Diabetes: To Biopsy or not to Biopsy - Part 2

In my experience the appetite to biopsy patients with clinical renal disease varies widely between clinician, institution and country. This is most apparent when it comes to the diabetic patient with renal disease. In my opinion there is a fear among nephrologists of biopsying patients with potential diabetic nephropathy (DN). Of course there are clinical features that increase the likelihood that a diabetic with renal disease has DN. Retinopathy in a type 1 diabetic, longstanding DM and progressive proteinuria over years preceding an elevated creatinine. However, the role of microalbuminuria and proteinuria in predicting CKD progression and the traditional course of rising albuminuria in DM1 has been challenged. In DM type 2 the picture is less clear and these patients frequently have many comorbidities. Gearoid posted on this subject about a year ago now. In CJASN (October) Sharma et al from Columbia University reviewed the characteristics and renal diagnoses in 620 diabetics who had a renal biopsy. Over 90% had type 2 diabetes. In Columbia in 2011 approximately ¼ of all biopsies were on patients with diabetes. The results of this retrospecive review were that 37% of patients had DN alone, 36% had non-diabetic renal disease (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.

In DN plus NDRD: ATN (43%), hypertensive nephrosclerosis (19%), FSGS (13%), and IgA nephropathy (7%).

In multivariate analysis longer duration of DM was associated with a greater likelihood of DN and less likelihood of NDRD.

The table illustrates the features of patients at the time of biopsy. Older age, having DM2 vs DM1, short duration of DM and less proteinuria are more likely in those with NDRD alone vs DN alone in this cohort. 

I think this study highlights the importance of considering biopsy in diabetics (especially type 2). I would be interested to hear about the experience of others with respect to biopsy in diabetics.

Posted by Andrew Malone

Characteristics	DN Alone	DN Plus NDRD	NDRD Alone
Participants (n)	227	164	220
Age (yr)	59 (49–65)	63 (55–72)	63 (54–70)
Male sex	129 (56.8)	100 (61.0)	142 (64.6)
Race
Unknown	108 (47.6)	57 (34.8)	104 (47.3)
White	62 (27.3)	63 (38.4)	70 (31.8)
African American	39 (17.2)	33 (20.1)	29 (13.2)
Hispanic	12 (5.3)	7 (4.3)	8 (3.6)
Asian	4 (1.8)	4 (2.4)	7 (3.2)
Other	2 (0.9)	0 (0.0)	2 (0.9)
DM type 1	9 (4.0)	5 (3.1)	2 (0.9)
Duration of DM (yr)	13 (8–17)	10 (7–18)	5 (3–10)
Serum creatinine (mg/dl)	2.3 (1.6–3.8)	3.1 (1.7–5.2)	2.3 (1.5–4.4)
eGFR (ml/min per 1.73 m2)	31.3 (17.5–55.2)	21.4 (12.5–46.6)	32.5 (14.3–60.0)
Proteinuria (g/d)	5.0 (2.8–8.8)	5.0 (2.0–8.0)	2.9 (1.4–7.1)