Acute renal failure

Question 1

definition and diagnostic criteria for acute kidney injury

Answer 1

an abrupt (within 48 hours) reduction in kidney function currently defined as an absolute increase in serum creatinine of either >.3 mg/dL or a percentage increase of >50% or a reduction in UOP (documented as oliguria of 6hr

Question 2

epidemiology of ARF

Answer 2

1% all patients admitted to hospital. 10-30% patients admitted to ICU.

Question 3

etiology of ARF

Answer 3

hemodynamic- not enough blood. parenchymal (acute tubular necrosis, acute GN, vasculopathy, acute interstitial nephritis. obstruction

Question 4

oliguric renal failure

Answer 4

functionally urine output less than that required to maintain solute balance (can’t excrete all solute taken in). defined as urine output <400 ml/24 hr

Question 5

anuric renal failure

Answer 5

defined as urine output <100 ml/24 hr. less common-suggests complete obstruction, major vascular catastrophy, or more commonly severe ATN

Question 6

is the renal failure acute or chronic?

Answer 6

lab values don’t discriminate between acute vs chronic. oliguria supports a diagnosis of acute renal failure.

Question 7

clues to chronic disease

Answer 7

pre-existing illness-DM, HTN, age, vascular disease
uremic sxs-fatigue, nausea, anorexia, pruritis, altered taste sensation, hiccups
small, echogenic kidneys by US

Question 8

pre-renal ARF

Answer 8

anytime you don’t get enough blood to the kidney (NSAIDS/cox2 inhibitors). anything that interrupts blood flow to kidney

Question 9

intra renal ARF

Answer 9

kidney ds itself causes intra renal failure

Question 10

post-renal ARF

Answer 10

anything that obstructs the kidney some will cause anuria but most wont. urine not getting out.

Question 11

5 key steps in evaluating acute renal failure

Answer 11

1. obtain a thorough history and physical; review the chart in detail.
2. do everything you can to accurately assess volume status
3. always order a renal us
4. look at the urine
5. review urinary indices

Question 12

symptoms of ARF

Answer 12

fever, rash, joint pains, myalgias, concern for SLE, vaculitis, acute interstitial nephritis. dyspnea-heart failure. hemoptysis-goodpasture’s, wegener’s. preceding bloody diarrhea-HUS. preceding pharyngitis- post strep gn, post infectious GN.

Question 13

urine output of ARF

Answer 13

abrupt anuria: acute obstruction, severe acute GN, sudden vascular catastrophe. slowly diminishing: ureteral stricture, prostatic enlargement. presence of hematuria: painless-suggests GN, painful-suggest ureteral obstruction

Question 14

ARF physical exam findings

Answer 14

skin-new rashes: livedo reticularis-atheroemboli, SLE, cryoglobulins. petechiae-HSP. malar rash-SLE
eye: papilledema-malignant HTN. Roth’s spots-endocarditis.
CV: rub-suggestive of uremic pericarditis, lupus. gallop-suggesting CHF

Question 15

BUN creatinine ratio

Answer 15

> 20:1 suggests prerenal or obstruction. can be elevated by anything leading to increased urea production/absorption-GI bleed, TPN, steroids, drugs

Question 16

when to renal bx

Answer 16

exclude pre and post-renal failure, and clinical findings are not typical for acute tubular necrosis. extra-renal manifestations that suggest a systemic disorder. heavy proteinuria. RBC casts

Question 17

ischemic acute renal failure

Answer 17

a form of ATN often following a prerenal insult. late proximal tubule and medullary thick ascending limn most susceptible. severity of renal failure correlates with duration of insult. treatment is to optimize renal perfusion, avoid additional nephrotoxic insults and other supportive measures.

Question 18

acute interstitial nephritis etiology

Answer 18

allergic/drug induced
autoimmune: sarcoid, sjogren’s, SLE
toxins: chinese herb nephropathy, heavy metals, light chain cast nephropathy
infiltrative: leukemia, lymphoma
infections (legionella, CMV, HIV, toxoplasma

Question 19

acute interstitial nephritis clinical presentation

Answer 19

non-oliguric ARF
fever in allergic and infectious types (excepts NSAID type)
rash in allergic type (except NSAID use)
eosinophilia 
UA: WBC casts, eosinophiluria, hematuria

Question 20

rhabdomyolysis

Answer 20

often develops in the setting of crush injury, especially if superimposed circulatory shock
hallmarks of diagnosis (CK >10,000 + dipstick for blood but no RBCs.

Question 21

treatment of rhabdo

Answer 21

volume expansion (judiciously if severe oliguria or azotemia) fasciotomy when indicated for compartment syndrome (second wave phenomenon) avoid calcium repletion unless neuromuscular manifestations present. rebound hypercalcemia in recovery phase