2. Acute Tubular Necrosis

Question 1

What is Acute Tubular Necrosis

Answer 1

Tubular Cell Death due to damage

In hospital setting, ATN is the most common cause of Acute Renal Failure (AKI)

Potentially reversible if the cause is removed and the patient adequately managed

Question 2

What are the 4 main causes of Acute Tubular NEcrosis

Answer 2

1. Ischaemia (very common)
2. Direct Toxicity to tubule cells
3. Acute Tubulointerstitial Nephritis
4. Urinary Obstruction

Question 3

Describe the Pathogenesis of Ischaemia in the occurrence of Acute Tubular Necrosis

Answer 3

Reduced perfusion to the kidneys results in activation of RAS > SNS

This results in intense intrarenal vascoconstriction

This diverts blood away from the cortical glomeruli (which account for about 90%) and towards juxtamedullary nephrons which have a greater capacity for Na+ and H2O retention

Immediate Result = Decreased GFR, and UO decrease

If prolonged, can eventually cause ischaemic damage.

Question 4

Tests for Acute Tubular Necrosis be evidenced?

Answer 4

Presence of Epithelial Cell Casts and Granular Casts in Urine Sediment

Need fresh urine: <1hr

Question 5

Describe the Pathogenesis of Acute Tubular Necrosis

Answer 5

Tubular cells are very metabolically active and thus very sensitive to ischaemic or toxic damage

Intrarenal ischaemia triggers formation of oxygen free radicals - which can cause damage to tubular cells even after blood flow reinstated

There is tubular cell damage, causing back leak of filtrate and thus decrease in GFR

Dying cells slough off and form epithelial cell casts

The casts can also obstruct tubules, further decreasing GFR

Acute Tubular Necrosis is typically patchy, and has good prognosis because the basement membrane is generally preserved

Question 6

Micro Features of Acute Tubular NEcrosis

Answer 6

Focal areas of tubular necrosis with skip areas

Sometimes rupture of BM

Occlusion of tubular lumen with epithelial cell casts or protein casts