How do you know the SUB is patent?

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

Yassmina Habib 1, Catherine Vachon 2, Tristan Juette 2, Marilyn Dunn 2

Background:
Benign ureteral obstruction (BUO) in cats, often due to ureterolithiasis or strictures, is typically managed surgically using subcutaneous ureteral bypass (SUB) devices. Despite widespread use of these devices, limited data exist on the patency of native ureters post-implantation. This study aimed to evaluate ureteral patency in cats with SUBs using fluoroscopy and ultrasonography, and to correlate imaging findings with patency status.

Methods:
Eighteen cats (10 with unilateral and 8 with bilateral SUBs) with prior SUB placement for BUO underwent routine follow-up including ultrasound-guided SUB irrigation and fluoroscopic evaluation using iodinated contrast. Patency was assessed based on the continuity of contrast flow along the ureter. Cats with nonfunctional nephrostomy catheters or ports were excluded. Sensitivity and specificity of ultrasonographic signs (specifically, trigonal irrigation) were calculated relative to fluoroscopic findings.

Results:
Of 23 assessable ureters, 19 (82.6%) were patent. Most cases of previous ureteral obstruction were due to ureteroliths (n=20) or presumed strictures (n=3). Trigonal irrigation on ultrasound was observed in 14/18 cats and corresponded to fluoroscopic patency in all cases, yielding a sensitivity of 87.5% and specificity of 100%. Fluoroscopy was often technically challenging in bilateral SUBs due to unequal renal pelvis filling. Supraphysiologic irrigation volumes may mask partial obstructions.

Limitations:
Limitations include a small sample size, single imaging time point per cat, and variable intervals post-SUB placement. Additionally, fluoroscopic evaluations might not reflect physiologic urine flow, potentially underestimating partial obstructions.

Conclusions:
Most native ureters remain or regain patency after SUB placement in cats. Trigonal irrigation observed during ultrasound-guided SUB flushes is a reliable non-invasive indicator of ureteral patency. This technique may assist in clinical decision-making regarding SUB management without necessitating further invasive imaging.

Disclaimer: The summary generated in this email was created by an AI large language model. Therefore errors may occur. Reading the article is the best way to understand the scholarly work. The figure presented here remains the property of the publisher or author and subject to the applicable copyright agreement. It is reproduced here as an educational work. If you have any questions or concerns about the work presented here, reply to this email.