EFFECTS OF GLUCOCORTICOID THERAPY ON URINE PROTEIN-TO-CREATININE RATIOS AND RENAL MORPHOLOGY IN DOGS

Glomerulonephritis has been associated with exogenous glucocorticoid a dministration and spontaneous hyperadrenocorticism in the dog. The pur pose of this study was to determine the effects of long-term glucocort icoid therapy on urine protein:creatinine ratios (UP/Cs) and renal mor phology. Nine young-adult male dogs were determined to be healthy and have normal renal function as assessed by physical examination, CBC, s erum biochemistry analysis, Knott's test for Dirofilaria immitis, urin alysis, urine culture, urine protein electrophoresis, endogenous creat inine clearance, 24-hour urinary protein excretion, and UP/C. Predniso ne was administered to each dog at a dosage of 2.2 mg/kg PO bid for 42 days. Urinalysis and UP/C were performed on days 0, 7, 14, 21, 28, an d 42 of treatment. Mean UP/C on day 0 was 0.29 +/- 0.10. Mean UP/C inc reased progressively to a maximum of 1.27 +/- 1.02 on day 28, Mean UP/ C on day 42 decreased slightly (0.92 +/- 0.56) but remained significan tly increased above baseline. The most consistent renal light microsco pic finding on necropsy examination was generalized hypercellular glom erular tufts, suggestive of mesangial cell proliferation. Four dogs al so had occasional adhesions of glomerular tufts to Bowman's capsule, a ccompanied by thickening of the capsule. Direct immunofluorescence for immunoglobulin deposition was negative in all dogs. Electron microsco py, evaluated in 7 dogs, was characterized by occasional mild segmenta l thickening of basement membranes, fusion of visceral cell foot proce sses, and glomerular adhesions. The results of this study indicate tha t long-term administration of glucocorticoids results in significant p roteinuria and glomerular changes in the dog. Copyright (C) 1997 by th e American College of Veterinary Internal Medicine.