Assessing Ureteral Patency by Fluoroscopy and Ultrasonography After Subcutaneous Ureteral Bypass Device Placement for the Treatment of Benign Ureteral Obstruction in Cats

ABSTRACT Background Limited information on the patency of native ureters after subcutaneous ureteral bypass (SUB) device placement is available. Objective Evaluate the patency of native ureters in cats treated with SUB device placement for benign ureteral obstruction. Animals Cats with SUB presented for routine evaluation. Methods Routine ultrasound‐guided SUB irrigations were performed, focusing on ureteral irrigation in the trigone and proximal urethra. Cats with obstructed nephrostomy catheters or subcutaneous ports were excluded. Fluoroscopic‐guided SUB irrigations with iodinated contrast then were used to assess patency. Ureters were deemed patent if contrast filled the lumen evenly along their length, and obstructed if the contrast column was interrupted on consecutive images. Intraoperative fluoroscopy was reviewed to confirm the cause and location of the obstructions. Results Overall, 18 cats (18 SUBs; 10 unilateral, 8 bilateral) were included. The causes of obstruction were ureteroliths (23 ureters) and presumed stricture (3 ureters). A trigonal irrigation was visible in 14/18 cats (77%; 95% confidence interval [CI]: 54.8%–91.0%); the patent side in bilateral SUBs could not be differentiated. Three ureters were excluded (nondiagnostic study, n = 1; obstructed nephrostomy, n = 2). Of the remaining 23 ureters, 19 (82.6%; 95% CI: 62.9%–93.0%) were patent: 16/20 patent ureters were obstructed with ureteroliths (80%; 95% CI: 58.4%–91.9%) and 3/3 with presumed stricture (100%; 95% CI: 43.9%–100%). Ureteral irrigations at the trigone were associated with patency. Conclusions A high patency rate of native ureters after SUB placement was observed. Ureteral irrigations at the trigone reliably indicate patency. Supraphysiologic SUB irrigations may result in underdiagnosed persistent partial obstructions.