The modified Whitaker test is a reliable adjunctive rule-out tool for evaluating efficacy after ureteral reimplantation.

Ureteral reimplantation (UR) is the standard surgical procedure for distal ureteral stricture, with a success rate exceeding 90% ( 1 - 4 ). However, anastomotic restenosis remains a critical factor compromising surgical outcomes ( 5 ). Some patients develop restenosis secondary to anastomotic ischemia and fibrosis, which necessitates reoperation ( 6 ). Therefore, accurate postoperative evaluation of anastomotic patency and occult obstruction is essential for predicting the risk of medium- and long-term surgical failure and guiding clinical management. In the efficacy evaluation after UR, traditional examination methods include intravenous pyelography, enhanced computed tomography (CT) of the urinary system, magnetic resonance imaging (MRI), and diuretic renography. However, the above methods have limitations in accurately quantifying the severity of obstruction, the relationship between stricture site and pressure changes, and cannot fully meet the needs of precise clinical diagnosis and treatment ( 3 , 7 ). As examination for functional diagnosis of obstruction, the modified Whitaker test can exactly make up for this deficiency. Regarding the clinical application limitations of the modified Whitaker test, the core concern is that it requires invasive nephrostomy. Notably, placing a nephrostomy tube to achieve ureteral rest before UR has become a routine clinical procedure, and no additional nephrostomy is needed to complete the modified Whitaker test, which reduces the application threshold of the test to a certain extent ( 8 , 9 ). Affected by the invasiveness of nephrostomy, the modified Whitaker test is not widely used in clinical practice. The establishment of its standardized operation process and verification of the accuracy of measurement results still need to be improved by more clinical studies ( 10 ). Based on this, this study aims to explore the application value of the modified Whitaker test in the efficacy evaluation after UR, and summarize its preliminary clinical experience, to provide a reference for subsequent clinical diagnosis and treatment. We present this article in accordance with the STROBE reporting checklist (available at https://tau.amegroups.com/article/view/10.21037/tau-2026-0467/rc ).

This study prospectively enrolled patients who underwent UR and were evaluated with modified Whitaker test from January 2022 to December 2025. This was a multi-center study involving Beijing Miyun District Hospital, Jiangong Hospital, and Peking University First Hospital. A total of 100 patients with 105 renal units were enrolled. The patients’ demographics, perioperative results and follow-up outcomes were prospectively collected in Reconstruction of Urinary Tract: Technology, Epidemiology and Result (RECUTTER) database. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. This study was approved by the Institutional Review Board of Peking University First Hospital (No. 2020-283). All patients provided informed consent. All participating hospitals were informed of and agreed to the study. Inclusion criteria: (I) age ≥18 years old; (II) patients undergoing UR for distal ureteral stricture; (III) modified Whitaker test performed postoperatively; (IV) preoperative nephrostomy tube placement. Exclusion criteria: (I) nephrostomy tube removed before modified Whitaker test; (II) loss of follow-up data. All patients had a nephrostomy tube placed before UR, and surgery was performed after sufficient recovery of renal function. Modified Whitaker test was performed 3 months after surgery ( Figure 1 ). Overall flowchart of the modified Whitaker test. In our center, both standing and supine positions were used ( Figure 2 ) ( 11 - 13 ). Before examination, a 16F Foley catheter was used to drain urine in the bladder. The patients of the nephrostomy tube and catheter were confirmed. The original nephrostomy tube was replaced with a Fr 9 pressure tube, and a Fr 8 pressure tube was inserted into the bladder. Detection positions for the modified Whitaker test, including standing and supine positions. The 30% iodinated contrast agent was diluted 1:1 with normal saline, perfused at an initial rate of 5 mL/min, and gradually increased to 10 mL/min for observation. If no obvious obstruction was found, the rate gradually increased to 25 mL/min to assess high-flow obstruction. Perfusion was stopped if the patient developed lumbago or intrapelvic pressure continuously higher than 22 cmH 2 O. Compared with the traditional Whitaker test, we adjusted the perfusion rate ( 14 ). The pressure in the renal pelvis and bladder was recorded, and the relative pressure between them was calculated. In addition, X-rays were taken every 30–90 seconds to observe the morphology of the upper urinary tract. Residual contrast agent in the ureter suggested possible obstruction. After the test, residual fluid in the bladder was drained. Based on pressure changes during perfusion and imaging development characteristics, the results of modified Whitaker test were divided into the following 3 types. Type I: the renal pelvis-bladder pressure difference remained stable at baseline, the reconstructed ureter was clearly developed during perfusion, and the absolute pelvic pressure was <22 cmH 2 O ( Figure 3A,3B ). Type II: the renal pelvis-bladder pressure difference gradually increased with perfusion, but ureteral peristalsis was preserved and the pressure could return to normal range; at the end of examination, the renal pelvis-bladder pressure difference ≤15 cmH 2 O, and the absolute pelvic pressure ≤22 cmH 2 O ( Figure 3C,3D ). Type III: the renal pelvis-bladder pressure difference continued to rise with perfusion, always >15 cmH 2 O, accompanied by weak or even complete disappearance of ureteral peristalsis ( Figure 3E,3F ). We defined Type III as obstructed, and Types I and II as unobstructed. Classification of modified Whitaker test results. (A) Contrast imaging of Type I. (B) Renal pelvic and bladder pressure curves of Type I. (C) Contrast imaging of Type II. (D) Renal pelvic and bladder pressure curves of Type II. (E) Contrast imaging of Type III. (F) Renal pelvic and bladder pressure curves of Type III. Nephrostomy was performed 2 weeks before UR to allow sufficient rest of the kidney and ureter ( 9 ). The nephrostomy tube remained in situ after surgery. The nephrostomy tube was clamped about 2 weeks after surgery, and the patient was observed for discomfort such as lumbago. If any discomfort occurred, the clamped tube was opened. The ureteral stent was removed 2 months after surgery. Routine blood test, renal function and urinary ultrasound were performed 3 months after surgery. Modified Whitaker test was performed 3 months after surgery. After comprehensive evaluation, the nephrostomy tube was removed after the modified Whitaker test. Follow-up was performed at 3 months, 6 months, 1 year and other time points after surgery. The follow-up mainly focused on hydronephrosis and symptoms such as lumbago after nephrostomy tube removal. In this study, surgical efficacy was defined as objective efficacy and overall efficacy. Overall efficacy was defined as the disappearance of clinical symptoms of lumbago, no aggravation of hydronephrosis compared with preoperative and no significant decrease in renal function ( 15 , 16 ). Objective efficacy was defined as no aggravation of hydronephrosis compared with preoperative and no significant decrease in renal function. SPSS 24.0 statistical software was used for data processing. Measurement data conforming to normal distribution were expressed as mean ± standard deviation, and measurement data with non-normal distribution were expressed as median (first quartile–third quartile, Q1–Q3). Enumeration data were expressed as cases (%).

The baseline characteristics of patients are shown in Table 1 . A total of 100 patients with 105 renal units were included in this study, of which the left side accounted for 47.62% (50/105) and the right side 52.38% (55/105). The median age of patients was 47 (37.50, 53.00) years old. The median preoperative creatinine was 72.00 (62.40, 84.50) µmol/L, the median eGFR was 108.46 (95.36, 126.46) mL/min/1.73 m 2 , the median creatinine at the latest postoperative reexamination was 77.27 (65.25, 83.59) µmol/L, and the median eGFR was 98.07 (84.82, 116.95) mL/min/1.73 m 2 . Data are presented as n (%) or median (interquartile range). BMI, body mass index; eGFR, estimated glomerular filtration rate. All patients had no obvious discomfort after postoperative modified Whitaker test. The median perfusion volume was 71.00 (37.00, 115.00) mL, and the median maximum flow rate was 15.00 (12.50, 25.00) mL/min. The median intrapelvic pressure was 20.00 (16.00, 25.50) cmH 2 O, the median intravesical pressure was 14.00 (9.50, 20.00) cmH 2 O, and the median pressure difference was 5.00 (2.00, 9.00) cmH 2 O. In modified Whitaker test results, Type I accounted for 69.52% (73/105), Type II 22.86% (24/105) and Type III 7.62% (8/105). Only 1 patient with Type III had unrelieved lumbago and aggravated hydronephrosis, and subsequent intestinal replacement was performed. The remaining 7 patients had relieved or disappeared lumbago, and no progression of hydronephrosis ( Table 2 ). The median follow-up time was 12.63 (6.92, 25.80) months, and only 7.62% (8/105) of patients had no significant improvement in postoperative lumbago. Among them, 1.90% (2/105) of patients had aggravated hydronephrosis, and these two patients underwent ileal ureteral replacement again after surgery. In this study, the overall surgical success rate was 92.38% (97/105), and the objective surgical success rate was 98.10% (103/105). During follow-up, 8 patients had lumbago or aggravated hydronephrosis, of which only 1 patient had a renal pelvis-bladder pressure difference ≥15 cmH 2 O, reaching 28 cmH 2 O. The pressure difference of the other patients was 22 cmH 2 O ( Table 3 ). The concordance rates between unobstructed results on the modified Whitaker test and successful overall postoperative outcomes, successful objective postoperative outcomes were 85.71% (90/105) and 91.43% (96/105), respectively ( Table 4 ).

Since Roger H. Whitaker first proposed the Whitaker test in 1973 and applied it to the diagnosis of upper urinary tract obstruction ( 17 ), this technique has been continuously explored and improved for half a century. In 2009, Lupton EW et al. ( 10 ) further clarified the indications of the Whitaker test, and in 2021, Yang et al. ( 12 ) proposed a modified version of the Whitaker test, making this diagnostic technology increasingly mature and perfect. At present, some hospitals have taken nephrostomy as a routine preoperative operation for upper urinary tract reconstruction. Under this background, the Whitaker test can be regarded as a non-invasive evaluation method after ureteral reconstruction to a certain extent ( 9 ). The modified Whitaker test used in this study was proposed by the Urology team of Peking University First Hospital ( 11 - 13 ). The modified scheme mainly optimized and adjusted two core parameters: patient examination position and perfusion flow rate. In terms of position selection, it broke through the limitation of traditional single supine position. Considering the potential influence of gravity on urinary tract dynamics under daily physiological state, some subjects were tested in upright position. All examinations were performed by three urologists with rich clinical experience, and the position selection could be flexibly determined according to the operator’s habits. Clinical practice confirmed that both positions could obtain stable and reliable test results. In terms of perfusion flow rate setting, to ensure the safety and tolerance of the test, the initial perfusion flow rate was set at 5 mL/min. After eliminating the abnormal fluctuation in the initial perfusion stage, the flow rate gradually increased to the upper limit of 25 mL/min, to accurately identify urinary tract obstruction under high flow state. In this study, at the initial perfusion flow rate of 5 mL/min, all patients had no obvious discomfort after postoperative modified Whitaker test. The results of this study suggest that the modified Whitaker test still has certain clinical value in evaluating the efficacy of UR and guiding subsequent treatment. Among the 105 renal units in this group, 73 (69.52%) were Type I, 24 (22.86%) Type II, and 8 (7.62%) Type III according to the modified Whitaker test classification. Patients with Type II and III were advised to avoid excessive urination retention after surgery. Previous studies mostly guided the timing of nephrostomy tube removal based on the results of modified Whitaker test ( 11 , 12 ). In this study, all Type III patients successfully clamped the tube for 24 hours without obvious discomfort after completing the modified Whitaker test, and then the nephrostomy tube was removed without prolonged indwelling time. For the results of modified Whitaker test, we believe that attention should be paid to Type III patients with combined elevated upper urinary tract pressure and poor peristalsis. Only 1 patient in this group with Type III had obvious upper urinary tract peristalsis dysfunction and pressure difference ≥15 cmH 2 O. This patient received ileal ureteral replacement shortly after UR. The other 7 patients only showed elevated pressure difference. During follow-up, lumbago symptoms were relieved or disappeared, and upper urinary tract hydrops did not progress. Therefore, we believe that simple elevated pressure difference may not be sufficient as an independent indicator of poor prognosis. Comprehensive evaluation combining pressure difference with upper urinary tract peristalsis is more helpful to accurately judge the prognosis of patients and guide subsequent treatment. A total of 2 patients in this study had aggravated hydronephrosis after surgery and finally received ileal ureteral replacement. One case was radiation-related ureteral stricture. The modified Whitaker test showed that the renal pelvis-bladder pressure difference reached 28 cmH 2 O, and antegrade radiography showed significantly weakened ureteral peristalsis. Combined with the above examinations, it was comprehensively determined that mechanical obstruction still existed, so ileal ureteral replacement was performed in a short time. During postoperative follow-up, the patient’s hydronephrosis and renal function remained stable. The poor effect of the initial reconstruction surgery in this case was closely related to the basic etiology of radiation injury. Radiation can cause extensive damage to the microvessels around the ureter, leading to persistent ischemia, hypoxia and progressive fibrosis of the ureteral wall, thereby resulting in decreased ureteral peristalsis and anastomotic cicatricial restenosis. The other case was gynecological surgery-related ureteral stricture, complicated with contralateral renal atrophy and basically lost function. Postoperative modified Whitaker test showed no obvious obstruction, and the renal pelvis-bladder pressure difference was only 2 cmH 2 O, but progressive aggravation of hydronephrosis and decline of renal function occurred in mid-term follow-up. The restenosis was related to the functional solitary kidney state caused by contralateral renal atrophy. The affected ureter was in a state of high flow and high-pressure compensation for a long time, with continuous high tension of ureteral wall, mucosal congestion and chronic inflammation. The anastomosis bore high fluid shear force and dilatation stress for a long time, which was easy to induce local scar hyperplasia, intimal fibrosis and luminal restenosis. The modified Whitaker test performs poorly in predicting surgical failure or obstructive positive outcomes, yet exhibits excellent negative predictive value. The concordance rates between unobstructed findings on the modified Whitaker test and successful overall postoperative outcomes as well as successful objective postoperative outcomes were 85.71% (90/105) and 91.43% (96/105), respectively. However, its efficacy in predicting postoperative obstruction is limited, with a positive predictive value of 12.50% (1/8) and a sensitivity of 50.00% (1/2). Even when subjective symptoms such as lumbago were excluded and only progression of hydronephrosis and changes in renal function were adopted as objective outcome criteria, the sensitivity of the modified Whitaker test for detecting true postoperative recurrent upper urinary tract obstruction was merely 50.00%, indicating that this test has limited capacity to identify patients with obstructive positive findings. This may be related to the small number of surgical failure cases in this study, leading to unstable test sensitivity. This study still has several limitations, which need to be further improved in subsequent studies. The diagnosis of preoperative upper urinary tract obstruction relied on imaging and other auxiliary examination methods, lacking corresponding preoperative pressure detection data, so horizontal comparative analysis with postoperative modified Whitaker test results could not be carried out. Although the cohort of this study is the largest sample size among the reported studies on modified Whitaker test after UR, the overall sample size is still relatively limited, which may affect the extrapolation of the study conclusions. At the same time, this study did not conduct a head-to-head comparison between the modified Whitaker test and similar diagnostic techniques such as diuretic renography, so it is difficult to clarify the advantages and positioning of the modified technique in clinical diagnostic efficacy.

The modified Whitaker test exhibits excellent negative predictive performance and favorable consistency with mid-term postoperative follow-up outcomes. It serves as a reliable adjunctive tool for ruling out upper urinary tract obstruction and guiding nephrostomy tube removal after UR.

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