is to reportedly to allow less bladder irritation and vesicoureteral reflux if the bladder portion degrades first. The concerning issue with the described degradation parameter in this study is the finding of several moderate sized fragments in the bladder of one animal (10%) at 4 weeks. Presumably, the fragments were from the proximal ureter (given degradation design) and passed into the bladder. Although the imaging studies did not demonstrate obstruction, it is difficult to know if transient obstruction was occurring. This is also true of the rise in creatinine of the study pigs at 7 days (anticipated time that the stents start the degradation process). Last, the IVP showed worsening obstruction of the traditional biostable stented ureters at 14 days which questions whether the porcine model is adequate for comparison of stents.

Overall, this research group has made great strides in the development of a biodegradable stent. I wait to see the additional modifications in design and the results in human trials. A few more kinks need to be worked out, but the idea of a biodegradable stent is coming closer to fruition.

David A. Duchene, MD

ROBOTICS

Preventing perioperative complications of robotic-assisted radical prostatectomy. Liss MA, Skarecky D, Morales B, Osann K, Eichel L, Ahlering TE, Department of Urology, University of California, Irvine, CA.

Urology 2013;81:319-23.

Objective: To report the change in complication rates after the identification and modification of technique to reduce their incidence during robot-assisted radical prostatectomy (RARP).

Methods: This study retrospectively reviewed 1000 consecutive patients who underwent RARP from June 2002 to June 2011. A number of technical changes were made after complications were noted and changes in technique were documented. The Fisher exact test and multivariate analysis were used for comparison of techniques, and values of P<.05 were considered significant.

Results: The overall rate of major and minor complications was 10.8% (108 of 1000). The complication rates of lymphoceles (0.4%), ileus (0.4%), and wound infection (0.4%) were low and did not require technical changes. There were no significant changes in rates of femoral nerve palsies, rectal injuries, or bladder neck contractures. There was statistically significant change in corneal abrasions (P=.03), fossa navicularis strictures (P=.03), and camera-site hernias (P<.001) after a directed intervention adjusted for age, body mass index, and learning curve. Clavien 3 and 4 complications all significantly decreased to ≤0.6%, with the most occurring in the first 200 cases.

Conclusion: Identification and correction of perioperative complications in patients undergoing robotic prostatectomy has decreased the incidence of major and minor complications adjusted for learning curve. The conscientious monitoring of adverse events can provide targeted change in technique to decrease complications and provide information to those early in learning robotic-assisted radical prostatectomy.

Copyright © 2013 Elsevier Inc. All rights reserved.

DOI: 10.1016/j.urology.2012.09.033

Commentary

Robotic-assisted laparoscopic radical prostatectomy (RARP) has become prevalent in urology. Numerous studies in the literature have addressed the complications of RARP, often comparing them to open radical retropubic prostatectomy or laparoscopic radical prostatectomy. In this study, the authors reviewed complications in a series of 1000 RARP cases and also reported specific strategies to reduce observed complications. Changes in technique were assessed to determine whether there were statistically significant differences in observed complications. Some of the complications noted were so rare, including ileus, lymphoceles, and wound infection that there were no changes in technique implemented. The overall complication rate was 10.8%.

The authors identified three specific complications that were reduced when technical modifications were instituted. First, the risk of corneal abrasions decreased significantly by applying foam-based safety goggles on all patients, being placed during the operation (to reduce eye edema) as well as for 90 minutes in the recovery room to prevent the patient from rubbing his eyes. Second, the authors noted that decreasing the size of the Foley catheter from 22 French to 16 French reduced the incidence of fossa navicularis strictures by 10% with virtually no occurrences in the last 850 cases. Finally, changing the incision for the camera port and for specimen retrieval from vertical to horizontal (based on general surgery literature) reduced the risk of port site hernia from 5.4% to 0.4%. The incidence of other complications studied, including nerve palsy, rectal injury, pulmonary embolus, and bladder neck contracture were not affected by minor changes in technique. Also, not surprisingly, the overall rate of major complications decreased after the first 200 cases, presumably when the surgeon had overcome the learning curve.

This study examines complications of a large series of patients undergoing RARP at an academic center by an experienced surgeon. More importantly, it provides evidence that minor modifications in technique, all of which are very easy to implement, can decrease complications. As surgeons we must be willing to study our own complications and strive to modify techniques to reduce them. It is the willingness to try to change our technique that will help improve safety and outcomes of our patients undergoing RARP and other urologic operations.

David S. Wang, MD

THERMAL/ABLATIVE TECHNOLOGY

Usefulness of R.E.N.A.L. nephrometry scoring system for predicting outcomes and complications of percutaneous ablation of 751 renal tumors. Schmit GD, Thompson RH, Kurup AN, Weisbrod AJ, Boorjian SA, Carter RE, Geske JR, Callstrom MR, Atwell TD, Department of Radiology, Mayo Clinic School of Medicine, Rochester, MN.

J Urol 2013;189:30-5.

Purpose: We applied the R.E.N.A.L. (radius, exophytic/endophytic, nearness to collecting system or sinus, anterior/posterior and location relative to polar lines) nephrometry scoring system to renal tumors treated with percutaneous ablation to determine whether this score is associated with oncological outcomes and complications.

Materials and Methods: A total of 751 renal tumors were treated at 679 percutaneous ablation sessions in 627 patients at our institution between 2000 and 2012. Of these renal masses 430 (57%) were treated with cryoablation and the remaining 321 were treated with radio frequency ablation. R.E.N.A.L. tumor scores were analyzed to determine the association of the score with ablation treatment outcomes and complications according to Clavien criteria.

Results: The mean±SD R.E.N.A.L. nephrometry score of all ablated tumors was 6.7±1.9. Those treated with cryoablation had higher scores than those treated with radio frequency ablation (mean 7.2±1.9 vs 6.1±1.8, p<0.001). We identified a total of 28 local treatment failures (3.7%) in the 751 tumors during a mean computerized tomography/magnetic resonance imaging followup of 27.9±27.8 months. There was a significant association between R.E.N.A.L. nephrometry score and local treatment failure. Mean nephrometry score was 7.6±2.2 vs 6.7±1.9 for tumors with vs without local treatment failure (p<0.001). Of the 679 ablation treatments 38 (5.6%) major (grade 3 or greater) patient complications occurred. There was a significant association between R.E.N.A.L. nephrometry score and major complications. Patients with vs without a major complication had a mean nephrometry score of 8.1±2.0 vs 6.8±1.9 (p<0.001).

Conclusions: The R.E.N.A.L. nephrometry scoring system predicts treatment efficacy and complications following percutaneous renal ablation.

Copyright © 2013 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

DOI: 10.1016/j.juro.2012.08.180

Commentary

The advent of nephrometry scoring has undoubtedly improved our ability to objectify tumor complexity and to finally allow the possibility of comparing different studies as well the assessment of different techniques. Thus, applying the nephrometry score to renal ablative therapy is intuitive and logical. This large single institution study from the Mayo clinic in Rochester retrospectively assessed R.E.N.A.L. nephrometry scoring in their experience of 751 renal tumors in 627 patients between 2000 and 2012. A little over half (57%) of the tumors underwent radiofrequency ablation while the rest were treated with cryoablation. The authors determined the association of the nephrometry score with outcomes, including complications. As would be expected with a retrospective study, there were baseline differences between patients and groups. Patients undergoing cryoablation had higher nephrometry scores (7.2 versus 6.1, P<0.001) and mean nephrometry score for all tumors was 6.7. The average follow-up was about 28 months but with a very large standard deviation of about the same magnitude.

The authors found a significant association between the nephrometry score and treatment failure and as well with major complications. Patients with treatment failure had a mean score of 7.6 and patients with major complications had a mean nephrometry score of 8.1. Figure 1 is interesting, showing local failure rates based on the classification score of low (4–6), moderate (7–9), and high (10–12). The low and moderate complexity tumors have nearly parallel lines, but the high complexity tumors show a steeper line, with more rapid and more frequent treatment failures. A similar concept is presented in Figure 2, whereby the major complication rate is seen to be substantially higher for the high complexity tumors as opposed to the low and moderate complexity tumors; the odds of major procedural complications increased by 1.491 per unit increase in the nephrometry score. The authors conclude that the nephrometry scoring system can help predict treatment efficacy as well as complications after percutaneous renal ablation.

The evaluation of ablation based on nephrometry scoring is not novel, and this has been done before, as have prior studies that showed a tumor size-treatment efficacy relationship.^1,2 This study represents a very high volume experience for which statistical power exists to find less common associations. The authors performed logistic regression analysis, but interestingly, multivariable analysis was not performed and, curiously, individual components of the nephrometry score were not assessed to see if one particular component (especially tumor size) could be driving the results. Other limitations of this study include the fact that 11% of patients did not have imaging after three months, although this may have been followed-up locally. The scoring did not take into account hilar tumors (‘h’ designation). Finally, as is commonly the problem with ablative studies, less than half of the treated renal masses were biopsy-proven to be renal cell carcinoma, which significantly limits the ability to perform oncologic evaluation. Nevertheless, this is a useful study that one can apply in the clinic when evaluating a patient for ablative therapy. The nephrometry scoring is easily learned, and can be easily and intuitively applied in the clinic setting, introducing a more objective parameter when counseling patients about their options and risks. Based on this study, patients with higher scores, particularly those above 8 and those with very high complexity, are at much higher risk for failure as well as complications.

References

1. Reyes J, Canter D, Putnam S, et al. Thermal ablation of the small renal mass: case selection using the R.E.N.A.L.-nephrometry score. Urol Oncol 2012; Apr. 20 [epub ahead of print].

2. Zagoria RJ, Traver MA, Werle DM, et al. Oncologic efficacy of CT-guided percutaneous radiofrequency ablation of renal cell carcinomas. AJR Am J Roentgenol 2007;189:429–36.

Surena F. Matin, MD