Renal biopsy in diabetic patients

Diabetic nephropathy with superimposed postinfectious GN

The reason for renal biopsy in diabetic patients is mainly due to clinical suspicion of renal diseases other than diabetic nephropathy (DN). Most common causes of concern are sudden increase in proteinuria and rising serum creatinine. With increased proportion of diabetic patients being biopsied, Sharma et al. performed the largest study of renal biopsies in diabetic patients (N = 620). Almost one quarters of their biopsies came from diabetic patients. 384 of 611 (63%) had other renal diseases with or without DN.

The renal diseases found in non-DN group are the usual suspects: FSGS, hypertensive nephrosclerosis, IgA nephropathy, etc. The surprising finding is acute tubular necrosis (ATN) as the most common disease in DN group with other diseases. The explanation is that the functional and hemodynamic compromise in DN coupled with the drug angiotensin converting enzyme inhibitor make the kidneys vulnerable to ATN.
The best predictor of patients having DN alone is the longer duration of diabetes before biopsy (>12 years). The shorter duration and lower degree of proteinuria suggest non-DN renal diseases alone. Active urine sediment is more associated with DN with other diseases than DN alone.