In a specimen of kidney, fibrinoid necrosis is seen and onion peel appearance is also present. Most probable pathology is –
**Core Concept**
Fibrinoid necrosis and onion peel appearance are classic pathological features associated with a specific type of vascular injury in the kidney. This condition involves damage to the arterioles and small arteries, leading to the deposition of fibrin and other proteins in the vessel walls.
**Why the Correct Answer is Right**
The onion peel appearance, also known as layered laminations, is characteristic of malignant hypertension, which causes repeated episodes of fibrinoid necrosis and subsequent healing with the formation of new layers of collagen. This leads to the characteristic onion peel appearance under histological examination. The fibrinoid necrosis is a result of the breakdown of the vascular basement membrane and the deposition of fibrin, leading to the loss of vascular integrity. The kidneys are particularly susceptible to this type of injury due to their high blood pressure and the presence of renin-angiotensin system.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because fibrinoid necrosis and onion peel appearance are not typically associated with diabetic nephropathy, which is characterized by mesangial expansion and basement membrane thickening.
**Option B:** This option is incorrect because fibrinoid necrosis and onion peel appearance are not characteristic of IgA nephropathy, which typically presents with mesangial deposition of IgA and C3.
**Option C:** This option is incorrect because fibrinoid necrosis and onion peel appearance are not typical of membranous nephropathy, which is characterized by the formation of immune complexes on the subepithelial side of the glomerular basement membrane.
**Clinical Pearl / High-Yield Fact**
Malignant hypertension is a medical emergency that requires immediate attention to prevent further renal damage. The presence of fibrinoid necrosis and onion peel appearance in a kidney specimen should prompt a thorough search for underlying causes, including renovascular disease, primary aldosteronism, and pheochromocytoma.
**Correct Answer: D. Malignant hypertension.**