Ultrasonography in the diagnosis and management of cats with ureteral obstruction

Abstract

Objectives The objective was to identify clinical or ultrasonographic results associated with ureteral obstruction or outcome in cats with azotaemia. Methods This was a retrospective cross-sectional study of cats with azotaemia (serum creatinine >180 μmol/l) that had ultrasonography of the urinary tract, ultrasound images available for review and received treatment for azotaemia. Cats with pre-renal azotaemia or urethral obstruction were excluded. Associations between clinical and ultrasonographic results and the dependent variables 'tentative diagnosis of ureteral obstruction', 'pyelography positive for ureteral obstruction' and 'death in hospital' were tested using binary logistic regression. Results In total, 238 cats satisfied the inclusion criteria. Median age was 7 years (range 2 weeks to 20 years), duration of clinical signs was 7 days (range 1 day to 6.3 years) and serum creatinine was 417 μmol/l (range 184-2100 μmol/l). Tentative diagnosis of ureteral obstruction in 92/238 (39%) cats was significantly associated with unilateral enlarged kidney on palpation, and dilated renal pelvis and calculi within the ureter on ultrasonography. Pyelography was performed in 49/92 (53%) cats (16 bilateral) with a tentative diagnosis of ureteral obstruction, and was positive for obstruction in 46/65 (71%) instances. No significant differences in ultrasonographic signs were found between cats with obstructed and non-obstructed ureters. Receiver-operating characteristic analysis of renal pelvic diameter as a diagnostic test for ureteral obstruction found an area under the curve not significantly different from 0.5. There was good agreement between results of radiography and ultrasonography for presence of urinary calculi (kappa 0.67). Treatment was medical in 171 (72%) cats and surgical (ureteral stent or bypass device) in 67 (28%). Death in hospital was significantly associated with serum creatinine and presence of peritoneal fluid, but not with clinical diagnosis, ultrasonographic signs or treatment method. Conclusions and relevance Ultrasonography may be used to identify azotaemic cats at greatest risk of ureteral obstruction, but when using pyelography as the reference test ultrasonography appears to be inaccurate for diagnosis of ureteral obstruction.

Diagnostic imaging observations in cats treated with the subcutaneous ureteral bypass system

“…, Lamb et al . ). The median decrease in renal pelvic diameter observed after SUB placement in the present study was 5 mm.…”

“…, Lamb et al . ). Furthermore, renal pelvic size cannot be reliably assessed in fluoroscopic images because of the tendency for the renal pelvis to dilate with the pressure of contrast medium injection.…”

“…, Lamb et al . ). In our study, 94% of the ureters that became patent remained patent over time, although 64% of ureters had an abnormal appearance, likely reflecting the effects of chronic inflammation associated with lodgement of calculi and/or secondary infection (Kyles et al .…”

“…Clinical suspicion of ureteral obstruction was based primarily on azotaemia with supporting ultrasound findings, including renal pelvic dilatation, ureteral dilatation and diagnosis of a ureteral calculus (Lamb et al . ). Diagnosis of partial or complete ureteral obstruction was confirmed in all cats using intra‐operative antegrade pyelography immediately before SUB placement.…”

“…Medical records of cats surgically treated for uni-or bi-lateral ureteral obstruction using the first version of the SUB device between April 2012 (when our institution first started using the device) and June 2017 were reviewed retrospectively. Clinical suspicion of ureteral obstruction was based primarily on azotaemia with supporting ultrasound findings, including renal pelvic dilatation, ureteral dilatation and diagnosis of a ureteral calculus (Lamb et al 2018). Diagnosis of partial or complete ureteral obstruction was confirmed in all cats using intra-operative antegrade pyelography immediately before SUB placement.…”