RFT – Acute Kidney Injury

ABCs

  • Check vital signs
  • If unstable → call for assistance
  • Repeat RFTs with VBG urgently
  • Monitor urine output and fluid balance

Definition of AKI

  • ↑ Creatinine by ≥ 1.5× baseline within 7 days
  • OR ↑ Creatinine by ≥ 26.5 μmol/L within 48 hours
  • OR Urine output < 0.5 mL/kg/hr for ≥ 6 hours
AKI Differential Diagnosis

AKI Differential Diagnosis

Pre-renal (Hemodynamic)
  • Hypovolemia (dehydration, bleeding, GI losses)
  • Low effective volume (CHF, cirrhosis, nephrotic syndrome)
  • NSAIDs, ACEi, ARBs, SGLT2i
  • Renal venous congestion (e.g., RHF)
Intrinsic Renal
  • ATN: ischemia, toxins (aminoglycosides, cisplatin, myoglobin)
  • Glomerular: RPGN, nephritic/nephrotic syndromes
  • AIN: drugs (NSAIDs, PPIs, antibiotics), autoimmune
  • Vascular: vasculitis, emboli, TTP/HUS
  • Others: myeloma, TLS, phosphate nephropathy
Post-renal (Obstructive)
  • BPH, prostate cancer
  • Stones, strictures, tumors
  • Bladder outlet obstruction
Other/Mixed
  • CKD + AKI overlap
  • Atheroembolism
  • Multifactorial (e.g., sepsis + meds)

HPI & EXAMINATION

  • Pre-Renal Causes
    • Dehydration, vomiting, diarrhea, bleeding
    • Sepsis, hypotension
  • Post-Renal Causes
    • Oliguria, anuria, incontinence, retention
    • Dysuria, frequency, h/o stones, BPH
  • Medication History
    • NSAIDs, antibiotics, diuretics
    • ACEi / ARBs
    • IV contrast
  • Symptoms Suggestive of Uremia
    • Anorexia, nausea, vomiting
    • Metallic taste, confusion
  • Other Relevant History
    • UTI symptoms: dysuria, fever, frequency
    • CHF, liver disease, CKD, dialysis
  • Review baseline Cr & urea
  • Check for AV fistula (if known CKD patient)
  • Look for signs of uremia: encephalopathy, asterixis, ecchymosis
  • Palpate bladder, check for distention or flank pain
  • Assess volume status (depletion vs overload)
  • Signs of liver disease: ascites, jaundice, gynecomastia

MANAGEMENT

  • Stop nephrotoxic drugs (NSAIDs, ACEi/ARBs, contrast)
  • Determine if patient needs:
    • IV fluids (hypovolemic)
    • Loop diuretics (volume overloaded)
  • Treat underlying cause
  • Monitor creatinine, electrolytes, urine output
  • Insert or replace foley’s
  • Post-obstructive diuresis:
    • UOP > 200 mL/hr for 2+ hours
    • OR > 3 L in 24 hours
      • Consider confirmed obstruction
      • Start volume replacement and monitor
  • VBG, RFTs, U&Es, urine routine + microscopy
  • If rhabdomyolysis suspected → check CK
  • Correct electrolytes K⁺, PO₄, Ca²⁺, HCO₃⁻
  • Suspect obstruction → renal ultrasound or CT KUB
  • If unstable or refractory to initial treatment: Call for assistance, consult nephrology/urology
  • Anticoagulation Considerations
    • LMWH: Safe if eGFR > 30, platelets > 30, no bleeding
    • UFH 5,000 U BD: Use if eGFR < 30

ESCALATION

  • If unstable or refractory → call nephrology/urology
  • Dialysis if any of the following:

URGENT DIALYSIS

  • Refractory acidosis (pH <7)
  • Refractory hyperkalemia
  • Intoxication (ethylene glycol, methanol)
  • Refractory volume overload with anuria
  • Uremia causing encephalopathy or clinically significant pericarditis
MOC