12.2 Acute Renal Failure

Question 1

What is the hallmark of renal failure?

Answer 1

Azotemia

Question 2

What are the 3 etiologies of acute renal failure?

Answer 2

• Prerenal
• Renal
• Postrenal

Question 3

Prerenal - ARF

Answer 3

Decreased blood flow

Question 4

Renal - ARF

Answer 4

Intrinsic renal diseases causing ARF

Question 5

Postrenal - ARF

Answer 5

Obstruction to the outflow

Question 6

What are some signs of prerenal ARF?

Answer 6

Decreased GFR, azotemia and oliguria

Question 7

What is the ratio of BUN:Cr in prerenal azotemia?

Answer 7

BUN:Cr greater than 15

Question 8

What is the FENa in prerenal azotemia?

Answer 8

FENa less than 1%

Question 9

How does aldosterone affect BUN reabsorption?

Answer 9

It will increase the reabsorption of BUN and increase the BUN:Cr ratio

Question 10

How does postrenal obstruction lead to ARF?

Answer 10

It will cause back pressure against the GFR decreasing the GFR as less blood is filtered

Question 11

What is the BUN:Cr in early postrenal obstruction?

Answer 11

BUN:Cr is greater than 15

Question 12

What is the FENa in early postern obstruction?

Answer 12

FENa will be less than 1%

Question 13

What is the main cause of ARF?

Answer 13

Acute Tubular Necrosis

Question 14

How does ATN decrease the GFR?

Answer 14

Necrotic cells will obstruct the tubules and cause back pressure

Question 15

What are some signs of ATN?

Answer 15

Brown granular epithelial casts will be seen in the urine

Question 16

What is the BUN:Cr ratio in ATN?

Answer 16

BUN:Cr ratio will be less than 15

Question 17

What is the FENa in ATN?

Answer 17

FENa will be greater than 2%

Question 18

What are the major etiologies of ATN?

Answer 18

• Ischemia

- Nephrotoxicity

Question 19

What can prolong prerenal azotemia lead to?

Answer 19

ATN

Question 20

What are the main causes of nephrotoxicity?

Answer 20

• Aminoglycosides
• Myoglobin
• Radiocontrast dye
• Heavy metals
• Urate
• Ethylene glycol (oxalate crystals in urine)

Question 21

What will happen to K+ in ATN?

Answer 21

Hyperkalemia

Question 22

What are the main causes of acute interstitial nephritis?

Answer 22

Drugs - NSAIDs, penicillin, diuretics

Question 23

What does the finding of eosinophils in the urine indicate?

Answer 23

Acute interstitial nephritis

Question 24

Renal Papillary Necrosis

Answer 24

Necrosis of the renal papillae as a sequelae of acute interstitial nephritis

Question 25

What is the presentation of renal papillary necrosis?

Answer 25

Hematuria and flank pain

Question 26

What are some of the causes of renal papillary necrosis?

Answer 26

• Chronic analgesic abuse
• Diabetes
• Sickle Cell Anemia/Trait
• Severe acute pyelonephritis