NU02 - Correlation of Ammonia Excretion with Renal Function and Serum Bicarbonate in Cats with Kidney Disease

Abstract: Background
Metabolic acidosis is common in cats with chronic kidney disease (CKD). Inadequate ammonia excretion is thought to drive development of metabolic acidosis in people with CKD and correlates with worse outcomes. There is limited information about ammonia excretion in cats with CKD.

Hypothesis/Objectives
The primary aim was to determine if urine ammonia-to-creatinine ratio (UACR) correlated with renal function (serum creatinine) or serum bicarbonate in cats with CKD. A secondary aim was to evaluate if ammonia excretion was different in healthy (abstract: 1431493) and CKD cats.

Animals
Twenty-one client-owned cats with stable CKD IRIS stage 2-4 were assessed via history, physical examination, serum chemistry, PCV/TP, urinalysis, urine protein-to-creatinine ratio, and blood pressure measurement. Urine samples were processed and stored under mineral oil at -80◦C.

Methods
Urinary ammonia and creatinine concentrations were measured using commercially available enzymatic assays and used to calculate UACR. Coefficient of determination (Pearson correlation coefficient squared) between UACR and serum creatinine, UACR and serum bicarbonate was calculated. Mean UACR of healthy versus CKD cats was compared using unpaired Student’s T-test.

Results
UACR weakly correlates with serum creatinine (R² = 0.22) and serum bicarbonate (R² = 0.10). There was a significant difference (p< 0.001) between UACR in healthy (8.9 ± 4.4) and CKD (2.8 ± 1.5) cats.

Conclusions and Clinical Importance
Clinical significance of the difference in ammonia excretion between healthy and CKD cats is unknown. Future research is warranted to determine if ammonia excretion alteration in CKD patients provides prognostic information or influences clinical management.