Clinic for Small Animal Internal Medicine, Vetsuisse Faculty, University of Zurich, Zürich, Switzerland
Ureteral Obstruction in Cats: Diagnosis and Management
Ureteral obstructions in cats may be luminal, intramural or extramural. Causes for intraluminal obstructions are stones, blood clots or debris (Adams 2017). Intramural causes are strictures, edema of the mucosa or neoplasia. Extramural causes are compression because of circumcaval ureters, masses compressing the ureters or trauma. The most common cause of ureteral obstruction in cats is urolithiasis. Most of these stones contain calcium oxalate and therefore dissolution by dietary interventions or medications is not possible. A ten-fold increase in ureteral stones has been reported in cats between 1980 and 1999 (Lekcharoensuk et al. 2005).
Ureteral obstruction can lead to severe kidney damage.
Common clinical signs of ureteral obstruction are not specific. Inappetence, lethargy, signs of lower urinary tract disease, vomiting, and weight loss were the most common signs in one study (Wormser et al. 2016). Eight percent of the cats showed no clinical signs.
Radiographs and ultrasound are used to identify the causes and the severity of the obstruction. In one study, sensitivity of these two modalities to identify ureteral calculi was 90% (Kyles et al. 2005). Computer tomography can provide additional information.
Treatment options for ureteral obstruction are surgical removal of the intraluminal obstruction, placing a ureteral stent placing a subcutaneous bypass system.
Traditional surgery was considered not very successful as 19% of the patients died or were euthanized during or shortly after the procedure (Kyles et al. 2005). In another study, 21% of the cats did not survive to discharge (Roberts et al. 2011). However, in a more recent study where ureteral surgery was compared with ureteral stents, perioperative mortality of traditional surgery was 8% (Wormser et al. 2016).
Because traditional surgery was unsatisfactory, other options for treatment were developed. Ureteral stents provided an option to treat the cats without opening the ureter. Ureteral stenting seems to be more successful than traditional surgery. In one study of 69 cats, stent placement was successful in 75 of 79 ureters (95%) (Berent et al. 2014). The perioperative mortality rate was 7%. The median survival time was 498 days. Long-term complications included re-obstruction of the ureters and were seen in 19% of the ureters. Over all, stents had to be replaced in 27% of the ureters.
Subcutaneous ureteral bypass devices are considered easier to place. In a study presented at the ACVIM forum 2016, in 137 cats, the device was successfully placed in all 174 ureters (Berent et al. 2016). Ninety-four percent (94%) of the cats survived to discharge. Median survival time was 827 days. Thirteen percent (13%) of the SUBs had to be replaced due to obstruction.
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