Definition
KDIGO Criteria- increase in serum creatinine by 0.3mg/dL within 48 hours or
- > 1.5x fold increase in serum creatinine from baseline within 7 days or
- Urine output < 0.5 ml/kg/hr for at least 6 hours (least validated criteria)
Etiologies
Two Most Common Causes:- Prerenal
- Acute Tubular Necrosis
both are 65 - 75% the cause
Classification
AKI in three categories:- Prerenal
- Intrinsic
- Postrenal
Prerenal
Due to true volume loss or decreased effective arterial blood volume
- Hypovolemia: GI losses, Dehydration, diuretics, hemorrhage, 3rd spacing, burns
- Drugs: ACEI/ARB, NSAIDs
- Decreased effective arterial supply: cardiorenal, hepatorenal, sepsis
Intrinsic
Due to damage to the glomeruli, tubules, or interstitium
Causes:
- GN (glomerulonephritis)
- AIN (acute interstitial nephritis)
- ATN (Acute tubular necrosis)
- Ischemic
Postrenal
Due to damage/obstruction along the urinary tract system
Causes:
- Tumor
- Kidney stone
- Trauma to the urinary tract
- Cellular debri
- Prostate enlargement
General Approach
History- Signs of infection
- IV contrast exposure
- Vomiting or diarrhea
- P.O. intake
- Recent procedures Medications (including NSAIDs and antibiotics)
- History/features of CHF/cirrhosis
- Urinary symptom history
Physical Exam
- Pulse - tachycardia
- Blood pressure - hypotension
- Signs of dehydration
- Orthostatics
- Signs of fluid overload
Labs
- Urinalysis
- Basic Metabolic Panel
- If appearing hypovolemic, can give fluid trial
Second Tier Tests:
- Fractional excretion of sodium (FeNa) or
- Fractional excretion of Urea (FeUrea) if on diuretics
FeNa= Na(urine) X Cr(serum)/ Na(serum) X Cr(urine)
- Urine sodium
- Urine/serum osmolality
- Urine protein/creatinine
- Urine eosinophils
- Imaging (renal US, CT abdomen)
- Post-void residual (can consider with the initial phase of workup)
Third Tier Testing:
- Serologic testing
- Complement levels (C3, C4)
- Serum and urine protein electrophoresis/ (SPEP/UPEP)
- Renal biopsy
Treatment
- P.O. or IV fluids (if prerenal)
- Avoid nephrotoxic meds
- Close kidney function monitoring (follow strict I/O's + creatinine)
- Correct abnormal electrolytes/acid-base
Indications for Urgent Dialysis (A,E,I,O,U)
- Acid-base disturbance
- Electrolyte disturbance (K+)
- Intoxications
- Overload of Volume
- Uremia
3 TAKE HOME POINTS
- Get a good history: dehydration, infection, known CHF or cirrhosis, recent meds (including OTCs)
- Majority of AKI is secondary to prerenal or ATN etiology
- If the patient does no appear volume up, start with a fluid trial
Take a good history and consider fluids
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