Sketchy Path: Acute Tubular Necrosis

Question 1

The most common cause of AKI is ____________.

Answer 1

acute tubular necrosis

Question 2

ATN is usually caused by _____________.

Answer 2

decreased renal perfusion (like the kid trying to shoot the zombie with the super soaker that’s depleted)

This is basically a prerenal azotemia (decreased perfusion) leading to an intrinsic azotemia (acute tubular necrosis).

Question 3

Common scenarios that lead to decreased perfusion with subsequent AKI include ___________________.

Answer 3

• Hemorrhage such as from trauma (like the kid’s bleeding)
• MI with decreased cardiac output (broken guitar by his feet)
• Sepsis with hypotension

Question 4

Part of what damages the nephrons of the kidney during a low perfusion episode is _______________.

Answer 4

ischemic damage to the afferent arteriole that leads to vasoconstriction from release of endothelin and decreased release of NO (like the zombie riding the bumper car with NO pipes grabbing the kid’s sleeve and twisting it); this prevents blood flow to the glomerulus and worsens the ischemic damage to the glomerulus (like how the other zombies can’t get through the afferent gate)

Question 5

By what two ways does GFR decrease in acute tubular necrosis?

Answer 5

• Decreased blood flow through the afferent arteriole (described in another card)
• Nephrons clogged with sloughed off tubule epithelium cause back pressure to the glomerulus (like the gutter clogged with muddy leaves)

Question 6

Which parts of the kidney are most susceptible to ischemic damage?

Answer 6

• PCT (like the cracked sign for the cart track)
• Ascending loop of Henle (zombie reaching for ascending cart)
• Medulla

The top two are the most metabolically active, so it makes sense that they would suffer the most from ischemic damage. The medulla is less perfused than the cortex, so it also is vulnerable.

Question 7

What will histologic exam of the kidney show in acute tubular necrosis?

Answer 7

• Dilated tubules with patchy loss of epithelium (like the patches of the inner pipe missing)
• Ruptured basement membrane with vacuolized epithelial cells (like the holes in the drain pipe)

Question 8

List the three stages of ATN.

Answer 8

• Initiation phase (first 36 hours): renal function stays normal (like the clown smiling over the “come on IN” sign)
• Maintenance phase (36 hours to 1-2 weeks): oliguria (trickle of water from GFR machine); azotemia (BUN next to coffee machine and credit card on coffee machine); acidosis, hyperkalemia, and hyperphosphatemia
• Recovery phase (after 1-2 weeks): reepithelialization (girl covering her friend in a pink jacket); profound diuresis (guy peeing everywhere); loss of all electrolytes (banana, magnets, ice cream, and peanuts knocked over from the trash can)

Question 9

Which part of the kidney is damaged in toxic acute tubular necrosis?

Answer 9

The PCT (like the toxic barrels dumping on the PCT sign)

Question 10

What things can cause nephrotoxic ATN?

Answer 10

• Aminoglycosides (kid with sais)
• Rhabdomyolysis (ninja with chicken bucket)
• Contrast agents (like the contrasting yin-yang symbol on his jacket)