Acute Renal Failure Flashcards

1
Q

What is acute renal failure?

A

Severe, acute decrease in renal function (develops within days)

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2
Q

What is the hallmark of ARF?

A

Azotemia

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3
Q

What is azotemia?

A

Increased BUN and creatinine, often with oliguria

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4
Q

What causes prerenal azotemia?

A

Decreased blood flow to the kidneys; common cause of ARF

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5
Q

What are the results of the decreased blood flow in prerenal azotemia?

A

Decreased GFR

Azotemia

Oliguria

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6
Q

How are serum BUN:Cr ratio, fractional excretion of sodium, and urine osmolality affected in prerenal azotemia?

A

Serum BUN:Cr ratio > 15

[FENa] < 1%

Urine osm > 500mOsm/kg

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7
Q

What causes postrenal azotemia?

A

Obstruction of urinary tract dwonstream from the kidney

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8
Q

What are the results of the decreased outflow in postrenal azotemia?

A

Decreased GFR

Azotemia

Oliguria

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9
Q

How are serum BUN:Cr ratio, fracional excretion of sodium and urine osmolality affected in postrenal azotemia?

A

EARLY:

serum BUN:Cr ratio > 15

FENa < 1%

Urine osm > 500 mOsm/kg

LATE:

serum BUN:Cr ratio < 15

FENa > 2%

Urine osm < 500mOsm/kg

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10
Q

What causes intrarenal azotemia?

A

Injury and necrosis of tubular epithelial cells

MCC of ARF

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11
Q

How does a decrease in GFR arise in acute tubular necrosis (intrarenal azotemia)?

A

Necrotic cells plug the tubules, obstructing the filtration flow

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12
Q

What kind of casts are seen in acute tubular necrosis?

A

Brown granular casts are seen in the urine

Arise from the necrotic cells that plug the tubulues

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13
Q

How are serum BUN:Cr ratio, fracional excretion of sodium and urine osmolality affected in acute tubular necrosis?

A

serum BUN:Cr ratio < 15

FENa > 2%

urine osm < 500 mOsm/kg

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14
Q

What are the two possible etiologies of acute tubular necrosis?

A

Ischemia

Nephrotoxic

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15
Q

What often precedes ischemic acute tubular necrosis?

A

prerenal azotemia

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16
Q

What parts of the kidneys are especially susceptible to ischemic damage?

A

Proximal tubule and medullary segment of the thick ascending limb

17
Q

What part of the kidney is most susceptible to nephrotoxic damage?

A

Proximal tubule

18
Q

What are the clinical features of acute tubular necrosis?

A

Oliguria with brown granular casts

Elevated BUN and creatinine

Hyperkalemia (due to decreased renal excretion) with metabolic acidosis

19
Q

What is acute interstitial nephritis?

A

Drug-induced hypersensitivity involving teh interstitium and tubulues; results in acute renal failure (intrarenal azotemia)

20
Q

What are common causes of acute interstitial nephritis?

A

NSAIDs

Penicillin

Diuretics

21
Q

Clinical presentations of acute interstitial nephritis?

A

Oliguria, Fever, Rash days to weeks after starting a drug

Eosinophils may be seen in the urine

22
Q

What can acute interstitial nephritis progress to?

A

Renal papillary necrosis

23
Q

What does renal papillary necrosis present with?

A

Gross hematuria

Flank pain

24
Q

Causes of renal papillary necrosis

A

chronic analgesic abuse

DM

sickle cell trait or disease

severe acute pyelonephritis