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Factors affecting complications according to the modified Clavien classification in complete supine percutaneous nephrolithotomy.

Introduction

Presently, percutaneous nephrolithotomy (PCNL) is preferred as a safe and effective way to remove large or multiple upper urinary tract calculi.1 (-7) An increase in PCNL has been accompanied by variations in positions, techniques, and instruments, and these may have led to increased complications. (1,2,4,5) Following PCNL, 79.5% of patients may experience an uncomplicated postoperative period, (5,8) although there are reports of an early complication rate of 50.8%. (4) PCNL complications may occur during puncturing, access, or stone removal. (4) A standardized classification allow us to compare complications among different instruments, techniques, and centres. (3,4,7,9) In 2004, the modified Clavien system (MCC) was introduced and allowed us to classify complications based on life-threatening conditions, interventions required, and disability. (9) In recent years, this classification has been used to report PCNL complications instead of using simply "minor" and "major" distinctions. (3-8,10-12) In this study, we reported on the PCNL complications according to the MCC and identified the parameters affecting the severity of complications based on this classification.

Methods

In a prospective analytical cross-sectional study, 330 patients with upper urinary tract stones underwent PCNL by 1 experienced surgeon from January 2008 to September 2013. We included patients with upper caliceal, middle caliceal and renal pelvic stones with stone burden [greater than or equal to] 2 cm, lower caliceal stones [greater than or equal to] 1.5 cm, upper ureteral stones [greater than or equal to] 1 cm, extracorporeal shock wave lithotripsy-resistant stones [greater than or equal to] 1 cm, multiple location stones with stone burden [greater than or equal to] 2 cm, and staghorn stones. We excluded patients with uncontrolled bleeding diathesis, untreated preoperative urinary tract infection (UTI), immunosuppression, and pregnant patients. Our ethics committee approved this study. Before surgery, we evaluated patients using blood cell count, coagulation tests, serum creatinine, urinalysis, urine culture, kidneys-ureters-bladder radiography, intravenous urography, ultrasonography, and computed tomography scan (in select cases). We considered preoperative serum creatinine >1.4 mg/dL as renal dysfunction. Also staghorn and multiple locations stones, and moderate and severe hydronephrosis were considered as complex stones and significant hydronephrosis, respectively. If patients were taking antiplatelet drugs, these drugs were discontinued for 10 to 14 days before surgery. Patients with UTI were treated by appropriate antibiotic therapy before the PCNL. Also appropriate prophylactic antibiotics were administered for all patients before and after the operation. All PCNLs were performed with patients in the complete supine position (13) due to the surgeon's experience. Compared with the prone PCNL, the complete supine PCNL is a safe and effective procedure; patients do not need to be repositioned after intubation and catheterization. The complete supine position also allows us to control the airway appropriately during anesthesia and to sit during surgery. (13) The procedure was initiated by cystoscopy and retrograde insertion of the ureteral stent and followed by puncturing the collecting system with an 18-gauge needle and inserting a 0.035-inch J-tip guidewire using the posterior subcostal access. A one-shot dilation technique (9-Fr dilator, 28-Fr Amplatz dilator), insertion of a 30-Fr Amplatz sheath (by possible and easy slipping and manipulating it over the 28-Fr Amplatz dilator into the collecting system), (13,14) rigid nephroscopy, and pneumatic lithotripsy were performed. Multiple tracts and nephrostomy tube were used according to surgeon preference. After PCNL, the ureteral stent and Foley catheter were removed within 24 and 48 hours, unless patients had serious complications (i.e., significant blood loss or hematuria and leakage) necessitating irrigation or prolonged drainage. A blood transfusion was performed in patients with hemodynamic changes following blood loss or bleeding, especially in patients with postoperative hemoglobin less than 10 mg/dL.

All patients were followed up to 3 months after surgery. We defined stone-free as the absence of stone fragments in intra-operative fluoroscopy or ultrasonography (and nephrostography in radiolucent stones) and in postoperative kidneys-ureters-bladder radiography and ultrasonography. We graded the complications according to severity using the MCC in 4 grades (0, I, II, [greater than or equal to] III) (Table 1). (9) Grade 0 included patients without complications. All patients with the grades of IIIa-V were classified as the grade [greater than or equal to] III (major complications).

We assessed the impact of the following factors on complication severity based on the MCC: age, gender, body mass index (BMI), preoperative hemoglobin, renal dysfunction, preoperative UTI, hypertension, diabetes mellitus (DM), ischemic heart disease (IHD), previous stone surgery and extracorporeal shockwave lithotripsy (ESWL), anatomic upper urinary tract abnormality (AUUTA), significant hydronephrosis, stone-related parameters (number, burden, opacity, location, staghorn and complex stones), type of anesthesia, kidney side, imaging for access, calyx for access, tract number, tubeless approach, operative time, postoperative hemoglobin, postoperative hemoglobin drop, and stone-free result.

The SPSS version 16.0 software was used for data statistical analysis. The univariate analyses (Spearman test for quantitative variables, Mann-Whitney test for categorical variables, and Kruskal-Wallis test for qualitative variables with >2 categories) were used to evaluate the association between the above parameters and MCC. Also multivariate analysis using ordinal logistic regression was used to predict the factors affecting MCC and severity of complications (with control and adjustment of other variables). All p values were two-tailed and <0.05 was considered statistically significant.

Results

The mean patient age was 49.38 [+ or -] 12.63. The mean stone burden was 35.11 [+ or -] 17.09 mm. The complication rate was 19.7% (n = 65). The most common complications were blood transfusion and transient low-grade fever. Significant life-threatening bleeding, including gross hematuria, hematoma formation and hemoperitoneum, occurred in 15 patients (4.5%), who were treated conservatively (2.4%) or with interventions (2.1%). The rates of the Clavien grades of 0, I, II, III, IV and V were 80.3%, 6.4%, 11.2%, 1.5%, 0.3% and 0.3%, respectively. Grade [greater than or equal to] III included 7 patients (2.1%) (Table 2). We also detailed patient complications, grading, and management (Table 3).

On univariate analysis, the following factors has no significant effect on MCC: age, BMI, preoperative UTI, hypertension, DM, IHD, previous stone surgery and ESWL, stone-related parameters, anesthesia type, kidney side, tubeless approach, and operative time. Although the group with renal dysfunction (grade 0: 66.7%; grade I: 18.5%; grade II: 14.8%; grade [greater than or equal to] III: 0.0%) had higher complications compared with group without renal dysfunction (grade 0: 81.5%; grade I: 5.3%; grade II: 10.9%; grade [greater than or equal to] III: 2.3%), this difference was not significant (p = 0.111) in univariate analysis due to a lack of control or adjustment of other variables. The following all affected the MCC: gender (p = 0.040), upper tract abnormality (p = 0.002), significant hydronephrosis (p < 0.0001), imaging for access (p = 0.054), calyx for access (p = 0.019), tract number (p = 0.004), and stone-free result (p = 0.032). The groups with significant hydronephrosis, ultrasonography, and stone-free also had lower complications. The groups with upper tract abnormality, multiple calices, and multiple tracts accesses had significantly lower rates of grade 0 complications and higher rates of other grades compared with the groups without abnormality, single calyx, and single tract accesses. Each MCC grade had significantly different mean preoperative hemoglobin (p = 0.015), postoperative hemoglobin (p < 0.0001), and postoperative hemoglobin drop (p < 0.0001) (Table 4).

In multivariate ordinal logistic regression analysis, anatomic upper tract abnormality (odds ratio [OR] 0.05), renal dysfunction (OR 0.32), the absence of significant hydronephrosis (OR 2.32), multiple tracts (OR 0.37), lower postoperative hemoglobin (OR 0.64), and higher postoperative hemoglobin drop (OR 1.57) were the significant parameters affecting MCC and predicting higher grades. We found that renal dysfunction, anatomic upper urinary tract abnormality, number of tract and postoperative hemoglobin protected this effect and prediction. A postoperative hemoglobin drop and significant hydronephrosis promoted the PCNL complication to a higher Clavien grade (Table 5).

Discussion

In PCNL, many complications are minor and their precise reporting is necessary, although major complications or death may occur. (1-8,10,12) Compared with others studies, we had comparative results about complete supine PCNL complications according to the MCC. (3-8,10,12,15-17) The types of complications, their management, and outcomes affect this classification. (9,12) Therefore the MCC can be used to evaluate the severity of complications, yet it has its limitations. The MCC cannot predict the occurrence of a specific complication and cannot reveal its reason. Also due to different surgical managements, the subclassification of the higher Clavien grades has low reliability. If a single standardized manner is used for reporting and managing complications, the MCC can be applied to assess and compare PCNL complications at different centers or with techniques. (12,18,19) Improvement in the management of complications and detection of the factors affecting MCC can influence the severity of complications. Age, gender, BMI, hypertension, DM, cardiovascular disease, previous kidney or stone treatment and surgery, prior ESWL, preoperative hematocrit and kidney side had no significant effect on the mean Clavien score, risk of grade [greater than or equal to] IIIa, major complications or complication rate. (6,8,15,16,20-25) Some studies reported positive preoperative urine culture or pre-existent UTI as a significant parameter predicting complications. (15,16,20) However, in other studies, positive urine culture had no significant effect on the mean Clavien score, grade [greater than or equal to] IIIa or complications in multivariate analysis. (3,8,21) In our experience, age, gender, BMI, hypertension, DM, IHD, previous stone surgery and ESWL, preoperative hemoglobin, preoperative UTI and kidney side did not affect MCC. Positive preoperative urine culture does not predict urosepsis and systemic inflammatory response syndrome in PCNL. (26,27) Although antibiotic prophylaxis can decrease infectious complications, (28) the use of renal pelvic urine and stone cultures, and treatment of preoperative UTI should not be forgotten especially in patients with renal anomalies, hydronephrosis, large or staghorn stones and multiple tracts. (26,27)

One study reported no difference in the complication rates between groups with normal and impaired renal function. (29) However, another study reported that chronic kidney disease stages had significantly different complication rates and Clavien scores, and decreased kidney function came with an increase in complication rates. (30) In our study, renal dysfunction predicted complications and higher Clavien grades. Preoperative renal function may indeed predict PCNL complications and their severity.

Osther and colleagues reported similar complications and mean Clavien scores between groups with and without renal malformation. (31) In children, renal anomalies and solitary kidney had no significant effects on complication rates. (21) In our study, anatomic upper urinary tract abnormalities significantly affected MCC and came with higher complications. The following factors may affect surgical techniques regarding access to the collecting system, manipulation and removal of stone and increase the complication rate: alteration in position and axis of the kidney, renal morphology, vasculature and mobility of the kidney, morphology of calices, pelvis and upper ureter. (31,32) Laparoscopy, computed tomography or simultaneous use of fluoroscopy and ultrasonography might provide safe and easier access and manipulation in these cases. (31-33) Also case volume, surgeon experience, and type of anomaly can affect the PCNL outcomes. (3,15,31,32)

Pre-existent hydronephrosis did not predict major complications in the Olbert study. (20) Renal morphology (including hydronephrosis) had no significant effect on complications in staghorn stones. (15) In our study, significant hydronephrosis predicted lower complications in MCC. An appropriate anatomic space facilitates calyx puncturing, access to the collecting system and stone manipulation, and reduces renal and pelvi-calyceal trauma and complications. (32)

Stone-related parameters (opacity, number, burden, location, staghorn and complex stones) did not affect MCC in our experience. In multiple studies, stone burden had no significant effect on the mean Clavien score, risk of grade [greater than or equal to] IIIa, major complications, or complication rate. (8,15,16,20,21) In other studies, stone surface area or stone size significantly affected complications and mean Clavien score. (3,17) Moreover, stone location, staghorn and complex stones had a significant influence on mean Clavien score, Clavien grades, or complications in some studies. (3,10,16,21,34) In other studies, stone distribution and staghorn stone had no significant effect on complications or grade [greater than or equal to] IIIa. (6,17) Puncturing, access and stone removal largely affect PCNL complications. (4) Stone characteristics may have eligible effects on the occurrence and severity of PCNL complications.

Multiple studies (35-37) demonstrated comparative complication rates and Clavien classification of complications for general and spinal anesthesia similar to our results, although Cicek and colleagues reported higher minor complications (grades I-II), lower major complications (grades [greater than or equal to] IIIa), and lower rates of the grades of II-IIIb and IVb for spinal anesthesia. (35)

We found that imaging for access did not affect MCC in multivariate analysis. Different studies demonstrated similar complications between ultrasonography and fluoroscopy, and imaging type had no significant effect on complication rates in children. (21,38,39) Ultrasonography can be an appropriate alternative for fluoroscopy due to suitable outcomes, minimum radiation exposure, proper anatomical identification despite longer access and operative times, and the need for adequate skills or experience. (32,33,38-40)

In children, mid-calyceal puncture had a significant effect on complications. (21) Shin and colleagues found that a punctured calyx did not predict grade [greater than or equal to] IIIa. (6) Aron and colleagues reported similar complication rates for superior and inferior calyceal punctures in complex inferior calyceal stones. (41) In another study, middle and lower calices accesses had similar complication rates and MCC. (42) In our study, calyx for access did not predict MCC in multivariate analysis. If the calyx is selected for access based on renal anatomy, stone location, operation condition and surgeon preference, the safe and successful access and removal of stone can be achieved.

The meta-analysis study revealed no significant difference between tubeless and standard PCNL regarding complication rate. (43) In our study, the tubeless approach had no significant effect on MCC.

There are different results about the effect of operative time on complications. (3,6,8,16,21) Onal and colleagues found that operative time significantly affected the complication rate in children. (21) Labate and colleagues found that prolonged operative time significantly predicted a higher mean Clavien score and risk of grade [greater than or equal to] IIIa. (8) However, operative time did not predict grade [greater than or equal to] IIIa or complications in others studies. (3,6,16) In our study, operative time did not affect MCC. All PCNLs were performed by a single experienced endourologist. The learning curve and experience can affect performance of access, operative time, and complications. (3,15,18)

Hegarty and colleagues reported similar complication rates for single tract and multiple tracts accesses without consideration of transfusion. (44) Multi-puncture was not a significant factor predicting grade [greater than or equal to] IIa. (6) Tract number (15,21) had no significant effect on complications in staghorn stones or children. But Netto and colleagues reported higher complication rates for multiple accesses versus upper pole and lower/middle calices accesses in staghorn stones. (45) In our experience, multiple tracts predicted higher complications in MCC. Many of our complications were related to vascular events, bleeding, and transfusion. The multiple tracts approach comes with increased blood loss and transfusion. (46,47)

In Onal study, postoperative hematocrit had no significant effect on complication rate in children. (21) In our experience, postoperative hemoglobin and hemoglobin drop significantly affected MCC. Most of our complications were bleeding events. Lower postoperative hemoglobin and higher postoperative hemoglobin drop can imply serious injury to the vascular system or parenchyma and predict increased Clavien grades.

Similarly, the success or stone-free status affected complications in the Onal (21) study and the group with residual fragments also had higher complications in univariate analysis. The PCNL complication was an outcome independent of the PCNL success. In multivariate analysis, the success had no significant effect on complication rates in children. (21) Similarly, the stone-free result did not predict complications based on MCC in multivariate analysis in our study.

Our study has its limitations. Although we included all cases during the study period, we had low number of cases in the higher Clavien grades and some subgroups of variables. Also some techniques were not used due to surgeon. We did not assess the following factors that may affect access to the collecting system, stone manipulation and complication rate: vertebral column, pelvis and upper ureter anatomy, mobility of kidney, location of calyceal puncture, diameter of calyceal infundibulum, angle between calyces, angle between calyx tract with pelvis and long axis of kidney or vertebra, inflammation around ureteropelvic junction or upper ureteral stone, adequate visibility during access (in severe bleeding or complete space-occupying stone and stone fragments migration into other calyces.

Conclusion

In complete supine PCNL, many complications were in the lower Clavien grades and major complications were uncommon. We found that renal dysfunction, upper urinary tract abnormality, significant hydronephrosis, multiple tracts, postoperative hemoglobin and hemoglobin drop predicted MCC complications.

Acknowledgments: The authors acknowledge that Dr. Siavash Falahatkar performed all PCNLs in this research.

Competing interests: Authors declare no competing financial or personal interests.

This paper has been peer-reviewed.

References

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Correspondence: Dr. Keivan Gholamjani Moghaddam, Urology Research Center, Guilan University of Medical Sciences, Rasht, Iran; keivan_ghm@yahoo.com

Siavash Falahatkar, MD; Keivan Gholamjani Moghaddam, MD; Ehsan Kazemnezhad, PhD; Alireza Farzan, MD; Hamidreza Baghani Aval, MD; Ali Ghasemi, MD; Elaheh Shahab, MD; Seyednaser Seyed Esmaeili, MD; Reza Motiee, MD; Seyedeh Alaleh Motiei Langroodi, MD; Mohadeseh Nemati, MD; Aliakbar Allahkhah, MD

Urology Research Center, Guilan University of Medical Sciences; and the Razi Hospital, Rasht, Iran

http://dx.doi.org/10.5489/cuaj.2248

Published online February 9, 2015.
Table 1. Modified Clavien classification of surgical complications

Grade         Definition

Grade I       Any deviation from the normal postoperative course
              without the need for pharmacological treatment or
              surgical, endoscopic, and radiological interventions.

              Allowed therapeutic regimens are: drugs as
              antiemetics, antipyretics, analgesics, diuretics,
              electrolytes, and physiotherapy. This grade also
              includes wound infection opened at the bedsides.

Grade II      Requiring pharmacological treatment with other
              than such allowed for grade I complications. Blood
              transfusion and total parenteral nutrition are also
              included.

Grade III     Requiring surgical, endoscopic or radiological
              intervention

Grade IIIa    Intervention not under general anesthesia

Grade IIIb    Intervention under general anesthesia
              Life-threatening complication (including CNS
              complications)* requiring IC/ICU management

Grade IV      Single organ dysfunction (including dialysis)
Grade IVa     Multiorgan dysfunction
Grade IVb

Grade V       Death of a patient

Suffix "d"    If the patient suffers from a complication at the time
              of discharge, the suffix "d" (for "disability") is added
              to the respective grade of complication. This label
              indicated the need for a follow-up to fully evaluate
              the complication.

Adapted from Dindo et al. (9) * Brain hemorrhage, ischemic
stroke, subarachnoidal bleeding, but excluding transient
ischemic attacks. CNS: central nervous system; IC:
intermediate care; ICU: intensive care unit.

Table 2. Patient-, stone- and operation-related data and PCNL
outcomes

Mean age (SE, range), year                          49.38 [+ or -]
                                                 12.63 (0.70, 16-78)

Age groups                 15-44 years, n (%)        114 (34.6%)
                           45-59 years, n (%)        139 (42.1%)
                           > 60 years, n (%)          77 (23.3%)

Male/female ratio, n (%)                             184 (55.8%)/
                                                     146 (44.2%)
Mean BMI (SE, range), kg/[m.sup.2]               28.03 [+ or -] 4.79
                                                 (0.27, 15.88-46.71)

BMI groups
                           <25 kg/[m.sup.2],          94 (28.5%)
                             n (%)
                           25-29.9 kg/               128 (38.8%)
                             [m.sup.2], n (%)
                           [greater than or          108 (32.7%)
                             equal to] 30 kg/
                             [m.sup.2], n (%)

Mean preoperative   hemoglobin (SE, range),      13.39 [+ or -] 1.63
  g/dL                                             (0.09, 9.1-19.1)
Mean preoperative serum creatinine (SE,           1.14 [+ or -] 0.62
  range), mg/dL                                   (0.03, 0.50-8.80)
Hypertension, n (%)                                  111 (33.6%)
Diabetes mellitus, n (%)                              64 (19.4%)
Ischemic heart disease, n (%)                         25 (7.6%)
Previous stone surgery (open, PCNL) at the            89 (27.0%)
  same side, n (%)
Previous ESWL at the same side, n (%)                139 (42.1%)
Renal dysfunction (preoperative serum                 27 (8.2%)
  creatinine >1.4 mg/dl), n (%)

Anatomic upper urinary
  tract abnormality, n
  (%)
                           Duplication of                   3 (0.9%)
                             collecting
                             system, n (%)
                           Single kidney, n                 1 (0.3%)
                             (%)
                           Polycystic            8 (2.4%)   1 (0.3%)
                             kidney, n (%)
                           Medullary sponge                 1 (0.3%)
                             kidney, n (%)
                           Malrotation of                   1 (0.3%)
                             kidney, n (%)
                           Lower calyx                      1 (0.3%)
                             diverticulum, n
                             (%)
                           Pre-operative               99 (30%)
                             urinary tract
                             infection, n (%)

Significant (moderate-severe)                        194 (58.8%)
  hydronephrosis, n (%)
Mean stone burden (SE, range), millimeter           35.11 [+ or -]
                                                 17.09 (0.95, 10-200)
Stone number (single/multiple), n (%)           87 (26.4%)/243 (73.6%)
Stone opacity (radio-opaque/radiolucent), n     285 (86.4%)/45 (13.6%)
  (%)

Stone location             Only one calyx,            71 (21.5%)
                             n (%)
                           Only pelvis, n (%)         55 (16.7%)
                           Only upper                  8 (2.4%)
                             ureter, n (%)
                           Multiple                  163 (49.4%)
                             locations, n (%)
                           Staghorn, n (%)            33 (10.0%)

Complex stones, n (%)                                196 (59.4%)
Type of anesthesia         General, n (%)            320 (97.0%)
                           Spinal, n (%)              10 (3.0%)

Kidney side (right/left), n (%)                    170 (51.5%)/160
                                                       (48.5%)
Imaging for access         Fluoroscopy, n (%)        301 (91.2%)
Calyx for access           Ultrasonography,           29 (8.8%)
                             n (%)
                           Upper calyx                21 (6.4%)
                             group, n (%)
                           Middle calyx               77 (23.3%)
                             group, n (%)
                           Lower calyx               219 (66.4%)
                             group, n (%)
                           Multiple calices           13 (3.9%)
                             group, n (%)

Number of tract (single / multiple), n (%)      300 (90.9%)/30 (9.1%)
Tubeless approach (without nephrostomy tube          307 (93.0%)
  insertion), n (%)
Mean operative time (SE, range), minute          57.16 [+ or -] 28.94
                                                    (1.65, 10-195)
Mean postoperative hospital Stay (SE,             2.23 [+ or -] 1.18
  range), day                                        (0.06, 1-9)
Mean postoperative hemoglobin (SE, range),       12.13 [+ or -] 1.88
  g/dL                                             (0.10, 7.0-16.5)
Mean postoperative hemoglobin drop (SE,           1.27 [+ or -] 1.33
  range), g/dL                                     (0.07, 0.0-7.5)

Stone-free result          Stone-free, n (%)         254 (77.0%)
                           Residual                   76 (23.0%)
                             fragments, n (%)

Success (stone-free or residual fragments            279 (84.5%)
  <4 mm at one day after operation), n (%)
Complication, n (%)                                   65 (19.7%)
Blood transfusion, n (%)                              42 (12.7%)
Transient low-grade fever, n (%)                      25 (7.6%)
Significant life-threatening bleeding (gross          15 (4.5%)
  hematuria, hematoma, hemoperitoneum), n (%)

                  Grade 0,                           265 (80.3%)
                    n (%)
                  Grade I,                            21 (6.4%)
                    n (%)
                  Grade II,                           37 (11.2%)
                    n (%)
MCC of                        Grade III,                    5 (1.5%)
  complications                 n (%)
                 Grade        Grade IV, n (%)    7 (2.1%)   1 (0.3%)
                   [greater   Grade V, n (%)                1 (0.3%)
                   than or
                   equal
                   to] III,
                   n (%)

SE: standard error of the mean; MCC: modified Clavien classification;
PCNL: percutaneous nephrolithotomy; BMI: body mass index; ESWL:
extracorporeal shock wave lithotripsy

Table 3. MCC and managements of PCNL complications

Type of complication                   N (%)     Clavien grade

Transient low-grade fever            17 (5.2%)     Grade I

Bleeding requiring blood             24 (7.3%)     Grade II
transfusion

Transient low-grade fever and         6 (1.8%)     Grade II
bleeding requiring blood
transfusion

Extravasation                         1 (0.3%)     Grade I

Bleeding requiring blood              1 (0.3%)     Grade II
transfusion, extravasation

Gross hematuria                       3 (0.9%)     Grade I

Gross hematuria, bleeding             1 (0.3%)     Grade II
requiring blood transfusion

Transient low-grade fever, gross      1 (0.3%)     Grade II
hematuria, bleeding requiring
blood transfusion

Transient low-grade fever,            1 (0.3%)     Grade II
bleeding requiring blood
transfusion, urinary leakage

Gross hematuria, bladder              1 (0.3%)     Grade III
retention with blood clot,
bleeding requiring blood
transfusion

Gross hematuria, bladder              1 (0.3%)     Grade III
retention with blood clot,
bleeding requiring blood
transfusion

Delayed gross hematuria, bleeding     2 (0.6%)     Grade II
requiring blood transfusion

Delayed gross hematuria, bladder      1 (0.3%)     Grade III
retention with blood clot,
ureteral obstruction with clot

Delayed recurrent gross               1 (0.3%)     Grade III
hematuria, bladder retention with
blood clot, bleeding requiring
blood transfusion, interlobar
artery pseudoaneurism of lower
pole of kidney

Gross hematuria, bladder              1 (0.3%)     Grade III
retention with blood clot,
bleeding requiring blood
transfusion, retroperitoneal
hematoma and renal vein
thrombosis

Perinephric hematoma, bleeding        1 (0.3%)     Grade II
requiring blood transfusion

Extravasation, delayed gross          1 (0.3%)     Grade IV
hematuria, bladder retention with
blood clot and organized hematoma
formation, ureteral obstruction
with clot, bleeding requiring
blood transfusion, impaired renal
function (serum creatinine 9.5
mg/dL)

Colon injury, hemoperitoneoum and     1 (0.3%)     Grade V
bleeding requiring blood
transfusion leading to acute
renal failure and death

Type of complication                             Management

Transient low-grade fever            Conservative management

Bleeding requiring blood             Blood transfusion
transfusion

Transient low-grade fever and        Conservative management for
bleeding requiring blood             fever, blood transfusion
transfusion

Extravasation                        WW and conservative management

Bleeding requiring blood             Blood transfusion, WW and
transfusion, extravasation           conservative management for
                                     extravasation

Gross hematuria                      WW and conservative management

Gross hematuria, bleeding            WW and conservative management
requiring blood transfusion          for hematuria, blood transfusion

Transient low-grade fever, gross     Conservative management for
hematuria, bleeding requiring        fever, WW and conservative
blood transfusion                    management for hematuria, blood
                                     transfusion

Transient low-grade fever,           Blood transfusion, conservative
bleeding requiring blood             management for fever, WW and
transfusion, urinary leakage         conservative management for
                                     urinary leakage

Gross hematuria, bladder             WW and conservative management
retention with blood clot,           for hematuria, bladder
bleeding requiring blood             catheterization and multiple
transfusion                          washouts/irrigations and removal
                                     of clots, blood transfusion

Gross hematuria, bladder             WW and conservative management
retention with blood clot,           for hematuria, bladder
bleeding requiring blood             catheterization and multiple
transfusion                          washouts/irrigations and removal
                                     of clots, blood transfusion,
                                     angiography

Delayed gross hematuria, bleeding    Watchful waiting and conservative
requiring blood transfusion          management for hematuria, blood
                                     transfusion

Delayed gross hematuria, bladder     WW and conservative management
retention with blood clot,           for hematuria, bladder
ureteral obstruction with clot       catheterization and multiple
                                     washouts-irrigations and removal
                                     of clots, cystoscopy and ureteric
                                     double-J stent insertion

Delayed recurrent gross              Conservative management for
hematuria, bladder retention with    hematuria, bladder
blood clot, bleeding requiring       catheterization and multiple
blood transfusion, interlobar        washouts/irrigations and removal
artery pseudoaneurism of lower       of clots, blood transfusion,
pole of kidney                       angiography and coil
                                     angioembolization

Gross hematuria, bladder             Bladder catheterization and
retention with blood clot,           multiple washouts-irrigations and
bleeding requiring blood             removal of clots, blood
transfusion, retroperitoneal         transfusion, cystoscopy and
hematoma and renal vein              ureteric double-J stent
thrombosis                           insertion, WW and conservative
                                     management for hematuria and
                                     hematoma and renal vein
                                     thrombosis

Perinephric hematoma, bleeding       WW and conservative management
requiring blood transfusion          for hematoma, blood transfusion

Extravasation, delayed gross         WW and conservative management
hematuria, bladder retention with    for extravasation and hematuria,
blood clot and organized hematoma    bladder catheterization and
formation, ureteral obstruction      multiple washouts/irrigations and
with clot, bleeding requiring        removal of clots and organized
blood transfusion, impaired renal    hematoma, cystoscopy and ureteric
function (serum creatinine 9.5       double-J stent insertion, blood
mg/dL)                               transfusion, hemodialysis

Colon injury, hemoperitoneoum and    Nephrectomy, blood transfusion,
bleeding requiring blood             IV fluid and antibiotics, ICU
transfusion leading to acute         management
renal failure and death

MCC: modified Clavien classification; PCNL: percutaneous
nephrolithotomy; WW: watchful waiting; IV: intravenous; ICU:
intensive care unit.

Table 4. Patient-, stone-and operation-related parameters and
modified Clavien grading of complications

Parameter                                             Grade 0

Mean age (SE, range), year                     49.64 [+ or -] 12.79
                                                   (0.80, 16-78)

Age grouping, years, n          15-44               88 (77.2%)
(%)
                                45-59               112 (80.6%)

                            [greater than           65 (84.4%)
                           or equal to] 60

Gender, n (%)                   Male                155 (84.2%)

                               Female               110 (75.3%)

Mean BMI (SE, range), kg/[m.sup.2]              28.14 [+ or -] 4.93
                                                (0.31, 15.88-46.71)

BMI grouping, n (%)            <25 kg/              78 (83.0%)
                              [m.sup.2]

                               25-29.9              97 (75.8%)
                            kg/ [m.sup.2]

                            [greater than           90 (83.3%)
                           or equal to] 30
                            kg/[m.sup.2]
                               (obese)

Mean preoperative hemoglobin (SE, range),       13.49 [+ or -] 1.51
g/dL                                             (0.09, 9.6-18.0)

Hypertension, n (%)              Yes                89 (80.2%)

                                 No                 176 (80.4%)

DM, n (%)                        Yes                54 (84.4%)

                                 No                 211 (79.3%)

IHD, n (%)                       Yes                20 (80.0%)

                                 No                 245 (80.3%)

Renal dysfunction                Yes                18 (66.7%)
(serum Cr >1.4 mg/dL, n
(%)                              No                 247 (81.5%)

Anatomic upper urinary           Yes                 3 (37.5%)
tract abnormality, n (%)
                                 No                 262 (81.4%)

Preoperative UTI, n (%)          Yes                82 (82.8%)
                                                    183 (79.2%)

Previous stone surgery,          Yes                69 (77.5%)
n (%)
                                 No                 196 (81.3%)

Previous ESWL, n (%)             Yes                113 (81.3%)

                                 No                 152 (79.6%)

Stone number, n (%)            Single               72 (82.8%)
                                                    193 (79.4%)

Mean stone burden (SE, range), mm              34.97 [+ or -] 17.26
                                                  (1.06, 10-200)

Stone opacity, n (%)        Radio-opaque            229 (80.3%)

                             Radiolucent            36 (80.0%)

Stone location, n (%)         One calyx             55 (77.5%)

                               Pelvis               46 (83.6%)

                            Upper ureter             7 (87.5%)

                              Multiple              130 (79.8%)
                              locations

                              Staghorn              27 (81.8%)

Staghorn stone, n (%)            Yes                27 (81.8%)

                                 No                 238 (80.1%)

Complex stones, n (%)            Yes                157 (80.1%)

                                 No                 108 (80.6%)

Hydronephrosis, n (%)         Moderate              171 (88.1%)
                              or severe
                            (significant)
                             Nil or Mild            94 (69.1%)

Type of anesthesia, n          General              256 (80.0%)
(%)
                               Spinal                9 (90.0%)

Kidney side, n (%)              Right               136 (80.0%)

                                Left                129 (80.7%)

Imaging for access, n        Fluoroscopy            238 (79.1%)
(%)
                           Ultrasonography          27 (93.1%)

                             Upper calyx            16 (76.2%)
                                group

Calyx for access, n (%)     Middle calyx            64 (83.1%)
                                group

                             Lower calyx            179 (81.7%)
                                group

                              Multiple               6 (46.1%)
                            calices group

Number of tract, n (%)      Single tract            247 (82.3%)
                           Multiple tracts          18 (60.0%)

Nephrostomy tube           Yes (standard)           17 (73.9%)
insertion, n (%)            No (tubeless)           248 (80.8%)

Mean operative time (SE, range), minute        56.37 [+ or -] 29.80
                                                  (1.89, 10-195)

Mean postoperative hemoglobin                   12.49 [+ or -] 1.60
(SE, range), g/dL                                (0.10, 8.1-16.4)

Mean postoperative hemoglobin drop              1.02 [+ or -] 1.04
(SE, range), g/dL                                 (0.06, 0.0-7.5)

Stone-free result, n (%)     Stone-free             211 (83.1%)

                              Residual              54 (71.1%)
                              fragments

Parameter                                             Grade I

Mean age (SE, range), year                     45.43 [+ or -] 10.42
                                                   (2.27, 26-66)

Age grouping, years, n          15-44                9 (7.9%)
(%)
                                45-59                11 (7.9%)

                            [greater than            1 (1.3%)
                           or equal to] 60

Gender, n (%)                   Male                 11 (6.0%)

                               Female                10 (6.8%)

Mean BMI (SE, range), kg/[m.sup.2]              27.15 [+ or -] 3.70
                                                (0.81, 20.95-36.99)

BMI grouping, n (%)            <25 kg/               6 (6.4%)
                              [m.sup.2]

                               25-29.9               10 (7.8%)
                            kg/ [m.sup.2]

                            [greater than            5 (4.6%)
                           or equal to] 30
                            kg/[m.sup.2]
                               (obese)

Mean preoperative hemoglobin (SE, range),        13.71[+ or -]2.18
g/dL                                             (0.47, 9.1-19.1)

Hypertension, n (%)              Yes                 7 (6.3%)

                                 No                  14 (6.4%)

DM, n (%)                        Yes                 4 (6.2%)

                                 No                  17 (6.4%)

IHD, n (%)                       Yes                 1 (4.0%)

                                 No                  20 (6.6%)

Renal dysfunction                Yes                 5 (18.5%)
(serum Cr >1.4 mg/dL, n
(%)                              No                  16 (5.3%)

Anatomic upper urinary           Yes                 2 (25.0%)
tract abnormality, n (%)
                                 No                  19 (5.9%)

Preoperative UTI, n (%)          Yes                10 (10.1%)
                                                     11 (4.8%)

Previous stone surgery,          Yes                 6 (6.7%)
n (%)
                                 No                  15 (6.2%)

Previous ESWL, n (%)             Yes                 10 (7.2%)

                                 No                  11 (5.7%)

Stone number, n (%)            Single                4 (4.6%)
                                                     17 (7.0%)

Mean stone burden (SE, range), mm              33.90 [+ or -] 16.86
                                                   (3.68, 20-78)

Stone opacity, n (%)        Radio-opaque             17 (6.0%)

                             Radiolucent             4 (8.9%)

Stone location, n (%)         One calyx              5 (7.0%)

                               Pelvis                6 (10.9%)

                            Upper ureter             0 (0.0%)

                              Multiple               9 (5.5%)
                              locations

                              Staghorn               1 (3.0%)

Staghorn stone, n (%)            Yes                 1 (3.0%)

                                 No                  20 (6.7%)

Complex stones, n (%)            Yes                 10 (5.1%)

                                 No                  11 (8.2%)

Hydronephrosis, n (%)         Moderate               11 (5.7%)
                              or severe
                            (significant)
                             Nil or Mild             10 (7.3%)

Type of anesthesia, n          General               20 (6.2%)
(%)
                               Spinal                1 (10.0%)

Kidney side, n (%)              Right                12 (7.0%)

                                Left                 9 (5.6%)

Imaging for access, n        Fluoroscopy             19 (6.3%)
(%)
                           Ultrasonography           2 (6.9%)

                             Upper calyx             1 (4.8%)
                                group

Calyx for access, n (%)     Middle calyx             5 (6.5%)
                                group

                             Lower calyx             12 (5.5%)
                                group

                              Multiple               3 (23.1%)
                            calices group

Number of tract, n (%)      Single tract             17 (5.7%)
                           Multiple tracts           4 (13.3%)

Nephrostomy tube           Yes (standard)            1 (4.4%)
insertion, n (%)            No (tubeless)            20 (6.5%)

Mean operative time (SE, range), minute        61.39 [+ or -] 32.30
                                                  (7.61, 15-120)

Mean postoperative hemoglobin                   12.61 [+ or -] 1.95
(SE, range), g/dL                                (0.42, 9.0-16.5)

Mean postoperative hemoglobin drop              1.13 [+ or -] 1.06
(SE, range), g/dL                                 (0.23, 0.0-3.1)

Stone-free result, n (%)     Stone-free              13 (5.1%)

                              Residual               8 (10.5%)
                              fragments

Parameter                                            Grade II

Mean age (SE, range), year                     49.05 [+ or -] 12.21
                                                   (2.01, 26-75)

Age grouping, years, n          15-44               15 (13.2%)
(%)
                                45-59               15 (10.8%)

                            [greater than            7 (9.1%)
                           or equal to] 60

Gender, n (%)                   Male                 14 (7.6%)

                               Female               23 (15.8%)

Mean BMI (SE, range), kg/[m.sup.2]              27.29 [+ or -] 4.49
                                                (0.76, 18.60-37.11)

BMI grouping, n (%)            <25 kg/              10 (10.6%)
                              [m.sup.2]

                               25-29.9              16 (12.5%)
                            kg/[m.sup.2]

                            [greater than           11 (10.2%)
                           or equal to] 30
                            kg/[m.sup.2]
                               (obese)

Mean preoperative hemoglobin (SE, range),       12.39 [+ or -] 1.79
g/dL                                             (0.30, 9.2-16.5)

Hypertension, n (%)              Yes                 10 (9.0%)

                                 No                 27 (12.3%)

DM, n (%)                        Yes                 5 (7.8%)

                                 No                 32 (12.0%)

IHD, n (%)                       Yes                 1 (4.0%)

                                 No                 36 (11.8%)

Renal dysfunction                Yes                 4 (14.8%)

(serum Cr >1.4 mg/dL, n          No                 33 (10.9%)
(%)

Anatomic upper urinary           Yes                 1 (12.5%)
tract abnormality, n (%)
                                 No                 36 (11.2%)

Preoperative UTI, n (%)          Yes                 3 (3.0%)
                                                    34 (14.7%)

Previous stone surgery,          Yes                11 (12.4%)
n (%)
                                 No                 26 (10.8%)

Previous ESWL, n (%)             Yes                 13 (9.3%)

                                 No                 24 (12.6%)

Stone number, n (%)            Single                9 (10.3%)
                                                    28 (11.5%)

Mean stone burden (SE, range), mm              37.10 [+ or -] 16.84
                                                   (2.85, 12-85)

Stone opacity, n (%)        Radio-opaque            32 (11.2%)

                             Radiolucent             5 (11.1%)

Stone location, n (%)         One calyx              9 (12.7%)

                               Pelvis                3 (5.5%)

                            Upper ureter             0 (0.0%)

                              Multiple              20 (12.3%)
                              locations

                              Staghorn               5 (15.2%)

Staghorn stone, n (%)            Yes                 5 (15.2%)

                                 No                 32 (10.8%)

Complex stones, n (%)            Yes                25 (12.8%)

                                 No                  12 (9.0%)

Hydronephrosis, n (%)         Moderate               7 (3.6%)
                              or severe
                            (significant)
                             Nil or Mild            30 (22.1%)

Type of anesthesia, n          General              37 (11.6%)
(%)
                               Spinal                0 (0.0%)

Kidney side, n (%)              Right               20 (11.8%)

                                Left                17 (10.6%)

Imaging for access, n        Fluoroscopy            37 (12.3%)
(%)
                           Ultrasonography           0 (0.0%)

                             Upper calyx             4 (19.0%)
                                group

Calyx for access, n (%)     Middle calyx             6 (7.8%)
                                group

                             Lower calyx            24 (11.0%)
                                group

                              Multiple               3 (23.1%)
                            calices group

Number of tract, n (%)      Single tract            30 (10.0%)
                           Multiple tracts           7 (23.4%)

Nephrostomy tube           Yes (standard)            5 (21.7%)
insertion, n (%)            No (tubeless)           32 (10.4%)

Mean operative time (SE, range), minute        62.41 [+ or -] 21.04
                                                  (3.61, 20-110)

Mean postoperative hemoglobin                   9.47 [+ or -] 1.33
(SE, range), g/dL                                (0.22, 7.0-13.7)

Mean postoperative hemoglobin drop              2.92 [+ or -] 1.72
(SE, range), g/dL                                 (0.29, 0.0-6.7)

Stone-free result, n (%)     Stone-free              23 (9.0%)

                              Residual              14 (18.4%)
                              fragments

                                              Grade [greater than or
Parameter                                          equal to] III

Mean age (SE, range), year                     53.29 [+ or -] 14.76
                                                   (5.58, 27-70)

Age grouping, years, n          15-44                2 (1.7%)
(%)
                                45-59                1 (0.7%)

                            [greater than            4 (5.2%)
                           or equal to] 60

Gender, n (%)                   Male                 4 (2.2%)

                               Female                3 (2.1%)

Mean BMI (SE, range), kg/[m.sup.2]              30.63 [+ or -] 2.85
                                                (1.16, 28.34-36.20)

BMI grouping, n (%)            <25 kg/               0 (0.0%)
                              [m.sup.2]

                               25-29.9               5 (3.9%)
                            kg/ [m.sup.2]

                            [greater than            2 (1.9%)
                           or equal to] 30
                            kg/[m.sup.2]
                               (obese)

Mean preoperative hemoglobin (SE, range),       13.55 [+ or -] 1.92
g/dL                                             (0.78, 10.0-15.4)

Hypertension, n (%)              Yes                 5 (4.5%)

                                 No                  2 (0.9%)

DM, n (%)                        Yes                 1 (1.6%)

                                 No                  6 (2.3%)

IHD, n (%)                       Yes                 3 (12.0%)

                                 No                  4 (1.3%)

Renal dysfunction                Yes                 0 (0.0%)
(serum Cr >1.4 mg/dL, n
(%)                              No                  7 (2.3%)

Anatomic upper urinary           Yes                 2 (25.0%)
tract abnormality, n (%)
                                 No                  5 (1.5%)

Preoperative UTI, n (%)          Yes                 4 (4.1%)
                                                     3 (1.3%)

Previous stone surgery,          Yes                 3 (3.4%)
n (%)
                                 No                  4 (1.7%)

Previous ESWL, n (%)             Yes                 3 (2.2%)

                                 No                  4 (2.1%)

Stone number, n (%)            Single                2 (2.3%)
                                                     5 (2.1%)

Mean stone burden (SE, range), mm              34.14 [+ or -] 15.24
                                                   (5.76, 17-61)

Stone opacity, n (%)        Radio-opaque             7 (2.5%)

                             Radiolucent             0 (0.0%)

Stone location, n (%)         One calyx              2 (2.8%)

                               Pelvis                0 (0.0%)

                            Upper ureter             1 (12.5%)

                              Multiple               4 (2.4%)
                              locations

                              Staghorn               0 (0.0%)

Staghorn stone, n (%)            Yes                 0 (0.0%)

                                 No                  7 (2.4%)

Complex stones, n (%)            Yes                 4 (2.0%)

                                 No                  3 (2.2%)

Hydronephrosis, n (%)         Moderate               5 (2.6%)
                              or severe
                            (significant)
                             Nil or Mild             2 (1.5%)

Type of anesthesia, n          General               7 (2.2%)
(%)
                               Spinal                0 (0.0%)

Kidney side, n (%)              Right                2 (1.2%)

                                Left                 5 (3.1%)

Imaging for access, n        Fluoroscopy             7 (2.3%)
(%)
                           Ultrasonography           0 (0.0%)

                             Upper calyx             0 (0.0%)
                                group

Calyx for access, n (%)     Middle calyx             2 (2.6%)
                                group

                             Lower calyx             4 (1.8%)
                                group

                              Multiple               1 (7.7%)
                            calices group

Number of tract, n (%)      Single tract             6 (2.0%)
                           Multiple tracts           1 (3.3%)

Nephrostomy tube           Yes (standard)            0 (0.0%)
insertion, n (%)            No (tubeless)            7 (2.3%)

Mean operative time (SE, range), minute        47.50 [+ or -] 18.64
                                                   (7.61, 20-75)

Mean postoperative hemoglobin                   11.00 [+ or -] 2.36
(SE, range), g/dL                                (0.96, 8.0-14.0)

Mean postoperative hemoglobin drop              2.55 [+ or -] 2.74
(SE, range), g/dL                                 (1.12, 0.0-7.4)

Stone-free result, n (%)     Stone-free              7 (2.8%)

                              Residual               0 (0.0%)
                              fragments

Parameter                                             p value

Mean age (SE, range), year                       0.471 ([dagger])

Age grouping, years, n          15-44            0.582 ([section])
(%)
                                45-59

                            [greater than
                           or equal to] 60

Gender, n (%)                   Male          0.040 ([double dagger])

                               Female

Mean BMI (SE, range), kg/[m.sup.2]               0.476 ([dagger])

BMI grouping, n (%)            <25 kg/           0.238 ([section])
                              [m.sup.2]

                               25-29.9
                            kg/ [m.sup.2]

                            [greater than
                           or equal to] 30
                            kg/[m.sup.2]
                               (obese)

Mean preoperative hemoglobin (SE, range),        0.015 ([dagger])
g/dL

Hypertension, n (%)              Yes          0.883 ([double dagger])

                                 No

DM, n (%)                        Yes          0.339 ([double dagger])

                                 No

IHD, n (%)                       Yes          0.790 ([double dagger])

                                 No

Renal dysfunction                Yes          0.111 ([double dagger])
(serum Cr >1.4 mg/dL, n
(%)                              No

Anatomic upper urinary           Yes          0.002 ([double dagger])
tract abnormality, n (%)
                                 No

Preoperative UTI, n (%)          Yes          0.368 ([double dagger])

Previous stone surgery,          Yes          0.410 ([double dagger])

n (%)                            No

Previous ESWL, n (%)             Yes          0.650 ([double dagger])

                                 No

Stone number, n (%)            Single         0.546 ([double dagger])

Mean stone burden (SE, range), mm                0.846 ([dagger])

Stone opacity, n (%)        Radio-opaque      0.941 ([double dagger])

                             Radiolucent

Stone location, n (%)         One calyx          0.860 ([section])

                               Pelvis

                            Upper ureter

                              Multiple
                              locations

                              Staghorn

Staghorn stone, n (%)            Yes          0.847 ([double dagger])

                                 No

Complex stones, n (%)            Yes          0.818 ([double dagger])

                                 No

Hydronephrosis, n (%)         Moderate       <0.0001 ([double dagger])
                              or severe
                            (significant)
                             Nil or Mild

Type of anesthesia, n          General        0.377 ([double dagger])
(%)
                               Spinal

Kidney side, n (%)              Right         0.975 ([double dagger])

                                Left

Imaging for access, n        Fluoroscopy      0.054 ([double dagger])
(%)
                           Ultrasonography

                             Upper calyx
                                group

Calyx for access, n (%)     Middle calyx         0.019 ([section])
                                group

                             Lower calyx
                                group

                              Multiple
                            calices group

Number of tract, n (%)      Single tract      0.004 ([double dagger])
                           Multiple tracts

Nephrostomy tube           Yes (standard)     0.404 ([double dagger])
insertion, n (%)            No (tubeless)

Mean operative time (SE, range), minute          0.124 ([dagger])

Mean postoperative hemoglobin                   <0.0001 ([dagger])
(SE, range), g/dL

Mean postoperative hemoglobin drop              <0.0001 ([dagger])
(SE, range), g/dL

Stone-free result, n (%)     Stone-free       0.032 ([double dagger])

                              Residual
                              fragments

SE: standard error of the mean; BMI: body mass index; DM: diabetes
mellitus; IHD: ischemic heart disease; UTI: urinary tract infection;
ESWL: extracorporeal shock wave lithotripsy; ([dagger]) Spearman
test; ([double dagger]) Mann-Whitney test;  ([section]) Kruskal-Wallis
test.

Table 5. Factors affecting modified Clavien grading of complications
in multivariate analysis

Parameter                                   Estimate    SE     p value

Postoperative hemoglobin                     -0.444    0.106   <0.0001

Postoperative hemoglobin drop                0.448     0.124   <0.0001

Renal dysfunction                   No       -1.125    0.504    0.026
                                   Yes         0

Anatomic upper urinary tract        No       -3.085    0.734   <0.0001
abnormality                        Yes         0

Significant (moderate-severe)       No       0.841     0.331    0.011
hydronephrosis                     Yes         0

Number of tract                   Single     -0.999    0.471    0.034
                                 Multiple      0

Parameter                                    OR    95% CI of OR

Postoperative hemoglobin                    0.64    0.52-0.79

Postoperative hemoglobin drop               1.57    1.23-2.00

Renal dysfunction                   No      0.32    0.12-0.87
                                   Yes

Anatomic upper urinary tract        No      0.05    0.01-0.19
abnormality                        Yes

Significant (moderate-severe)       No      2.32    1.21-4.43
hydronephrosis                     Yes

Number of tract                   Single    0.37    0.15-0.93
                                 Multiple

SE: standard error of the mean; OR: odds ratio; CI: confidence interval.
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Title Annotation:ORIGINAL RESEARCH
Author:Falahatkar, Siavash; Moghaddam, Keivan Gholamjani; Kazemnezhad, Ehsan; Farzan, Alireza; Aval, Hamidr
Publication:Canadian Urological Association Journal (CUAJ)
Article Type:Report
Date:Feb 1, 2015
Words:8546
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