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Factors Affecting Stone-free Rate and Complications of Percutaneous Nephrolithotomy for Treatment of Staghorn Stone
Endourology Factors Affecting Stone-free Rate and Complications of Percutaneous Nephrolithotomy for Treatment of Staghorn Stone Ahmed R. El-Nahas, Ibrahim Eraky, Ahmed A. Shokeir, Ahmed M. Shoma, Ahmed M. El-Assmy, Nasr A. El-Tabey, Shady Soliman, Ahmed M. Elshal, Hamdy A. El-Kappany, and Mahmoud R. El-Kenawy OBJECTIVE METHODS
RESULTS
CONCLUSION
To determine factors affecting the stone-free rate and complications of percutaneous nephrolithotomy (PNL) for treatment of staghorn stones. The computerized database of patients who underwent PNL for treatment of staghorn stones between January 2003 and January 2011 was reviewed. All perioperative complications were recorded and classified according to modified Clavien classification system. The stone-free rate was evaluated with low-dose noncontrast computed tomography (CT). Univariate and multivariate statistical analyses were performed to determine factors affecting stone-free and complication rates. The study included 241 patients (125 male and 116 female) with a mean age of 48.7 ⫾14.3 years. All patients underwent 251 PNL (10 patients had bilateral stones). The stone-free rate of PNL monotherapy was 56% (142 procedures). At 3 months, the stone-free rate increased to 73% (183 kidneys) after shock wave lithotripsy. Independent risk factors for residual stones were complete staghorn stone and presence of secondary calyceal stones (relative risks were 2.2 and 3.1, respectively). The complication rate was 27% (68 PNL). Independent risk factors for development of complications were performance of the procedure by urologists other than experienced endourologist and positive preoperative urine culture (relative risks were 2.2 and 2.1, respectively). Factors affecting the incidence of residual stones after PNL are complete staghorn stones and the presence of secondary calyceal stones. Complications are significantly high if PNL is not performed by an experienced endourologist or if preoperative urine culture is positive. UROLOGY 79: 1236 –1241, 2012. © 2012 Elsevier Inc.
T
he goals of surgical treatment of staghorn stones are complete stone clearance with minimal morbidity. Percutaneous nephrolithotomy (PNL) has become the recommended treatment for staghorn stones.1,2 However, it is challenging to achieve a stonefree status using PNL because multiple percutaneous tracts may be needed to remove all stone branches.3 These multitract PNL may lead to higher complication rates, such as bleeding.4 Other major complications of PNL are sepsis and adjacent organ injuries.5 Achieving a stone-free status may also require multiple sessions of PNL or using secondary procedures, such as extracorpoFinancial Disclosure: The authors declare that they have no relevant financial interests. From the Urology Department, Urology and Nephrology Center, Mansoura University, Mansoura, Egypt Reprint requests: Ahmed R. El-Nahas, M.D., Urology and Nephrology Center, Elgomhoria Street, 35516 Mansoura, Egypt. E-mail: [email protected] Submitted: October 31, 2011, accepted (with revisions): January 16, 2012
1236
© 2012 Elsevier Inc. All Rights Reserved
real shock wave lithotripsy (SWL) for treatment of residual fragments. The importance of not leaving residual fragments in patients with staghorn stones was obvious in a previous study that demonstrated growth of residual stones in 65% during long-term follow-up.6 Previous studies used plain x-ray films3, nephrostography, or CT in some patients7 for detection of stone-free rates after PNL for staghorn stones. For complications, studies had focused on technical aspects (such as the use of single vs multiple tracts) that affected the incidence and severity of complications.7 Moreover, studying factors affecting complications was applied to all renal stone burdens, including single, multiple or staghorn stones. We conducted this study to determine factors affecting the stone-free and complications of PNL for treatment of staghorn stones. Stone-free status was determined using a highly sensitive method (noncontrast CT) in all patients and complications were classified according to modified Clavien classification system.9 0090-4295/12/$36.00 doi:10.1016/j.urology.2012.01.026
Table 1. Univariate analysis for factors affecting stone-free rate after PNL for staghorn stone Factor Gender (240 patients) Male Female Side (250 kidneys) Right Left Obesity (250 PNL) No Yes (BMI ⬎ 30 kg/m2) Renal morphology (250 kidneys) No hydronephrosis Hydronephrosis Pyelonephritis Stone burden (250 kidneys) Partial staghorn Complete staghorn Stone opacity (250 kidneys) Radiopaque Radiolucent Secondary stones (250 kidneys) No Yes Urinary tract infection (250 kidneys) No Yes Recurrence (250 kidneys) No Yes Percutaneous tracts (250 kidneys) Single Multiple Operator (250 kidneys) Experienced endourologist General urologist Skin puncture (250 kidneys) Subcostal Supracostal Punctured calyx (250 kidneys) Upper calyx Other calyces Complications (250 PNL) No Yes Continuous Factors Age (y): mean (SD) Body mass index: mean (SD) Creatinine (mg/dL): mean (SD)
Patients, n
Stone-Free Patients, n (%)
P Value
124 116
71 (57.3) 65 (56)
98 152
54 (55) 88 (58)
92 158
51 (55.4) 91 (57.6)
115 88 47
73 (63.5) 47 (53.4) 22 (46.8)
110 140
76 (69) 66 (47)
168 82
91 (54.2) 51 (62.2)
100 150
74 (74) 68 (45.3)
193 57
105 (54.4) 37 (65)
178 72
106 (59.6) 36 (50)
146 104
92 (63) 50 (48)
194 56
110 (56.7) 32 (57)
147 103
88 (60) 54 (52.4)
95 155
48 (50.5) 94 (60.6)
183 67
106 (58) 36 (53.7)
Stone-free
Residual Stones
P Value
50.1 (14.3) 32.3 (6.7) 1 (0.5)
46.7 (14.2) 31.89 (7.3) 1.1 (0.5)
.065 .609 .708
.848 .663 .739 .110
.001 .229 ⬍.001 .159 .167 .019 .953 .243 .117 .553
One patient was excluded from the statistical analysis of stone-free rate because of death.
MATERIAL AND METHODS The computerized database of patients who underwent PNL for treatment of staghorn stones between January 2003 and January 2011 were reviewed. This study included staghorn stones that were present in the renal pelvis and branched to 2 or more major calices (ie, partial and complete staghorn stones). Borderline stones that branched to one major calyx only were not included. Patients with congenital renal anomalies, such as horse-shoe and ectopic kidneys, were also excluded. Intravenous urography (IVU) was the primary radiological investigation; however, noncontrast computed tomography (NCCT) was performed for patients with high serum creatinine (⬎ 1.6 mg/dL), or those allergic to iodinated contrast. UROLOGY 79 (6), 2012
Preoperative urinary tract infections were treated with culture specific antibiotics for 5 days before PNL. Other patients with negative urine culture results received intravenous third generation cephalosporins at the time of induction of anesthesia. The technique of PNL for staghorn stones was previously described in detail.6 The most important steps were performance of the percutaneous access by the attending urologist under fluoroscopic guidance and placement of guidewires through all planned tracts before dilatation of the first tract. If the stone could be retrieved through one tract, the guidewires in the other tracts were removed without dilatation. In some patients, flexible nephroscopy was used during the initial pro1237
cedure to retrieve stones away from the initial puncture. A second session of PNL was performed in cases of residual stones larger than 10 mm or if they were accessible through the present tracts. SWL was used for residual calyceal fragments of 4 mm to 10 mm that were inaccessible through the nephrostomy tracts and follow-up was elected for residual fragments smaller than 4 mm. The outcome was evaluated with low-dose NCCT after the last PNL session and after 3 months for patients who required SWL. Stone-free was defined as no residual stones. Complications were classified according to the modified Clavien classification system.9
Statistical Analysis Univariate analyses (2 and t test) and multivariate logistic regression model were used to determine factors affecting complications and stone-free rate. The data were analyzed using Statistical Package for Social Sciences, version 15 (SPSS Inc., Chicago, IL). A P value of ⬍.05 was considered statistically significant.
RESULTS The study included 241 patients (125 male and 116 female) with a mean age of 48.7 ⫹ 14.3 years. The patient group underwent a total of 251 PNL because 10 patients had bilateral staghorn stones. In 104 procedures (41.4%), multitract PNL was used (2 tracts in 83 PNL cases and 3 tracts in 21). Multiple sessions of PNL were needed in 73 cases (30%; 2 sessions in 66 patients and 3 sessions in 7). The stone-free rate of PNL monotherapy was 56% (142 kidneys). Univariate analysis for factors affecting stone-free of PNL monotherapy are summarized in Table 1. SWL was performed after 43 PNL (17%). Unplanned secondary procedures were needed after 26 PNL (10.4%) in the form of double-J stent for 21 patients, ureteroscopy for 3, and open surgery for 2. The mean number of procedures per patient was 1.6 ⫾ 0.7 (range 1-4). The mean hospital stay was 5.7 ⫾ 3.6 days (range, 2-22 days). At 3 months, the stone-free rate increased to 73% (183 kidneys). Overall complication rate was 27% (68 PNL). Modified Clavien classification results and type of complications are summarized in Table 2. Hemorrhagic complications requiring blood transfusion were encountered in 40 procedures (16%). They included 22 intraoperative bleeding, 14 cases of postoperative hematuria, and 4 PNL complicated by both intraoperative bleeding and postoperative hematuria. Bleeding was successfully treated with clamping of the nephrostomy and hemostatic drugs, whereas 5 cases (2%) required angiographic embolization and one patient died during exploration for severe bleeding. Urinary leakage was considered when leakage of urine through the nephrostomy site after removal of the nephrostomy tube remained for more than 24 hours; it was treated by fixation of double-J ureteral stents. Hydrothorax was treated with intercostal chest tube and urinomas were drained with percutaneous tube drain. Fever was 1238
Table 2. Modified Clavien classification and type of complications after PNL for staghorn stones Modified Clavien classification Grade I Grade II Grade IIIa Grade IIIb Grade IVa Grade IVb Grade V Intraoperative complications Bleeding Pelvic tear Postoperative complications Urinary leakage Hematuria Hydrothorax Perirenal urinoma Fever (⬎38.5°C) Septic shock
n 9 31 24 1 1 1 1
(%) 3.6 12.4 9.6 0.4 0.4 0.4 0.4
26 3
10.4 1.2
20 18 6 3 3 1
8 7.2 2.4 1.2 1.2 0.4
Some patients had more than 1 complication.
treated with culture specific antibiotics and antipyretics. Septic shock was treated in the intensive care unit with cardiac enotropic drugs and antibiotics. Univariate analysis for factors affecting complication rates after PNL for staghorn stones are summarized in Table 3. Multivariate analysis results for factors affecting the stone-free and complication rates are presented in Table 4. Independent risk factors for residual stones were complete staghorn stone and presence of secondary calyceal stones (relative risks were 2.2 and 3.1, respectively). Independent risk factors for development of complications were performance of the procedure by urologists who had less than 3 years of experience as an endourologist and positive preoperative urine culture (relative risks were 2.2 and 2.1, respectively).
COMMENT Since the first report of PNL for staghorn stones by Clayman et al in 1983,10 there has been significant improvement in techniques, instruments, and experience in percutaneous renal surgery. Therefore, PNL has become the recommended treatment for staghorn stones.1 The ultimate goal of treatment is to reach a stone-free status with minimal morbidity. The stone-free rate of 73% at 3 months in our series was comparable to the stone-free rate of combination therapy published in the last version of AUA nephrolithiasis guidelines panel on staghorn calculi.1 The stonefree rate of 56.6% after PNL monotherapy among our cases was also comparable to the 56.9% published by Desai et al, in their series of 1466 cases.11 However our result was lower than the average rate published in the last AUA guidelines.1 This can be explained by the large stone burden in our study because we included only patients with staghorn stones that branched to 2 or more major calyces. In series showing higher stone-free rate UROLOGY 79 (6), 2012
Table 3. Univariate analysis for factors affecting complications after PNL for staghorn stone Categorical factor
Patients, n
Complications, n (%)
125 116
38 (30.4) 28 (24)
98 153
28 (28.6) 40 (26)
92 159
25 (27.2) 43 (27)
161 90
45 (28) 23 (25.6)
115 89 47
28 (24.3) 27 (30.3) 13 (27.7)
237 14
63 (26.6) 5 (35.7)
110 141
27 (24.5) 41 (29)
101 150
27 (26.7) 41 (27.3)
194 57
47 (24.2) 21 (36.8)
179 72
50 (28) 18 (25)
147 104
37 (25.2) 31 (29.8)
194 57
46 (23.7) 22 (38.6)
148 103
39 (26.4) 29 (28.2)
No Complication
Complication
P Value
48.3 (14.5) 32.5 (7.3) 1 (0.5)
49.6 (13.6) 30.9 (5.8) 1.1 (0.6)
.524 .107 .240
Gender (241 patients) Male Female Side (251 kidneys) Right Left Obesity (251 PNL) No Yes (BMI ⬎ 30 kg/m2) Co-morbidity (251 PNL) No Yes Renal morphology (251 kidneys) No hydronephrosis Hydronephrosis Pyelonephritis Solitary kidney (251 kidneys) No Yes Stone burden (251 kidneys) Partial staghorn Complete staghorn Secondary stones (251 kidneys) No Yes Urinary tract infection (251 PNL) No Yes Previous stone treatment (251 kidneys) No Yes Percutaneous tracts (251 kidneys) Single Multiple Operator (251 PNL) Experienced endourologist General urologist Skin puncture (251 kidneys) Subcostal Supracostal Continuous Factors Age (y): mean (SD) Body mass index: mean (SD) Creatinine (mg/dL): mean (SD)
.276 .673 .982 .682 .631
.445 .423 .916 .060 .636 .415 .026 .752
(78%) like that reported by Soucy et al, 67% of their patients had stones branching to only one calyx.7 By contrast, Al-kohlany et al published a lower stone-free rate (49%) when PNL was used for treatment of complete staghorn stones.12 Moreover, we preferred to perform SWL for treatment of residual calyceal fragments of 4 mm to 10 mm that were away from the original percutaneous tracts. Finally, we determined the stone-free rate by NCCT, unlike many series of PNL for staghorn stones. Evaluation of the stone-free rate using NCCT was more accurate in detection of small residual stones but detected more small residual stones.13 The requirement of multiple sessions of PNL in 30% and SWL in 17% in addition to the 10.4% incidence of unplanned secondary procedures in the present study UROLOGY 79 (6), 2012
P Value
highlights the importance of patient’s counseling before PNL of staghorn stones. The surgeon must explain to the patients the need of multiple interventions. Independent risk factors for residual stones after PNL for staghorn stones were all related to stone characteristics. The first was branching of the stone to all major calyces (ie, complete staghorn). The second was presence of secondary calyceal stones. The stone branching and secondary stones might require multiple tracts or the use of flexible nephroscopy to render the kidney free of stones, but sometimes these techniques were not enough. The surgeon had to decide whether to continue making more percutaneous tracts for retrieval of all residuals or to manage these residuals with the less invasive SWL. Our policy was to avoid performing more than 3 tracts be1239
Table 4. Multivariate analysis for factors affecting stone-free rate and complications after PNL for staghorn stone Independent Factor* Factors affecting stone-free rate Staghorn stone burden Partial (reference) Complete Secondary stone No (references) Yes Factors affecting complications Experience Experienced endourologist (reference) Not experienced endourologist UTI No (references) Yes
B
Exp B
95% CI
P Value
0.777
2.176
1.265-3.744
.005
1.131
3.098
1.768-5.428
⬍.001
0.786
2.195
1.153-4.179
.017
0.723
2.061
1.076-3.950
.029
B ⫽ regression coefficient; Exp B ⫽ relative risk. * Logistic regression analysis.
cause of the increased incidence of bleeding complications with too many tracts.8 The AUA nephrolithiasis guidelines panel on staghorn calculi reported complication rates of 7%-27% and a transfusion rate up to 18%.1 The complication rate of 27% and transfusion rate of 16% in the present study were within these ranges. The most dangerous complication in this study was severe bleeding requiring angiographic embolization in 2% of cases and leading to mortality in 1 patient. This high incidence of embolization was attributed to the complexity of the procedure and the need of multiple tracts in 41.4% of cases. Staghorn stone had been identified as an independent risk factor for post-PNL severe bleeding,4 and multiple tracts had been also detected as an independent risk factor for blood loss during PNL.8 In the present study, performance of PNL for staghorn stones by urologists other than experienced endourologist was independent risk factor for development of complications. It is known that PNL for treatment of staghorn stones is a challenging procedure. It requires considerable experience in gaining percutaneous tracts, performing delicate and judicious intrarenal manipulations, mastering all techniques of intracorporeal stone disintegration, and weighing the benefits of complete stone clearance against the risks of complications.4 Therefore, we recommend that PNL for staghorn stones be performed by an experienced endourologist. The second risk factor for development of complications was positive preoperative urine culture. Despite culture-specific antibiotic treatment for 5 days, the complication rate was significantly higher than in patients with negative urine culture results. In addition to fever and sepsis, patients with positive culture developed other complications, such as intraoperative bleeding, postoperative hematuria, and urinary leakage. It is obvious that septic complications were due to release of bacteria during stone disintegration or entering obstructed infected calyx during PNL manipulations. Postoperative hematuria may result from secondary hemorrhage, but the causes of intraoperative bleeding and postoperative urinary leak1240
age among these patients are still unclear. This issue needs further study for identifications of the mechanisms of noninfectious complications in patients with positive preoperative urine culture. Limitations of this study include the retrospective design, with its associated drawbacks. Therefore, some preoperative data (eg, stone size in cubic millimeters), intraoperative details (eg, operative time, the exact number of patients who needed flexible nephroscopy, and estimated blood loss) and postoperative data (eg, stone composition) were not recorded for all procedures. Recently, there were some studies that presented technical modifications, such as tubeless PNL or bilateral simultaneous PNL for staghorn stones.14,15 We did not use these techniques in our patients because of the significant stone burden with the need for multiple tracts, long operative time and multiple sessions of treatment. We believe that future research for PNL in treatment of staghorn stone must focus on improvement of the stonefree rate and minimizing complications.
CONCLUSIONS Patients with staghorn stones who will be treated with PNL need to know that the probability of requiring multiple sessions of PNL is 30%, complementary SWL is 17% and secondary procedures is 10%. Factors affecting the incidence of residual stones after PNL are complete staghorn stones and the presence of secondary calyceal stones. Complications are significantly high if PNL is not performed by experienced endourologist or if preoperative urine culture results are positive. References 1. Preminger GM, Assimos DG, Lingeman JE, et al. (AUA Nephrolithiasis Guideline Panel Chapter 1). AUA guideline on management of staghorn calculi: diagnosis and treatment recommendations. J Urol. 2005;173:1991-2000. 2. Healy K, Ogan K. Pathophysiology and management of infectious staghorn calculi. Urol Clin North Am. 2007;34:363-74.
UROLOGY 79 (6), 2012
3. Desai M, Jain P, Ganpule A, et al. Developments in technique and technology: the effect on the results of percutaneous nephrolithotomy for staghorn calculi. BJU Int. 2009;104:542-548. 4. El-Nahas AR, Shokeir AA, El-Assmy AM, et al. Post-percutaneous nephrolithotomy extensive hemorrhage: a study of risk factors. J Urol. 2007;177:576-579. 5. Michel MS, Trojan L, Rassweiler JJ. Complications in percutaneous nephrolithotomy. Eur Urol. 2007;51:899-906. 6. EL-Nahas AR, Eraky I, Shokeir AA, et al. Long-term results of percutaneous nephrolithotomy for treatment of staghorn stones. BJU Int. 2011;108:750-754. 7. Soucy F, Ko R, Duvdechai M, et al. Percutaneous nephrolithotomy for staghorn calculi: a single center experience of 15 years. J Endourol. 2009;10:1-5. 8. Kukreja R, Desai M, Patel S, et al. Factors affecting blood loss during percutaneous nephrolithotomy: prospective study. J Endourol. 2004;18:715-722. 9. Tefekli A, Ali Karadag M, Tepeler K, et al. Classification of percutaneous nephrolithotomy complications using the modified clavien grading system: looking for a standard. Eur Urol. 2008;53: 184-90.
UROLOGY 79 (6), 2012
10. Clayman RV, Surya V, Miller RP, et al. Percutaneous nephrolithotomy; an approach to branched and staghorn renal calculi. JAMA. 1983;250:73-75. 11. Desai M, De Lisa A, Turna B, et al. The clinical research office of the endourological society percutaneous nephrolithotomy global study: staghorn versus nonstaghorn stones. J Endourol. 2011;25: 1263-1268. 12. Al-Kohlany KM, Shokeir AA, Mosbah A, et al. Treatment of complete staghorn stones: a prospective randomized comparison of open surgery versus percutaneous nephrolithotomy. J Urol. 2005; 173:469-473. 13. Osman Y, El-Tabey N, Refai H, et al. Detection of residual stones after percutaneous nephrolithotomy: role of non-enhanced spiral computerized tomography. J Urol. 2008;179:198-200. 14. Falahatkar S, Khosropanah I, Roshani A, et al. Tubeless percutaneous nephrolithotomy for staghorn stones. J Endourol. 2008;22: 1447-1451. 15. Wang CJ, Chang CH, Huang SW. Simultaneous bilateral tubeless percutaneous nephrolithotomy of staghorn stones: a prospective randomized controlled study. Urol Res. 2011;39:289-294.
1241
RESULTS
CONCLUSION
To determine factors affecting the stone-free rate and complications of percutaneous nephrolithotomy (PNL) for treatment of staghorn stones. The computerized database of patients who underwent PNL for treatment of staghorn stones between January 2003 and January 2011 was reviewed. All perioperative complications were recorded and classified according to modified Clavien classification system. The stone-free rate was evaluated with low-dose noncontrast computed tomography (CT). Univariate and multivariate statistical analyses were performed to determine factors affecting stone-free and complication rates. The study included 241 patients (125 male and 116 female) with a mean age of 48.7 ⫾14.3 years. All patients underwent 251 PNL (10 patients had bilateral stones). The stone-free rate of PNL monotherapy was 56% (142 procedures). At 3 months, the stone-free rate increased to 73% (183 kidneys) after shock wave lithotripsy. Independent risk factors for residual stones were complete staghorn stone and presence of secondary calyceal stones (relative risks were 2.2 and 3.1, respectively). The complication rate was 27% (68 PNL). Independent risk factors for development of complications were performance of the procedure by urologists other than experienced endourologist and positive preoperative urine culture (relative risks were 2.2 and 2.1, respectively). Factors affecting the incidence of residual stones after PNL are complete staghorn stones and the presence of secondary calyceal stones. Complications are significantly high if PNL is not performed by an experienced endourologist or if preoperative urine culture is positive. UROLOGY 79: 1236 –1241, 2012. © 2012 Elsevier Inc.
T
he goals of surgical treatment of staghorn stones are complete stone clearance with minimal morbidity. Percutaneous nephrolithotomy (PNL) has become the recommended treatment for staghorn stones.1,2 However, it is challenging to achieve a stonefree status using PNL because multiple percutaneous tracts may be needed to remove all stone branches.3 These multitract PNL may lead to higher complication rates, such as bleeding.4 Other major complications of PNL are sepsis and adjacent organ injuries.5 Achieving a stone-free status may also require multiple sessions of PNL or using secondary procedures, such as extracorpoFinancial Disclosure: The authors declare that they have no relevant financial interests. From the Urology Department, Urology and Nephrology Center, Mansoura University, Mansoura, Egypt Reprint requests: Ahmed R. El-Nahas, M.D., Urology and Nephrology Center, Elgomhoria Street, 35516 Mansoura, Egypt. E-mail: [email protected] Submitted: October 31, 2011, accepted (with revisions): January 16, 2012
1236
© 2012 Elsevier Inc. All Rights Reserved
real shock wave lithotripsy (SWL) for treatment of residual fragments. The importance of not leaving residual fragments in patients with staghorn stones was obvious in a previous study that demonstrated growth of residual stones in 65% during long-term follow-up.6 Previous studies used plain x-ray films3, nephrostography, or CT in some patients7 for detection of stone-free rates after PNL for staghorn stones. For complications, studies had focused on technical aspects (such as the use of single vs multiple tracts) that affected the incidence and severity of complications.7 Moreover, studying factors affecting complications was applied to all renal stone burdens, including single, multiple or staghorn stones. We conducted this study to determine factors affecting the stone-free and complications of PNL for treatment of staghorn stones. Stone-free status was determined using a highly sensitive method (noncontrast CT) in all patients and complications were classified according to modified Clavien classification system.9 0090-4295/12/$36.00 doi:10.1016/j.urology.2012.01.026
Table 1. Univariate analysis for factors affecting stone-free rate after PNL for staghorn stone Factor Gender (240 patients) Male Female Side (250 kidneys) Right Left Obesity (250 PNL) No Yes (BMI ⬎ 30 kg/m2) Renal morphology (250 kidneys) No hydronephrosis Hydronephrosis Pyelonephritis Stone burden (250 kidneys) Partial staghorn Complete staghorn Stone opacity (250 kidneys) Radiopaque Radiolucent Secondary stones (250 kidneys) No Yes Urinary tract infection (250 kidneys) No Yes Recurrence (250 kidneys) No Yes Percutaneous tracts (250 kidneys) Single Multiple Operator (250 kidneys) Experienced endourologist General urologist Skin puncture (250 kidneys) Subcostal Supracostal Punctured calyx (250 kidneys) Upper calyx Other calyces Complications (250 PNL) No Yes Continuous Factors Age (y): mean (SD) Body mass index: mean (SD) Creatinine (mg/dL): mean (SD)
Patients, n
Stone-Free Patients, n (%)
P Value
124 116
71 (57.3) 65 (56)
98 152
54 (55) 88 (58)
92 158
51 (55.4) 91 (57.6)
115 88 47
73 (63.5) 47 (53.4) 22 (46.8)
110 140
76 (69) 66 (47)
168 82
91 (54.2) 51 (62.2)
100 150
74 (74) 68 (45.3)
193 57
105 (54.4) 37 (65)
178 72
106 (59.6) 36 (50)
146 104
92 (63) 50 (48)
194 56
110 (56.7) 32 (57)
147 103
88 (60) 54 (52.4)
95 155
48 (50.5) 94 (60.6)
183 67
106 (58) 36 (53.7)
Stone-free
Residual Stones
P Value
50.1 (14.3) 32.3 (6.7) 1 (0.5)
46.7 (14.2) 31.89 (7.3) 1.1 (0.5)
.065 .609 .708
.848 .663 .739 .110
.001 .229 ⬍.001 .159 .167 .019 .953 .243 .117 .553
One patient was excluded from the statistical analysis of stone-free rate because of death.
MATERIAL AND METHODS The computerized database of patients who underwent PNL for treatment of staghorn stones between January 2003 and January 2011 were reviewed. This study included staghorn stones that were present in the renal pelvis and branched to 2 or more major calices (ie, partial and complete staghorn stones). Borderline stones that branched to one major calyx only were not included. Patients with congenital renal anomalies, such as horse-shoe and ectopic kidneys, were also excluded. Intravenous urography (IVU) was the primary radiological investigation; however, noncontrast computed tomography (NCCT) was performed for patients with high serum creatinine (⬎ 1.6 mg/dL), or those allergic to iodinated contrast. UROLOGY 79 (6), 2012
Preoperative urinary tract infections were treated with culture specific antibiotics for 5 days before PNL. Other patients with negative urine culture results received intravenous third generation cephalosporins at the time of induction of anesthesia. The technique of PNL for staghorn stones was previously described in detail.6 The most important steps were performance of the percutaneous access by the attending urologist under fluoroscopic guidance and placement of guidewires through all planned tracts before dilatation of the first tract. If the stone could be retrieved through one tract, the guidewires in the other tracts were removed without dilatation. In some patients, flexible nephroscopy was used during the initial pro1237
cedure to retrieve stones away from the initial puncture. A second session of PNL was performed in cases of residual stones larger than 10 mm or if they were accessible through the present tracts. SWL was used for residual calyceal fragments of 4 mm to 10 mm that were inaccessible through the nephrostomy tracts and follow-up was elected for residual fragments smaller than 4 mm. The outcome was evaluated with low-dose NCCT after the last PNL session and after 3 months for patients who required SWL. Stone-free was defined as no residual stones. Complications were classified according to the modified Clavien classification system.9
Statistical Analysis Univariate analyses (2 and t test) and multivariate logistic regression model were used to determine factors affecting complications and stone-free rate. The data were analyzed using Statistical Package for Social Sciences, version 15 (SPSS Inc., Chicago, IL). A P value of ⬍.05 was considered statistically significant.
RESULTS The study included 241 patients (125 male and 116 female) with a mean age of 48.7 ⫹ 14.3 years. The patient group underwent a total of 251 PNL because 10 patients had bilateral staghorn stones. In 104 procedures (41.4%), multitract PNL was used (2 tracts in 83 PNL cases and 3 tracts in 21). Multiple sessions of PNL were needed in 73 cases (30%; 2 sessions in 66 patients and 3 sessions in 7). The stone-free rate of PNL monotherapy was 56% (142 kidneys). Univariate analysis for factors affecting stone-free of PNL monotherapy are summarized in Table 1. SWL was performed after 43 PNL (17%). Unplanned secondary procedures were needed after 26 PNL (10.4%) in the form of double-J stent for 21 patients, ureteroscopy for 3, and open surgery for 2. The mean number of procedures per patient was 1.6 ⫾ 0.7 (range 1-4). The mean hospital stay was 5.7 ⫾ 3.6 days (range, 2-22 days). At 3 months, the stone-free rate increased to 73% (183 kidneys). Overall complication rate was 27% (68 PNL). Modified Clavien classification results and type of complications are summarized in Table 2. Hemorrhagic complications requiring blood transfusion were encountered in 40 procedures (16%). They included 22 intraoperative bleeding, 14 cases of postoperative hematuria, and 4 PNL complicated by both intraoperative bleeding and postoperative hematuria. Bleeding was successfully treated with clamping of the nephrostomy and hemostatic drugs, whereas 5 cases (2%) required angiographic embolization and one patient died during exploration for severe bleeding. Urinary leakage was considered when leakage of urine through the nephrostomy site after removal of the nephrostomy tube remained for more than 24 hours; it was treated by fixation of double-J ureteral stents. Hydrothorax was treated with intercostal chest tube and urinomas were drained with percutaneous tube drain. Fever was 1238
Table 2. Modified Clavien classification and type of complications after PNL for staghorn stones Modified Clavien classification Grade I Grade II Grade IIIa Grade IIIb Grade IVa Grade IVb Grade V Intraoperative complications Bleeding Pelvic tear Postoperative complications Urinary leakage Hematuria Hydrothorax Perirenal urinoma Fever (⬎38.5°C) Septic shock
n 9 31 24 1 1 1 1
(%) 3.6 12.4 9.6 0.4 0.4 0.4 0.4
26 3
10.4 1.2
20 18 6 3 3 1
8 7.2 2.4 1.2 1.2 0.4
Some patients had more than 1 complication.
treated with culture specific antibiotics and antipyretics. Septic shock was treated in the intensive care unit with cardiac enotropic drugs and antibiotics. Univariate analysis for factors affecting complication rates after PNL for staghorn stones are summarized in Table 3. Multivariate analysis results for factors affecting the stone-free and complication rates are presented in Table 4. Independent risk factors for residual stones were complete staghorn stone and presence of secondary calyceal stones (relative risks were 2.2 and 3.1, respectively). Independent risk factors for development of complications were performance of the procedure by urologists who had less than 3 years of experience as an endourologist and positive preoperative urine culture (relative risks were 2.2 and 2.1, respectively).
COMMENT Since the first report of PNL for staghorn stones by Clayman et al in 1983,10 there has been significant improvement in techniques, instruments, and experience in percutaneous renal surgery. Therefore, PNL has become the recommended treatment for staghorn stones.1 The ultimate goal of treatment is to reach a stone-free status with minimal morbidity. The stone-free rate of 73% at 3 months in our series was comparable to the stone-free rate of combination therapy published in the last version of AUA nephrolithiasis guidelines panel on staghorn calculi.1 The stonefree rate of 56.6% after PNL monotherapy among our cases was also comparable to the 56.9% published by Desai et al, in their series of 1466 cases.11 However our result was lower than the average rate published in the last AUA guidelines.1 This can be explained by the large stone burden in our study because we included only patients with staghorn stones that branched to 2 or more major calyces. In series showing higher stone-free rate UROLOGY 79 (6), 2012
Table 3. Univariate analysis for factors affecting complications after PNL for staghorn stone Categorical factor
Patients, n
Complications, n (%)
125 116
38 (30.4) 28 (24)
98 153
28 (28.6) 40 (26)
92 159
25 (27.2) 43 (27)
161 90
45 (28) 23 (25.6)
115 89 47
28 (24.3) 27 (30.3) 13 (27.7)
237 14
63 (26.6) 5 (35.7)
110 141
27 (24.5) 41 (29)
101 150
27 (26.7) 41 (27.3)
194 57
47 (24.2) 21 (36.8)
179 72
50 (28) 18 (25)
147 104
37 (25.2) 31 (29.8)
194 57
46 (23.7) 22 (38.6)
148 103
39 (26.4) 29 (28.2)
No Complication
Complication
P Value
48.3 (14.5) 32.5 (7.3) 1 (0.5)
49.6 (13.6) 30.9 (5.8) 1.1 (0.6)
.524 .107 .240
Gender (241 patients) Male Female Side (251 kidneys) Right Left Obesity (251 PNL) No Yes (BMI ⬎ 30 kg/m2) Co-morbidity (251 PNL) No Yes Renal morphology (251 kidneys) No hydronephrosis Hydronephrosis Pyelonephritis Solitary kidney (251 kidneys) No Yes Stone burden (251 kidneys) Partial staghorn Complete staghorn Secondary stones (251 kidneys) No Yes Urinary tract infection (251 PNL) No Yes Previous stone treatment (251 kidneys) No Yes Percutaneous tracts (251 kidneys) Single Multiple Operator (251 PNL) Experienced endourologist General urologist Skin puncture (251 kidneys) Subcostal Supracostal Continuous Factors Age (y): mean (SD) Body mass index: mean (SD) Creatinine (mg/dL): mean (SD)
.276 .673 .982 .682 .631
.445 .423 .916 .060 .636 .415 .026 .752
(78%) like that reported by Soucy et al, 67% of their patients had stones branching to only one calyx.7 By contrast, Al-kohlany et al published a lower stone-free rate (49%) when PNL was used for treatment of complete staghorn stones.12 Moreover, we preferred to perform SWL for treatment of residual calyceal fragments of 4 mm to 10 mm that were away from the original percutaneous tracts. Finally, we determined the stone-free rate by NCCT, unlike many series of PNL for staghorn stones. Evaluation of the stone-free rate using NCCT was more accurate in detection of small residual stones but detected more small residual stones.13 The requirement of multiple sessions of PNL in 30% and SWL in 17% in addition to the 10.4% incidence of unplanned secondary procedures in the present study UROLOGY 79 (6), 2012
P Value
highlights the importance of patient’s counseling before PNL of staghorn stones. The surgeon must explain to the patients the need of multiple interventions. Independent risk factors for residual stones after PNL for staghorn stones were all related to stone characteristics. The first was branching of the stone to all major calyces (ie, complete staghorn). The second was presence of secondary calyceal stones. The stone branching and secondary stones might require multiple tracts or the use of flexible nephroscopy to render the kidney free of stones, but sometimes these techniques were not enough. The surgeon had to decide whether to continue making more percutaneous tracts for retrieval of all residuals or to manage these residuals with the less invasive SWL. Our policy was to avoid performing more than 3 tracts be1239
Table 4. Multivariate analysis for factors affecting stone-free rate and complications after PNL for staghorn stone Independent Factor* Factors affecting stone-free rate Staghorn stone burden Partial (reference) Complete Secondary stone No (references) Yes Factors affecting complications Experience Experienced endourologist (reference) Not experienced endourologist UTI No (references) Yes
B
Exp B
95% CI
P Value
0.777
2.176
1.265-3.744
.005
1.131
3.098
1.768-5.428
⬍.001
0.786
2.195
1.153-4.179
.017
0.723
2.061
1.076-3.950
.029
B ⫽ regression coefficient; Exp B ⫽ relative risk. * Logistic regression analysis.
cause of the increased incidence of bleeding complications with too many tracts.8 The AUA nephrolithiasis guidelines panel on staghorn calculi reported complication rates of 7%-27% and a transfusion rate up to 18%.1 The complication rate of 27% and transfusion rate of 16% in the present study were within these ranges. The most dangerous complication in this study was severe bleeding requiring angiographic embolization in 2% of cases and leading to mortality in 1 patient. This high incidence of embolization was attributed to the complexity of the procedure and the need of multiple tracts in 41.4% of cases. Staghorn stone had been identified as an independent risk factor for post-PNL severe bleeding,4 and multiple tracts had been also detected as an independent risk factor for blood loss during PNL.8 In the present study, performance of PNL for staghorn stones by urologists other than experienced endourologist was independent risk factor for development of complications. It is known that PNL for treatment of staghorn stones is a challenging procedure. It requires considerable experience in gaining percutaneous tracts, performing delicate and judicious intrarenal manipulations, mastering all techniques of intracorporeal stone disintegration, and weighing the benefits of complete stone clearance against the risks of complications.4 Therefore, we recommend that PNL for staghorn stones be performed by an experienced endourologist. The second risk factor for development of complications was positive preoperative urine culture. Despite culture-specific antibiotic treatment for 5 days, the complication rate was significantly higher than in patients with negative urine culture results. In addition to fever and sepsis, patients with positive culture developed other complications, such as intraoperative bleeding, postoperative hematuria, and urinary leakage. It is obvious that septic complications were due to release of bacteria during stone disintegration or entering obstructed infected calyx during PNL manipulations. Postoperative hematuria may result from secondary hemorrhage, but the causes of intraoperative bleeding and postoperative urinary leak1240
age among these patients are still unclear. This issue needs further study for identifications of the mechanisms of noninfectious complications in patients with positive preoperative urine culture. Limitations of this study include the retrospective design, with its associated drawbacks. Therefore, some preoperative data (eg, stone size in cubic millimeters), intraoperative details (eg, operative time, the exact number of patients who needed flexible nephroscopy, and estimated blood loss) and postoperative data (eg, stone composition) were not recorded for all procedures. Recently, there were some studies that presented technical modifications, such as tubeless PNL or bilateral simultaneous PNL for staghorn stones.14,15 We did not use these techniques in our patients because of the significant stone burden with the need for multiple tracts, long operative time and multiple sessions of treatment. We believe that future research for PNL in treatment of staghorn stone must focus on improvement of the stonefree rate and minimizing complications.
CONCLUSIONS Patients with staghorn stones who will be treated with PNL need to know that the probability of requiring multiple sessions of PNL is 30%, complementary SWL is 17% and secondary procedures is 10%. Factors affecting the incidence of residual stones after PNL are complete staghorn stones and the presence of secondary calyceal stones. Complications are significantly high if PNL is not performed by experienced endourologist or if preoperative urine culture results are positive. References 1. Preminger GM, Assimos DG, Lingeman JE, et al. (AUA Nephrolithiasis Guideline Panel Chapter 1). AUA guideline on management of staghorn calculi: diagnosis and treatment recommendations. J Urol. 2005;173:1991-2000. 2. Healy K, Ogan K. Pathophysiology and management of infectious staghorn calculi. Urol Clin North Am. 2007;34:363-74.
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3. Desai M, Jain P, Ganpule A, et al. Developments in technique and technology: the effect on the results of percutaneous nephrolithotomy for staghorn calculi. BJU Int. 2009;104:542-548. 4. El-Nahas AR, Shokeir AA, El-Assmy AM, et al. Post-percutaneous nephrolithotomy extensive hemorrhage: a study of risk factors. J Urol. 2007;177:576-579. 5. Michel MS, Trojan L, Rassweiler JJ. Complications in percutaneous nephrolithotomy. Eur Urol. 2007;51:899-906. 6. EL-Nahas AR, Eraky I, Shokeir AA, et al. Long-term results of percutaneous nephrolithotomy for treatment of staghorn stones. BJU Int. 2011;108:750-754. 7. Soucy F, Ko R, Duvdechai M, et al. Percutaneous nephrolithotomy for staghorn calculi: a single center experience of 15 years. J Endourol. 2009;10:1-5. 8. Kukreja R, Desai M, Patel S, et al. Factors affecting blood loss during percutaneous nephrolithotomy: prospective study. J Endourol. 2004;18:715-722. 9. Tefekli A, Ali Karadag M, Tepeler K, et al. Classification of percutaneous nephrolithotomy complications using the modified clavien grading system: looking for a standard. Eur Urol. 2008;53: 184-90.
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10. Clayman RV, Surya V, Miller RP, et al. Percutaneous nephrolithotomy; an approach to branched and staghorn renal calculi. JAMA. 1983;250:73-75. 11. Desai M, De Lisa A, Turna B, et al. The clinical research office of the endourological society percutaneous nephrolithotomy global study: staghorn versus nonstaghorn stones. J Endourol. 2011;25: 1263-1268. 12. Al-Kohlany KM, Shokeir AA, Mosbah A, et al. Treatment of complete staghorn stones: a prospective randomized comparison of open surgery versus percutaneous nephrolithotomy. J Urol. 2005; 173:469-473. 13. Osman Y, El-Tabey N, Refai H, et al. Detection of residual stones after percutaneous nephrolithotomy: role of non-enhanced spiral computerized tomography. J Urol. 2008;179:198-200. 14. Falahatkar S, Khosropanah I, Roshani A, et al. Tubeless percutaneous nephrolithotomy for staghorn stones. J Endourol. 2008;22: 1447-1451. 15. Wang CJ, Chang CH, Huang SW. Simultaneous bilateral tubeless percutaneous nephrolithotomy of staghorn stones: a prospective randomized controlled study. Urol Res. 2011;39:289-294.
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