Paper II
Question
Gross and microscopic changes in kidney in a long standing case of Diabetes Mellitus.
Answer
Diabetic nephropathy is a major microvascular complication of long-standing diabetes mellitus, and one of the leading causes of end-stage renal disease.
Gross changes
- Early stage: kidneys may be normal-sized or slightly enlarged (due to hyperfiltration/hypertrophy)
- Later/advanced stage: kidneys become contracted, with a finely granular cortical surface, reflecting glomerulosclerosis and progressive nephron loss
Microscopic changes
Glomerular changes
- Capillary basement membrane thickening — the earliest detectable change, due to increased basement membrane matrix synthesis
- Diffuse mesangial sclerosis — diffuse increase in mesangial matrix, present in nearly all long-standing cases
- Nodular glomerulosclerosis (Kimmelstiel-Wilson lesions) — pathognomonic finding; ball-like, eosinophilic, PAS-positive nodules of matrix material in the periphery of the glomerulus, often with a laminated appearance
- Progressive glomerulosclerosis (global sclerosis) with advancing disease
Vascular changes
- Hyaline arteriolosclerosis, affecting both afferent AND efferent arterioles (efferent arteriolar hyalinosis is relatively distinctive for diabetes, as most other causes of hyaline arteriolosclerosis, e.g., hypertension, spare the efferent arteriole)
Tubulointerstitial changes
- Tubular basement membrane thickening
- Interstitial fibrosis and tubular atrophy with disease progression
- Increased susceptibility to pyelonephritis and papillary necrosis
Clinical correlation
- Progressive proteinuria (initially microalbuminuria, progressing to overt nephrotic-range proteinuria) and declining glomerular filtration rate, ultimately progressing to chronic kidney disease/end-stage renal disease if uncontrolled