










































This is an open access article under the terms of a license that permits non-commercial use, provided the original work is properly cited.  
© 2021 The Authors. Société Internationale d'Urologie Journal, published by the Société Internationale d'Urologie, Canada.

Predictors for Retrograde Ureteral Stenting  
Failure as an Initial Drainage Method for  
Emergent Complicated Acute Calculus  
Obstructive Uropathy
M. A. Elbaset, Mohamed Edwan, Rasha T. Abouelkheir, Rawdy Ashour, Mohamed Ramez,  
Abdalla Abdelhamid, Yasser Osman

Urology and Nephrology Center, Mansoura University, Egypt

Abstract

Objective To define predictors for initial retrograde ureteral stenting (RUS) failure with the need for the 
percutaneous nephrostomy (PCN) insertion as a drainage method in patients with complicated acute calculus 
obstructive uropathy.

Methods We undertook a retrospective evaluation of patients who presented with complicated obstructive calculus 
uropathy (acute renal failure or obstructive pyelonephritis) between January 2016 and January 2020. Patients in whom 
there was failure to visualize ipsilateral ureteric orifice and those with extrinsic ureteral obstruction were excluded. 
Patient demographics and radiological data including stone site, hydronephrosis grade, maximum transverse stone 
diameter, periureteral density (PUD) and pericalcular ureteric thickness (P-CUT) at the maximum transverse stone 
diameter were assessed using non-contrast computed tomography at the time of admission.

Results The study included 256 patients who were managed initially by RUS trial. Of them, 48 (18.8 %) had RUS 
failure. The presence of acute pyelonephritis, increased maximum transverse stone diameter ≥ 9.5 mm, P-CUT ≥ 
7.5 mm, and PUD at stone level ≥ 17.5 HU were risk factors associated with RUS failure (P = 0.007, 0.002, < 0.001,  
and < 0.001, respectively).

Conclusion Initial radiological stone and ureteric characteristics, in addition to the clinical diagnosis of obstructive 
pyelonephritis, can be used to determine PCN insertion as the preferred option over RUS for urinary drainage.

Introduction

Intrinsic calculus obstructive uropathy is one of the most commonly encountered conditions in daily urological 
practice. In this situation, urgent temporary drainage of the urinary tract is indispensable, especially in the presence 
of infection also with infection or higher serum creatinine[1]. In this situation, retrograde ureteral stenting (RUS), 
percutaneous nephrostomy (PCN) placement, or percutaneous placement of a JJ stent are considered viable options 
for urinary system drainage [2-4].

This is an open access article under the terms of a license that permits non-commercial use, provided the original work is properly cited.  
© 2021 The Authors. Société Internationale d'Urologie Journal, published by the Société Internationale d'Urologie, Canada.

Key Words Competing Interests Article Information

Retrograde stenting, ureteral wall density, 
percutaneous nephrostomy, pyelonephritis, 
ureteral wall thickness, obstructive uropathy, 
stone, JJ stent

None declared. Received on February 10, 2021 
Accepted on May 1, 2021 
Soc Int Urol J.2021;2(4):229–238

DOI: 10.48083/OZUL6913

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Abbreviations 
PCN percutaneous nephrostomy
P-CUT pericalcular ureteric thickness
PUD periureteral density
RUS retrograde ureteral stenting
URS ureteroscopy

PCN insertion and RUS have been shown to achieve 
comparable success rates in patients with obstructive 
urolithiasis. Nonetheless, rates of sepsis, hospital stay, 
radiation exposure, and increased costs were higher 
in patients who were managed by PCN insertion[5,6]. 
Likewise, failure of the retrograde approach for the 
urinary system might increase the risk of ureteral 
bleeding, perforation, and stricture formation. There 
is little evidence to suggest that either RUS or PCN is 
a better choice as a primary treatment in complicated 
acute calculus obstruction[7].

Both radiologists and urologists have indicated that 
the choice of drainage method is largely inf luenced 
by personal assessment and stone size[8-10]. In most 
studies, the larger the stone size, the more likely it was 
that PCN was chosen as a drainage method. Other 
factors, including institutional burden and clinician 
familiarity with the procedure can direct treatment, and 
there are no universally applied rules for making the 
choice[11]. In a previous study, the presence of extrinsic 
obstruction and a higher degree of hydronephrosis were 
associated with increased risk for RUS failure. Inclusion 

of heterogeneous intrinsic causes of obstruction in 
addition to extrinsic causes was a limitation of this 
study[12].

We aimed to define a precise objective model to select 
the optimal way to decompress the urinary system 
obstruction by urolithiasis exclusively. The primary 
outcome was to define the predictors for initial RUS 
trial failure in acute complicated calculus obstructive 
uropathy. The secondary outcome was to delineate 
the short- and long-term clinical outcomes post initial 
drainage.

Materials and Methods 
Subjects 
After institutional review board approval, we undertook 
a retrospective evaluation of patients who presented 
with acute calculus obstructive uropathy complicated 
with acute renal failure or obstructive pyelonephritis 
in a single center between January 2016 and January 
2020. Patients were excluded if there was failure to 
visualize ipsilateral ureteric orifice at the time of RUS or 
if they had multiple obstructing stones, renal infection  
(eg, emphysematous pyelonephritis), previous history 
of urinary diversion or renal transplants, extrinsic 
ureteral obstruction, or causes of obstruction other than 
urolithiasis.

Patient demographics and laboratory investigations 
were collected, including age, gender, body mass index, 
clinical presentation, medical and surgical history, 
previous history of ipsilateral stone passage, definitive 

FIGURE 1.

Radiological measurements for P-CUT and PUD at and below the stone level

An impacted lumbar ureteral calculus is 
demonstrated in axial section. The maximum 
transverse stone diameter (4.85 mm) is subtracted 
from the overall ureteral width (13.4 mm) at this 
same level to get the P-CUT (8.55 mm). 

An elliptical region of interest is drawn over  
the ureter at the level of the calculus (PUD at  
the level of maximum transverse stone  
diameter) is 35.4 HU.

Another region of interest is drawn over 
the ureter distal to the calculus. (9.4 HU). 
Average Hounsfield Unit density is 
calculated by the imaging software. Care is 
taken not to include the retroperitoneal fat 
or calculus in the region of interest.

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TABLE 1. 

Univariate analysis for RUS failure in acute emergent calcular obstruction 

Variable 
Failed RUS 

(n=48)
Successful RUS 

(n=208)
P -value 

Age in years (mean±SD)* 60.3±15.6 57.3±15.2 0.2

Gender, n (%)**

• Male 27 (56.3) 122 (58.7)

• Female 21 (43.7) 86 (41.3) 0.4

Presenting symptoms, n (%)**

• Obstructive pyelonephritis 33 (68.8) 72 (34.6)

• Acute renal failure 15 (31.2) 136 (65.4) 0.005

Duration of symptoms before initial drainage in days***  
(median & range) 

7 (3-30) 5 (1-21) 0.1

Medical history, n (%)**

• Irrelevant 17(35.4) 32(15.4)

• Diabetes mellitus 13 (27.1) 82 (39.4) 0.2

• Hypertension 18 (37.5) 94 (45.2)

* Independent sample t-test **chi-square test ***Mann-Whitney test

intervention, and ureteral stenting post definitive 
intervention, hospital stay, and serum creatinine and 
leucocytic count at admission.

Radiologica l parameters were collected using 
preoperative non-contrast computed tomography 
(120 kV and 100 mA, slice thickness was 5 mm with a 
2 mm overlap using a 64-multislice helical CT scanner 
[Brilliance, Philips, The Netherlands]), eg, average 
stone density in Hounsfield unit (HU), laterality, site 
of the stones (proximal, iliac, or pelvic according to 
the location to the sacroiliac joints), and degree of 
hydronephrosis (lower and higher grade)[13,14] were 
analyzed. Also, maximum transverse stone diameter 
in mm was calculated on axial images (Figure 1). Peri-
ureteral density (PUD) in HU was measured below 
the stone level and at the stone level at its maximum 
transverse diameter[15]. The pericalcular ureteric 
thick ness (P-CUT) was measured as the widest 
transverse measurement of the ureter involving the stone 
and the corresponding maximum transverse diameter 
of the stone at this level. P-CUT was then calculated 
by subtracting the stone width from the overall stone 
and ureteral width[16] (Figure 1). Radiological data 
were interpreted by 2 expert radiologists (> 10 years’ 
experience) blinded to the study objectives.

Methods
Trial RUS was performed under fluoroscopic guidance 
by urology senior residents under the supervision of the 
consultant in charge. With the patient in the lithotomy 
position, a Terumo hydrophilic guidewire was gently 
introduced into the collecting system, using a 22 Fr 
cystoscopy sheath and 30° telescope, and was followed 
by the introduction of a 6 Fr open tip catheter (minimal 
amount of contrast could be injected to ensure the 
correct position inside the pelvicalyceal system). A 6 
Fr JJ stent was later introduced over a PTFE straight 
guidewire. If the RUS trial failed, patients were referred 
for ultrasound-guided PCN placement, using Xario 
100 system (Toshiba Medical System Corp., Tokyo, 
Japan) ultrasound scanner, with the patient in the 
prone position. A 12 or 14 Fr pigtail nephrostomy tube 
was placed over the guidewire inside the pelvicalyceal 
system. Contrast was instilled via the PCN to confirm its 
location in the renal pelvis.

After initial drainage, alpha-blockers were given 
in case of stones ≤ 10 mm to promote spontaneous 
expulsion. Patients were selected for definitive treatment 
according to European Association of Urology and 
American Urological Association guidelines[2,3].  
A ureteral stent post definitive intervention was inserted 

continued on page 232

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TABLE 1. 

Univariate analysis for RUS failure in acute emergent calcular obstruction 

Variable 
Failed RUS 

(n=48)
Successful RUS 

(n=208)
P -value 

ASA score, n (%)**

• I 28 (58.3) 110 (52.9)

• II 20 (41.7) 96 (46.2) 0.4

• III 0 2 (0.9)

Hx of previous stone passage, n (%)**

• Yes 17 (35.4) 128 (61.5) 0.4

• No 31 (64.6) 80 (38.5)

Past surgical history on the same side, n (%)**

• Irrelevant 34 (70.8) 132 (63.5)

• PNL 5 (10.4) 14 (6.7)

• SWL 1 (2.1) 20 (9.6) 0.1

• URS 5 (10.4) 20 (9.6)

• Previous JJ stenting 3 (6.3) 22 (10.6)

BMI (Kg/m2) (mean ± SD)* 27.4±6.7 28.8 ±6.9 0.8

Serum creatinine mg/dl  (median & range )*** 1.8 (1-13.1) 2.4 (0.7-18) 0.07

WBCS at admission x 103 (mean ± SD)* 17.2 ± 6.5 14.1 ± 7 0.2

Side, n (%) **

• Right 25 (52.1) 118 (56.7) 0.4

• Left 23 (47.9) 90 (43.3)

Stone location, n (%)**

• Proximal 30 (62.5) 118 (56.7)

• Mid-ureter 11 (22.9) 40 (19.2) 0.3

• Distal 7 (14.6) 50 (24.1)

Degree of hydronephrosis, n (%)**

• Low grade 17 (35.4) 158 (76)

• High grade 31 (64.6) 50 (24) <0.001

Maximum  transverse stone diameter in mm (mean ± SD)* 10.6 ± 3.5 7.9 ± 2.7 <0.001

Average stone HU (median &range)*** 915 (580-1461) 825 (162-1517) 0.2

P-CUT at maximum transverse stone diameter in mm  
(mean ± SD)*

13.5 ± 6 5.5 ± 2.6 <0.001

PUD at maximum transverse stone diameter in HU  
(mean ± SD)*

26 ± 7.9 14.2 ± 6.9 <0.001

PUD below the stone level in HU  
(mean ± SD)*

21.6 ± 10.3 11.3 ± 5.9 <0.001

* Independent sample t-test **chi-square test ***Mann-Whitney test

, Cont’d

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in case of ureteral edema or presence of stone fragments, 
or to promote healing in case of ureteral injury[17].

Analysis
Patient demographics and laboratory and radiological 
data were compared using t he chi-square test, 
independent sample t-test, or Mann-Whitney test as 
appropriate. Univariate and multivariate analyses 
were performed to identify factors predicting RUS 
failure. Receiver operating characteristic (ROC) was 
used to identify the cut-off value for the best sensitivity 
and specificity for significant continuous variables in 
the univariate analysis. All statistical analyses were 
performed using SPSS version 21, and P < 0.05 was 
considered statistically significant.

Results
The study included 256 patients who presented with 
acute complicated calculus obstructive uropathy and 
were managed initially by RUS trial (Figure 2). Four 
patients were excluded because of failure to visualize 
ipsilateral ureteric orifice associated with obstructing 
stones located in sites in the ureter other than the pelvic 
ureter (2 in the lumbar ureter and others in the iliac 
ureter away from intramural ureter). Forty-eight patients 
(18.8 %) had RUS failure and then were managed by PCN 
insertion. The patient characteristics were illustrated in 
Table 1. 

In univariate analysis, acute pyelonephritis, higher 
maximum transverse stone diameter, the higher degree 
of hydronephrosis, increased P-CUT, and increased 
PUD below and at the stone level were predictors for 

initial RUS failure (Table 1). ROC curve was then 
calculated to identify the cut-off values associated with 
the best greatest sensitivity and specificity for significant 
continuous variables in univariate analysis (Figure 3).

In multivariate analysis, acute pyelonephritis, 
increased the maximum transverse stone diameter 
≥ 9.5 mm, P-CUT ≥7.5 mm, and PUD at stone level ≥ 17.5 

TABLE 2. 

Multivariate analysis for predictors of RUS failure 

Variable 
Multivariable logistic regression analysis

 OR (95% CI)    P -value

Presentation (obstructive pyelonephritis ) 2.9 (1.2–7.2) 0.007

Degree of hydronephrosis (high grade) 1.1 (0.3–6.1) 0.8

Maximum transverse stone diameter  ≥ 9.5 mm 2.1 (1.6–6.8) 0.002

P-CUT at the maximum transverse stone  diameter ≥ 7.5 mm 6.1 (2.4–15.6) <0.001

PUD at the maximum transverse stone  diameter ≥ 17.5 HU 12.8 (4.7–23.1) <0.001

PUD below the stone ≥ 19.5 HU 0.8 (0.3–2.1) 0.6

Failed RUS = 48 patients Successful RUS = 208 patients

Excluded = 46

• Failure to visualize ureteric 
 ori�ce associated with obstructing 
 stone (all stones were not located 
 at the pelvic ureter) = 4

• Multiple ureteric stones = 22

• Extrinsic obstruction = 20

Initial patients included = 302

FIGURE 2.

Flow chart of the study

233SIUJ.ORG SIUJ  •  Volume 2, Number 4  •  July 2021

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AUC: 0.67 

P-value: < 0.0001

Cut-off value:  19.5 HU (sensitivity 67% and 
specificity 73%)

AUC: 0.82

P-value: < 0.0001

Cut-off value:  9.5 mm (sensitivity 80% and 
specificity 75%)

AUC: 0.9

P-value: < 0.0001

Cut-off value:  17.5 HU (sensitivity 83% and 
specificity 85%)

AUC: 0.86 

P-value: < 0.0001

Cut-off value:  7.5 mm (sensitivity 81.5% and 
specificity 91%)

FIGURE 3.

ROC curve for RUS failure predictors

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HU were associated with increased the risk for RUS 
failure (P = 0.007, 0.002, <0.001, and <0.001, respectively)  
(Table 2).

The median (range) of the hospital stay between 
both groups was comparable at the time of temporary 
drainage (P = 0.4) (2[2 to 7] days in RUS failure versus 
2[2 to 10] in RUS success). Only one patient in each 
group required intensive care unit (ICU) admission due 
to urosepsis post the primary drainage, and both were 
subsequently discharged.

In the RUS failure group, ureteral stenting post 
definitive endourological procedures were required in 
23 patients (60.5%), and of these, 20 patients (52.6%) had 
prior RUS failure due to stone impaction and ureteral 
mucosal laceration. Of patients with successful RUS, 
8 (3.8%) passed the stone spontaneously (mean stone 
size was 5 ± 1.2 mm). Ureteral stenting post definitive 
intervention was required in only 35 patients (18.5%) 
because of stone impaction with a significant difference 
compared to patients with RUS failure (P < 0.0001) 
(Table 3).

At a median of 14 (6 to 32) months at follow-up, 3 
patients were admitted in the RUS failure group. One 
patient with recurrent stone on the same side and 

managed by semirigid URS with evidence of passable 
narrowing below the stone level. The other 2 patients 
were diagnosed with ureteric strictures; one was 
managed by open surgery and the other was managed by 
retrograde laser endoureterotomy).

Discussion
Stone disease concomitant with pyelonephritis or acute 
renal failure is a commonly encountered complication 
in urology. Using RUS, PCN insertion, or percutaneous 
placement of a JJ stent as temporary relief of the 
urinary tract obstruction is unavoidable[4,5]. In some 
situations, using the RUS approach may be associated 
with intraoperative complications such as the failure 
of t he procedure, retroperitonea l extravasation, 
abscess formation, and sepsis. Using the PCN as a 
primary drainage method could guard against these 
complications.

Opinions on the management of obstructive uropathy 
vary considerably. Urologists are prone to insert ureteral 
stents especially in patients with benign disease and in 
those with coagulopathy[11,18]. Studies have indicated 
that RUS is an efficient method for drainage in 80% 
to 100% of patients in comparison with 95% to 100% 

TABLE 3. 

Clinical outcome post RUS trial 

Variable 
RUS failure 

(n = 48)
RUS Success 

(n = 208)

Type of management post RUS trial, n (%)

• Ureteroscopy (semirigid or flexible ) 24 (50) 169 (82.6)

• Percutaneous nephrolithotomy (PNL) 14 (29.2) 20 (9.6)

• Shockwave lithotripsy (SWL) 7 (14.6) 11 (5.3)

• Open surgery 3 (6.3) 0

Duration between initial management and definitive treatment in days 30 (15–120) 20 (7–90)

Stone status at radiological follow-up, n (%)

• Static in previous place 48 (100) 135 (64.9)

• Pushed upwards 0 58 (27.9)

• Migrated downwards 0 7 (3.4)

• Passed spontaneously 0 8 (3.8)

Need for JJ stenting post definitive intervention, n (%) 23 (60.5) /38 58 (30.7) /189

• Passage of fragments (without evidence of edema and perforation) 3 (13) 23 (39.7)

• Mucosal laceration and stone impaction 5 (21.7) 1 (1.7)

• Stone impaction without laceration 15 (65.3) 34 (58.6)

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of patients managed by PCN placement in cases with 
urinary obstruction[6,12,19].

The preoperative physician preference was the main 
factor controlling the selection of diversion type in 
patients with obstructive uropathy. Only stone size, 
independent of other factors, is a reliable predictor 
of procedure chosen. The overall RUS failure rate in 
obstructive calculus uropathy complicated with sepsis 
was 2.3%[9]. In this study, patients who were selected 
for PCN insertion had a higher stone burden than 
those selected for RUS (10 [2 to 145] mm2 versus 7[2 to 
40] mm2). According to these data, we could elucidate 
the lower failure rate during the RUS trial. In another 
study, the mean stone size was 9.7 mm in patients who 
were selected for PCN placement versus 2.6 mm in 
patients managed by RUS. Additionally, the median 
surface area of the stone in patients selected for PCN 
placement was 92 mm2 versus 47 mm2 in patients 
managed by RUS[8,10].

The cut-off stone size that would indicate a high risk 
of RUS failure has yet to be determined. In our study, 
a maximum transverse stone diameter of 9.5 mm was 
associated with 2.1 times increased risk for RUS failure. 
The RUS failure rate in our study was identified as 
18.8%. In addition to the larger stone size in the RUS 
failure group, we also noticed that the time between 
the initial symptoms and the first drainage was greater 
in patients with failed RUS, reflecting greater ureteral 
inflammation.

Not only stone para meters but a lso uretera l 
characteristics on imaging should be considered in the 
decision to proceed with URS versus PCN. We have 
identified stone impaction as an additional parameter 
that predicts clinical outcome[15,16,20]. Stone impaction 
can be explained by pathological changes in the ureteral 
wall, such as edema and hypertrophy at the site of the 
stone[21]. This pathological change may in turn lead to 
endourological procedures failure[22]. In a retrospective 
study of patients who had undergone ureteroscopic 
treatment of an impacted ureteral stone, Tran et al. 
used a Likert scale to classify stone impaction into non-
impacted (1: mobile stone with no edema or 5: stone 
stuck to the ureter with mild edema) and impacted 
stones (6: stone stuck in ureter with moderate edema 
and requiring moderate pressure/irrigation) or 10: stone 
embedded within ureteral tissue with disimpaction 
failure.

Numerous studies have highlighted the predictors 
for stone impaction during URS and determined 
preoperative radiological parameters such as increased 
ureteral wall thickness and ureteral wall density at the 
stone level to be predictors for stone impaction[15,16,23]. 
Higher PUD below the stone level has been considered 
to be another co-factor responsible for URS failure 

as it may represent more ureteral inf lammation and 
spasm precluding passage of the ureteroscope to reach 
stones[15,16]. Other studies have found the severity 
of hydronephrosis and increased serum creatinine to 
be associated with impacted ureteral stones during 
URS[24, 25]. In our study, neither PUD below the stone 
level nor the degree of hydronephrosis was a significant 
predictor for RUS failure. Conversely, P-CUT ≥ 7.5 
mm and PUD at maximum transverse stone diameter 
≥ 17.5 HU were associated with a 6.1-fold and a 12.8-
fold increase, respectively, in the rate of RUS failure 
necessitating subsequent PCN insertion for emergent 
urinary drainage.

Pearl et al. showed that RUS failure was more 
obvious in the elderly with high grade fever[19]. Also, in 
previous studies predicting RUS failure in the presence 
of intrinsic obstructive factors rather than urolithiasis, 
including male sex, a higher degree of hydronephrosis, 
and increased serum creatinine at presentation[12,26]. 
Acute pyelonephritis was a predictor of RUS failure in 
our experience. This could be indicated by the presence 
of a higher degree of hydronephrosis, urine stasis, and 
pathogen proliferation for a prolonged period before 
sepsis occurrence.

Spont a ne ou s stone pa s s a ge a nd dow nwa rd 
displacement of stones were encountered in 3.8 % and 
3.4% of patients with successful URS, respectively. 
Yoshida et al. concluded that in addition to the passive 
ureteral dilation caused by the ureteral stent, ureteral 
wall thickness is a substantial factor for spontaneous 
passage of ureteric stones ≤ 10 mm[27]. On the contrary, 
it was reported that spontaneous stone passage in 
patients with PCN was higher than in patients with 
RUS[8]. In our study, all patients in the RUS failure 
group had a static stone position after the initial drainage 
and before the definitive intervention. Higher PUD 
below the stone level and at the stone level in addition to 
increased P-CUT might explain the progressive ureteral 
inflammation and spasm that hindered stone movement.

Cevik et al. showed that routine placement of a 
ureteral stent is not mandatory in patients without 
complications after URS for impacted ureteral stones[17]. 
Even though the time interval between emergent urinary 
drainage and definitive endurological stone treatment 
was short, the rate of ureteral stenting in patients with 
successful RUS was only 18.5%. The rate of stenting 
was higher at 52.6% in patients with initial failed RUS. 
There was a higher rate of ureteral stenting in patients 
with RUS failure after the definitive intervention: 
52.6 % versus 18.5 % in patients with successful RUS. 
Also, the rates of ureteral laceration associated with 
stone impaction during definitive intervention and 
ureteral stricture occurrence during follow-up were 
higher in patients with RUS failure. Morgentaler et al. 

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higher in patients with RUS failure. Morgentaler et al. 
concluded that 28.5% of patients (12/42) with impacted 
ureteral stones developed ureteral trauma during stone 
manipulation. Two patients later developed ureteral 
stricture[28]. In addition to the beneficial role of alpha-
blockers use to facilitate ureteral dilation and stone 
access during ureteroscopy[29,30]. The use of NSAIDS 
and/or chymotrypsin as add-on therapy in severely 
impacted stones before definitive intervention has also 
been suggested.

The study was limited by small sample size and 
inherent selection bias due to the retrospective nature 
of the study. Failure to assess the quality of life, lack 
of radiation exposure estimation, and financial cost 
calculation were other limitations.

Conclusion

In acute obstructive uropathy complicated with acute 
pyelonephritis and associated with a stone diameter 
around 1 cm, it is not only the stone profile index that 
is responsible for RUS failure. The ureteral profile is 
also substantial finding which can help in drainage 
type selection. Increased P-CUT ≥ 7.5 mm, and PUD 
≥ 17.5 HU were predictive parameters for initial RUS 
trial failure and the necessity of PCN placement. In this 
group of patients after definitive intervention, ureteral 
stenting is still needed in 52.6 % due to persistent ureteral 
edema and lacerations. Pre-definitive intervention use  
of alpha-blockers besides NSAIDS or chymotrypsin may 
reduce stone impaction ureteral lacerations and facilitate  
stone passage.

237SIUJ.ORG SIUJ  •  Volume 2, Number 4  •  July 2021

Predictors for Retrograde Ureteral Stenting Failure as an Initial Drainage Method

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20. Elbaset M, Elkarta A, Eraky A, Badawy M, Sheir K, Shokeir A. Role 
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doi: 10.1007/s11255-020-02465-3. Epub 2020 Apr 15.

21. Brito AH, Mitre AI, Srougi M. Ureteroscopic pneumatic lithotripsy 
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22. Oliver R, Wells H, Traxer O, Knoll T, Aboumarzouk O, Biyani CS, et 
al. Ureteric stents on extraction strings: a systematic review of 
literature. Urolithiasis.2018;46(2):129–136.

23. Legemate JD, Wijnstok NJ, Matsuda T, Strijbos W, Erdogru T, 
Roth B, et al. Characteristics and outcomes of ureteroscopic 
treatment in 2650 patients with impacted ureteral stones. World 
J Urol.2017;35(10):1497–1506.

24. Tran TY, Hernandez Bustos N, Kambadakone A, Eisner B, Pareek G. 
Emergency ureteral stone treatment score predicts outcomes of 
ureteroscopic intervention in acute obstructive uropathy secondary 
to urolithiasis. J Endourol.2017;31(9):829–834.

25. Sarica K, Er yildirim B, Sahin C, Sabuncu K, Cetinel C, Narter F. 
Impaction of ureteral stones into the ureteral wall: Is it possible to 
predict? Urolithiasis.2016;44(4):371–376.

26. Wenzler DL, Kim SP, Rosevear HM, Faerber GJ, Rober ts W W, 
Wolf J, J Stuart. Success of ureteral stents for intrinsic ureteral 
obstruction. J Endourol.2008;22(2):295–300.

27. Yoshida T, Inoue T, Taguchi M, Omura N, Kinoshita H, Matsuda 
T. Ureteral wall thickness as a significant factor in predicting 
spontaneous passage of ureteral stones of≤ 10 mm: a preliminary 
report. World J Urol.2019;37(5):913–919.

28. Morgentaler A, Bridge SS, Dretler SP. Management of the impacted 
ureteral calculus. J Urol.1990;143(2):263–266.

29. Alsaikhan B, Koziarz A, Lee JY, Pace K T. Preoperative alpha-
blockers for ureteroscopy for ureteral stones: a systematic 
review and met a-analysis of randomized controlled trials.  
J Endourol.2020;34(1):33–41.

30. Koo KC, Yoon J-H, Park N-C, Lee HS, Ahn HK, Lee KS, et al. The 
impact of preoperative α-adrenergic antagonists on ureteral 
access sheath insertion force and the upper limit of force required 
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