Pathoma: Acute Renal Failure

Question 1

Azotemia means ____________.

Answer 1

increased serum creatinine and BUN

Question 2

Oliguria means ___________.

Answer 2

low production of urine

Question 3

Prerenal azotemia results from ____________.

Answer 3

decreased blood flow to the kidneys

Question 4

In prerenal azotemia, the BUN:creatinine ratio will be greater than ___________.

Answer 4

15

Question 5

Why is the BUN:cr ratio greater than 15 in patients with prerenal azotemia?

Answer 5

Because BUN gets reabsorbed in the collecting duct, and with more aldosterone (which will happen in prerenal azotemia) more BUN will get reabsorbed into the blood, thus raising the ratio

Question 6

Urine osmolarity will be _________ in prerenal azotemia.

Answer 6

greater than 500

Question 7

The BUN:cr ratio will also be _________ in early postrenal azotemia. Later on, with tubular damage, it will be __________.

Answer 7

greater than 15; less than 15

Question 8

How does tubular damage affect FENa, BUN:cr, and urine osmolarity?

Answer 8

It increases FENa, decreases BUN:cr, and decreases urine osmolarity.

Question 9

Brown, granular casts will be seen in the urine of those with ____________.

Answer 9

acute renal failure from tubular necrosis

Question 10

What are the two most common etiologies of tubular necrosis?

Answer 10

Ischemic injury

Nephrotoxic event

Question 11

What substances can cause nephrotoxic injury?

Answer 11

Ethylene glycol
Aminoglycosides
Radiocontrast dye
Heavy metals (lead, mercury)
Urate (tumor lysis syndrome)
Myoglobin (crush injuries)

Question 12

Clinically, patients with tubular necrosis will have ________.

Answer 12

brown, granular casts in the urine; oliguria; hyperkalemia with metabolic acidosis (due to decreased excretion of organic acids); and elevated BUN and creatinine

Question 13

Eosinophils will be in the urine of those with ___________.

Answer 13

acute interstitial nephritis