Acute Kidney Injury

On this page

Definition & Staging - Kidney Crisis Code

Error generating content for this concept group: Failed to process successful response

Etiology - AKI's Usual Suspects

  • Prerenal (↓ Perfusion):
    • Hypovolemia: Hemorrhage, dehydration, burns
    • ↓ Effective volume: CHF, cirrhosis, sepsis/shock
    • Drugs: NSAIDs, ACEi/ARBs
    • Renal Artery Stenosis
  • Intrinsic Renal (Parenchymal Damage):
    • ATN (most common): Ischemic; Nephrotoxic (contrast, aminoglycosides, amphotericin B, rhabdomyolysis)
    • AIN: Drugs (antibiotics, NSAIDs, PPIs), infections, autoimmune
    • Glomerulonephritis (e.g., RPGN)
    • Vascular: HUS, TTP, vasculitis, malignant HTN
  • Postrenal (Obstruction):
    • Ureteric/Bladder neck/Urethral: BPH, stones, tumors, strictures

Causes of AKI

⭐ Acute Tubular Necrosis (ATN) is the most common cause of AKI in hospitalized patients, often due to ischemia or nephrotoxins.

Diagnosis & Evaluation - Kidney Detective Kit

  • Clues: History (drugs, ↓intake), exam (volume, bladder).
  • Urinalysis (U/A):
    • Pre-renal: Bland, high SpGr.
    • ATN: Muddy brown casts.
    • AIN: WBC casts, eosinophils (📌 Wright/Hansel).
    • GN: RBC casts.
  • Urine Indices:
    • FeNa: <1% (Pre-renal) vs >2% (ATN).
    • FeUrea: <35% (Pre-renal, on diuretics).
  • Bloods: ↑SCr, BUN:Cr >20:1 (Pre-renal), K↑, acidosis.
  • Imaging: US KUB (obstruction? kidney size?).

Muddy brown granular casts in urine sediment

⭐ Muddy brown granular casts in urine sediment are highly suggestive of Acute Tubular Necrosis (ATN).

Complications - AKI's Ripple Effect

  • Fluid Overload: Pulmonary edema, hypertension, heart failure.
  • Electrolyte Imbalances:
    • Hyperkalemia (≥5.5 mEq/L): Peaked T waves, arrhythmias. ⚠️ Most critical!
    • Hyponatremia, Hyperphosphatemia, Hypocalcemia.
    • Metabolic Acidosis (High Anion Gap).
  • Uremic Syndrome:
    • Encephalopathy (asterixis).
    • Pericarditis (friction rub, tamponade risk).
    • Platelet dysfunction (bleeding tendency).
  • Increased Infection Risk.
  • Cardiovascular: MI, arrhythmias.
  • Progression to CKD.

⭐ Uremic pericarditis is an absolute indication for dialysis in AKI.

Management Principles - Kidney Rescue Plan

  • Stop nephrotoxic drugs (e.g., NSAIDs, contrast).
  • Optimize volume status & maintain MAP >65 mmHg.
  • Rule out/Relieve obstruction (e.g., bladder scan, catheter).
  • Treat hyperkalemia, severe acidosis.
  • Adjust drug dosages to renal function.
  • Diuretics (furosemide) for volume overload; not for anuria/oliguria without overload.

⭐ RRT Indications (AEIOU): Acidosis (severe); Electrolytes (refractory hyperK+ >6.5); Intoxications; Overload (refractory); Uremia (symptomatic: pericarditis, encephalopathy).

High‑Yield Points - ⚡ Biggest Takeaways

  • AKI (KDIGO): ↑SCr ≥0.3 mg/dL (48h) or ≥1.5x baseline (7d); UO <0.5 mL/kg/h (6h).
  • Prerenal: Most common; BUN:Cr >20, FENa <1%; due to hypoperfusion.
  • ATN: Intrinsic AKI; muddy brown casts, FENa >2%.
  • Postrenal: Obstruction; anuria/polyuria; ultrasound is key.
  • Dialysis (AEIOU): Refractory Acidosis, Electrolytes (K⁺>6.5), Intoxications, Overload, Uremia.
  • CIN Prevention: IV hydration (isotonic saline) pre-contrast.
  • Rhabdomyolysis AKI: ↑CK, myoglobinuria; treat with aggressive hydration, urine alkalinization.

Practice Questions: Acute Kidney Injury

Test your understanding with these related questions

Which of the following is the most effective treatment for severe acute hyperkalemia requiring definitive management?

1 of 5

Flashcards: Acute Kidney Injury

1/9

The presence of casts in the urine indicates that hematuria/pyuria is of _____ or renal tubular origin

TAP TO REVEAL ANSWER

The presence of casts in the urine indicates that hematuria/pyuria is of _____ or renal tubular origin

glomerular

browseSpaceflip

Enjoying this lesson?

Get full access to all lessons, practice questions, and more.

Start Your Free Trial