An autopsy study suggests that diabetic nephropathy is underdiagnosed.

The reported prevalence of diabetic nephropathy (DN) among patients with diabetes varies widely. Most studies use the presence of microalbuminuria for clinical onset of DN in the absence of a histopathologic evaluation. In this autopsy study, we collected and analyzed data from a cohort of patients with type 1 or 2 diabetes and determined the prevalence of histologically proven DN in patients with or without clinical manifestations of renal disease. We also examined the distribution among histopathologic classes with respect to clinical parameters. Renal tissue specimens from autopsies and clinical data were collected retrospectively from 168 patients with diabetes. The histopathologic classification for DN was scored as were interstitial and vascular parameters. In this cohort, 106 of 168 patients had histopathologic changes in the kidney characteristic of DN. Twenty of the 106 histologically proven DN cases did not present with DN-associated clinical manifestations within their lifetime. Glomerular and interstitial lesions were associated with renal function but not with proteinuria. We also found that underdiagnosed DN may encompass all histopathologic classes except the sclerotic class. Thus, the prevalence of histologically proven DN was higher than previously appreciated, and we found a relatively high proportion of DN that was clinically underdiagnosed yet histologically proven, suggesting that DN lesions may develop before the onset of clinical findings.