Postmortem urinary tract changes in cats with urethral obstruction

OBJECTIVE: To report the gross and histopathological postmortem findings of the urinary tract and compare them to clinical severity of disease in cats with urethral obstruction (UO). DESIGN: Retrospective, observational, descriptive study. SETTING: University teaching hospital. ANIMALS: Fourteen cats from 2000 to 2014 with UO that had a complete postmortem examination. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Bladder lesions were moderate-severe in 10 of 14 (71%) and mild in 4 of 14 (29%) cats. Bladder lesions were diffuse in 8 of 14 (57%), multifocal in 3 of 14 (21%), and focal in 3 of 14 (21%) cats. Lymphocytic cystitis was noted in 11 of 14 cats (78%), and neutrophilic cystitis was noted in 10 of 14 (71%) bladders. Urethral lesions were moderate-severe in 4 of 14 (29%), mild in 4 of 14 (29%), and no urethral lesions were identified in 6 of 14 (43%) cats. Ureteral lesions were mild in 1 of 14 (7%), and no ureteral lesions were identified in 13 of 14 (93%) cats. There were moderate-severe histopathological renal lesions in 5 of 14 cats (36%), mild renal lesions in 6 of 14 (43%), and no renal lesions were identified in 3 of 14 cats (21%). Renal lesions were multifocal in 10 of 14 (71%) and regional in 1 of 14 cats (7%). In the kidneys, the most common inflammatory infiltrate was lymphoplasmacytic. The severity of urethral lesions was not associated with the severity of bladder lesions (P = 1.0). Hyperkalemia paralleled the severity of bladder (P = 0.02) and renal lesions (P = 0.04). An association between the severity of bladder lesions and degree of azotemia could not be determined due to small sample size and removal of the most azotemic cats. CONCLUSIONS: Substantial renal and urinary bladder inflammatory lesions were found in cats with UO. The severity of these findings paralleled the severity of blood potassium concentrations.