Small Animal Internal Medicine Resident The Ohio State University Veterinary Medical Center Columbus, Ohio, United States
Abstract:
Background: Impaired ammonia excretion plays a role in the pathogenesis of metabolic acidosis in CKD, and may have prognostic value. Gold standard evaluation involves measurement of ammonia excretion as urine ammonia-to-creatinine ratio (UACR). The influence of eating on UACR is unknown.Hypothesis/
Objectives: To investigate the effect of fasting vs feeding on urine ammonia levels in cats with and without CKD. We hypothesized that UACR would increase after feeding and this effect would be blunted in cats with CKD.Animals: Cats with stable IRIS stages 1-4 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 two visits approximately one week apart; once 2-3 hours post meal, and once fasted. Urinary ammonia and creatinine concentrations were measured using commercially available assays and used to calculate UACR.
Results: UACR was significantly lower in fed (median = 0.77, range 0.11-6.59) versus fasted state (median = 2.55, range 0.49-9.58) in CKD cats (P = 0.01). There was no difference in control cats (fed median = 4.305, range 0.19-11.54; fasted median 4.98, range 0.65-10.81) (P = 0.49). There was a significant negative correlation between serum creatinine and UACR in both the fed (r = -0.84; P = 0.0006) and fasted state (r = -0.92; P < 0.0001). Conclusions and Clinical Importance: Prandial state affects UACR in cats with CKD and should be kept consistent in longitudinal sampling.
