Pathology MCQ Answer 498

1. Tubular epithelial cell destruction with acute renal cell suppression
1. Most common cause of renal failure, also caused by
1. Severe glomerular disease (RPGN)
1. Diffuse renal vascular disease (polyarteritis nodosa)
2. Acute papillary necrosis
3. Acute drug induced interstitial nephritis
4. Diffuse cortical necrosis
2. ATN Causes
1. Ischemic ATN Setting of hypotension and shock – ischemic ATN
2. Nephrotoxic ATN:
1. metal (Hg), CCl₄,
2. drugs(gentamicin)
3. contrast agents
3. Pathogenesis
1. Tubular injury (reversible & irreversible)
2. Persistent & severe blood flow disturbance
1. RAS system is involved: positive feedback for vasoconstriction
4. MOST COMMON CAUSE OF RENAL FAILURE
1. Suppression of renal function with urine flow falling below 400ml (oliguria)
5. Tubular injury – LOSS OF CELL POLARITY
1. Redistribution of MEM protein from basolateral to luminal side of tubular cells
1. Increased Na to distal tubules – vasoconstriction
2. Interstitial edema from damaged tubules can increase pressure and cause collapse
2. Disturbance in blood flow – ischemic renal injury causing reduced GFR
1. intrarenal vasoconstriction due to sublethal endothelial injury causing increased
1. endothelin release and
2. decreased nitric oxide
2. direct effect of ischemia or toxins on the glomerulus
3. Tubulorrhexis – rupture of BM
1. Casts in distal tubules and collecting ducts
2. Tamm-Horsfall protein hemoglobin, plasma protein
3. PMN, lymphocytes, PC
4. Toxic ATN – similar with most damage in proximal tubule, BM spared
5. Epithelial regeneration within a week – cuboidal epithelial covering
6. Clinical course
1. Initiating phase ~ 36hrs,
1. ischemia with slight decline in urine output, ↑ BUN
2. Maintenance phase – up to 3 weeks, urine output <400ml
3. Recovery phase
1. ↑urine output (up to 3L/day for a few days), increased infection
2. 25% OF DEATHS IN RECOVERY PHASE
3. gradual return of well-being,
1. urine volume normalizes,
2. subtle functional impairment for months,
• 90-95% survival

Category: Pathology MCQs