EM@3AM – Acute Kidney Injury

Author: Erica Simon, DO, MHA (@E_M_Simon, EM Chief Resident, SAUSHEC, USAF) // Edited by: Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UTSW / Parkland Memorial Hospital) and Brit Long, MD (@long_brit, EM Attending Physician, SAUSHEC, USAF)

Welcome to EM@3AM, an emdocs series designed to foster your working knowledge by providing an expedited review of clinical basics. We’ll keep it short, while you keep that EM brain sharp.

A 66-year-old male with a history of hypertension, diabetes mellitus, and benign prostatic hypertrophy presents to the ED for weakness and persistent nausea of two weeks duration. The patient denies slurred speech, visual deficits, motor and sensory dysfunction, chest pain, shortness of breath, fevers, sick contacts, and recent travel. Review of systems is remarkable for a recent hospitalization secondary to malignant otitis externa (ciprofloxacin and gentamicin). The male reports completion of oral antibiotic therapy 48 hours prior to arrival. When questioned regarding his BPH, he notes extreme difficulty initiating voiding.

VS: BP 128/78, HR 88, T 99.4 Oral, RR 14, SpO2 97% on room air.

EKG: HR 87 bmp, NSR, normal axis, no acute ST-T wave changes

Physical examination, to include a complete neurologic examination, is unremarkable.

What do you suspect as a diagnosis? What’s the next step in your evaluation and treatment?

Answer: Acute Kidney Injury1-4

  • Definition: Numerous previously established criteria:1-4
    • 2002: RIFLE (Risk, Injury, Failure, Loss of Function, ESRD) Criteria => Developed by the Second International Consensus Conference of the Acute Dialysis Quality Initiative Group.2
    • 2004: AKIN (Acute Kidney Injury Network) Criteria => Created to characterize the full spectrum of renal injury. As compared to the RIFLE Criteria the AKIN Criteria:3
      • Describes renal function changes occurring within 48 hours prior to presentation, whereas the RIFLE criteria includes a period of 7 days prior to presentation.
      • Excludes the glomerular filtration rate as a marker of AKI.
      • May be employed only in the setting of euvolemia, in the absence of a urinary tract infection.
    • 2012: KDIGO (Kidney Disease Improving Global Outcomes) Clinical Practice Guidelines => Built upon the RIFLE Criteria and AKIN Criteria:
      • KDIGO defines an AKI as:
        • An increase in serum Cr by 0.3mg/dL from baseline within 48 hours or
        • An increase in serum Cr to 1.5x baseline or more within the previous 7 days or
        • Urine output less than 0.5mg/kg/h for 6 hours
      • The KDIGO consensus classification also offers a recommended AKI staging system (outside of the scope of this brief review).4
  • Presentation:
    • Patients may present with lethargy, malaise, anorexia, nausea, and decreased urine output. In severe cases patients may report palpitations, muscle cramps, peripheral edema, and/or chest pain with associated shortness of breath (i.e. electrolyte disturbances, hypervolemia resulting in pulmonary edema and heart failure, or pericardial effusion/uremic pericarditis). Individuals may also present with altered mental status or seizure.
  • Etiologies:
    • Pre-renal => secondary to renal hypoperfusion.
      • Examples: Hypovolemia, CHF, cirrhosis, septic shock
    • Intrinsic renal
      • Examples: glomerulonephtritis, allergic interstitial nephritis (AIN), acute tubular necrosis (ATN) (often precipitated by hypotension or shock), drug toxicity (e.g., aminoglycosides), rhabdomyolysis, contrast-induced nephropathy.
    • Post-renal => bladder obstruction, ureteral obstruction, or bilateral renal vein occlusion.
      • Examples: BPH, bladder mass, bladder/ureteral stones
  • Evaluation:1
    • Perform a thorough history.  Question specifically regarding previous medical history (CHF, cirrhosis, BPH, bladder stones, etc.), risk factors for malignancy (e.g. transitional cell carcinoma: smoking, etc.), and pharmaceutical therapy.
    • When performing the physical examination assess for:
      • Neuro: altered mental status, asterixis, or myoclonus
      • Cardiac: arrhythmias or pericardial friction rub
      • Pulmonary: rales or diminished breath sounds (pulmonary edema)
      • Abdomen: distended bladder
      • MSK: peripheral pitting edema
    • Point of care ultrasound may be utilized to:
      • Assess for genitourinary pathology: evaluate for a mass lesion, the absence of ureteral jets, or urinary retention. In Post-renal AKI: identify increased renal size and dilated calyces.
      • Assess volume status: evaluate the IVC during the respiratory cycle.
    • Laboratory studies:
      • CMP, serum phosphate, UA
    • Ancillary testing:
      • EKG => Consider in the setting of hyperkalemia or if concern for arrhythmia
      • CXR => Detect signs of CHF or pulmonary renal syndromes (i.e. – pulmonary alveolar hemorrhage (Goodpasture’s or Granulomatosis with Polyangiitis))
      • Renal US with Doppler => assess renal vascular status
      • Non-contrast CT of the abdomen and pelvis if concern for obstructing ureteral stones.
  • Treatment:1
    • As appropriate to the underlying etiology. 
  • Pearls:1
    • In oliguric patients with an AKI, urinary sodium and urinary creatinine levels should be obtained to calculate the fractional excretion of sodium.
    • Urine microscopic examination often facilitates diagnosis in patients with an AKI secondary to intrinsic renal pathology: granular casts = ATN, red blood cell casts = glomerulonephritis, white blood cell casts = AIN.


  1. Heung M. Acute Kidney Injury. In Ferri’s Clinical Advisor 2017. Philadelphia, Saunders Elsevier. 2017; 30-34.e1.
  2. Bellomo R, Ronco C, Kellum J, Mehta R, Palevsky P. Acute renal failure – definition, outcome measures, animal models, fluid therapy, and information technology needs: the Second International Consensus Conference of the Acute Dialysis Quality Initiative (ADQO) Group. Crit Care. 2004; 8(4): R204-12.
  3. Mehta R, Kellum J, Shah S, Molitoris B, Ronco C, et al. Acute Kidney Injury Network: report of an initiative to improve outcomes in acute kidney injury. Crit Care. 2007; 11(2): R31.
  4. Acute Kidney Injury Work Group. Kidney Disease: Improving Global Outcomes (KDIGO) – Clinical Practice Guideline for Acute Kidney Injury. Kidney Inter. 2012; 2:1-138.


For Additional Reading:

 Acute Kidney Injury: Pearls and Pitfalls:

Acute Kidney Injury: Pearls and Pitfalls


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