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All the things > 12.2: Acute renal failure > Flashcards

12.2: Acute renal failure Flashcards

1
Q

What are the two hallmark s/sx of acute renal failure?

A

Azotemia with oliguria

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2
Q

What are the three major divisions of acute renal failure?

A
  • Prerenal
  • Intrarenal
  • Post renal
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3
Q

How do you diagnose azotemia?

A

Increase in BUN and Cr

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4
Q

What is the cause of prerenal azotemia?

A

Decreased blood flow to the kidneys

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5
Q

What are the s/sx of prerenal azotemia?

A
  • Decreased GFR
  • Azotemia
  • Oliguria
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6
Q

What is the BUN:Cr ratio with prerenal azotemia? Why does this occur?

A
  • more than 15
  • Cr is not reabsorbed, but BUN is. When there is an increase in renin, there is increased Na and BUN reuptake from the tubule, but not Cr. Thus the ratio increases
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7
Q

What are the two measures that indicate good tubule function? What happens to these with prerenal azotemia?

A
  • FENa (fractional excretion of Na) = less than 1%
  • urine osm more than 500

-These are normal (above) with prerenal azotemia

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8
Q

What are the signs of postrenal azotemia?

A

Decreased GFR, azotemia and oliguria

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9
Q

What causes the early rise in BUN:Cr ratio with POSTrenal azotemia? Why does it decrease later on?

A

Back pressure from blocked outflow increases hydro static pressure in the tubule, and increased BUN reabsorption

Tubular damage ensures and decreases BUN resorption

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10
Q

What happens to FENa and Urine osm with postrenal azotemia? Early Post Renal? Late posternal?

A

Early= Both remain intact (FEN less than 1% and urine osm more than 500

Late post-renal = tubular damage, leading to higher FENa, and lower urine osmolality

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11
Q

What is the most common cause of acute renal failure?

A

Acute tubular necrosis

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12
Q

What is acute tubular necrosis? What happens to GFR? Why? What appears in the urine?

A

Injury and necrosis of the tubular epithelium. Necrotic cells plug tubules to decrease GFR.

Brown, granular casts appear in the urine

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13
Q

Brown, granular casts in the urine = ?

A

Acute tubular necrosis

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14
Q

What are the major histological findings of acute tubular necrosis?

A

Loss of tubular epithelial nuclei and lumen, detachment of epithelial cells from BM

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15
Q

What happens to the following with acute tubular necrosis:

  • BUN:Cr
  • FENa
  • Urine [c]
A
  • Decreased BUN:Cr (less than 15)
  • Increase FENa (more than 2%)
  • osm less than 500
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16
Q

What are the two major etiologies of acute tubular necrosis?

A

Ischemic

Nephrotoxic

17
Q

What parts of the nephron are particularly susceptible to ischemia?

A

Proximal tubule and medullary segment of the thick ascending limb

18
Q

What causes nephrotoxic ATN? Which part of nephron is particularly susceptible?

A

Toxic agents cause necrosis of tubules

Proximal tubule

19
Q

What are the toxic agents that can cause toxic ATN? (abx, environmental toxin, crush injury, automobile fluid type, radiology things?

A
  • Aminoglycosides
  • Heavy metals
  • Myoglobinuria
  • Ethylene glycol
  • Radiocontrast dye
20
Q

Oxalate crystals in the urine is suspicious for what type of poisoning?

A

Ethylene glycol

21
Q

What produces urate to cause ATN?

A

Tumor lysis syndrome

22
Q

What are the two measures to ensure that chemo does not induce ATN via tumor lysis syndrome?

A
  • IVF to dilute urate

- Allopurinol

23
Q

What are the urinary findings of ATN? (2)

A
  • Oliguria

- Brown, granular casts

24
Q

What happens to BUN and Cr with ATN?

A

Increases

25
Q

What metabolic disturbance is seen with ATN? What causes this?

A

Hyperkalemia with metabolic acidosis

  • Hyperkalemia from decreased K excretion
  • Acidosis from decreased excretion of organic acids
26
Q

What is the calculation for anion gap?

A

Na - (Cl + HCO3)

27
Q

What is the treatment for hyperkalemia and acidosis 2/2 ATN? Will the necrotic tissues heal?

A

Dialysis

Yes

28
Q

How long does it take for the necrotic tissue in ATN to regenerate? Why? What sign signifies healing?

A

2-3 weeks, since tubular cells are stable cells, and need time to reenter the cycle

Increasing urine output

29
Q

What is acute interstitial nephritis?

A

Drug-induced HSR of the interstitium and tubules, resulting in intrarenal ARF

30
Q

What are the drugs that classically cause acute interstitial nephritis? (3)

A
  • NSAIDs
  • PCN
  • Diuretics
31
Q

What are the histologic characteristics of interstitial nephritis?

A

Inflammation between the tubules, but relatively normal looking tubules

32
Q

What are the three major s/sx of interstitial nephritis?

A
  • Oliguria
  • Fever
  • Rash
33
Q

What WBC can be seen in the urine with interstitial nephritis?

A

Eosinophils

34
Q

What is the treatment for interstitial nephritis?

A

Remove offending drug

35
Q

What can interstitial nephritis progress to?

A

Renal papillary necrosis

36
Q

Eosinophils in the urine = ?

A

Acute interstitial nephritis

37
Q

What are the s/sx of renal papillary necrosis?

A

Gross hematuria and flank pain

38
Q

What are the 4 major causes of renal papillary necrosis?

A
  • Chronic analgesic use
  • DM
  • Sickle cell dz
  • Acute pyelonephritis

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