Mislabeling No More: What Kidney Biopsies Reveal in Diabetes.

BACKGROUND

Diabetic kidney disease (DKD) is a leading cause of chronic kidney disease (CKD); however, diagnosis based solely on clinical criteria may result in substantial misclassification. We hypothesized that histopathological evaluation of kidney biopsy specimens would reveal a high prevalence of non-diabetic kidney disease (NDKD) among patients clinically diagnosed with DKD and identify factors associated with diabetic nephropathy (DN).

METHODS

We retrospectively analyzed 68 adult patients with diabetes mellitus who underwent kidney biopsy between 2013 and 2023, including type 1 diabetes mellitus (T1DM, n = 7), type 2 diabetes mellitus (T2DM, n = 41), and steroid-induced diabetes mellitus (SIDM, n = 20). Demographic, clinical, biochemical, and histopathological data were assessed.

RESULTS

Kidney biopsy revealed isolated DN in 14.7% of cases, NDKD in 75%, and mixed DN + NDKD lesions in 10.3%. DN was most prevalent in T1DM (57.1%), less common in T2DM (29.3%), and rare in SIDM (5.0%) (P = .014; χ2 = 11.62; Cramér's V = 0.26). Diabetic retinopathy was present in 11.8% of patients and hypertension in 88.2%. Among NDKD cases, the most frequent diagnoses were membranoproliferative glomerulonephritis (17.6%), membranous nephropathy (14.7%), and AL amyloidosis (10.3%).

CONCLUSIONS

In most patients with diabetes mellitus, kidney lesions are not consistent with classical diabetic nephropathy. The limited specificity of clinical parameters underscores the need for kidney biopsy to establish the true etiology of kidney injury. These findings support the KDIGO 2024 paradigm promoting a causal diagnostic approach ("CKD due to DM") and highlight the role of kidney biopsy in preventing DKD misclassification.