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Nephrology > Renal failure > Flashcards

Renal failure Flashcards

1
Q

How do you calculate FENa

A

FENa = 100(SCr x UNa)/(SNa x UCr)

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2
Q

What does the FENa measure?

A

tubular resorption of Na
FENa = (Na excreted/Na filtered)100

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3
Q

What does a FENa of < 1%, UNa < 20, Uosm > 500 indicate?

A

a pre-renal source (most common, 60%)

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4
Q

What does a FENa > 1% and a UNa > 40 indicate?

A

an intrinsic source of renal failure (35%)

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5
Q

What does a FENa > 4%, UNa > 40, and Uosm < 350 indicate?

A

a post-renal source of renal failure (5%)
-BPH
-bladder stones
-b/l ureteral obstruction
-neurogenic bladder

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6
Q

What are the KDIGO criteria stages of an AKI?

A

-1 = creatinine increase x1.5 - 1.9 or >/= 0.3mg/dL in 48hrs
UOP < 0.5mL/kg/hr for 6-12hrs
-2 = creat x2-2.9 baseline
UOP < 0.5 for >/= 12hrs
-3 = creat x3 baseline or >/= 4; initiation of RRT; or if < 18yrs a decrease in GFR to < 35
UOP < 0.3 for >/= 24hrs or anuria for >/= 12hrs

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7
Q

What is the definition of CKD?

A

persistent impairment of kidney function
-abnormally elevated serum creat for >3 months or GFR < 60mL

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8
Q

What GFR is associated w/ stage 4 CKD?

A

<15

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9
Q

What are some typical causes of ATN?

A

-prolonged pre-renal failure
-contrast nephropathy
-amioglycosides

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10
Q

What type of AKI has a BUN:creat of >20:1?

A

pre-renal

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11
Q

What type of AKI has a BUN:creat <10:1?

A

intrinsic

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12
Q

What type of AKI has a BUN:creat that is normal (10-20:1)?

A

post-renal

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13
Q

When is a FENa inacurate and a FeUrea should be used instead?

A

pts on diuretics d/t the increase in UNa d/t the diuretic

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14
Q

How do you calculate FEUrea?

A

FEUrea = 100(SCr x Uurea)/(Surea x UCr)

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15
Q

What does a FEUrea < 35% indicate?

A

prerenal cause of AKI

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16
Q

What does a FEUrea >50% indicate?

A

intrinsic cause of AKI

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17
Q

How does muscle mass influence creatinine?

A

low muscle mass can have a falsely low serum creatinine

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18
Q

What are cause of pre-renal ARF?

A

-hypovolemia
-decreased effective blood volume
-heart failure
-cirrhosis
-nephrotic syndrome
-renal vasoconstriction
-renal artery stenosis
-NSAIDs
-drug related: tacrolimus, cyclosporine
-hypercalcemia

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19
Q

What are the intrinsic renal causes of ARF?

A

-ATN
-AIN
-acute vascular syndromes
-intratubular obstruction
-intrarenal depositions (tumor-lysis syndrome)
-rhabdomyolitis
-glomerulonephritides

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20
Q

What type of infiltrate do you get w/ acute interstitial nephritis?

A

eosinophilic

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21
Q

What is the classic triad of acute intersitital nephritis?

A

-fever
-rash
-eosinophilia

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22
Q

Which medications hypersensitives can lead to acute interstitial nephritis?

A

-PCNs
-cephalosporins
-sulfa drugs
-diuretics
-anticonvulsants

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23
Q

What is seen on an UA of a pt w/ acute glomerulonephritis?

A

-hematuria
-RBC casts

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24
Q

How is acute glomerulonephritis dianosed?

A

renal bx

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25
Q

What is the pathophysiology of acute tubular necrosis?

A

-oxidative injury to renal tubular epithelial cells
-sloughing of cells into lumen
-this creates an obstruction
-tubular pressure increases
-net filtration across glomerular capillaries decreases
-GFR decreases

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26
Q

What are the ischemic causes of acute tubular necrosis?

A

-circulatory shock
-sepsis
-hypotension (for any reason)
-hypoperfusion causing drugs (ACE-inhibitors, NSAIDs)

27
Q

What are the nephrotoxic causes of acute tubular necrosis?

A

-drugs (aminoglycosides, amphotericin B, cisplatin)
-radiocontrast dye
-myoglobin

28
Q

What part of the nephron is most susceptible to ischemia causing acute tubular necrosis?

A

loop of Henle

29
Q

What is the definition of oliguria?

A

UOP < 400mL/day

30
Q

What is the UOP of a patient w/ acute tubular necrosis?

A

can be oliguric or nonoliguric
-nonoliguric can have a normal UOP or elevated up to 8L/day

31
Q

What is the mortality of a patient w/ oliguric acute tubular necrosis?

A

60-90%

32
Q

What is the mortality of a patient w/ nonoliguric acute tubular necrosis?

A

10 - 20%

33
Q

What are some of the main complications seen w/ acute tubular necrosis?

A

-hyperkalemia
-metabolic acidosis
-electrolyte imbalance
-excess total body water
-malnutrition
-abnormal drug metabolism
-uremia

34
Q

What are some sequela of AKI?

A

-hyperkalemia
-often paired hypocalcemia and hyperphosphatemia
-volume overload
-metabolic acidosis

35
Q

What are risk factors for developing an AKI in the ICU?

A

-age
-CHF
-liver failure
-CKD
-anemia
-nephrotoxic exposures
-infections/sepsis/shock
-mechanical ventilation
-surgery

36
Q

What are non-AKI causes of increased BUN?

A

-rhabdo
-increased protein ingestion
-GI bleed
-corticosteroid use

37
Q

What is the RIFLE criteria for AKI?

A

-Risk = serum creat increase x1.5, GFR decrease > 25%
UOP < 0.5 x6hr
-Injury = serum creat increase x2, GFR decrease > 50%
UOP < 0.5 x12hr
-Failure = serum creat increase x3, serum creat >/= 4, GFR decr > 75%,
UOP < 0.3 x24hr or anuria x12hr
-Loss = persistent ARF defined as loss of kidney function > 4wks
-ESKD = persists > 3 months

38
Q

In the hospital setting what accounts for half of all cases of AKI?

A

hypoperfusion

39
Q

What UNa, Uosm, and Usg is typical for prerenal AKI?

A

-UNa < 20
-Uosm > 500
-Usg > 1.015
(tubules reabsorb Na and water creating concentrated urine w/ low Na)

40
Q

What does a UA significant for red cell casts indicate?

A

glomerulonephritis, vasculitis, trauma

41
Q

What does a UA significant for heme pigmented casts indicate?

A

hemoglobinuria, myoglobinuria

42
Q

What does a UA significant for leukocyte casts indicate?

A

pyelonephritis, papillary necrosis

43
Q

What does a UA significant for renal tubular casts indicate?

A

ATN

44
Q

What does a UA significant for “muddy” granular casts indicate?

A

ATN

45
Q

What does a UA significant for leukocytes indicate?

A

URI, interstitial nephritis

46
Q

What does a UA significant for eosinophils indicate?

A

acute interstitial nephritis (AIN)

47
Q

What does a UA significant for crystals indicate?

A

urate, oxalate (ethylene glycol)

48
Q

Which medications can cause ATN?

A

-aminoglycosides
-amphotericin B
-contrast
-cyclosporine
-platinum-based chemo
-ACE inhibitors
-NSAIDs

49
Q

What pt factors make them more at risk for drug induced ATN?

A

-elderly
-dehydrated
-HTN
-DM
-those w/ mild underlying renal dysfunction
-those w/ myeloma

50
Q

How do aminoglycosides cause renal insufficiency?

A

by binding and injuring cellular proteins in proximal tubules

51
Q

When should trough levels of aminoglycosides be drawn?

A

after 5.5 half lives when steady-state concentration has been acheived

52
Q

Which type of contrast can be dialyzed off?

A

gadolinium, but it’s still avoided in high-risk pts

53
Q

How do NSAIDs cause kidney damage?

A

-prostaglandin E2 is a vasodilator that is pivotal in maintaining renal blood flow in pts w/ high renin/angiotensin states
-NSAIDs block PGE2 formation and decrease renal blood flow
-also encourage sodium, potassium, and fluid retention while inhibiting diuretic action

54
Q

What electrolyte abnormalities are seen in rhabdo?

A

-rapidly increasing creatinine
-disproportionate rise in K, phos, and uric acid

55
Q

What electrolyte abnormalities are seen w/ tumor lysis syndrome?

A

-hyperkalemia
-hyperphosphatemia
-hypocalcemia
-increased uric acid

56
Q

Which medications are associated w/ the development of AIN?

A

-PCNs
-cephalosporins
-sulfonamides
-quinolones
-rifampin
-thiazides
-furosemide
-NSAIDs
-allopurinol
-cimetidine

57
Q

Which stain is needed to find urinary eosinophilia?

A

Hansel stain (urinary eosinophilia = AIN)

58
Q

What are the major electrolyte disturbances of an AKI?

A

-hyperkalemia
-hypermagnesemia (avoid antacids)
-hyperphosphatemia
-hyponatremia

59
Q

Why do pts w/ AKI develop bleeding disorders?

A

inhibitory action of uremic toxins on PLTs and factor 8

60
Q

Which factor is inhibited by uremia?

A

factor 8
-replace w/ DDAVP (an arginine vasopressor), FFP, cryo

61
Q

Which minerals are lost through HD and should be replaced?

A

-folate
-pyridoxine (B6)

62
Q

What are the indications for HD/HF?

A

-fluid overload
-refractory hyperkalemia or hypermagnesemia
-symptomatic uremia (pericarditis, seizures, encephalopathy)
-presence of a dialyzable toxin (salicylate, methanol, ethylene glycol)

63
Q

What is the renal threshold when you start seeing myoglobin in the urine?

A

0.5 - 1.5mg/dL

Nephrology (3 decks)

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