The modern spectrum of renal biopsy findings in patients with diabetes

Abstract

Background and objectives: Renal biopsies performed in diabetic patients are increasing in number and complexity. This study sought to determine the usefulness of renal biopsy in patients with diabetes and the predictability of diagnosing diabetic nephropathy (DN) versus nondiabetic renal disease (NDRD) from clinical and laboratory data.

Design, setting, participants, & measurements: To assess modern trends, a retrospective study was performed of clinical-pathologic findings in all patients with diabetes who had a biopsy in 2011. Among 2642 native kidney biopsies, 620 (23.5%) were from patients with diabetes.

Results: The cohort included 371 men (60.7%) aged a median (interquartile range) 62 years (52-69) with 10-year (5-15) duration of diabetes mellitus (DM). Median serum creatinine was 2.5 mg/dl (1.6-4.4), and 52% of patients had stage 4-5 CKD. On biopsy, 37% of patients had DN alone, 36% had NDRD alone, and 27% had DN plus NDRD. In NDRD alone, FSGS (22%), hypertensive nephrosclerosis (18%), acute tubular necrosis (ATN) (17%), IgA nephropathy (11%), membranous GN (8%), and pauci-immune GN (7%) comprised 80% of diagnoses, compared with ATN (43%), hypertensive nephrosclerosis (19%), FSGS (13%), and IgA nephropathy (7%) for DN plus NDRD. In multivariate analyses, longer duration of DM was associated with a greater likelihood of DN and a lower likelihood of NDRD: each added year of DM reduced the odds of NDRD by 5% (odds ratio, 0.95; 95% confidence interval, 0.91 to 0.98; P=0.004). DM duration ≥ 12 years was the best predictor (58% sensitivity, 73% specificity) of DN alone.

Conclusions: Approximately one-quarter of all renal biopsies are performed in patients with DM. Judicious use of renal biopsy has uncovered NDRD alone or superimposed on DN in the majority of such biopsies. ATN is emerging as an important category of NDRD, which has not been reported previously.

Figure 1.

Diabetic nephropathy with superimposed IgA nephropathy. (A) A glomerulus with moderate nodular mesangial sclerosis and glomerular basement membrane thickening exhibits mild segmental mesangial hypercellularity (staining with periodic acid–Schiff). (B) A representative glomerulus shows mesangial expansion by increased mesangial cell number and matrix (staining with hematoxylin and eosin). (C) Immunofluorescence staining for IgA shows global mesangial immune deposits within the expanded mesangium. (D) By electron microscopy, there is a paramesangial electron dense deposit typical of IgA nephropathy associated with mesangial sclerosis and mild uniform glomerular basement membrane thickening owing to underlying diabetic nephropathy. Original magnification, ×400 in A–C; ×10,000 in D.