Predictive factors for non-diabetic nephropathy in diabetic patients. The utility of renal biopsy

Diabetic renal lesions can only be diagnosed by kidney biopsy. These biopsies have a high prevalence of non-diabetic lesions. The aims of the study were to determine the predictability of non-diabetic nephropathy (NDN) in diabetics and study differences in survival and renal prognosis. In addition, we evaluated histological lesions and the effect of proteinuria on survival and renal prognosis in patients with diabetic nephropathy (DN).

A descriptive, retrospective study of kidney biopsies of diabetics between 1990 and 2013 in our centre.

110 patients were included in the study: 87 men (79%), mean age 62 years (50-74), mean serum creatinine 2.6mg/dl (0.9-4.3) and proteinuria 3.5g/24hours (0.5-6.5). 61.8% showed NDN, 34.5% showed DN and 3,6% showed DN+NDN. The most common NDN was IgA nephropathy (13,2%). In the multivariate analysis, creatinine (OR: 1.48, 1.011-2.172, p=0.044), proteinuria/24hours (OR: 0.813, 0.679-0.974, p=0.025), duration of diabetes (OR: 0.992, 0.987-0.998, p=0.004), age (OR: 1.068, 95% CI: 1.010-1.129, p=0.022), and diabetic retinopathy (OR: 0.23, 0.066-0.808, p=0.022) were independently associated with NDN. We did not find any differences in survival or renal prognosis. Concerning patients with DN, increased nodular mesangial expansion (p=0.02) and worse renal prognosis (p=0.004) were observed in nephrotic proteinuria as compared to non-nephrotic proteinuria. We did not find differences in patient survival.

The most common cause of NDN was IgA nephropathy. Higher creatinine levels, shorter duration of diabetes, absence of diabetic retinopathy, lower proteinuria, and older age were risk factors for NDN. Patients with DN and nephrotic-range proteinuria had worse renal prognosis.