Acute renal failure Flashcards
definition and diagnostic criteria for acute kidney injury
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
epidemiology of ARF
1% all patients admitted to hospital. 10-30% patients admitted to ICU.
etiology of ARF
hemodynamic- not enough blood. parenchymal (acute tubular necrosis, acute GN, vasculopathy, acute interstitial nephritis. obstruction
oliguric renal failure
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
anuric renal failure
defined as urine output <100 ml/24 hr. less common-suggests complete obstruction, major vascular catastrophy, or more commonly severe ATN
is the renal failure acute or chronic?
lab values don’t discriminate between acute vs chronic. oliguria supports a diagnosis of acute renal failure.
clues to chronic disease
pre-existing illness-DM, HTN, age, vascular disease
uremic sxs-fatigue, nausea, anorexia, pruritis, altered taste sensation, hiccups
small, echogenic kidneys by US
pre-renal ARF
anytime you don’t get enough blood to the kidney (NSAIDS/cox2 inhibitors). anything that interrupts blood flow to kidney
intra renal ARF
kidney ds itself causes intra renal failure
post-renal ARF
anything that obstructs the kidney some will cause anuria but most wont. urine not getting out.
5 key steps in evaluating acute renal failure
- obtain a thorough history and physical; review the chart in detail.
- do everything you can to accurately assess volume status
- always order a renal us
- look at the urine
- review urinary indices
symptoms of ARF
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.
urine output of ARF
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
ARF physical exam findings
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
BUN creatinine ratio
> 20:1 suggests prerenal or obstruction. can be elevated by anything leading to increased urea production/absorption-GI bleed, TPN, steroids, drugs