Preoperative estimate of natural ureteral length based on computed tomography and/or plain radiography.

To predict natural ureter lengths based on clinical images. We reviewed our image database of patients who underwent multiphasic computed tomography urography from January 2019 to April 2020. Natural ureteral length (ULCTU) was measured using a three-dimensional curved multiplanar reformation technique. Patient parameters including age, height, and height of the lumbar spine, the index of ureteral length using kidney/ureter/bladder (KUB) radiographs (C-P and C-PS) and computed tomography (ULCT) were collected. ULCTU correlated most strongly with ULCT. R square and adjusted R square values from multivariate regression were 0.686 and 0.678 (left side) and 0.516 and 0.503 (right side), respectively. ULCTU could be estimated by the regression model in three different scenarios as follows: ULCT + C-P ULCTUL = 0.405 [Formula: see text] ULCTL [Formula: see text] 0.626 [Formula: see text] C-PL - 0.508 cm ULCTUR = 0.558 [Formula: see text] ULCTR [Formula: see text] 0.218 [Formula: see text] C-PR + 6.533 cm ULCT ULCTUL = 0.876 [Formula: see text] ULCTL [Formula: see text] 6.337 cm ULCTUR = 0.710 [Formula: see text] ULCTR [Formula: see text] 9.625 cm C-P ULCTUL = 0.678 [Formula: see text] C-PL [Formula: see text] 4.836 cm ULCTUR = 0.495 [Formula: see text] C-PR [Formula: see text] 10.353 cm We provide equations to predict ULCTU based on CT, KUB or CT plus KUB for different clinical scenarios. The formula based on CT plus KUB provided the most accurate estimation, while the others had lower validation values but could still meet clinical needs.

Can ureteral wall thickness (UWT) be used as a potential parameter for decision-making in uncomplicated distal ureteral stones 5-10 mm in size? A prospective study.

OBJECTIVE: To evaluate the correlation between ureteral wall thickness (UWT) and stone passage (SP) and its cut-off value in distal uncomplicated ureteral stones. PATIENTS AND METHODS: In the prospective study from January 2019 to January 2020 at a tertiary care hospital, we reviewed 212 patients aged above 18 years with single, symptomatic, radiopaque, and distal ureteric stone sized 5-10 mm, who were treated with MET (Silodosin 8 mg once daily) until SP or a maximum of 4 weeks. There were 2 groups: responders and non-responders. Demographic data of the patients and all stone radiological parameters including stone size, laterality, density, UWT, the diameter of the ureter proximal to the stone (PUD), and the degree of hydronephrosis were recorded and compared between the 2 groups. RESULTS: There were 126 (59.4%) in the responder group and 86 (40.6%) in the non-responder group. On univariate analysis, gender, stone density, stone size, PUD, UWT, and the degree of hydronephrosis were significant factors for stone passage. However, using multivariate analysis, only UWT and the degree of hydronephrosis were significant. ROC analysis showed that 3.75 mm is the cut-off value for UWT, with 86% and 87.3% sensitivity and specificity, respectively. CONCLUSIONS: UWT and hydronephrosis can be used as potential predictors for SP and can help with decision-making in patients with uncomplicated 5-10 mm lower ureteric stones.

There are no three physiological narrowings in the upper urinary tract: a new concept of the retroperitoneal anatomy around the ureter.

The widely held dogma of three physiological narrowings in the upper urinary tract has proven incorrect by recent several studies using computed tomography images. There are only two common obstruction sites: the upper ureter and the ureterovesical junction. The second narrowing, where the ureter crosses the iliac vessels, cannot be regarded anymore as a common obstruction site. The mechanism by which stones lodge in the upper ureter is explained anatomically by the change in ureteral mobility and compliance at the level where the ureter exits the perirenal space. This level can be identified radiologically as the point where the ureter crosses under the ipsilateral gonadal veins, termed the "crossing point". Kinking of the upper ureter is another manifestation of this anatomical phenomenon, visible in radiological images. It is caused by loosening of the ureter at or above the crossing point (within the perirenal space), corresponding with renal descent such as during the inspiratory phase. This new anatomical discovery in the retroperitoneum will not only bring about a paradigm shift in terms of the physiological narrowings in the upper urinary tract, but may also lead to the development of new surgical concepts and approaches in the area.

Can ultrasound guidance reduce radiation exposure significantly in percutaneous nephrolithotomy in pediatric patients?

In this study, we aimed to compare clinical and technical outcomes between pediatric patients who underwent percutaneous nephrolithotomy (PCNL) under fluoroscopy (FL) and those that underwent this procedure under FL with ultrasound assistance (FLUSA). The data of 66 PCNL patients were analyzed retrospectively. Renal puncture was successful in 22 patients in the FLUSA group and 44 patients in the FL group. In all cases, FL was used for tract dilation and confirmation of ureteral catheter positioning at the beginning of the procedure. The sample consisted of 46 males and 20 females with a mean age of 7.2 ± 2.1 years (range 1-17 years). Stone size varied from 8.0 to 75.4 mm, and 89% of patients achieved a completely stone-free state. The median puncture time was 130.5 ± 25.3 s for FLUSA and 295 ± 82.8 s for FL, the median fluoroscopic screening time was 95 ± 33 and 230 ± 116 s, respectively, and the median radiation dose was 19.04 ± 9.9 dGy/cm2 and 54 ± 21.4 dGy/cm2, respectively. The median puncture time, fluoroscopic screening time, and radiation dose were statistically lower in the FLUSA group (p = 0.001, Mann-Whitney U test). The greatest problem in PCNL is the use of fluoroscopy. Due to some anatomical differences from adults, applying PCNL in pediatric patients using only ultrasound may decrease the success rate. Puncture with ultrasound significantly reduces the radiation dose in children. Puncture with ultrasound and dilation under fluoroscopy is a successful and safe treatment method with low morbidity and high success rates and shorter hospital stay in pediatric patients.

[Three-dimensional MRI reconstruction research on the anatomical relationship among uterosacral ligament and ureter or rectum in pelvic organ prolapse patients].

Objective: To study the anatomical relationship among uterosacral ligament and ureter or rectum by using MRI three-dimensional reconstruction model in pelvic organ prolapse (POP) patients. Methods: According to the research standard, 67 POP patients were enrolled, who accepted pelvic MRI before surgery in Nanfang Hospital, Southern Medical University during May 2015 to March 2020. Three-dimensional model of uterosacral ligament was reconstructed. The intersection point of the fitting curve of uterosacral ligament and ischial spine level marked point P0, every 1 cm increasing from P0 towards the sacrum marked points P1, P2, and P3. Distances were measured between rectum or ureter to uterosacral ligament respectively at the P0-P3 horizontal levels. Results: (1) The distances between the left ureter and the left uterosacral ligament were (15.45±7.46) to (19.31±11.38) mm, and the distances between the right ureter and the right uterosacral ligament were (13.77±8.16) to (14.78±9.18) mm. At the P1 horizontal level ureters were the closest to uterosacral ligaments, and the right ureter was the closest to right uterosacral ligament [(13.45±9.34) mm] at P2 horizontal level in severe POP group. The farthest distance presented at the P3 horizontal level between bilateral ureters and uterosacral ligaments. (2) At the P0 horizontal level, the rectum was the closest to the bilateral uterosacral ligaments [left: (20.62±9.99) mm, right: (16.82±9.63) mm; P=0.026], and the rectum was closer to the right uterosacral ligament. There were no significant differences in the distance between rectum and bilateral uterosacral ligaments in mild POP group (P>0.05), and the results of severe POP group also showed the rectum was closer to the right uterosacral ligament [(15.64±10.31) mm at P0 horizontal level]. Conclusions: Right ureter and rectum are closer to the right uterosacral ligament. Gynecologists should pay more attention to avoid damaging the right ureter and rectum during the operation of the right uterosacral ligament in POP patients.

Surgical Technique Based on Space Anatomy for Laparoscopic Radical Trachelectomy with Uterine Artery Preservation.

Background: To introduce the surgical procedure based on special space anatomy that can safely and efficiently complete the dissociation of the ureter and uterine artery during laparoscopic radical trachelectomy with uterine artery preservation. Methods: We introduce the key technique elements of this surgical procedure using a patient we treated as an example. A 27-year-old patient was diagnosed as well-differentiated cervical adenocarcinoma, stage IB1, and had a strong desire for future fertility. Laparoscopic radical trachelectomy with uterine artery preservation was performed in this patient by using this new surgical technique based on space anatomy. Results: The ureteral space that needs to be dealt with during laparoscopic radical trachelectomy is actually a potential avascular space located medial to the ureter between the anterior leaf (from the axillary space to the fourth space of Yabuki) and posterior leaf (between the paravesical space and paravaginal space) of the vesicouterine ligament. Exposure of the axillary space can help to separate the ureter from the lower uterine segment and uterine artery (uterine side), which is necessary for radical trachelectomy with uterine artery preserved. Multiple "shafts" called potential avascular space can be drilled on the anterior leaf of vesicouterine ligament, and the connective tissue and blood vessels between the "shafts" were cutoff with ultrasonic scalpel. After the paravesical space and paravaginal space were developed, the posterior leaf was isolated and congealed completely by Ligasure. Conclusions: In brief, this new surgical procedure consists of four spaces that can safely and efficiently perform complete excision of the vesicouterine ligament, reduce blood loss, avoid ureteral injury, and shorten the operation time.

Ureteral Diameter as Predictor of Ureteral Injury during Ureteral Access Sheath Placement.

PURPOSE: We determined the association between ureteral diameter and ureteral injury during ureteral access sheath placement. MATERIALS AND METHODS: Patients were prospectively enrolled in the study from July 2014 to September 2015. All patients underwent preoperative noncontrast computerized tomography and had a 12Fr to 14Fr ureteral access sheath placement without pre-stenting. A measurement of proximal ureteral diameter was carried out by 2 urologists and 1 radiologist. Ureteral wall injuries were evaluated by 2 endourologists using the 5-grade classification. RESULTS: A total of 68 patients were included and the overall success rate for sheath placement was 94.1% (64). Among this group 46 patients (71.9%) had evidence of any type of injury to the ureter wall and the rate of high grade injuries was 26.1% (12). The ureteral diameter of patients who had a high grade injury was significantly smaller compared to those with low grade injuries (mean±SD 3.29±0.46 mm vs 4.5±0.97 mm, p <0.001). On multivariate analysis narrower proximal ureteral diameter was associated with a higher risk of high grade ureteral injury (OR 2.8, 95% CI 1.9-3.4, p <0.001), regardless of age, gender, body mass index, and middle and distal ureteral diameter. CONCLUSIONS: The proximal ureteral diameter is associated with high grade ureteral injury. A smaller ureteral diameter increases the risk and the severity of ureteral injury. Therefore, preoperative measurement of the ureteral diameter is recommended for ureteral access sheath placement to predict the risk of ureteral injury.

Robotic Ureteral Reconstruction.

Robotically assisted laparoscopic techniques may be used for proximal and distal ureteral strictures. Distal strictures may be approached with ureteroneocystotomy, psoas hitch, and Boari flap. Ureteroureterostomy, buccal mucosa graft ureteroplasty, and appendiceal flap ureteroplasty are viable techniques for strictures anywhere along the ureter. Ileal ureteral substitution is reserved for more extensive disease, and autotransplantation is reserved for salvage situations.

Korean ureter length: A computed tomography-based study.

Purpose: We measured ureter length in healthy Koreans using reformatted computed tomography (ULCT) and found ways to indirectly estimate ureter length by measuring LLCT, the length between the ureteropelvic junction and the ureterovesical junction, and standing and sitting height. Materials and Methods: A total of 508 ureters of 254 healthy patients (median age, 55.0 years; 148 males and 106 females) were included in this retrospective study. ULCT, LLCT, and sitting and standing body height were measured. Results: The mean left and right ULCT were 25.2±2.2 and 25.0±2.2 cm, respectively. The mean left and right LLCT were 21.1±1.8 and 20.3±1.9 cm, respectively. Standing and sitting body height were 164.1±8.9 and 88.3±4.3 cm, respectively. Height was significantly correlated with ULCT, but this relation was not linear (r2=0.064 standing height, 0.062 sitting height). However, LLCT showed a significant linear correlation with ULCT (r2=0.485). ULCT can be estimated indirectly by the following equation: ULCT=0.823×LLCT+8.093. Conclusions: We could measure the ureteral length of healthy Koreans by ULCT. ULCT could be estimated indirectly by LLCT and standing and sitting height. Of these variables, LLCT provided the most accurate estimate of ureteral length.

The magnetic resonance imaging appearances of the interureteric crest of the urinary bladder.

PURPOSE: This study was devised to evaluate the imaging appearances of the interureteric crest (IUC) of the bladder on magnetic resonance imaging (MRI). The primary objective was to determine how commonly the IUC was observed on pelvic MRI examinations. The secondary objectives were to determine the average size of the IUC, its MRI signal characteristics and whether there is variation between men and women. By defining the imaging findings we hope to prevent misinterpretation of normal anatomy on MRI and, therefore, prevent unnecessary further investigations and procedures. METHODS: We retrospectively reviewed 114 adult patient's magnetic resonance imaging examinations of the pelvis. Two readers independently recorded information about the presence and characteristics of the IUC with a third reader used to arbitrate in cases of disagreement. RESULTS: The IUC was demonstrated on MRI in 75% of patients. It was best observed on T2w sequences as a continual ridge of low signal intensity between the ureters. The mean AP diameter of the IUC at its mid-point on the sagittal images was 2.4 mm. CONCLUSIONS: The IUC is often seen on MRI on T2w images of a non-collapsed bladder. Its characteristic appearance can be used to help the reporting radiologist confidently differentiate identify this normal structure from an area of focal bladder wall thickening that might be misinterpreted as a bladder tumor.

A presumptive role of lower ureteral angles in the difficulty of ureteral access sheath insertion during retrograde intrarenal surgery.

PURPOSE: We aimed to investigate whether the angle created by the most lateral portion of the lower ureter is responsible for the difficulty in ureteral access sheath insertion. METHODS: All male patients scheduled to undergo flexible ureteroscopy were enrolled. Patients with ureteral stricture in any course of the ureter and patients with problems at the ureteral opening were excluded. We set the coordinates of the most lateral portion of the lower ureter as M (x, y, z) using computed tomography. The bladder outlet was marked as the zero point O (0, 0, 0). The vector that passed through the urethra and point O was expressed as Vuo (0, 0, - u). The vector that passed through points O and M was expressed as Vom (x, y, z). Thus, an angle (90° - α) could be calculated between Vuo and Vom using the rotation angle formula. RESULTS: A total of 671 male patients were enrolled, among whom the ureteral access sheath could not pass through the most lateral portion of the lower ureter in 14 patients. The mean values of the α angle were 38.56° and 48.48° in the patient and control groups, respectively, compared with the 42 age- and sex-matched control subjects (p < 0.001). CONCLUSION: The ureteral angle determined by the level of the bladder outlet and the most lateral portion of the lower ureter could be a causative factor for the failure of ureteral access sheath insertion.

Uterosacral Ligament Suspension: A Radiographic Study of Suture Location in Live Subjects.

OBJECTIVES: This study aimed to describe uterosacral ligament suspension (USLS) suture location relative to the surrounding anatomy in a living model using computed tomographic imaging. METHODS: This was an institutional review board-approved prospective descriptive study. Women aged 18 to 85 years undergoing vaginal hysterectomy with USLS were eligible. A size 'small' titanium vascular clip was applied to the base of each USLS suture. Computed tomography of the pelvis was performed on postoperative day 1. Preoperative and postoperative neurologic questionnaires and physical examinations were performed. A sample size of 15 subjects was deemed appropriate for this pilot study. RESULTS: Seventeen subjects were enrolled: 2 excluded and 15 analyzed. The median (interquartile range) age of the subjects was 57 (22) years. The closest branch of the internal iliac complex was 2.6 (0.9) cm (median [interquartile range]) from the proximal suture on the right and 2.6 (0.5) cm on the left. The right ureter was 2.1 (0.7) cm from the right proximal suture. The left ureter was 2.3 (1.0) cm from the left proximal suture. The rectal lumen were 3.0 (1.6) cm from the right proximal suture and 2.8 (1.4) cm from the left proximal suture. No subjects were found to have neurologic involvement of the sutures based on neurologic questionnaire responses and physical examination. CONCLUSIONS: In live subjects, our study confirms that the vasculature, ureter, and rectum of the pelvic side wall are near suture placement for USLS. This information highlights the importance of careful dissection and awareness of anatomic landmarks.

A comparative study of different surgical techniques for the management of distal ureter during laparoscopic radical nephroureterectomy. / Estudio comparativo de diferentes técnicas quirúrgicas para el manejo del uréter distal durante la nefroureterectomía laparoscópica.

OBJECTIVES: To compare the oncological outcomes between two open surgical techniques and two endoscopic approaches for the management of the distal ureter during laparoscopic radical nephroureterectomy (LRNU). MATERIAL AND METHODS: Retrospective review of 152 patients submitted to LRNU for the management of upper urinary tract tumors between 2007-2014. We analyzed the potential impact of two different open surgical (extravesical vs intravesical) and two endoscopic (resection of ureteral orifice and fragment removal vs endoscopic bladder cuff) techniques on the development of bladder recurrence, distant/local recurrence and cancer-specific survival (CSS). RESULTS: A total of 152 patients with a mean age of 69.9 years (±10.1) underwent LRNU. We reported 62 pTa-T1 (41%), 35 pT2 (23%) and 55 pT3-4 (36%). Thirty-two were low grade (21.1%) and 120 high grade (78.9%). An endoscopic approach was performed in 89 cases (58.5%), 32 with resection (36%) and 57 with bladder cuff (64%), and open approach in 63 (41.5%), 42 intravesical (66.7%) and 21 extravesical (33.3%). Within a median follow-up of 32 months (3-120), 38 patients (25%) developed bladder recurrence, 42 distant/local recurrence (27.6%) and 34 died of tumor (22.4%). In the univariate analysis, the type of endoscopic technique was not related to bladder recurrence (P=.961), distant/local recurrence (P=.955) nor CSS (P=.802). The open extravesical approach was not related to bladder recurrence (P=.12) but increased distant/local recurrence (P=.045) and decreased CSS (P=.034) compared to intravesical approach. CONCLUSIONS: LRNU outcomes are not dependant on the type of endoscopic approach performed. The open extravesical approach is a more difficult technique and could worsen the oncological outcomes when compared to the intravesical.

Could ureteral wall thickness have an impact on the operative and post-operative parameters in ureteroscopic management of proximal ureteral stones? / ¿Podría el espesor de la pared ureteral afectar a los parámetros intra y postoperatorios de la ureteroscopia para el tratamiento de piedras ureterales proximales?

AIM: To evaluate the possible impact of stone impaction in terms of ureteral wall thickness (UWT) on the success and procedure related parameters of ureteroscopic management in proximal ureteral calculi. PATIENTS AND METHODS: 82 patients with proximal ureteric stones were included and were divided into 2subgroups where UWT was> 5mm in 38 cases; and <5mm in 44 cases. Stone size, degree of hydronehrosis, diameter of proximal ureteral luz, UWT and patient's demographics were evaluated. Semi-rigid ureteroscopy with Ho-YAG laser was performed and the possible impact of UWT as an objective parameter for stone impaction on the success rates and procedure related parameters was evaluated. RESULTS: Mean patient age and stone size values were 47.55±1.78 years and 8.17±0.29mm respectively. Regarding the impact of UWT value at the stone site for the parameters mentioned above stone free rates particularly at 1-week after the procedure was higher in group 2 and the rate of residual fragments as well as the need for double J stent placement was higher in group 1. Additionally, mean duration of the procedures was significantly longer in Group 1 during which pathologic alterations were significantly higher in ureteral wall at stone site were observed in these cases (P=.0243). CONCLUSIONS: UWT may be used to predict the success of ureteroscopic management and other procedure related parameters for proximal ureteral stones in an effective manner. With this approach a more rational operative plan with higher success rates, limited complications and auxiliary procedures could be made.

Standardization of laparoscopic extrafascial hysterectomy: anatomic considerations to protect the ureter.

PURPOSE: To describe the procedure of laparoscopic extrafascial hysterectomy to avoid ureter injury. METHODS: Data were obtained from: (1) anatomic study of ten fresh female cadavers to measure the distance between the point where the ureter and uterine artery cross and the level of section of the ascending branch of the uterine artery during extrafascial dissection of the uterine pedicle and uterosacral ligament (Paris School of Surgery). The Wilcoxon test was used to compare measurements within each subject. P < 0.05 was considered to denote significance; (2) prospectively collected clinical data from women undergoing laparoscopic extrafascial hysterectomy from July 2006 to March 2014 at Poissy University Hospital, to describe the laparoscopic extrafascial hysterectomy technique with analysis of surgical complications using the Clavien-Dindo classification. RESULTS: Anatomic study: The mean (SD) distance between the point where the ureter and uterine artery cross and the level of the section of the ascending branch of the uterine artery were: 11.6 mm (5.2) in neutral position and 25 mm (7.5) after pulling the uterus laterally; and 25mm (8.9) after sectioning the ascending portion of the uterine pedicle and 38.6 mm (4.5) after complete uterine artery pedicle dissection through the uterosacral ligaments. After release of the ureter, the curve in front of the uterine artery disappeared. Clinical laparoscopic study: Sixty-eight patients underwent laparoscopic extrafascial hysterectomy. No ureteral complications occurred. CONCLUSION: Laparoscopic extrafascial hysterectomy is a safe and feasible procedure. Combined lateralization and elevation of the uterus, section of the ascending branch of the uterine artery, and its extrafascial dissection along the uterosacral ligament contribute to protecting the ureter during the procedure.

Gross and Histologic Anatomy of the Pelvic Ureter: Clinical Applications to Pelvic Surgery.

OBJECTIVE: To further evaluate relationships of the pelvic ureter to clinically relevant structures and to characterize the anatomy, histology, and nerve density of the distal ureter. METHODS: In this observational cadaveric study, 35 female cadavers were examined, 30 by gross dissections and five microscopically. Ureter length and segments of pelvic ureter were measured. Closest distances between the ureter and clinically relevant points were recorded. The distal pelvic ureter and surrounding parametrium were evaluated microscopically. Nerve density was analyzed using automated quantification of peripheral nerve immunostaining. Average measurements of nerve density in the anterior and posterior quadrants surrounding the ureter were statistically compared using a two-tailed t test. Descriptive statistics were used for analyses with distances reported as mean±SD (range). RESULTS: Gross dissections revealed ureter length of 26.3±1.4 (range 24-29) cm (right), 27.6±1.6 (25-30.5) cm (left). Lengths of ureter from pelvic brim to uterine artery crossover were 8.2±1.9 (4.4-11.5) cm (right), 8.5±1.5 (4.5-11.5) cm (left) and from crossover to bladder wall 3.3±0.7 (2.4-5.8) cm (right), 3.2±0.4 (2.6-4.1) cm (left). Intramural ureter length was 1.5±0.3 (1-2.2) cm (right) and 1.7±1.2 (0.8-2.5) cm (left). Distances from the ureter to uterine isthmus: median 1.7 (range 1-3.0) cm (right) and 1.7 (1.0-2.9) cm (left); lateral anterior vaginal fornix 1.5 (1.0-3.1) cm (right) and 1.7 (0.8-3.2) cm (left); lateral vaginal apex 1.3 (1.0-2.6) cm (right) and 1.2 (1.1-2.2) cm (left) were recorded. Microscopy demonstrated denser fibrovascularity posteromedial to the ureter. Peripheral nerve immunostaining revealed greater nerve density posterior to the distal ureter. CONCLUSION: Proximity of the ureter to the uterine isthmus and lateral anterior vagina mandates careful surgical technique and identification. The intricacy of tissue surrounding the distal ureter within the parametrium and the increased nerve density along the posterior distal ureter emphasizes the importance of avoiding extensive ureterolysis in this region.

[Is the ureteral length associated with the patient's size?] / La longueur de l'uretère est-elle liée à la taille du patient ?

OBJECTIVE: To assess the relation between the ureteral length and the patients' size. PATIENTS AND METHOD: Prospective study made between September 2012 and May 2014, on 87 patients with 42 men and 45 women, in whom the ureteral measure was performed during the various procedures that require the use of a pigtail stent. The average age of the population was 53 years old (±15.9) with an average height of 168.3cm (±8.4). This has been achieved through ureteral catheter combining fluoroscopy and endoscopy. RESULTS: The ureteral average length was 23.5cm (±2.33). The ureteral average length was 23.8cm (±2.18) for man and 23.2cm (±2.44) for women. In this population, there were a positive correlation between the size of the patients and the length of the ureters (r=0.75; P=0.01). However, this correlation was not found in all subgroups, particularly among women (r=0.16; P=0.30) and on the right side of men (r=0.34; P=0.12). This correlation was still true for the left side in the men's group (r=0.50; P=0.02). CONCLUSION: In this study, there is a positive correlation between the patients' size and the ureteral length. But this correlation is not found in some subgroups. It is better to perform in vivo the ureteral measurement to have the precise length in order to set up a pigtail stent adapted to the patient. LEVEL OF EVIDENCE: 3.