Long-Term Follow-Up of Renal Function in Dogs after Treatment for ACTH-Dependent Hyperadrenocorticism

Background Systemic hypertension and proteinuria are frequent complications in dogs with Cushing's syndrome and do not always resolve after treatment of hypercortisolism. Therefore, dogs with Cushing's syndrome may be at risk for renal dysfunction before and after treatment. Hypothesis/Objectives To assess renal function in dogs with ACTH-dependent hyperadrenocorticism (ADHAC) before and after treatment. Animals A total of 19 dogs with ADHAC and 12 control dogs. Methods Renal function was assessed before and at 1, 3, 6, and 12 similar to months after treatment. Twelve dogs were treated with trilostane and 7 dogs by transsphenoidal hypophysectomy. Routine renal markers were measured and urinary albumin (uALB), immunoglobulin G (uIgG), and retinol-binding protein (uRBP) were assessed by ELISA. Urinary N-acetyl-beta-D-glucosaminidase (uNAG) was determined colorimetrically. All urinary markers were indexed to urinary creatinine concentration (c). Plasma clearance of creatinine (Clcreat), exo-iohexol (Clexo), and endo-iohexol (Clendo) was used to measure glomerular filtration rate (GFR). Data were analyzed using a general linear model. Results Serum creatinine and urea concentrations increased post-treatment, but remained within reference ranges. Plasma Clcreat and Clendo were significantly lower post-treatment, whereas Clexo was not different. Urinary protein-to-creatinine ratio (UPC), uALB/c, uIgG/c, and uRBP/c were decreased post-treatment, but at 12 similar to months 5/13 dogs remained proteinuric. Urinary NAG/c did not change significantly. Conclusions and clinical importance A decrease in GFR and persistent proteinuria post-treatment may warrant the clinician's attention. Future research including renal histopathology of dogs with persistent proteinuria or low GFR is needed to further assess renal outcome.