Development of a reference interval for urinary ammonia‐to‐creatinine ratio in feline patients

Background Disruption of acid–base homeostasis can lead to many clinical problems. Ammonia excretion by the kidneys is critical to maintaining acid–base homeostasis through bicarbonate production. Measurement of ammonia excretion may help determine if the kidneys are properly functioning in maintaining acid–base balance. Reference intervals are essential tools for clinical decision‐making but do not currently exist for urinary ammonia‐to‐creatinine ratio (UACR) in feline patients. Objective This study aimed to generate a reference interval (RI) for UACR in healthy adult cats. Methods The study used samples from client‐owned adult healthy cats that presented to the University of Florida Primary Care and Dentistry service (n = 92). Physical examination, serum biochemistry, urinalysis, urine ammonia, and creatinine concentrations were measured. Cats were excluded if there were significant abnormalities in their urinalysis or biochemistry panel. The RI for UACR was calculated according to the recommendation of the American Society for Veterinary Clinical Pathology. The UACR was evaluated for correlation with serum bicarbonate, weight, age, and sex. Results The RI for UACR was 3.4–20.7 with 90% confidence intervals for the lower and upper limits of (3.0–3.7) and (16.0–23.7), respectively. No significant correlation with age, sex, or weight was found. There was no discernable relationship between serum bicarbonate and UACR. Conclusions Establishing an RI for UACR in healthy adult cats will allow further studies to determine if changes in UACR are observed during specific disease states.