The effect of prandial state on urine ammonia-to-creatinine ratio in cats with and without chronic kidney disease.

Abstract

BACKGROUND: Impaired ammonia excretion plays a role in the pathogenesis of metabolic acidosis in chronic kidney disease (CKD) and could have prognostic value. Evaluation involves measurement of ammonia excretion as urine ammonia-to-creatinine ratio (UACR). HYPOTHESIS/OBJECTIVES: To investigate the effect of unfed vs fed state on UACR in cats with and without CKD. We hypothesized that UACR is greater in the fed state, and this effect would be blunted in cats with CKD. ANIMALS: Cats with stable International Renal Interest Society (IRIS) stages I-IV CKD (n = 13) and healthy cats (n = 10). METHODS: Randomized, prospective cross-over study. CBC, serum biochemistry, T4, and urinalysis were performed in all cats to confirm health status. Urine was collected at 2 visits approximately 1 week apart; once unfed, and once 2-3 hours post meal. Urinary ammonia and creatinine concentrations were measured using commercially available assays and used to calculate UACR. RESULTS: Urine ammonia-to-creatinine ratio was significantly lower in fed (median = 0.77, range 0.11-6.59) vs unfed state (median 2.55, range 0.49-9.58) in cats with CKD (P = .01), but not in healthy cats (fed median 4.305, range 0.19-11.54; unfed median 4.98, range 0.65-10.81; P = .49). CONCLUSIONS AND CLINICAL IMPORTANCE: Prandial state affects UACR in cats with CKD, which suggests it should be kept consistent in longitudinal sampling.