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Acute Kidney Injury & Failure (AKI): A Guide to Diagnosis and Management | Definition, Etiologies, Classification, Symptoms, Causes, General Approach & Treatments

Acute_Kidney_Injury_Failure_AKI.jpg

    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

    Acute_Kidney_Injury_Failure_AKI_classification.png

    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)
                      - Toxic (contrast dye, heme pigment, some abx)
                      - 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)

    Acute_Kidney_Injury_Failure_AKI.png


    • 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

    Acute_Kidney_Injury_Failure_AKI.png

    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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