PA27.{11,15} | Vascular Diseases & Thrombotic Microangiopathies — Summary & Reflection

REFLECT

You have now encountered three patterns of renal arteriolar disease: hyaline change (benign nephrosclerosis, slow), fibrinoid necrosis and onion-skin (malignant hypertension, acute), and platelet-fibrin microthrombi (TMA, acute-to-subacute). Reflect on these questions before continuing:

1. If a renal biopsy shows onion-skin arteriolitis without fibrinoid necrosis, what clinical differentials would you consider? (Hint: malignant HTN, scleroderma renal crisis, and chronic TMA all share this lesion — how would you distinguish them?)

1. A patient with SLE develops TMA. ADAMTS13 is 35% (reduced but not severely). No diarrhoea. What additional investigation would you prioritise?

1. Why does E. coli O157:H7 preferentially damage the kidney in children but tend to produce more neurological complications in adults?

KEY TAKEAWAYS

Key take-home points — Vascular Diseases and TMA of the Kidney:

• Benign nephrosclerosis — chronic mild hypertension → hyaline arteriolosclerosis + fibroelastic hyperplasia → patchy ischaemia → bilateral shrunken finely granular kidneys; slow progression.

• Malignant nephrosclerosis — acute severe hypertension → fibrinoid necrosis of arterioles + onion-skin hyperplastic arteriolitis → flea-bitten kidney; medical emergency with AKI.

• Renal artery stenosis — atherosclerotic (proximal, older males) vs fibromuscular dysplasia (string-of-beads, young females) → RAAS activation → renovascular hypertension; FMD responds well to angioplasty.

• TMA — unifying pathological theme: endothelial injury → microthrombi → MAHA + thrombocytopenia + AKI; distinguish by diarrhoeal prodrome (HUS-typical), ADAMTS13 (TTP), complement (aHUS).

• Typical HUS — Shiga-toxin (E. coli O157:H7), children, renal failure dominant, supportive Rx.

• TTP — ADAMTS13 deficiency (acquired autoantibody), adults, CNS dominant, plasma exchange is life-saving; platelet transfusion contraindicated.

• aHUS — complement factor H mutation, eculizumab responsive.

• Bilateral cortical necrosis — obstetric catastrophe (abruptio placentae) + DIC → selective cortical ischaemia; may calcify.

• Renal infarction — embolic (AF, endocarditis) → wedge-shaped coagulative infarct.