- Email: [email protected]
Percutaneous Nephrolithotomy Versus Extracorporeal Shock Wave Lithotripsy for Moderate Sized Kidney Stones
Endourology and Stones Percutaneous Nephrolithotomy Versus Extracorporeal Shock Wave Lithotripsy for Moderate Sized Kidney Stones Samuel Deem, Brian DeFade, Asmita Modak, Mary Emmett, Fred Martinez, and Julio Davalos OBJECTIVE
METHODS
RESULTS
CONCLUSION
To compare the outcomes of percutaneous nephrolithotomy (PNL) and extracorporeal shock wave lithotripsy (ESWL) for moderate sized (1-2 cm) upper and middle pole renal calculi in regards to stone clearance rate, morbidity, and quality of life. All patients diagnosed with moderate sized upper and middle pole kidney stones by computed tomography (CT) were offered enrollment. They were randomized to receive either ESWL or PNL. The SF-8 quality of life survey was administered preoperatively and at 1 week and 3 months postoperatively. Abdominal radiograph at 1 week and CT scan at 3 months were used to determine stone-free status. All complications and outcomes were recorded. PNL established a stone-free status of 95% and 85% at 1 week and 3 months, respectively, whereas ESWL established a stone-free status of 17% and 33% at 1 week and 3 months, respectively. Retreatment in ESWL was required in 67% of cases, with 0% retreatment in PNL. Stone location, stone density, and skin-to-stone distance had no impact on stone-free rates at both visits, irrespective of procedure. Patient-reported outcomes, including overall physical and mental health status, favored a better quality of life for patients who had PNL performed. PNL more often establishes stone-free status, has a more similar complication profile, and has similar reported quality of life at 3 months when compared with ESWL for moderate-sized kidney stones. PNL should be offered as a treatment option to all patients with moderate-sized kidney stones in centers with experienced endourologists. UROLOGY 78: 739 –743, 2011. © 2011 Elsevier Inc.
E
xtracorporeal shock wave lithotripsy (ESWL) is a technique using sound waves to break a kidney stone without an incision. It has been the standard therapy recommended for most kidney stones since its arrival in the early 1980s primarily because of its noninvasive nature and relatively good outcomes. Newer-generation lithotripters have been designed to cause less trauma to the renal unit than earlier devices. However, worse stone-free rates have been reported and have been seen in our center with the newer generation lithotripters and this has led us to question ESWL as the most appropriate therapy for moderate-sized (1-2 cm) kidney stones. Percutaneous nephrolithotomy (PNL) consists of a small incision and placement of a scope inside the kidney to remove all kidney stones and is the standard therapy for larger stones. PNL is currently recommended by the American Urological Association Clinical Guidelines for Financial Disclosure: Dr. Julio Davalos is a consultant for Boston Scientific and Karl Storz Endoscopy America. From the Charleston Area Medical Center, Charleston, WV Reprint requests: Samuel Deem, D.O., Charleston Area Medical Center, 3110 MacCorkle Avenue, SE, Charleston, WV 25304. E-mail: [email protected] Submitted: January 26, 2011, accepted (with revisions): April 4, 2011
© 2011 Elsevier Inc. All Rights Reserved
management of staghorn calculi. Combined, the technologic advancement of instruments used for PNL and the advanced skill of the current endourologist have allowed PNL to become a much less complicated procedure. This increased effectiveness and safety of PNL allow it to be a more definitive treatment option with a more similar safety profile to ESWL than previously seen. In this study, we compared the outcomes of PNL and ESWL for 1-2-cm renal calculi.
PATIENTS AND METHODS This prospective, randomized study was approved by institutional review board. Every patient between the ages of 18 and 80 years who presented to Charleston Area Medical Center (CAMC) between November 2008 to March 2010 with kidney stones between 1 and 2 cm in largest dimension diagnosed by noncontrast computed tomography (CT) scan were offered enrollment. Before enrollment, patients were screened for contraindications, such as pregnancy, bleeding diathesis or need for anticoagulants, Hounsfield units ⬎1000 or skin-to-stone distance ⬎12 cm from skin surface measured on CT scan, ureteropelvic junction obstruction, and solitary kidney. Prospectively, these patients consented before enrollment. Patients were then 0090-4295/11/$36.00 doi:10.1016/j.urology.2011.04.010
739
randomized to either a PNL or ESWL for treatment of their stone by block randomization using statistical software SAS. All patients were asked to complete the SF-8 (Short Form) patient quality of life survey before their scheduled procedure. This questionnaire uses a single question to capture each of the 8 health domains originally validated in the widely used functional health status measurement tool SF-36. Follow-up was standardized to include a 1-week abdominal x-ray (kidney-ureter-bladder) and the completion of a second SF-8 before removal of the stent and/or nephrostomy tube. A noncontrast CT scan at 3 months after the procedure was performed in all patients to assess stone-free status and the SF-8 was administered for a final time during this office visit. The primary outcome measured was stone-free status on CT scan at three months. Secondary outcomes reviewed included complications, need for additional procedures, and quality of life as assessed by the SF-8 questionnaire. Other objectives included reviewing stone density as defined by Hounsfield units on CT and skin-to-stone distance and their correlation with ESWL and PNL success rates for middle and upper pole and renal pelvis moderate-sized stones.
using Statistical Analysis Software 9.2 (SAS Institute, Cary, NC). Descriptive statistics, such as means and standard deviations for continuous variables and proportions and frequencies for categorical variables, were used to analyze the data. The continuous outcome variables were tested using the two-sample t-test, and the categorical outcome variables were tested using the chi-square/Fisher’s exact test whenever appropriate. All independent predictors of stone-free rate were identified using multivariate logistic regression. Standardized quality of life questionnaire (SF-8) data were analyzed by using the standardized methods in the manual for users of the SF-8.4 The SF-8 is a self-reported questionnaire divided into 2 parts: Mental (MCS) and Physical (PCS). The scales are standardized such that the population mean equals 50, with a standard deviation of 10, with higher scores indicating better self-reported health. Paired t-test was used to assess 1-week and 3-month change in MCS and PCS scores for both PNL and ESWL separately. All comparisons were made at a 0.05 level of significance. The study was closed after 26 months when the retrospective power was found to be 84% for 3-month outcomes significantly in favor of PNL.
Percutaneous Nephrolithotomy Technique
RESULTS
Briefly, a flexible cystoscopy is performed with placement of a 6-Fr injectable ureteral stent. With coordination from the anesthesia team, the patient is then placed in the prone position and positioned comfortably. Using fluoroscopic guidance, renal mapping is then performed and desired access location is determined and achieved using the “eye of the needle” technique by the attending urologist or resident. Balloon dilation is then achieved and a 34-Fr clear access sheath is placed. The stone is then retrieved with graspers as possible or fragmented in situ with a combined ultrasonic and pneumatic device. Flexible nephroscopy is then performed to confirm all fragments are removed. Only when significant collecting system injury or bleeding was encountered was a 12-Fr nephrostomy tube placed in the collecting system. The patient was hospitalized for 24 hours for intravenous antibiotics and discharged home with a ureteral stent and/or nephrostomy tube in place. Follow-up was arranged at 1 week for stent and nephrostomy tube removal after checking an abdominal radiograph.
Extracorporeal Shock Wave Lithotripsy Technique Flexible cystoscopy was performed with placement of a 6-Fr double-J ureteral stent. The patient underwent general anesthesia and the Medispec Lithotripter (Montgomery Village, MD) used in our facility was fluoroscopically centered over the stone. As many as 2000 shocks were delivered, at a rate of 60, to the center of the stone or until the stone was completely fragmented. After recovery, the patient was discharged home with the ureteral stent in place. Follow-up was arranged at 1 week for stent removal after checking an abdominal radiograph.
Statistical Methods To determine an adequate sample size, Fisher’s test for 2 proportions was used. To achieve a better stone-free rate (success rate) of 95% with PNL than that of 60% with ESWL, we assumed a significance level of 0.05, 95% power, and with 20% dropout rate. This stone-free rate has been estimated based on research cited in previous studies.1,2,3 After power analysis, the number estimated to be needed for each group was 40 patients, with a total of 80 patients in the study. The data were analyzed 740
Thirty-five patients met all criteria for inclusion and were enrolled in the study. Thirty-two patients completed the entire protocol, including follow-up visits. Of the 32 patients, 20 underwent PNL and 12 underwent ESWL. Three additional patients had various reasons for being incomplete, including becoming pregnant immediately after treatment, loss of insurance, and failure to present for follow-up. All 3 patients underwent ESWL. Patient characteristics, such as age, gender, and comorbidities, were similar in both groups (Table 1). The 20 patients who underwent PNL had an 85% stone-free rate based on a 3-month CT scan of the renal unit (Fig. 1). There were no major complications and no blood transfusions; the minor complications included fever, renal colic, and urinary tract infection. Two patients did return to the emergency department within 48 hours of discharge for inability to tolerate pain but they were both discharged home after examination by the emergency department physician. There were no patients with stone burden significant enough to warrant a second procedure. ESWL had a 33% stone-free rate according to the aforementioned criteria with no major complications or blood transfusions; the few minor complications included renal colic and fever (Fig. 1). Sixty-seven percent required an additional procedure, with 17% requiring 2 or more procedures. Stone location (pThreemonth ⫽ 0.99), skin-tostone distance (pThreemonth ⫽ 0.12), and stone density (pThreemonth ⫽ 0.52) had no effect on stone-free rates at either visit irrespective of the procedure (Table 2). Calcium stones were the most common stone encountered in both groups. The ureteral stent and/or nephrostomy tube were removed at a median of 6 days after either procedure. With respect to quality of life (SF-8) questionnaire, for all patients significant statistical difference (P ⬍.001) was identified in PCS scores and no difference (P ⫽ .43) UROLOGY 78 (4), 2011
Table 1. Patient characteristics with respect to type of procedures PCNL (n ⫽ 20) Demographics Age Race (White) Gender (male) Primary outcome measure (stone-free rate) 1-week outcome 3-month outcome Stone characteristics Skin-to-stone distance Stone size Stone location Upper Middle Pelvis Stone density Stone type Calcium Cystine Other
ESWL (n ⫽ 12)
47.20 ⫾ 14.88 (25,73) 20 (100%) 11 (55.00%)
52.25 ⫾ 14.07 (28,74) 12 (100%) 6 (50.00%)
19 (95.00%) 17 (85.00%)
2 (16.67%) 4 (33.33%)
10.21 ⫾ 1.37 (7.4,12) 12.85 ⫾ 2.00 (11,18)
9.25 ⫾ 1.61 (6.8,11.8) 12.16 ⫾ 1.40 (10,14)
3 (15.00%) 15 (75.00%) 2 (10.00%) 831.2 ⫾ 131.5 (538.3,946.0) 19 (95%) 1 (5%) 0
1 (8.3%) 10 (83.3%) 1 (8.3%) 802.9 ⫾ 131.2 (578.3,953.7) 9 (81.82%) 0 2 (18.18%)
P Value .4900 NA ⬎.999 ⬍.0001* .0060* .0837 .3093 .7828 .5603 .5284
* Statistically significant (level of significance of .05) by Fisher’s exact test.
95.0
Percentage
100 90 80 70 60 50 40 30 20 10 0
85.0 33.33 16.67
One week Outcome (P=<.0001)
Three month Outcome (P=0.0060) Follow-up
PNL (N=20)
ESWL(N=12)
Figure 1. Distribution of stone-free rate over the course of treatment.
in the MCS scores at three months. In the PNL group (P ⬍.001), the PCS scores did show significantly higher improvement at 3 months, whereas the ESWL group (P ⫽ .05) (Fig. 2) did not. For the MCS scores, statistical difference was not achieved in either the PNL or the ESWL group at 3 months (Figure 3).
COMMENT The management of nephrolithiasis in today’s society demands expertise with minimally invasive techniques. Current treatment options include ESWL, ureteroscopy, and PNL, with laparoscopic or open pyelolithotomy being used in rare instances of altered renal anatomy or concomitant ureteropelvic junction (UPJ) obstruction. Management decisions are made on the basis of several factors pertaining to stone burden and patterns seen on radiologic imaging. The most sensitive and specific imaging for diagnosis and treatment planning is universal, UROLOGY 78 (4), 2011
with all literature supporting noncontrast CT.5,6 In this study, one can delineate accurately the size, number, and composition of kidney stones, as well as determine accurate location of the stones and better visualization of the renal anatomy. These factors must be considered when deciding which approach is best for the management of individual stones. The true analysis of efficacy of any therapy for kidney stones is the stone-free status. This is best measured using a noncontrast CT scan of the abdomen and pelvis. ESWL has been a successful management option since its arrival in the early 1980s.7 Reported efficacy varies, but clearly it is best for smaller stones ⱕ20 mm with a reported stone-free rate of between 57.4% and 76.5%.1 The stone-free rate is directly proportional to stone size, with stones ⬎30 mm reported as stone-free in only 29% of patients.8 ESWL can be done with or without ureteral stent placement depending on multiple factors; however, for stones ⬎10 mm, in our institution a stent is usually placed. ESWL has significant costs associated with each treatment, and the re-treatment increases from 12% for stones ⱕ10 mm up to 46% for stones ⬎30 mm, as noted in one study.9 Location of stones in the lower pole made ESWL even less effective, with reported stone-free rates of 67% for stones ⬍10 mm and 21% for stones ⬎10 mm.10 These overall poor rates of stone-free status with ESWL in 10-20-mm stones results in increased length of patient discomfort, increased use of narcotics and antibiotics, and sometimes multiple repeat treatments. Ureteroscopy is the newest approach to stone disease with the advantage of direct visualization of stones in the renal pelvis, allowing for complete removal. With the evolution of newer equipment for instrumentation, the complication rates have rapidly improved to ⬍1%.11 Stonefree rates in these cases are generally reported as excellent, but it can be a lengthy procedure under general 741
Table 2. Stone characteristics with respect to stone-free status 1-week Outcome Presence of Stone Absence of Stone (n ⫽ 11) (n ⫽ 21) Skin-to-stone distance Stone density Stone location Upper Middle Pelvis
9.07 ⫾ 1.56 (6.8, 11.8) 848.4 ⫾ 108.8 (675.0, 953.7) 1 (10.00%) 9 (90.00%) 1 (10.00%)
P Value
10.26 ⫾ 1.35
.0341*
(7.4, 12) 806.0 ⫾ 140.1 (538.3, 946.0)
.3899
3 (14.29%) 16 (76.19%) 2 (9.52%)
.7805
3-month Outcome Presence of Stone Absence of Stone (n ⫽ 11) (n ⫽ 21) 9.26 ⫾ 1.71 (6.8, 11.8) 841.6 ⫾ 120.0 (624.7, 953.7) 1 (9.09%) 9 (81.82%) 1 (9.09%)
P Value
10.16 ⫾ 1.35
.1161
(7.6, 12) 809.5 ⫾ 136.5 (538.3, 946.0)
.5163
3 (14.3%) 16 (76.2%) 2 (9.5%)
.9999
* Statistically significant (level of significance of .05) by Fisher’s exact test. 60
Mean Score
50 40 30 20 10 0 ESWL (P=0.0308)
PNL (P=0.0002)
Course of Treatment Pre-op
One-week
Three Month
Figure 2. SF-8 Physical Health Score.
60
Mean Score
50 40 30 20 10 0 ESWL (P=0.8883)
PNL (P=0.2601)
Course of Treatment Pre-op
One-week
Three Month
Figure 3. SF-8 Mental Health Score.
anesthesia for larger stones. Some current indications for ureteroscopy include failed ESWL and lower pole renal calculi as well as patient factors such as obesity, pregnancy, or coagulopathy precluding ESWL.12 The requirement of still having to pass the stone fragments and having subsequent pain have influenced patients to prefer other methods of treatment in our experience. PNL has become the procedure of choice for managing large and complex renal stones.13,14 Overall major complication rates are reported as 4-8% and have traditionally precluded its use in smaller stones. Technology and experience with the procedure is rapidly improving and 742
we believe the complication rates to be much lower than currently reported. The American Urological Association recommends PNL for all stones ⬎20 mm to achieve stone-free rates of 71-95%, which was higher than all other methods reviewed.2,3 In our institution, a device with combined ultrasound and percussion is used for the most efficient stone fragmentation and removal. However, for some stones, the overall length may be ⬎1 cm but with a width of ⬍1 cm, the stone can still be removed intact with no fragmentation. This allows complete removal of the stone with expected better stone-free rates as well as a faster and less traumatic procedure. Chung et al evaluated a group of 1-2-cm stones in a nonrandomized study evaluating PNL vs ureteroscopy. They found an overall stone-free rate of 87% for PNL vs 67% for ureteroscopy using plain abdominal imaging.15 Carr and colleagues showed that ESWL also had a higher recurrence rate than PNL, 22% vs 4%.16 These poor outcomes and need for further treatment all suggest that maybe being less invasive is actually more costly and more harmful to the patient in the long term. An algorithm proposed by Wen and Nakada suggests PNL for all stones ⬎2 cm, lower pole stones greater than 1 cm, and all stones with calculated Hounsfield units ⬎1000, skin-to-stone distance ⬎10 cm, all cystine stones, and known comorbidities in patients with failed ureteroscopy.17 After an extensive review of the literature, Deane and Clayman concluded that the best approach for lower pole stones with unfavorable calyceal anatomy and measured Hounsfield units ⬎500 would be PNL.18 Locally we believe that stones between 10 and 20 mm can be managed routinely with PNL, with excellent stone-free rates and minimal morbidity. To challenge ESWL as the current standard therapy of 10-20 mm stones, we designed a prospective analysis comparing both techniques in a select group of patients. Our outcomes reflect what we feel are comparable with the outcomes in similar studies. However, by using CT to determine stone-free status we have used more rigid criteria than those used in previous studies. This alone may account for the surprisingly low success rates seen in the ESWL group in the current study; however, the type of lithotripter may have been a contributor as well. We UROLOGY 78 (4), 2011
have seen excellent results locally for smaller kidney stones using the same device. This certainly raises the question: Would we see better quality of life data in a patient group with higher stone-free rates? Every effort was made to design the study to include patients who could be successfully treated with ESWL. We eliminated patients with Hounsfield units ⬎1000, skin-to-stone distance ⬎12 cm, and UPJ obstruction, all whom were more likely to have failed ESWL. The routine use of a ureteral stent for ESWL in our study could have affected the quality of life outcomes; however, not using the stent could also have led to more return visits and need for additional procedures. PNL continues to be an extremely effective treatment modality for moderate-sized stones, with a much improved complication profile than previously reported. Although PNL is considered more invasive, all of our patients in both procedures returned to a similar quality of life as the normal population at 3 months. This demonstrates that although PNL is initially more invasive, there is no long-term effect to the patients’ perception of quality of life. As health care continues to evolve into a patient and outcomes-driven field, we believe this will be the information patients desire to allow them to make a decision on methods used to treat their illness. Even with higher success rate with PNL, this study has some limitations. Some of the patients were lost to follow-up (eg, becoming pregnant immediately after treatment, loss of insurance with refusal for follow-up, and failure to complete follow-up). In addition, there were a small number of patients in the study because of a slow accrual in this very specific patient population. Use of ureteral stents in 1-2-cm stones is not standard for ESWL in all institutions and could be responsible for the lower quality-of-life scores seen in our ESWL patients. On the SF-8 health survey, significant P values were not found because of a lack of complete survey participation and the small number of participants. Multiple types and brands of lithotripters exist and we were only able to study 1 specific device for purposes of this study.
CONCLUSIONS Although PNL is considered a more invasive procedure, patient quality of life appears to be similar with PNL for these moderate-sized stones in our study. Overall, the complication profile for PNL is higher when considering pain and hematuria as complications, but technology has allowed us to diminish these differences. Significant complications in PNL have been decreasing in recent years owing to improvement in equipment and technique, and
UROLOGY 78 (4), 2011
no significant complications were seen in this small sample. Although multiple factors need to be considered before choosing a treatment modality for moderate-sized kidney stones, PNL should be considered an effective option and be offered to patients in institutions with adequately trained endourologists. References 1. Saw KC, Lingeman JE. Lesson 20 —management of calyceal stones. AUA Update Series. 1999;20:154-159. 2. Segura JW, Patterson DE, LeRoy AJ, et al. Percutaneous removal of kidney stones: review of 1,000 cases. J Urol. 1985;134:1077-1081. 3. Osman M, Wendt-Nordahl G, Heger K, et al. Percutaneous nephrolithotomy with ultrasonography-guided renal access: experience from over 300 cases. BJU Int. 2005;96(6):875-878. 4. Ware JE, Kosinski M, Dewey JE, Gandek B. How to Score and Interpret Single Item Health Status Measures: A Manual for Users of the SF– 8TM Health Survey. Lincoln, (RI): Quality Metric Incorporated, 2001. 5. Hamm M, Wawroschek F, Weckermann D, et al. Unenhanced helical computed tomography in the evaluation of acute flank pain. Eur Urol. 2001;39:460-465. 6. Smith RC, Rosenfield AT, Choe KA, et al. Acute flank pain: comparison of non-contrast-enhanced CT and intravenous urography. Radiology. 1995;194(3):789-794. 7. Chaussy C, Brendel W, Schmiedt E. Extracorporeally induced destruction of kidney stones by shock waves. Lancet. 1980;2(8207): 1265-1268. 8. Lingeman JE, Coruy TA, Newman DM, et al. Comparison of results and morbidity of percutaneous nephrostolithotomy and extracorporeal shock wave lithotripsy. J Urol. 1987;138(3):485-490. 9. Segura JW, Preminger GM, Assimos DG, et al. Nephrolithiasis clinical guidelines panel summary report on the management of staghorn calculi. The American Urological Association nephrolithiasis clinical guidelines panel. J Urol. 1994;151(6):1648-1651. 10. Albala DM, Assimos DG, Clayman RV, 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(6):2072-2080. 11. Grasso M. Ureteropyeloscopic treatment of ureteral and intrarenal calculi. Urol Clin North Am. 2000;27(4):623-631. 12. Miller NL, Lingeman JE. Clinical Review: Management of kidney stones. BMJ. 2007;334:468-472. 13. Preminger GM, Assimos DG, Lingeman JE, et al. Chapter 1 :AUA guideline on management of staghorn calculi: diagnosis and treatment recommendations. J Urol. 2005;173(6):1991-2000. 14. Denstedt JD, Razvi HA, Dushinski J, et al. Percutaneous treatment of large and staghorn renal calculi. J Endourol. 1996;10(Suppl 1):S140, P11-328 [Abstract]. 15. Chung B, Aron M, Hegarty N, et al. Ureteroscopic versus percutaneous treatment for medium-size (1-2cm) renal calculi. J Endourol. 2008;22(2):343-346. 16. Carr LK, D’A Honey J, Jewett MA, et al. New stone formation: A comparison of extracorporeal shock wave lithotripsy and percutaneous nephrolithotomy. J Urol. 1996;155:1565-1567. 17. Wen CC, Nakada SY. Treatment selection and outcomes: renal calculi. Urol Clin North Am. 2007;34:409-419. 18. Deane LA, Clayman RV. Advances in percutaneous nephrostolithotomy. Urol Clin North Am. 2007;34:383-395.
743
METHODS
RESULTS
CONCLUSION
To compare the outcomes of percutaneous nephrolithotomy (PNL) and extracorporeal shock wave lithotripsy (ESWL) for moderate sized (1-2 cm) upper and middle pole renal calculi in regards to stone clearance rate, morbidity, and quality of life. All patients diagnosed with moderate sized upper and middle pole kidney stones by computed tomography (CT) were offered enrollment. They were randomized to receive either ESWL or PNL. The SF-8 quality of life survey was administered preoperatively and at 1 week and 3 months postoperatively. Abdominal radiograph at 1 week and CT scan at 3 months were used to determine stone-free status. All complications and outcomes were recorded. PNL established a stone-free status of 95% and 85% at 1 week and 3 months, respectively, whereas ESWL established a stone-free status of 17% and 33% at 1 week and 3 months, respectively. Retreatment in ESWL was required in 67% of cases, with 0% retreatment in PNL. Stone location, stone density, and skin-to-stone distance had no impact on stone-free rates at both visits, irrespective of procedure. Patient-reported outcomes, including overall physical and mental health status, favored a better quality of life for patients who had PNL performed. PNL more often establishes stone-free status, has a more similar complication profile, and has similar reported quality of life at 3 months when compared with ESWL for moderate-sized kidney stones. PNL should be offered as a treatment option to all patients with moderate-sized kidney stones in centers with experienced endourologists. UROLOGY 78: 739 –743, 2011. © 2011 Elsevier Inc.
E
xtracorporeal shock wave lithotripsy (ESWL) is a technique using sound waves to break a kidney stone without an incision. It has been the standard therapy recommended for most kidney stones since its arrival in the early 1980s primarily because of its noninvasive nature and relatively good outcomes. Newer-generation lithotripters have been designed to cause less trauma to the renal unit than earlier devices. However, worse stone-free rates have been reported and have been seen in our center with the newer generation lithotripters and this has led us to question ESWL as the most appropriate therapy for moderate-sized (1-2 cm) kidney stones. Percutaneous nephrolithotomy (PNL) consists of a small incision and placement of a scope inside the kidney to remove all kidney stones and is the standard therapy for larger stones. PNL is currently recommended by the American Urological Association Clinical Guidelines for Financial Disclosure: Dr. Julio Davalos is a consultant for Boston Scientific and Karl Storz Endoscopy America. From the Charleston Area Medical Center, Charleston, WV Reprint requests: Samuel Deem, D.O., Charleston Area Medical Center, 3110 MacCorkle Avenue, SE, Charleston, WV 25304. E-mail: [email protected] Submitted: January 26, 2011, accepted (with revisions): April 4, 2011
© 2011 Elsevier Inc. All Rights Reserved
management of staghorn calculi. Combined, the technologic advancement of instruments used for PNL and the advanced skill of the current endourologist have allowed PNL to become a much less complicated procedure. This increased effectiveness and safety of PNL allow it to be a more definitive treatment option with a more similar safety profile to ESWL than previously seen. In this study, we compared the outcomes of PNL and ESWL for 1-2-cm renal calculi.
PATIENTS AND METHODS This prospective, randomized study was approved by institutional review board. Every patient between the ages of 18 and 80 years who presented to Charleston Area Medical Center (CAMC) between November 2008 to March 2010 with kidney stones between 1 and 2 cm in largest dimension diagnosed by noncontrast computed tomography (CT) scan were offered enrollment. Before enrollment, patients were screened for contraindications, such as pregnancy, bleeding diathesis or need for anticoagulants, Hounsfield units ⬎1000 or skin-to-stone distance ⬎12 cm from skin surface measured on CT scan, ureteropelvic junction obstruction, and solitary kidney. Prospectively, these patients consented before enrollment. Patients were then 0090-4295/11/$36.00 doi:10.1016/j.urology.2011.04.010
739
randomized to either a PNL or ESWL for treatment of their stone by block randomization using statistical software SAS. All patients were asked to complete the SF-8 (Short Form) patient quality of life survey before their scheduled procedure. This questionnaire uses a single question to capture each of the 8 health domains originally validated in the widely used functional health status measurement tool SF-36. Follow-up was standardized to include a 1-week abdominal x-ray (kidney-ureter-bladder) and the completion of a second SF-8 before removal of the stent and/or nephrostomy tube. A noncontrast CT scan at 3 months after the procedure was performed in all patients to assess stone-free status and the SF-8 was administered for a final time during this office visit. The primary outcome measured was stone-free status on CT scan at three months. Secondary outcomes reviewed included complications, need for additional procedures, and quality of life as assessed by the SF-8 questionnaire. Other objectives included reviewing stone density as defined by Hounsfield units on CT and skin-to-stone distance and their correlation with ESWL and PNL success rates for middle and upper pole and renal pelvis moderate-sized stones.
using Statistical Analysis Software 9.2 (SAS Institute, Cary, NC). Descriptive statistics, such as means and standard deviations for continuous variables and proportions and frequencies for categorical variables, were used to analyze the data. The continuous outcome variables were tested using the two-sample t-test, and the categorical outcome variables were tested using the chi-square/Fisher’s exact test whenever appropriate. All independent predictors of stone-free rate were identified using multivariate logistic regression. Standardized quality of life questionnaire (SF-8) data were analyzed by using the standardized methods in the manual for users of the SF-8.4 The SF-8 is a self-reported questionnaire divided into 2 parts: Mental (MCS) and Physical (PCS). The scales are standardized such that the population mean equals 50, with a standard deviation of 10, with higher scores indicating better self-reported health. Paired t-test was used to assess 1-week and 3-month change in MCS and PCS scores for both PNL and ESWL separately. All comparisons were made at a 0.05 level of significance. The study was closed after 26 months when the retrospective power was found to be 84% for 3-month outcomes significantly in favor of PNL.
Percutaneous Nephrolithotomy Technique
RESULTS
Briefly, a flexible cystoscopy is performed with placement of a 6-Fr injectable ureteral stent. With coordination from the anesthesia team, the patient is then placed in the prone position and positioned comfortably. Using fluoroscopic guidance, renal mapping is then performed and desired access location is determined and achieved using the “eye of the needle” technique by the attending urologist or resident. Balloon dilation is then achieved and a 34-Fr clear access sheath is placed. The stone is then retrieved with graspers as possible or fragmented in situ with a combined ultrasonic and pneumatic device. Flexible nephroscopy is then performed to confirm all fragments are removed. Only when significant collecting system injury or bleeding was encountered was a 12-Fr nephrostomy tube placed in the collecting system. The patient was hospitalized for 24 hours for intravenous antibiotics and discharged home with a ureteral stent and/or nephrostomy tube in place. Follow-up was arranged at 1 week for stent and nephrostomy tube removal after checking an abdominal radiograph.
Extracorporeal Shock Wave Lithotripsy Technique Flexible cystoscopy was performed with placement of a 6-Fr double-J ureteral stent. The patient underwent general anesthesia and the Medispec Lithotripter (Montgomery Village, MD) used in our facility was fluoroscopically centered over the stone. As many as 2000 shocks were delivered, at a rate of 60, to the center of the stone or until the stone was completely fragmented. After recovery, the patient was discharged home with the ureteral stent in place. Follow-up was arranged at 1 week for stent removal after checking an abdominal radiograph.
Statistical Methods To determine an adequate sample size, Fisher’s test for 2 proportions was used. To achieve a better stone-free rate (success rate) of 95% with PNL than that of 60% with ESWL, we assumed a significance level of 0.05, 95% power, and with 20% dropout rate. This stone-free rate has been estimated based on research cited in previous studies.1,2,3 After power analysis, the number estimated to be needed for each group was 40 patients, with a total of 80 patients in the study. The data were analyzed 740
Thirty-five patients met all criteria for inclusion and were enrolled in the study. Thirty-two patients completed the entire protocol, including follow-up visits. Of the 32 patients, 20 underwent PNL and 12 underwent ESWL. Three additional patients had various reasons for being incomplete, including becoming pregnant immediately after treatment, loss of insurance, and failure to present for follow-up. All 3 patients underwent ESWL. Patient characteristics, such as age, gender, and comorbidities, were similar in both groups (Table 1). The 20 patients who underwent PNL had an 85% stone-free rate based on a 3-month CT scan of the renal unit (Fig. 1). There were no major complications and no blood transfusions; the minor complications included fever, renal colic, and urinary tract infection. Two patients did return to the emergency department within 48 hours of discharge for inability to tolerate pain but they were both discharged home after examination by the emergency department physician. There were no patients with stone burden significant enough to warrant a second procedure. ESWL had a 33% stone-free rate according to the aforementioned criteria with no major complications or blood transfusions; the few minor complications included renal colic and fever (Fig. 1). Sixty-seven percent required an additional procedure, with 17% requiring 2 or more procedures. Stone location (pThreemonth ⫽ 0.99), skin-tostone distance (pThreemonth ⫽ 0.12), and stone density (pThreemonth ⫽ 0.52) had no effect on stone-free rates at either visit irrespective of the procedure (Table 2). Calcium stones were the most common stone encountered in both groups. The ureteral stent and/or nephrostomy tube were removed at a median of 6 days after either procedure. With respect to quality of life (SF-8) questionnaire, for all patients significant statistical difference (P ⬍.001) was identified in PCS scores and no difference (P ⫽ .43) UROLOGY 78 (4), 2011
Table 1. Patient characteristics with respect to type of procedures PCNL (n ⫽ 20) Demographics Age Race (White) Gender (male) Primary outcome measure (stone-free rate) 1-week outcome 3-month outcome Stone characteristics Skin-to-stone distance Stone size Stone location Upper Middle Pelvis Stone density Stone type Calcium Cystine Other
ESWL (n ⫽ 12)
47.20 ⫾ 14.88 (25,73) 20 (100%) 11 (55.00%)
52.25 ⫾ 14.07 (28,74) 12 (100%) 6 (50.00%)
19 (95.00%) 17 (85.00%)
2 (16.67%) 4 (33.33%)
10.21 ⫾ 1.37 (7.4,12) 12.85 ⫾ 2.00 (11,18)
9.25 ⫾ 1.61 (6.8,11.8) 12.16 ⫾ 1.40 (10,14)
3 (15.00%) 15 (75.00%) 2 (10.00%) 831.2 ⫾ 131.5 (538.3,946.0) 19 (95%) 1 (5%) 0
1 (8.3%) 10 (83.3%) 1 (8.3%) 802.9 ⫾ 131.2 (578.3,953.7) 9 (81.82%) 0 2 (18.18%)
P Value .4900 NA ⬎.999 ⬍.0001* .0060* .0837 .3093 .7828 .5603 .5284
* Statistically significant (level of significance of .05) by Fisher’s exact test.
95.0
Percentage
100 90 80 70 60 50 40 30 20 10 0
85.0 33.33 16.67
One week Outcome (P=<.0001)
Three month Outcome (P=0.0060) Follow-up
PNL (N=20)
ESWL(N=12)
Figure 1. Distribution of stone-free rate over the course of treatment.
in the MCS scores at three months. In the PNL group (P ⬍.001), the PCS scores did show significantly higher improvement at 3 months, whereas the ESWL group (P ⫽ .05) (Fig. 2) did not. For the MCS scores, statistical difference was not achieved in either the PNL or the ESWL group at 3 months (Figure 3).
COMMENT The management of nephrolithiasis in today’s society demands expertise with minimally invasive techniques. Current treatment options include ESWL, ureteroscopy, and PNL, with laparoscopic or open pyelolithotomy being used in rare instances of altered renal anatomy or concomitant ureteropelvic junction (UPJ) obstruction. Management decisions are made on the basis of several factors pertaining to stone burden and patterns seen on radiologic imaging. The most sensitive and specific imaging for diagnosis and treatment planning is universal, UROLOGY 78 (4), 2011
with all literature supporting noncontrast CT.5,6 In this study, one can delineate accurately the size, number, and composition of kidney stones, as well as determine accurate location of the stones and better visualization of the renal anatomy. These factors must be considered when deciding which approach is best for the management of individual stones. The true analysis of efficacy of any therapy for kidney stones is the stone-free status. This is best measured using a noncontrast CT scan of the abdomen and pelvis. ESWL has been a successful management option since its arrival in the early 1980s.7 Reported efficacy varies, but clearly it is best for smaller stones ⱕ20 mm with a reported stone-free rate of between 57.4% and 76.5%.1 The stone-free rate is directly proportional to stone size, with stones ⬎30 mm reported as stone-free in only 29% of patients.8 ESWL can be done with or without ureteral stent placement depending on multiple factors; however, for stones ⬎10 mm, in our institution a stent is usually placed. ESWL has significant costs associated with each treatment, and the re-treatment increases from 12% for stones ⱕ10 mm up to 46% for stones ⬎30 mm, as noted in one study.9 Location of stones in the lower pole made ESWL even less effective, with reported stone-free rates of 67% for stones ⬍10 mm and 21% for stones ⬎10 mm.10 These overall poor rates of stone-free status with ESWL in 10-20-mm stones results in increased length of patient discomfort, increased use of narcotics and antibiotics, and sometimes multiple repeat treatments. Ureteroscopy is the newest approach to stone disease with the advantage of direct visualization of stones in the renal pelvis, allowing for complete removal. With the evolution of newer equipment for instrumentation, the complication rates have rapidly improved to ⬍1%.11 Stonefree rates in these cases are generally reported as excellent, but it can be a lengthy procedure under general 741
Table 2. Stone characteristics with respect to stone-free status 1-week Outcome Presence of Stone Absence of Stone (n ⫽ 11) (n ⫽ 21) Skin-to-stone distance Stone density Stone location Upper Middle Pelvis
9.07 ⫾ 1.56 (6.8, 11.8) 848.4 ⫾ 108.8 (675.0, 953.7) 1 (10.00%) 9 (90.00%) 1 (10.00%)
P Value
10.26 ⫾ 1.35
.0341*
(7.4, 12) 806.0 ⫾ 140.1 (538.3, 946.0)
.3899
3 (14.29%) 16 (76.19%) 2 (9.52%)
.7805
3-month Outcome Presence of Stone Absence of Stone (n ⫽ 11) (n ⫽ 21) 9.26 ⫾ 1.71 (6.8, 11.8) 841.6 ⫾ 120.0 (624.7, 953.7) 1 (9.09%) 9 (81.82%) 1 (9.09%)
P Value
10.16 ⫾ 1.35
.1161
(7.6, 12) 809.5 ⫾ 136.5 (538.3, 946.0)
.5163
3 (14.3%) 16 (76.2%) 2 (9.5%)
.9999
* Statistically significant (level of significance of .05) by Fisher’s exact test. 60
Mean Score
50 40 30 20 10 0 ESWL (P=0.0308)
PNL (P=0.0002)
Course of Treatment Pre-op
One-week
Three Month
Figure 2. SF-8 Physical Health Score.
60
Mean Score
50 40 30 20 10 0 ESWL (P=0.8883)
PNL (P=0.2601)
Course of Treatment Pre-op
One-week
Three Month
Figure 3. SF-8 Mental Health Score.
anesthesia for larger stones. Some current indications for ureteroscopy include failed ESWL and lower pole renal calculi as well as patient factors such as obesity, pregnancy, or coagulopathy precluding ESWL.12 The requirement of still having to pass the stone fragments and having subsequent pain have influenced patients to prefer other methods of treatment in our experience. PNL has become the procedure of choice for managing large and complex renal stones.13,14 Overall major complication rates are reported as 4-8% and have traditionally precluded its use in smaller stones. Technology and experience with the procedure is rapidly improving and 742
we believe the complication rates to be much lower than currently reported. The American Urological Association recommends PNL for all stones ⬎20 mm to achieve stone-free rates of 71-95%, which was higher than all other methods reviewed.2,3 In our institution, a device with combined ultrasound and percussion is used for the most efficient stone fragmentation and removal. However, for some stones, the overall length may be ⬎1 cm but with a width of ⬍1 cm, the stone can still be removed intact with no fragmentation. This allows complete removal of the stone with expected better stone-free rates as well as a faster and less traumatic procedure. Chung et al evaluated a group of 1-2-cm stones in a nonrandomized study evaluating PNL vs ureteroscopy. They found an overall stone-free rate of 87% for PNL vs 67% for ureteroscopy using plain abdominal imaging.15 Carr and colleagues showed that ESWL also had a higher recurrence rate than PNL, 22% vs 4%.16 These poor outcomes and need for further treatment all suggest that maybe being less invasive is actually more costly and more harmful to the patient in the long term. An algorithm proposed by Wen and Nakada suggests PNL for all stones ⬎2 cm, lower pole stones greater than 1 cm, and all stones with calculated Hounsfield units ⬎1000, skin-to-stone distance ⬎10 cm, all cystine stones, and known comorbidities in patients with failed ureteroscopy.17 After an extensive review of the literature, Deane and Clayman concluded that the best approach for lower pole stones with unfavorable calyceal anatomy and measured Hounsfield units ⬎500 would be PNL.18 Locally we believe that stones between 10 and 20 mm can be managed routinely with PNL, with excellent stone-free rates and minimal morbidity. To challenge ESWL as the current standard therapy of 10-20 mm stones, we designed a prospective analysis comparing both techniques in a select group of patients. Our outcomes reflect what we feel are comparable with the outcomes in similar studies. However, by using CT to determine stone-free status we have used more rigid criteria than those used in previous studies. This alone may account for the surprisingly low success rates seen in the ESWL group in the current study; however, the type of lithotripter may have been a contributor as well. We UROLOGY 78 (4), 2011
have seen excellent results locally for smaller kidney stones using the same device. This certainly raises the question: Would we see better quality of life data in a patient group with higher stone-free rates? Every effort was made to design the study to include patients who could be successfully treated with ESWL. We eliminated patients with Hounsfield units ⬎1000, skin-to-stone distance ⬎12 cm, and UPJ obstruction, all whom were more likely to have failed ESWL. The routine use of a ureteral stent for ESWL in our study could have affected the quality of life outcomes; however, not using the stent could also have led to more return visits and need for additional procedures. PNL continues to be an extremely effective treatment modality for moderate-sized stones, with a much improved complication profile than previously reported. Although PNL is considered more invasive, all of our patients in both procedures returned to a similar quality of life as the normal population at 3 months. This demonstrates that although PNL is initially more invasive, there is no long-term effect to the patients’ perception of quality of life. As health care continues to evolve into a patient and outcomes-driven field, we believe this will be the information patients desire to allow them to make a decision on methods used to treat their illness. Even with higher success rate with PNL, this study has some limitations. Some of the patients were lost to follow-up (eg, becoming pregnant immediately after treatment, loss of insurance with refusal for follow-up, and failure to complete follow-up). In addition, there were a small number of patients in the study because of a slow accrual in this very specific patient population. Use of ureteral stents in 1-2-cm stones is not standard for ESWL in all institutions and could be responsible for the lower quality-of-life scores seen in our ESWL patients. On the SF-8 health survey, significant P values were not found because of a lack of complete survey participation and the small number of participants. Multiple types and brands of lithotripters exist and we were only able to study 1 specific device for purposes of this study.
CONCLUSIONS Although PNL is considered a more invasive procedure, patient quality of life appears to be similar with PNL for these moderate-sized stones in our study. Overall, the complication profile for PNL is higher when considering pain and hematuria as complications, but technology has allowed us to diminish these differences. Significant complications in PNL have been decreasing in recent years owing to improvement in equipment and technique, and
UROLOGY 78 (4), 2011
no significant complications were seen in this small sample. Although multiple factors need to be considered before choosing a treatment modality for moderate-sized kidney stones, PNL should be considered an effective option and be offered to patients in institutions with adequately trained endourologists. References 1. Saw KC, Lingeman JE. Lesson 20 —management of calyceal stones. AUA Update Series. 1999;20:154-159. 2. Segura JW, Patterson DE, LeRoy AJ, et al. Percutaneous removal of kidney stones: review of 1,000 cases. J Urol. 1985;134:1077-1081. 3. Osman M, Wendt-Nordahl G, Heger K, et al. Percutaneous nephrolithotomy with ultrasonography-guided renal access: experience from over 300 cases. BJU Int. 2005;96(6):875-878. 4. Ware JE, Kosinski M, Dewey JE, Gandek B. How to Score and Interpret Single Item Health Status Measures: A Manual for Users of the SF– 8TM Health Survey. Lincoln, (RI): Quality Metric Incorporated, 2001. 5. Hamm M, Wawroschek F, Weckermann D, et al. Unenhanced helical computed tomography in the evaluation of acute flank pain. Eur Urol. 2001;39:460-465. 6. Smith RC, Rosenfield AT, Choe KA, et al. Acute flank pain: comparison of non-contrast-enhanced CT and intravenous urography. Radiology. 1995;194(3):789-794. 7. Chaussy C, Brendel W, Schmiedt E. Extracorporeally induced destruction of kidney stones by shock waves. Lancet. 1980;2(8207): 1265-1268. 8. Lingeman JE, Coruy TA, Newman DM, et al. Comparison of results and morbidity of percutaneous nephrostolithotomy and extracorporeal shock wave lithotripsy. J Urol. 1987;138(3):485-490. 9. Segura JW, Preminger GM, Assimos DG, et al. Nephrolithiasis clinical guidelines panel summary report on the management of staghorn calculi. The American Urological Association nephrolithiasis clinical guidelines panel. J Urol. 1994;151(6):1648-1651. 10. Albala DM, Assimos DG, Clayman RV, 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(6):2072-2080. 11. Grasso M. Ureteropyeloscopic treatment of ureteral and intrarenal calculi. Urol Clin North Am. 2000;27(4):623-631. 12. Miller NL, Lingeman JE. Clinical Review: Management of kidney stones. BMJ. 2007;334:468-472. 13. Preminger GM, Assimos DG, Lingeman JE, et al. Chapter 1 :AUA guideline on management of staghorn calculi: diagnosis and treatment recommendations. J Urol. 2005;173(6):1991-2000. 14. Denstedt JD, Razvi HA, Dushinski J, et al. Percutaneous treatment of large and staghorn renal calculi. J Endourol. 1996;10(Suppl 1):S140, P11-328 [Abstract]. 15. Chung B, Aron M, Hegarty N, et al. Ureteroscopic versus percutaneous treatment for medium-size (1-2cm) renal calculi. J Endourol. 2008;22(2):343-346. 16. Carr LK, D’A Honey J, Jewett MA, et al. New stone formation: A comparison of extracorporeal shock wave lithotripsy and percutaneous nephrolithotomy. J Urol. 1996;155:1565-1567. 17. Wen CC, Nakada SY. Treatment selection and outcomes: renal calculi. Urol Clin North Am. 2007;34:409-419. 18. Deane LA, Clayman RV. Advances in percutaneous nephrostolithotomy. Urol Clin North Am. 2007;34:383-395.
743