Pseudomembranous cystitis in cats with presumed or confirmed mineralization: A retrospective study of 26 cases (2016‐2021)

BACKGROUND: Pseudomembranous cystitis (PMC) in cats is a recognized disease, but concurrent mineralization is reported rarely and its outcome is poorly described. HYPOTHESIS AND OBJECTIVES: Describe a population of cats with PMC and the prevalence of concurrent mineralization. ANIMALS: Twenty‐six cats with PMC. METHODS: Medical records were retrospectively reviewed (January 2016 to December 2021). Cats with an ultrasound diagnosis of PMC were included. Clinicopathologic results, imaging, treatment, and outcome were reviewed. RESULTS: All cats were male and 21 (80%) were diagnosed with urethral obstruction (UO). Five cats (23.8%) had positive urine culture (Staphylococcus felis, 3/5; Proteus mirabilis, 2/5) with a median urine pH of 8 (range, 6‐9). All cats had ultrasonographic changes suggestive of mineralization. On ultrasound examination, 10 cats (38.5%) had pseudomembranes with acoustic shadowing suggestive of mineralization, 15 (57.7%) had changes indicative of ulceration, and 8 (31%) had changes compatible with of a urachal anomaly. Twenty‐two cats received medical treatment, 4 underwent surgery (3 percutaneous cystolithotomy, 1 cystotomy). Twenty cats (77%) survived to discharge. Follow‐up ultrasound examination indicated resolution of PMC in 6/7 cats, 4 had persistent hyperechoic bladder lining. Five of 12 cats with follow‐up had a relapse of lower urinary tract signs. CONCLUSIONS AND CLINICAL IMPORTANCE: Pseudomembranous cystitis was diagnosed mainly in male cats with UO and imaging findings suggestive of mineralization were present in all cases. Frequent negative urine culture suggests a different etiology than encrusting cystitis related to urease‐positive bacteria. Good outcomes can be achieved with medical management.