Prevalence of immune-complex glomerulonephritides in dogs biopsied for suspected glomerular disease: 501 cases (2007-2012).

BACKGROUND Glomerulonephropathies are common causes of kidney disease in dogs. OBJECTIVE To determine the prevalence of immune-complex glomerulonephritis (ICGN) in North American dogs biopsied for suspected glomerular disease. ANIMALS Renal biopsies (n = 733) submitted to the Texas Veterinary Renal Pathology Service between January 1, 2007 and December 31, 2012 were reviewed. Dogs were included if the biopsy was performed for suspected glomerular disease. METHODS Specimens were evaluated by light microscopy (LM), immunofluorescence (IF), and transmission electron microscopy (TEM). Findings were retrospectively evaluated to categorize the diagnosis for each case. For the diagnosis of ICGN, TEM findings were considered conclusive when LM and IF were equivocal. RESULTS Of the 501 dogs included in the study, 241 (48.1%) had ICGN; 103 (20.6%) had primary glomerulosclerosis; 76 (15.2%) had amyloidosis; 45 (9.0%) had nonimmune complex (IC) glomerulopathy; 24 (4.8%) had non-IC nephropathy; and, 12 (2.4%) had primary tubulointerstitial disease. Many (66/241; 27.4%) ICGN cases required TEM for definitive diagnosis, including 14 cases (5.8%) that were not suspected on LM. Of cases not diagnosed as ICGN, a substantial proportion (60/260; 23.1%) required TEM to rule out immune complex deposits, including 14 of 189 cases (7.4%) presumptively diagnosed as ICGN on LM. CONCLUSIONS AND CLINICAL IMPORTANCE Approximately half of all dogs biopsied for suspected glomerular disease had conditions other than ICGN. Renal biopsy is needed to accurately categorize the underlying disease and direct appropriate treatment. Additionally, TEM and IF evaluations by experienced nephropathologists are necessary to obtain an accurate diagnosis in many cases.