Urine electrolytes do not predict desoxycorticosterone pivalate efficacy in dogs with hypoadrenocorticism.

Objective: To determine if urine electrolyte assessments can be used to monitor the adequacy of mineralocorticoid therapy in dogs with hypoadrenocorticism (HA).

Animals: 29 dogs with naturally occurring glucocorticoid- and mineralocorticoid-deficient HA.

Procedures: Urine sodium and potassium concentrations, sodium-to-potassium ratios, sodium-to-creatinine ratios, and potassium-to-creatinine (K:Cr) ratios were evaluated in dogs with newly diagnosed HA that were treated with desoxycorticosterone pivalate (DOCP). Dogs underwent measurements of urine and serum sodium, potassium, and creatinine concentrations and plasma renin activities twice monthly for up to 3 months. Regression analyses and calculation of coefficients of determination (R2) were performed to investigate potential associations between urine and serum variables. Urine variables also were compared between dogs considered to be undertreated or overtreated based on plasma renin activities.

Results: Urine K:Cr ratios were significantly associated with serum potassium concentrations 10 to 14 days (P = .002) and 30 days (P = .027) after the initial DOCP injection, but R2 values were only 0.35 and 0.17, respectively. Urine K:Cr ratios (median [IQR]) also were higher in dogs that were overtreated with DOCP (1.3 [0.7 to 2.3]) as compared to those dogs that were undertreated with DOCP (0.8 [0.5 to 0.9]) at 10 to 14 days after the initial DOCP injection (P = .039) but not at 30 days after the initial injection. Other urine variables were not significantly different between undertreated and overtreated dogs.

Clinical Relevance: Measures of urine electrolytes were not useful for assessing the adequacy of mineralocorticoid therapy in HA dogs that were treated with DOCP.