Diabetic kidney disease: Radiological assessment and clinical correlations

Table 1 Histological classes of diabetic kidney disease

Histologic class	Glomerular	Tubulointerstitial	Vascular
Class I	Isolated thickening of the GBM. Minimal or absent mesangial alterations[18]	Normal or tubular hypertrophy (secondary to hyperfiltration)	Normal or mild arteriolar hyalinosis (more common in the efferent arteriole)[17]
Class II	Diffuse mesangial matrix expansion, mild (IIa) or severe (IIb). Absence of nodular lesions (Kimmelstiel-Wilson) and global glomerulosclerosis < 50%[18]	Focal tubular atrophy and interstitial fibrosis (correlated with the severity of mesangial expansion). Glycogen accumulation in tubular epithelial cells (Armanni-Ebstein lesions)[19]	More evident arteriolar hyalinosis, often involving both afferent and efferent arterioles[17]
Class III	Presence of at least one Kimmelstiel-Wilson nodular lesion. Nodules are acellular and PAS-positive. Global glomerulosclerosis < 50%[19]	Moderate-to-severe IFTA. Infiltration of inflammatory cells[19]	Marked arteriolar hyalinosis. Atherosclerosis of interlobular arteries (characteristic of DKD, but not specific)[17,20]
Class IV	Diffuse global glomerulosclerosis > 50%. The most advanced form of diabetic glomerulosclerosis, with widespread involvement of all remaining glomeruli[18]	Severe and diffuse IFTA (a key predictor of progression to end-stage renal disease[19]	Extensive vascular sclerosis and vascular wall hypertrophy[20]

This table summarizes the histopathological classification of diabetic kidney disease, highlighting the progressive glomerular, tubulointerstitial, and vascular alterations that characterize each class. Class I is defined by isolated glomerular basement membrane thickening with minimal mesangial involvement and usually mild or absent vascular changes. Class II is marked by diffuse mesangial expansion, mild (IIa) or severe (IIb), accompanied by early tubulointerstitial injury and more evident arteriolar hyalinosis. Class III is characterized by the appearance of Kimmelstiel-Wilson nodules and moderate-to-severe interstitial fibrosis and tubular atrophy, together with marked arteriolar involvement. Class IV represents the most advanced stage, defined by diffuse global glomerulosclerosis affecting more than half of the glomeruli, extensive interstitial fibrosis and tubular atrophy, and widespread vascular sclerosis. GBM: Glomerular basement membrane; IFTA: Interstitial fibrosis and tubular atrophy; DKD: Diabetic kidney disease; PAS: Periodic acid-Schiff.