Relationship between Urinary Ammonia Excretion and Survival Time in Dogs with Kidney Disease

Abstract:

Background: Inadequate ammonia excretion drives the development of metabolic acidosis in people with chronic kidney disease (CKD) and is associated with worse clinical outcomes. Limited information exists about ammonia excretion in dogs with CKD. Hypothesis/

Objectives: We hypothesized that impaired urine ammonia-to-creatinine ratio (UACR) would be associated with worse clinical outcomes in dogs with stable CKD Animals: 60 client-owned dogs with stable IRIS stage II-IV CKD.

Methods: Single institution prospective longitudinal study. Dogs were followed until death or study end (12 months). Survival times were calculated from the date of study inclusion. Univariable Cox regression was used to assess variables associated with survival. Dogs with > 25% change in serum creatinine were classified as having progressive CKD and compared to dogs with stable CKD using Mann-Whitney test.

Results: Impaired ammonia excretion (UACR < 2.0) was associated with risk of death (hazard ratio 2.814; CI 1.067- 8.115), with significant survival difference between dogs with UACR < 2.0 (189 days) and dogs with UACR > 2.0 (445 days) (P =0.008). Progressive CKD dogs (n=27) had lower ammonia excretion (UACR 1.7; 0.2-5.5) compared to stable CKD dogs (n=23) (UACR 3.2; 0.3-7.7)(P=0.006). Conclusions and Clinical Importance: Dogs with CKD and impaired ammonia excretion (UACR < 2.0) had 2.8 times greater risk of death and shorter survival times compared to dogs with unimpaired ammonia excretion (UACR >2.0). Dogs with progression of their CKD had significantly lower ammonia excretion at enrollment compared to dogs with stable CKD. UACR may be a useful biomarker for determining alkali therapy use.