Association of impaired ammonia excretion with survival in dogs with stable chronic kidney disease.

A urine ammonia-to-creatinine ratio below 2.0 predicts shorter survival and faster progression in dogs with CKD.

This prospective, observational longitudinal study evaluated the prognostic significance of urine ammonia-to-creatinine ratio (UACR) in 50 client-owned dogs with IRIS stages II-IV chronic kidney disease (CKD) receiving therapeutic renal diets. Dogs were followed for up to 12 months or until death and categorized by UACR thresholds of <2.0 or ≥2.0. The majority of enrolled dogs were IRIS stage II (82%). Dogs with UACR <2.0 demonstrated a significantly greater risk of death (HR 3.045; 95% CI, 1.372–7.102) and shorter median survival compared to those with UACR ≥2.0 (189 vs. 445 days, P=0.008). Additionally, dogs with UACR <2.0 experienced significantly faster CKD progression, defined as a >25% increase in serum creatinine from baseline (median 132 vs. 445 days; P=0.0002). A urine protein-to-creatinine (UPC) ratio <1.0 was independently associated with a reduced risk of death (HR 0.351; 95% CI, 0.142–0.879). These findings parallel observations in human CKD patients, where impaired renal ammonia excretion contributes to metabolic acidosis and worsened outcomes. The study suggests that UACR may serve as a clinically meaningful biomarker for risk stratification in canine CKD and may help identify patients that could benefit from alkali supplementation therapy. Limitations include the relatively small sample size and predominance of early-stage (IRIS II) patients, which may limit generalizability across all CKD stages.

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