Retrograde Intrarenal Surgery Versus Percutaneous Nephrolithotomy in the Management of Lower-Pole Renal Stones with a Diameter of 15 to 20 mm

Abstract

Purpose:

To compare the outcomes of percutaneous nephrolithotomy (PCNL) and retrograde intrarenal surgery (RIRS) for 15 to 20 mm lower-pole (LP) renal calculi by evaluating stone-free rates and associated complications.

Patients and Methods:

The records of 79 patients who underwent either PCNL (n=42) or RIRS (n=37) by standard techniques for 15 to 20 mm LP renal calculi were reviewed retrospectively.

Results:

In the PCNL group, the stone-free rate was 92.8% (39/42 patients); this rate increased to 97.6% after a second intervention (shockwave lithotripsy in one and RIRS in one). After a single RIRS procedure, 33 of 37 (89.2%) patients were completely stone free. Two patients needed an additional procedure (rigid ureteroscopy in one and RIRS in one), after which they were all completely stone free, resulting in an overall success rate of 94.6%. Two patients had asymptomatic residual fragments <7 mm in the LP of the kidney, and these patients had been followed with ultrasonography of the kidney. For complications, there were minimal differences in both procedures, except for hemorrhage (necessitated transfusion) in three patients who were treated with PCNL. The overall stone-free rates and complication rates for PCNL were higher, but the differences were not statistically significant. Operative time was significantly longer in the RIRS group, and postoperative hospital stay was significantly longer in PCNL group.

Conclusion:

PCNL and RIRS are safe and effective methods for medium-sized LP calculi. For selected patients, RIRS may represent an alternative therapy to PCNL, with acceptable efficacy and low morbidity.

Introduction

T he European Association of Urology (EAU) and American Urological Association guidelines for the management of intrarenal calculi <20 mm recommend extracorporeal shockwave lithotripsy (SWL) as the first-line therapy.^1,2 SWL treatment, however, frequently fails for stones in dependent areas of the kidney, such as lower pole (LP) stones. For stones that are 15 to 20 mm, there is a decline in the use of SWL with a parallel increase in use of percutaneous nephrolithotomy (PCNL) and retrograde intrarenal surgery (RIRS), because they are associated with better stone-free rates.^3,4 PCNL has the advantage of achieving the highest stone-free rate for these calculi, but it is the most invasive technique.⁵ RIRS can minimize the risks associated with percutaneous renal surgery, such as bleeding, pleural and visceral injury, and urine leak, and can be performed as an outpatient procedure. To test this hypothesis, we compared the outcomes of RIRS and PCNL for management of 15 to 20 mm LP renal calculi by evaluating stone-free rates and associated complications.

Patients and Methods

Patients

We performed a retrospective analysis of 79 evaluable patients who underwent PCNL (n=42) or RIRS (n=37) for LP stones 15 to 20 mm in diameter between January 2009 to November 2010 at the urology department of Kecioren Research and Training Hospital. Data were collected from retrospective reviews of hospital and physician office records, and by contact with the patients. Patients were evaluated with plain radiography, intravenous urography, ultrasonography, and/or CT, urinalysis, urine culture, complete blood cell count, serum biochemistry, and coagulation tests before the procedure. Stone size was assessed as the surface area and calculated according to EAU guidelines.⁶

We decided the operation technique according to the LP pelvicaliceal anatomy and patient choice. We did not prefer the RIRS technique in patients who had narrow LP infundibulopelvic angle or infundibular width. And we did not prefer the PCNL technique in patients who had bleeding diathesis, musculosceletal deformities, chronic obstructive pulmonary disease, or morbid obesity. Patients with abnormal renal anatomy (horseshoe, pelvic, and malrotated kidneys, bifid pelvis, ectopic pelvic fusion anomaly), patients with nonopaque stones, and preschool-age patients (<8 years) were excluded from the study.

PCNL technique

All procedures were performed with the patient under general anesthesia. A 6F ureteral catheter was placed, and the bladder was drained with a 16F Foley catheter. After ureteral catheter insertion, patients were placed in the prone position, and percutaneous access was achieved under fluoroscopic guidance using an 18-gauge needle and guidewire. Tract dilation was accomplished using Amplatz or balloon dilators of up to 24F. Fragmentation and stone removal were accomplished in all patients using pneumatic or ultrasound energy and retrieval graspers through a rigid 22F nephroscope. A holmium laser and nitinol basket catheter were used through a flexible nephroscope for migrated stone fragments that were unreachable with the rigid instruments. Stone clearance was determined by a combination of fluoroscopy and rigid or flexible nephroscopy at the end of the procedure, sometimes with plain radiography or CT postoperatively if there was not confidence in the intraoperative assessment. The operations were completed when residual fragments were not detected on fluoroscopic imaging and rigid or flexible nephroscopic control.

After completion, a 16F reentry catheter or, alternatively, a 14F Nelaton catheter as a nephrostomy tube was inserted in standard PCNL (no nephrostomy tube was used in tubeless PCNL). The nephrostomy tube was removed on postoperative days 1 to 2, and the patient was discharged to home the next day.

RIRS technique

All procedures were performed by two surgeons (AU and BR) using a 7.5F (Karl Storz™) or 8.4 F (Olympus™) flexible ureteroscopes. Under general anesthesia, patients were placed in the lithotomy position on an endoscopy table with fluoroscopic imaging capability. All procedures were performed under direct videoscopic and fluoroscopic guidance. Fluoroscopic screening was performed using a mobile multidirectional C-arm fluoroscopy unit with an under-the-couch x-ray tube and an over-the-couch image intensifier. Rigid ureteroscopy was routinely performed before flexible ureteroscopy in all patients for detecting nonopaque ureteral stones, dilation of the ureter, and to place a hydrophilic guidewire to the renal pelvis.

After passing a 0.035/0.038-inch safety guidewire into the renal pelvis, flexible ureteroscopy was performed. A ureteral access sheath (9.5/11.5F or 12/14F) was placed in 31 (81%) patients to allow optimal visualization, to maintain low intrarenal pressure, and to facilitate flexible ureteroscopy. The stones were fragmented with a holmium:yttrium-aluminum-garnet laser until they were deemed small enough to pass spontaneously. Basket extraction of residual fragments was not routinly performed; however, some residual fragments were removed by nitinol baskets for stone analysis. In 40.5% of the patients, stones were relocated to a more favorable location in the pelvis or upper pole by basketing to allow better visualization during lithotripsy.

The decision to place a ureteral stent postoperatively is made based on the duration of the procedure, number of passes with the ureteroscope, and degree of visible ureteral trauma or edema at the conclusion of the procedure. A Double-J stent was placed at the end of the procedure and was removed using brief anesthesia approximately 10 to 14 days postoperatively (range 7 to 28 d).

Follow-up

Patients with postoperative residual fragments <3 mm were accepted as stone free (clinically insignificant residual fragments). The first follow-up evaluation was performed 2 months after the operation, after which patients were seen every 3 months during the first year and every 6 months thereafter. At each visit, urinalysis, urine culture, measurement of serum creatinine, plain radiography, and abdominal ultrasonography were performed. If stone recurrence was diagnosed, excretory urography or noncontrast spiral CT was performed.

Data analysis

The chi-square test was applied to compare the success rates, postoperative complications, and blood transfusion rates, and the t test was used to compare the means of hospital stay and operative time for PCNL and RIRS. Continuous variables are presented by means±standard deviations (SDs). Statistical significance was defined as P<0.05. All statistical analysis were performed using SPSS.

Results

The present study included 46 (58.2%) men and 33 (41.8%) women. Mean patient age was 44.5±17.6 years (8 to 67 y), and the mean follow-up was 11.5±3.69 months (range 2–18 mos). There were no differences between the two groups in age, sex, and stone laterality. With 1.7±0.12 cm² and 1.65±0.69 cm², the overall stone volume was comparable in two groups, although in the RIRS group, the portion of patients with multiple stones was higher. Table 1 lists patient demographics and stone characteristics.

Table 1.

Demographıc Data and Stone Characterıstıcs

	PCNL group	RIRS group	P value
No. patients (%)	42 (53.1%)	37 (46.9%)	–
Mean age±SD, y (min – max)	47.4±15.5 (14–67)	41.2±13.6 (8–61)	0.833
Male/female	25/17	21/16	0.804
Mean stone burden±SD, cm² (min – max)	1.7±0.12 (1.3–2.6)	1.65±0.69 (1.18–2.2)	0.053
Side (right/left)	20/22	19/18	0.740
Multiple stones (%)	17/42 (40.4%)	19/37 (54%)	0.330

PCNL=percutaneous nephrolithotomy; RIRS=retrograde intrarenal surgery; SD=standard deviation.

In the PCNL group, the stone-free rate was 92.8% (39/42 patients); this rate increased to 97.6% after a second intervention (SWL in 1 and RIRS in 1). All patients underwent a single access procedure. Mean operative time was 45.8±19.6 minutes (range 20–90 min), postoperative hospital stay was 2.3±1.6 days (range 1–6 d), and nephrostomy tube removal time was 1.6±0.9 days (range 0–3 d). Nine (21.4%) patients underwent tubeless PCNL. Three (7.1%) patients had fever postoperatively, which resolved spontaneously in one, while the remaining two patients needed antibiotic treatment because of positive urine cultures. The hemoglobin drop ranged from 0.2 to 4.2 g/dL (mean±SD is 1.7±0.8 g/dL), and three patients needed blood transfusion. One patient had a prolonged hospital stay because of urinary leakage from the nephrostomy tract after the removal of the tube. Leakage resolved spontaneously in 3 days without intervention. There were no adjacent neighboring organ injuries, no deaths, and no acute or delayed kidney loss.

In the RIRS group, 33 of 37 (89.2%) patients were completely stone free after a single procedure. Two patients needed an additional procedure (rigid ureteroscopy in one and RIRS in one), after which they were all completely stone-free, resulting in an overall success rate of 94.6%. Two patients had asymptomatic residual fragments <7 mm in the LP of the kidney, and these patients had been followed with ultrasonography of the kidney. The mean operative time was 67.5±24.3 minutes (range 25–105 min), and postoperative hospital stay was 1.3±0.7 days (range 1–3 d). A ureteral stent was placed at the end of the procedure in 28 (75.6%) cases. There were two (5.4%) intraoperative complications.

One patient had significant bleeding, which resulted in poor visibility and led to abortion of the procedure. No transfusions were necessary, however. This patient underwent an uncomplicated second treatment 3 weeks later. Another patient had ureteral perforation that was managed conservatively with a ureteral stent. Two minor postoperative complications (5.4%) occurred consisting of urinary tract infections, and all were managed with antibiotics.

For complications, there were minimal differences in both procedures, except for hemorrhage (necessitated transfusion) in three patients who were treated with PCNL. The overall stone-free rates and complication rates for PCNL were higher, but the differences were not statistically significant (P=0.483 and P=0.453, respectively). Postoperative hospital stay was longer in PCNL patients, and the difference was statistically significant (P=0.0002). The operative time was higher in RIRS, and it was statistically significant (P=0.0156). Intraoperative and postoperative findings of patients are summarized in Table 2.

Table 2.

Treatment Success and Complıcatıons

	PCNL group	RIRS group	P value
Mean operative time±SD (min)	45.8±19.6 (20–90)	67.5±24.3 (25–105)	0.0156^a
Initial stone-free rate (%)	39/42 (92.8%)	33/37 (89.2%)	0.571
Final stone-free rate (%)	41/42 (97.6%)	35/37 (94.6%)	0.483
Hospitalization time (d)	2.3±1.6 (1–6)	1.3±0.7 (1–3)	0.0002^a
Postoperative DJ stent (%)	2/42 (4.7%)	28/37 (75.6%)	<0.0001^a
Minor complications	7/42 (16.6%)	4/37 (10.8%)	0.453
Major complications	–	–	0.097
Transfusion rate (%)	3/42 (7.1%)	–

Significant at 0.05 level.

PCNL=percutaneous nephrolithotomy; RIRS=retrograde intrarenal surgery; SD=standard deviation; DJ=Double-J.

Discussion

SWL is the traditional treatment for patients with small and moderate-sized intrarenal calculi with a stone burden of <20 mm.⁷ The highest stone-free rates are for single calculi in the renal pelvis or ureteropelvic junction and range from 80% to 88%.^8,9 Stone-free rates drop below 50% to 70%, however, for stones located in the LP.^9

–12 The choice of therapy for LP stones 15 to 20 mm is controversial and based on various stone, patient, and surgeon factors. In this study, the outcomes of PCNL and RIRS in the management of medium-sized (15–20 mm) LP stones have been reported and compared with other reported studies.

PCNL has proved to be highly successful for LP renal calculi with uniformly high success rates independent of stone size. In the first LP study, stone-free rates of 100%, 93%, and 86% were reported after PCNL for stones <1, 1 to 2, and >2 cm, respectively.¹³ This study revealed that stone-free rates for PCNL were significantly better than SWL (95% vs 37%). The stone-free rates of SWL were only acceptable for stones <10 mm (63%). Because of this high degree of efficacy and acceptable low morbidity, the authors recommended PCNL as an initial modality for managing stones >10 mm. The success rates in this study were confirmed by Preminger,¹⁴ who compared SWL and PCNL for LP stones. For stones <1 cm in diameter, PCNL provided a 100% stone-free rate compared with 67% for SWL. The disparity was even more marked for stones 1.1 to 2 cm, for which the success rate for PCNL was 92%, whereas SWL was successful in only 21% of the cases. Other studies of LP renal stones also showed a high success rate for PCNL for all stone sizes.^15,16

On the other hand, PCNL is associated with greater morbidity than SWL. Despite its effectiveness, major complications have been identified as a result of PCNL and occur at reported rates of 0.03% to 10%.^17,18 Complications are often the result of obtaining percutaneous access,but can also result from the technique of stone removal and include hemorrhage, arteriovenous fistula, sepsis, hydrothorax, colocutaneous fistula, injury to surrounding viscera, ureteral avulsion, hypothermia, volume overload, electrolyte imbalance, myocardial infarction, pulmonary embolism, and death.

The postoperative measurements of renal function indicate that patients tolerate PCNL well, but the immediate effects on renal function are unknown. Moskovitz and colleagues¹⁹ measured the effect of PCNL on global and regional renal function in adult patients using single-photon emission CT measurement of dimercaptosuccinic acid uptake by the kidneys. Although no significant alteration of global uptake was noted, the total functional volume of the treated kidney was decreased slightly. Interestingly, the regional assessment revealed a statistically significant decrease in the functional volume at the PCNL site of entry.

RIRS for LP caliceal calculi is an acceptable alternative therapeutic method to PCNL. With the advent of new generation flexible ureteroscopes with greater deflection and control, there has been an increase in endoscopic ureteroscopy and laser lithotripsy for renal calculi.²⁰ Also, advances in lithotripsy, in particular the holmium laser, have resulted in increased treatment success for stones and decreased procedure-related morbidity. Holmium laser fibers have improved flexibility and come in a range of sizes to accommodate LP access vs more efficient ablation of renal pelvis and upper-pole stones. Several different basket and retrieval devices can now be applied in different scenarios to facilitate intrarenal maneuvers. The use of an access sheath increases the ease of passing the ureteroscope while minimizing intrarenal pressures and allowing removal of large stone fragments.²¹

In 1998, Fabrizio and colleagues²² examined the results of ureteroscopic management in those patients in whom SWL or PCNL was contraindicated or had failed previously and the stone-free rate after treatment was 77%. Grasso and Ficazzola²³ subsequently reported their results with a ureteroscopic approach, specifically for patients with LP calculi. In this series, the overall stone-free rate was 76%. When stratified by stone size, the stone-free rates were 82%, 71%, and 65% for patients with stones 1 to 10 mm, 11 to 20 mm, and >20 mm. Recent studies report stone-free rates above 90% for retrograde ureteroscopic management of renal stones and as high as 85% for management of LP stones.^8,24 Our study supports the finding that ureteroscopy can manage stones throughout the renal collecting system with a high success rate. To our knowledge, comparison of RIRS and PCNL for LP stones of 15 to 20 mm has not been published previously. Chung and coworkers³ compared the outcome of PCNL and RIRS for 1 to 2 cm renal calculi. Of 15 patients who underwent PCNL, 7 had LP calculi. There were 4 patients with LP calculi among 12 patients undergoing RIRS. The authors noted that the overall stone-free rate with PCNL was 87% and that for RIRS it was 67%.

One of the most common and worrisome complications after percutaneous renal surgery is renal hemorrhage.²⁵ Bleeding may occur at any point intraoperatively to the immediate or late postoperative period, and about 0.8% of the cases need angioembolization for the management of uncontrollable bleeding.²⁶ RIRS is known to have fewer overall complications compared with PCNL. Major complications secondary to ureteroscopy are less common, and they decrease in time. Significant complications, such as ureteral avulsion, are exceedingly rare, especially since the instrument size has decreased. Furthermore, RIRS has been proved safe in patients at high risk, such as pregnant women, obese patients, or those with coagulopathy, in whom PCNL may be contraindicated.

We report an overall 94.6% success rate with RIRS for LP stones that are 15 to 20 mm. Our study supports previous findings that the stone-free rate after RIRS is comparable to that of PCNL. We found that the stone-free rate and complications were higher with the percutaneous approach, although the difference was not statistically significant. When we compared the mean operative time per stone size in the groups, operative time was longer in the RIRS group. The hospital stay was longer in the PCNL group, comparing the need for postoperative percutaneous drainage. It is noteworthy that these procedures should be performed by an experienced endourologist.

There are some limitations to this study. This is a retrospective review from a single institution, and our results are based on a relatively small sample size. We performed the first follow-up evaluation with renal ultrasonography and plain radiography, and stone clearence status was confirmed at this control. Ultrasonography has clear advantages of convenience and lack of radiation exposure over CT scan and intravenous urography. Ultrasonography and plain radiography, however, may miss some of the residual stones, and this is the another limitation of our study.

Conclusion

The above data suggest that PCNL and RIRS are safe and effective methods for medium-sized LP calculi. Today, patients should be informed about the available modalities of treatment and their efficacy and safety. For selected patients, RIRS may represent an alternative therapy to PCNL, with acceptable efficacy and low morbidity.

Footnotes

Disclosure Statement

No competing financial interests exist.

Abbreviations Used

References

Tiselius

. Prospective, randomized trial comparing shock wave lithotripsy and ureteroscopy for lower pole caliceal calculi 1 cm or smaller. Eur Urol, 2006; 49:586–587.

Preminger

, Assimos

, Lingeman

et al. Chapter 1: AUA guideline on management of staghorn calculi: Diagnosis and treatment recommendations. J Urol, 2005; 173:1991–2000.

Chung

, Aron

, Hegarty

, Desai

. Ureteroscopic versus percutaneous treatment for medium-size (1-2-cm) renal calculi. J Endourol, 2008; 22:343–346.

Elbahnasy

, Clayman

, Shalhav

et al. Lower-pole caliceal stone clearance after shockwave lithotripsy, percutaneous nephrolithotomy, and flexible ureteroscopy: Impact of radiographic spatial anatomy. J Endourol, 1998; 12:113–119.

Yuruk

, Binbay

, Sari

et al. A prospective, randomized trial of management for asymptomatic lower pole renal calculi. J Urol, 2010; 183:1424–1428.

Türk

, Knoll

, Petrik

et al. Guidelines on Urolithiasis. Arnheim. The Netherlands: European Association of Urology, 2010.

Wen

, Nakada

. Treatment selection and outcomes: Renal calculi. Urol Clin North Am, 2007; 34:409–419.

Galvin

, Pearle

. The contemporary management of renal and ureteric calculi. BJU Int, 2006; 98:1283–1288.

Breda

, Ogunyemi

, Leppert

, Schulam

. Flexible ureteroscopy and laser lithotripsy for multiple unilateral intrarenal stones. Eur Urol, 2009; 55:1190–1196.

10.

Pearle

, Lingeman

, Leveillee

et al. Prospective, randomized trial comparing shock wave lithotripsy and ureteroscopy for lower pole caliceal calculi 1 cm or less. J Urol, 2005; 173:2005–2009.

11.

Kijvikai

, Haleblian

, Preminger

, de la Rosette

. Shock wave lithotripsy or ureteroscopy for the management of proximal ureteral calculi: An old discussion revisited. J Urol, 2007; 178:1157–1163.

12.

Cass

. Comparison of first generation (Dornier HM3) and second generation (Medstone STS) lithotriptors: Treatment results with 13,864 renal and ureteral calculi. J Urol, 1995; 153:588–592.

13.

Albala

, Assimos

, Clayman

et al. Lower pole I: A prospective randomized trial of extracorporeal shock wave lithotripsy and percutaneous nephrostolithotomy for lower pole nephrolithiasis—initial results. J Urol, 2001; 166:2072–2080.

14.

Preminger

. Management of lower pole renal calculi: Shock wave lithotripsy versus percutaneous nephrolithotomy versus flexible ureteroscopy. Urol Res, 2006; 34:108–111.

15.

Lingeman

, Siegel

, Steele

et al. Management of lower pole nephrolithiasis: A critical analysis. J Urol, 1994; 151:663–667.

16.

Resorlu

, Kara

, Senocak

et al. Effect of previous open renal surgery and failed extracorporeal shockwave lithotripsy on the performance and outcomes of percutaneous nephrolithotomy. J Endourol, 2010; 24:13–16.

17.

Unsal

, Resorlu

, Kara

et al. Safety and efficacy of percutaneous nephrolithotomy in infants, preschool age, and older children with different sizes of instruments. Urology, 2010; 76:247–252.

18.

Michel

, Trojan

, Rassweiler

. Complications in percutaneous nephrolithotomy. Eur Urol, 2007; 51:899–906.

19.

Moskovitz

, Halachmi

, Sopov

et al. Effect of percutaneous nephrolithotripsy on renal function: Assessment with quantitative SPECT of (99m)Tc-DMSA renal scintigraphy. J Endourol, 2006; 20:102–106.

20.

Johnson

, Portela

, Grasso

et al. Advanced ureteroscopy: Wireless and sheathless. J Endourol, 2006; 20:552–555.

21.

Kourambas

, Byrne

, Preminger

. Does a ureteral access sheath facilitate ureteroscopy? J Urol, 2001; 165:789–793.

22.

Fabrizio

, Behari

, Bagley

. Ureteroscopic management of intrarenal calculi. J Urol, 1998; 159:1139–1143.

23.

Grasso

, Ficazzola

. Retrograde ureteropyeloscopy for lower pole caliceal calculi. J Urol, 1999; 162:1904–1908.

24.

Mariani

. Combined electrohydraulic and holmium:YAG laser ureteroscopic nephrolithotripsy of large (greater than 4 cm) renal calculi. J Urol, 2007; 177:168–173.

25.

Srivastava

, Singh

, Suri

et al.

Vascular complications after percutaneous nephrolithotomy: Are there any predictive factors?

Urology, 2005; 66:38–40.

26.

Williams

, Leveillee

. Management of staghorn calculus: Single puncture with judicious use of the flexible nephroscope. Curr Opin Urol, 2008; 18:224–228.