Intermediate•7 min read•High Yield

Acute Kidney Injury (AKI) - CCS Case Guide

Key Takeaway: Acute kidney injury is characterized by a rapid decline in renal function with rising creatinine and decreased urine output. Identifying the etiology as prerenal, intrinsic, or postrenal guides management.

Acute kidney injury is characterized by a rapid decline in renal function with rising creatinine and decreased urine output. Identifying the etiology as prerenal, intrinsic, or postrenal guides management. CCS cases emphasize distinguishing the cause and knowing when to initiate dialysis.

Recognizing the AKI Presentation

  • History: Decreased urine output, fatigue, nausea, volume depletion (vomiting, diarrhea, poor intake), medication exposure (NSAIDs, ACEi, contrast), or urinary obstruction symptoms
  • Physical Exam: Signs of volume depletion (dry mucous membranes, poor skin turgor, hypotension) or volume overload (edema, JVD, crackles), suprapubic fullness (obstruction), flank tenderness
  • Vital Signs: Possible hypotension and tachycardia (prerenal), possible hypertension (volume overload or intrinsic disease)

Immediate Actions (First 5 Minutes)

These orders should be placed immediately — timing is scored:

Critical First Orders

  • ✓ Assess volume status
  • ✓ IV fluid bolus if prerenal (NS 500 mL-1 L)
  • ✓ Review and discontinue nephrotoxins (NSAIDs, ACEi/ARBs, aminoglycosides, contrast)
  • ✓ Foley catheter if obstruction suspected
  • ✓ Stat BMP (potassium, creatinine, BUN)
  • ✓ ECG if potassium elevated

Complete Workup

After initial stabilization, complete the diagnostic workup:

  • BMP (creatinine, BUN, potassium, bicarbonate)
  • CBC
  • Urinalysis with microscopy (muddy brown casts = ATN; RBC casts = GN; WBC casts = AIN)
  • Urine electrolytes (FENa, FEUrea)
  • Renal ultrasound (rule out obstruction)
  • Urine protein-to-creatinine ratio
  • Serum phosphate, calcium, magnesium
  • Hepatic panel
  • CK if rhabdomyolysis suspected
  • Complement levels, ANA, ANCA, anti-GBM if glomerulonephritis suspected

Treatment

Prerenal

  • IV fluid resuscitation (NS or LR)
  • Treat underlying cause (sepsis, hemorrhage, heart failure)
  • Discontinue offending agents (diuretics, ACEi, NSAIDs)

Intrinsic (ATN)

  • Supportive care and time
  • Avoid further nephrotoxins
  • Maintain euvolemia
  • Renal-dose medication adjustments

Postrenal (Obstructive)

  • Foley catheter for bladder outlet obstruction
  • Urology consult for ureteral obstruction
  • Percutaneous nephrostomy if ureteral stent not feasible
  • Monitor for post-obstructive diuresis

Dialysis Indications (AEIOU)

  • Acidosis (refractory metabolic acidosis)
  • Electrolyte abnormalities (refractory hyperkalemia)
  • Ingestion (toxic alcohol, lithium, salicylate)
  • Overload (refractory volume overload)
  • Uremia (encephalopathy, pericarditis, bleeding)

Common Pitfalls

Scoring Tip: These are the most commonly missed actions for AKI cases.

  • Failing to check volume status before giving fluids (fluid overload in intrinsic AKI)
  • Not discontinuing nephrotoxic medications
  • Missing obstruction (always obtain renal ultrasound)
  • Overlooking hyperkalemia and its cardiac complications
  • Not adjusting medications for renal function
  • Ordering contrast CT without considering contrast-induced nephropathy

Disposition

  • ICU if requiring emergent dialysis, severe hyperkalemia, or hemodynamic instability
  • Telemetry floor for monitoring creatinine trend and electrolytes
  • Discharge when creatinine trending toward baseline and cause addressed
  • Nephrology follow-up for persistent AKI or need for outpatient dialysis

Key Orders Checklist

  • ☐ BMP every 12-24 hours
  • ☐ Urinalysis with microscopy
  • ☐ Renal ultrasound
  • ☐ Foley catheter (if obstruction)
  • ☐ IV fluids (if prerenal)
  • ☐ Discontinue nephrotoxins
  • ☐ ECG if hyperkalemia
  • ☐ Strict I/O

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