Non-diabetic renal diseases in a multi-ethnic New Zealand cohort with type 2 diabetes mellitus: clinical and histopathological features

SummaryThe aims of this study were to identify non-diabetic renal disease (NDRD), including obesity related glomerulopathy (ORG) in diabetic patients, and compare the findings with those of pure diabetic nephropathy (DN). Ninety-three renal biopsies from diabetic patients were reviewed retrospectively along with their clinical findings at biopsy and their estimated glomerular filtration rate (eGFR) over 5 years follow-up. DN and focal segmental glomerulosclerosis (FSGS) were diagnosed on blinded histology review, together with assessment of renal compartment histology. Other NDRD were diagnosed on full review. Most patients were obese with poor renal function at biopsy. NDRD occurred in more than two-thirds of biopsies. FSGS and interstitial nephritis were common. Patients with pure FSGS presented earlier, and had favourable histological features and clinical course. Most FSGS patients fulfilled criteria for ORG. Biopsies with interstitial nephritis showed more functional glomerular tissue, and most patients retained good renal function. Adverse prognostic features were DN versus NDRD, nodular grade of DN, low eGFR at biopsy, and severe chronic histological changes. In this population, ORG mechanisms contribute to renal injury. FSGS is frequent, and should be diagnosed separately from any DN. Biopsy to confirm suspicion of interstitial nephritis should be performed even if retinopathy is present.