Retrograde Intrarenal Surgery in Treatment of Nephrolithiasis: Is a 100% Stone-Free Rate Achievable?

Abstract

Purpose:

To achieve an almost 100% stone-free rate by means of further developing and standardizing the procedure.

Patients and Methods:

100 consecutive patients with single or multiple renal calculi were prospectively enrolled in the study. Flexible ureterorenoscopy was performed as a completely standardized operation by the same two experienced surgeons. Primary outcome was an “endoscopic” (immediate) stone-free status as determined by endoscopic inspection at the end of surgery. In cases of residual fragments, a reevaluation by CT was performed after 3 months.

Results:

The endoscopic stone-free rate was 97%. In three patients with a cumulative stone size >20 mm, a completely stone-free status could not be achieved in the primary procedure. In these patients, a CT scan after 3 months showed complete clearance from all residual fragments in two; this translates into a primary (after one procedure) stone-free rate after 3 months of 99%. Medium cumulative stone size was 9.8 mm (4–40 mm); in 44 patients, multiple calculi were extracted. Forty-nine patients received a ureteral stent at the end of the operation; two patients had to have stent placement for new onset hydronephrosis and/or colicky pain or fever. Overall complication rate was 7%. Results are limited, because no routine CT scan was used to evaluate stone clearance.

Conclusion:

By means of a standardized surgical approach and use of technical equipment of the newest generation, it is possible to achieve very high stone-free rates without compromising safety. This approach, however, necessitates use of considerable resources, both technical/surgical and financial.

Introduction

B ecause of major improvements in available technology, flexible ureterorenoscopy (FURS) has gained wider acceptance, not only as a tool for diagnostic procedures, but also for therapeutic approaches to the kidney. From its introduction to clinical use in 1971¹ to the newest generations of instruments, substantial modifications have led to an enhanced feasibility of retrograde intrarenal surgery (RIRS).² Growing experience in conducting RIRS has led to broader applications of this approach, particularly in the treatment of nephrolithiasis. Although existing guidelines³ still recommend shockwave lithotripsy (SWL) or percutaneus nephrolithotomy (PCNL) as the standard therapies, FURS is gaining more and more acceptance as a first-line alternative treatment option for renal stones up to 20 mm or more.⁴

The authors hypothesized that when using the most advanced technology in a completely standardized FURS technique, it would be possible to achieve a stone-free rate (SFR) of close to 100% for unilateral intrarenal stones.

Patients and Methods

From November 2009 to April 2011, a prospective data collection of 100 consecutive patients with intrarenal calculi who were treated by FURS/RIRS was performed. The designated intention of the trial was to achieve an “endoscopic SFR” as high as possible without compromising on safety. Endoscopic stone-free status was defined as a complete removal of all stone fragments during the primary intervention—ie, not leaving any visible residuals behind.

Preoperative imaging was performed by ultra–low-dose CT scan and abdominal ultrasonography in all patients. Patients were then counseled concerning treatment options according to the existing guidelines.³ At our institution, RIRS is offered as a first-line treatment for patients with multiple stones and/or concomitant ureteral stones with a cumulative stone burden <20 mm (maximum diameters of stones added) or as an alternative treatment to SWL or PCNL for single stones <20 mm and in selected cases (obese patients) as alternative treatment to PCNL for stones >20 mm. If a patient opted for RIRS, he or she would be included into the study. To avoid confounding, patients with concomitant ureteral stones were excluded. No patient was lost for evaluation.

Technique

The standardized approach includes preoperative Double-J (DJ) ureteral stent placement in all cases—ie, patients have received a stent for previous colicky pain or hydronephrosis in cases of concomitant ureteral calculi (with consecutive translocation of the stone into the pelvicaliceal system) or patients receive a ureteral stent 5 to 10 days before the planned operation.

The procedure is performed with the patient in a dorsal lithotomy position under general anesthesia. In a first step, the indwelling DJ catheter is extracted with a semirigid ureterorenoscope, and by doing so, a hydrophilic safety wire (HiWire,^® Cook Medical, Bloomington, IN) is placed through the DJ catheter before complete removal. The following semirigid ureterorenoscopy provides indirect and direct visualization of the upper urinary tract by retrograde pyelography and macroscopic inspection (assessment of the ureter in terms of caliber and possible applicable ureteral access sheath). Subsequently, a second wire is placed through the ureteroscope, and the instrument removed. In cases of a stone burden >5 mm, a large-bore ureteral access sheath (12/14F or, as in most cases 14/16F, Cook Medical, Bloomington, IN) is inserted over the second wire under fluoroscopic guidance, and the flexible ureterorenoscope (6/9.9F, The Cobra,^® Richard Wolf GmbH, Knittlingen, Germany) is introduced. In cases without an access sheath, the ureterorenoscope is inserted over the second wire.

Flexible renoscopy starts with active flushing of the pelvicaliceal system using a 20-mL syringe that is incorporated into the irrigation line through a three-way plug valve. After complete clearing of the system, a systematic inspection of all calices follows. Calculi up to 4 mm might be extracted in toto by means of a nitinol grasper (1.5F, NGage,™ Cook Medical, Bloomington, IN). Bigger calculi are fragmented using a holmium–yttrium-aluminum-garnet (YAG) laser and a 200-μm laser fiber (AMS, Minnetonka, MN). Stones in the lower calices might be relocated to the renal pelvis or an upper calix to simplify fragmentation and removal. Great importance is attached not to “vaporize” the stones (producing numerous small fragments) but rather to “cut” them into few large pieces, because only in that way does a complete removal of all fragments seem feasible.

Cutting of stones is achieved by applying a lower power level at a lower frequency (6 W, 5 Hz) compared with a vaporizing effect of the laser when choosing higher power levels at a higher frequency (15 W, 10 Hz). Closing inspection of all calices allows for determination of an endoscopic stone-free status. Any residuals ≥1 mm would be considered “not stone-free.”

During joint removal of the endoscope and access sheath, the ureter is assessed and DJ-stent placement applied according to the following system: A ureter showing no injury is graded 0, and no DJ stent is inserted postoperatively. In patients with ureteral injuries graded I (superficial, no significant bleeding), a DJ catheter would be inserted for 2 days (and pulled by an attached string); those graded II (deeper or longer injury, bleeding) would have stent placement for 2 weeks. In grade III injuries (extravasation of contrast media and/or transsection of the ureter <50%) a DJ catheter would be left in for 4 weeks. For a grade IV injury (partial transsection of ureter >50%), a stent would remain for 2 months, and grade V injuries (complete transsection of the ureter) would be treated by open (or laparoscopic) reconstruction.

Primary outcome was the endoscopic stone-free status as stated by the team of surgeons intraoperatively. This would be confirmed by intraoperative fluoroscopy and postoperative ultrasonography on postoperative days 1 or 2 and after 2 to 4 months. Only in cases with suspected residual fragments, a low-dose CT scan to confirm further stone clearance was performed after 3 months.

Secondary outcomes were operative time, intraoperative complications, postoperative insertion of DJ ureteral stents, and early and late postoperative complications (fever, secondary hydronephrosis, readmittance to the hospital, ureteral stricture as diagnosed by secondary hydronephrosis in sonography performed after 2–4 months). We also calculated the cost of equipment (costs for the endoscopes and single use material) per treatment.

Results

An endoscopic stone-free status could be achieved in 97/100 patients. This was confirmed in all cases by intraoperative fluoroscopy and postoperative ultrasonography as described above. In three patients, fragments between 1 and 3 mm of an initial cumulative stone burden of >20 mm were left behind because of a self- limitation of operative time of a maximum of 150 minutes. Two of those patients experienced spontaneous passage of all residuals as confirmed by CT scan after 3 months. The third patient with a cumulative stone size of 40 mm could be rendered stone free through a second FURS. Patients' demographic data and stone characteristics are shown in Table 1. Operative data and complications are listed in Table 2.

Table 1.

Patients' Demographic Data and Stone Characteristics (100 Patients, n=%)

Patients	100
Sex
Male	80
Female	20
Age (y, range)	49.8 (17–80)
Stone location
Single stone	56
multiple stones	44
Single, lower pole	39
Single, other than lower pole	17
Multiple, including lower pole	38
Multiple, other than lower pole	6
Medium cumulative stone size (mm, range)	9.8 (4–40)
Cumulative stone burden
4–10 mm	65
11–15 mm	25
16–20 mm	5
>20 mm	5
Stone composition (predominant component)
Calcium oxalate Monohydrate	46
Dihydrate	27
Calcium phosphate	13
Uric acid	2
Cystine	1
Struvite	1
No analysis available	10
Preoperative ureteral stent placement
Preexisting	6
Elective	94

Table 2.

Operative Data and Postoperative Complications (100 Patients, n=%)

Operative time (min, range)		67 (25–150)
Access sheath		63
Postoperative DJ stent	2 days	27
	10–14 days	21
	30–34 days	3
Complications		7
Intraoperative:	Perforation (extravasation of contrast media, no visible perforation)	3
Postoperative:	Fever	3
	Hydronephrosis/colicky pain and secondary DJ stent	2
Readmittance to hospital		2

DJ=Double-J.

By definition of the protocol, all patients had insertion of a DJ ureteral stent preoperatively. None of the ureteral stents had to be removed because of discomfort or complications. In five cases, however, surgery was advanced 2 or 3 days because of significant discomfort, and a significant portion of patients used nonsteroidal anti-inflammatory drugs while awaiting surgery.

During surgery, none of the patients needed active intramural dilation of the ureter. In 63 patients with a stone burden >5 mm, a ureteral access sheath was used. It was possible to achieve access to the renal calculi in all cases. At the end of surgery, ureters were graded and DJ stent placement was performed according to the system described above. Fifty-one patients were graded 0 (no injury), 27 patients graded I, 19 patients graded II, and 3 patients graded III. No patient showed an injury grade IV or V. Two patients had no visible injury at the end of surgery but needed secondary stent placement for hydronephrosis and/or colicky pain. With this line of action, follow-up by ultrasonography after 2 to 4 months did not show secondary hydronephrosis as a sign for ureteral stricture formation in any patient.

The series was started with two new flexible ureterorenoscopes. During the course of the study, none of the two instruments needed maintenance or repair. Indeed, so far, no damage occurred to the instruments until after 76 and 84 cases, respectively. That is to say that the durability of the instruments exceeded 75 cases. Therefore, we calculated the cost for the instrument (depending on actual wholesale price) at around 174 euros ($253) per patient.

Single-use equipment for most cases (including preoperative stent placement and stone extraction) consisted of one or two flexible hydrophilic guidewires, a ureteral access sheath, and a nitinol grasper, a reusable 200 M laser fiber, one or two DJ ureteral stents, and a transurethral catheter, as well as minor items such as sterile gloves and gowns, surgical coverage, irrigation fluid, infusion lines, and anesthetic gel. This adds up to an average cost for single-use equipment of 732 euros ($977) per patient.

Discussion

SWL is still recommended in guidelines as first-line therapy for most locations and sizes of stones.³ Indeed, the only prospective randomized trial comparing SWL and FURS for the management of renal stones (lower pole caliceal calculi 1 cm or less),⁵ including 78 patients, showed similar SFRs (35% vs 50%, P not significant), but patient-derived quality of life measures were in favor of SWL. Nevertheless, recent years have seen a considerable shift in modalities applied in stone therapy, and FURS/RIRS now accounts for more than 70% of stone therapies at our institution.

Contemporary series describe SFRs ranging from 54% to 96%^4

–10 for renal stones <20 mm (single or multiple stones, one treatment) and 86% to 92%^10,11 for renal stones >20 mm (1–4 treatments). Determination of SFR in these studies is heterogeneous (endoscopic, sonography, radiography of the kidneys, ureters and bladder [KUB], or CT at different times after the procedure, “insignificant” residual fragments of up to 4 mm). Two studies describe an “immediate” SFR^12,13 at the end of the procedure of 70%. In the large series of Johnson et al,⁶ a high access rate to the lower pole calix (98.5%) and an overall SFR of 94% for calculi up to 20 mm in diameter could be achieved without the use of an ureteral access sheath. Another group reported good results in single-stage RIRS (use of an access sheath without preoperative ureteral stent placement) with a SFR of 94.2% after 3 months as demonstrated by KUB radiography.⁷

We believe that the high success rate in our series (97% endoscopic SFR, 99% primary SFR after 3 months, and 100% after a two-stage procedure in one case) was achieved because of our complex technique. As described by Mariani¹¹ and others, a stone size of more than 20 mm might afford a staged procedure, as we performed in one patient with a cumulative stone size of 40 mm. We also found that struvite stones might not be cleared completely in one operation because of their physical characteristics—ie, it might not be possible to cut the stone because it will fall apart into numerous pieces with any power/frequency setting of the holmium laser.

Complication rates of FURS now are very low. As described in several series,^6,8,9 perforation of the ureter occurs in 0% to 4% with consecutive ureteral strictures described in one publication⁹ in 2/84 patients. This is consistent with our finding of complications in 7% and ureteral injuries (minimal extravasation of contrast media at the end of surgery, no macroscopic perforations) in 3%. After postoperative DJ stent placement according to our scheme as described above, follow-up by ultrasonography after 2 to 4 months did not show hydronephrosis as a sign for secondary ureteral strictures in any patient.

The following technical aspects of the procedure might be worth a discussion:

New generation flexible ureterorenoscopes

Flexible instruments of the latest generation offer active tip deflection in both directions of at least 270 degrees, increased diameters of working channels (3.3F to 3.6F), and allow for enhanced irrigation and visibility¹⁴ and therefore optimal inspection of the collecting system, including the lower pole in more than 98% of cases.^2,15 This translates into an increased “immediate” SFR (70% vs 38%; P=0.003) with the use of new generation endoscopes compared with their predecessors.¹² The special design of the instrument used in our series includes two working channels of 3.3F, which allows for a very good flow through the instrument and/or a combined use of a laser fiber (200 μm) and a grasper/basket. Continuous active flushing as described above further enhances visibility.

Preoperative DJ stent placement

There exist very little data on the routine use of preoperative DJ stent placement in the ureter. A retrospective analysis showed differences, but not significantly so, in SFR and complication rate in favor of preoperative stent placement in ureteroscopic management of urolithiasis.¹⁶ Hubert and Palmer¹⁷ showed that passive dilation by means of DJ prestent placement allowed for ureteroscopic access in previously inaccessible ureters in a pediatric population.

Use of access sheath

Pros and cons for the use of an ureteral access sheath have been discussed extensively over the past decade.^6,18
–20 There is also a debate as to whether a large diameter sheath causes shear forces¹⁹ and reduced blood flow to the ureter²¹ and thus may potentially cause ureteral strictures. In contrast to all published series, we perform a two-step procedure in all cases for FURS. Passive dilation of the ureter by means of ureteral stent placement 5 to 10 days before ureterenoscopy allows for a safe insertion of a large ureteral access sheath (14/16F in most cases). A large lumen of the access sheath permits good flushing with consecutive enhanced vision and enhanced maneuverability. Fragments up to 4 mm can be extracted without having to worry about multiple ureteral passages.

Surgical technique

It has been shown that so-called clinically insignificant fragments ≤4 mm after SWL²² or FURS²³ are associated with a re-treatment rate of approximately 20% within 5 years. Therefore, it seems of major importance to clear the pelvicaliceal system of all residual fragments. Using a holmium-YAG laser, stone fragmentation can be performed by a vaporizing technique that results in numerous small parts that are left for spontaneous passage (using a high frequency and high power setting). With this technique, follow-up imaging is mandatory.

We prefer a technique of cutting the stones into bigger pieces (at 5 Hz/6 W). These fragments can be removed in toto with a grasper or basket. We are convinced that with the enhanced visibility of newer systems, an endoscopic stone-free status can be assessed sufficiently by the end of the procedure, and a CT follow-up is not indicated.

The design of our study as a prospective series of 100 consecutive patients scheduled for FURS management of nephrolithiasis (intention to treat) reduces selection bias. Results are limited by the endoscopic/sonographic assessment of a stone-free status. A low-dose CT scan to confirm stone clearance after 3 months was only performed in cases with residual fragments. Outside of randomized clinical trials, we would consider routine CT follow-up a unneccesary exposure to radiation.

Conclusion

Continuous improvement of technical equipment and in surgical techniques has led to increasing SFRs in RIRS/ FURS for renal stones. Our series shows that with the use of technical equipment of the newest generation in a standardized surgical approach, it is possible to achieve very high SFRs without compromising on safety. This approach, however, necessitates use of considerable resources, both technical/surgical and financial.

Footnotes

Disclosure Statement

No competing financial interests exist.

Abbreviations Used

References

Takayasu

, Aso

, Takagi

, Go

. Clinical application of fiber-optic pyeloureteroscope. Urol Int, 1971; 26:97–104.

Traxer

. Flexible ureterorenoscopic management of lower-pole stone: Does the scope make the difference? J Endourol, 2008; 22:1847–1850.

Preminger

, Tiselius

, Assimos

et al. EAU/AUA Nephrolithiasis Guideline Panel. 2007 guideline for the management of ureteral calculi. J Urol, 2007; 178:2418–2434.

Breda

, Ogunyemi

, Leppert

, Schulam

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

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.

Johnson

, Portela

, Grasso

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

Mahajan

, Padhye

, Bhave

et al. Is stenting required before retrograde intrarenal surgery with access sheath. Indian J Urol, 2009; 25:326–328.

Perlmutter

, Talug

, Tarry

et al. Impact of stone location on success rates of endoscopic lithotripsy for nephrolithiasis. Urology, 2008; 71:214–217.

Portis

, Rygwall

, Holtz

et al. Ureteroscopic laser lithotripsy for upper urinary tract calculi with active fragment extraction and computerized tomography followup. J Urol, 2006; 175:2129–2134.

10.

Hussain

, Acher

, Penev

, Cynk

. Redefining the limits of flexible ureterorenoscopy. J Endourol, 2011; 25:45–49.

11.

Mariani

. Combined electrohydraulic and holmium:YAG laser ureteroscopic nephrolithotripsy for 20 to 40 mm renal calculi. J Urol, 2004; 172:170–174.

12.

Wendt-Nordahl

, Michel

, Knoll

et al. Is it worth to upgrade your flexible ureterorenoscope? A clinical analysis. J Urol, 2009; 181:627.

13.

Lim

, Jeong

, Seo

et al. Treatment outcomes of retrograde intrarenal surgery for renal stones and predictive factors of stone-free. Korean J Urol, 2010; 51:777–782.

14.

Abdelshehid

, Ahlering

, Chou

et al. Comparison of flexible ureteroscopes: Deflection, irrigant flow and optical characteristics. J Urol, 2005; 173:2017–2021.

15.

Ankem

, Lowry

, Slovick

et al. Clinical utility of dual active deflection flexible ureteroscope during upper tract ureteropyeloscopy. Urology, 2004; 64:430–434.

16.

Shields

, Bird

, Graves

, Gómez-Marín

. Impact of preoperative ureteral stenting on outcome of ureteroscopic treatment for urinary lithiasis. J Urol, 2009; 182:2768–2774.

17.

Hubert

, Palmer

. Passive dilation by ureteral stenting before ureteroscopy: Eliminating the need for active dilation. J Urol, 2005; 174:1079–1080.

18.

Kourambas

, Byrne

, Preminger

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

19.

L'esperance

, Ekeruo

, Scales

et al. Effect of ureteral access sheath on stone-free rates in patients undergoing ureteroscopic management of renal calculi. Urology, 2005; 66:252–255.

20.

Abrahams

, Stoller

. The argument against the routine use of ureteral access sheaths. Urol Clin North Am, 2004; 31:83–87.

21.

Lallas

, Auge

, Raj

et al. Laser Doppler flowmetric determination of ureteral blood flow after ureteral access sheath placement. J Endourol, 2002; 16:583–590.

22.

Osman

, Alfano

, Kamp

et al. 5-year-follow-up of patients with clinically insignificant residual fragments after extracorporeal shockwave lithotripsy. Eur Urol, 2005; 47:860–864.

23.

Tatman

, Heinisch

, Portis

et al. Long-term retreatment after ureterorenoscopic laser lithotripsy depends on effectiveness of initial fragment clearance. J Urol, 2010; 183,suppl:e738.