Acute Kidney Injury

AKI: Definition & Staging - Kidney SOS Stages

• Definition: Sudden ↓ kidney function: ↑ serum creatinine (sCr) & ↓ urine output (UO).
• Staging (KDIGO-based / Kidney SOS adapted):
  • Stage 1:
    • sCr: ↑ ≥0.3 mg/dL (in 48h) OR 1.5-1.9x baseline
    • UO: < 0.5 mL/kg/hr for 6-12 hrs
  • Stage 2:
    • sCr: ↑ 2.0-2.9x baseline
    • UO: < 0.5 mL/kg/hr for ≥12 hrs

    ⭐ Oliguria in neonates is defined as urine output < 1 mL/kg/hr, and < 0.5 mL/kg/hr in older children.

  • Stage 3:
    • sCr: ↑ ≥3.0x baseline OR sCr ≥4.0 mg/dL OR RRT init.
    • UO: < 0.3 mL/kg/hr for ≥24 hrs OR Anuria ≥12 hrs

AKI: Etiology - Tiny Trouble Triggers

• AKI arises from prerenal, intrinsic renal, or postrenal causes.
• Prerenal (most common in children, ~70%):
  • ↓ Perfusion: Dehydration (diarrhea, vomiting), sepsis, shock, hemorrhage.
  • ↓ Effective volume: Heart failure, nephrotic syndrome.
• Intrinsic Renal (~20%):
  • Acute Tubular Necrosis (ATN): Ischemia (prolonged prerenal), nephrotoxins (aminoglycosides, NSAIDs).
  • Glomerulonephritis (GN): PSGN, IgA nephropathy.
  • Hemolytic Uremic Syndrome (HUS). 📌 (D+ HUS: E.coli O157:H7)
  • Acute Interstitial Nephritis (AIN): Drugs, infections.
• Postrenal (~5-10%):
  • Posterior Urethral Valves (PUV) in boys.
  • Stones, tumors, neurogenic bladder.

⭐ Hemolytic Uremic Syndrome (HUS) is a leading cause of intrinsic AKI in young children, often post-diarrheal (D+ HUS).

AKI: Diagnosis - Spotting Sick Kidneys

Clinical Clues:

• ↓UO: Oliguria (<0.5-1 mL/kg/hr), Anuria (<0.1 mL/kg/hr)
• Edema, Hypertension
• Hematuria, pallor, nausea

Key Investigations:

AKI: Management & Complications - Fixing & Future Foes

• General: Treat cause, optimize hemodynamics, avoid nephrotoxins, monitor I/O, weight.
• Fluids: Euovolemia goal. Challenge: 10-20 mL/kg isotonic crystalloid if hypovolemic. Restrict if overloaded/oliguric.
• Electrolytes:
  • Hyperkalemia (K+ > 6.5 mEq/L or ECG changes): Ca gluconate, Insulin-Dextrose, Salbutamol.
  • Acidosis (pH < 7.1): Bicarbonate (cautiously).
• Complications: CKD, HTN, anemia.

⭐ Life-threatening hyperkalemia (K+ > 6.5 mEq/L with ECG changes) is a critical emergency in AKI requiring immediate intervention including calcium gluconate, insulin-glucose, and beta-agonists.

High‑Yield Points - ⚡ Biggest Takeaways

• Prerenal azotemia (hypovolemia, sepsis) is the most common cause of pediatric AKI.
• Oliguria is a key sign; non-oliguric AKI also occurs.
• FeNa < 1% typically indicates prerenal AKI.
• Urine microscopy is vital: muddy brown casts suggest Acute Tubular Necrosis (ATN).
• Manage by treating cause, ensuring fluid balance, and correcting electrolytes.
• Hemolytic Uremic Syndrome (HUS) is a major cause of intrinsic renal AKI.
• Dialysis indications: AEIOU (Acidosis, Electrolytes, Intoxication, Overload, Uremia).