12.2 - Acute renal failure

Question 1

what is the hallmark of acute renal failure?

Answer 1

azotemia (increased BUN and creatinine, often with oliguria)

Question 2

what is the general cause of prerenal azotemia?

Answer 2

decreased blood flow to kidneys

Question 3

what is the BUN : creatinine ratio in prerenal azotemia?

Answer 3

over 15

Question 4

is the tubular function in prerenal azotemia intact or damaged?

Answer 4

intact

Question 5

what is the [FENa] in prerenal azotemia? what is the urine osmolarity?

Answer 5

- [osm]: over 500 mOsm/kg

Question 6

why is the [FENa] under 1% in prerenal azotemia?

Answer 6

tubules are able to absorb sodium (tubular function is intact)

Question 7

why is the urine osmolarity over 500 in prerenal azotemia?

Answer 7

tubules can concentrate urine (tubular function is intact)

Question 8

what is the general cause of postrenal azotemia?

Answer 8

obstruction of urinary tract downstream from kidneys (ureters)

Question 9

what is the BUN : creatinine ratio in long standing postrenal azotemia?

Answer 9

under 15

Question 10

what is the [FENa] in postrenal azotemia? what is the urine osmolarity?

Answer 10

- [osm]: under 500 mOsm/kg

Question 11

what explains the [FENa]: over 2% and [osm]: under 500 mOsm/kg in postrenal azotemia?

Answer 11

tubular damage

Question 12

muddy brown casts - diagnosis?

Answer 12

acute tubular necrosis

Question 13

what is the BUN : creatinine ratio in ATN? why?

Answer 13

• under 15

- dysfunctional tubular epithelium results in decreased reabsorption of BUN

Question 14

what is the [FENa] in ATN? what is the urine osmolarity?

Answer 14

- [osm]: under 500 mOsm/kg

Question 15

which two areas of the nephron are most susceptible to ischemic damage?

Answer 15

• proximal tubule

- medullary segment of thick ascending limb

Question 16

which part of the nephron is most susceptible to toxins?

Answer 16

proximal tubule

Question 17

which is seen in ATN - hypo- or hyperkalemia? why? what is seen in conjunction with this?

Answer 17

• hyperkalemia
• due to decreased renal excretion
• metabolic acidosis also occurs

Question 18

what is pathognomonic for acute interstitial nephritis? what is the presentation?

Answer 18

• eosinophils in the urine
• oliguria
• fever
• rash

Question 19

drug-induced acute interstitial nephritis may lead to ___________

Answer 19

papillary necrosis

Question 20

how does renal papillary necrosis present?

Answer 20

• gross hematuria

- flank pain

Question 21

what conditions can cause renal papillary necrosis?

Answer 21

• CHRONIC analgesic abuse
• DM
• sickle cell trait or disease
• severe acute pyelonephritis