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Acute kidney injury

Medicine > Renal

Differential Diagnosis Schema 🧠

Pre-Renal Causes

  • Hypovolemia: due to dehydration, hemorrhage, or excessive diuresis.
  • Cardiac failure: leading to reduced renal perfusion pressure.
  • Systemic vasodilation: caused by sepsis, anaphylaxis, or severe liver failure.
  • Renal artery stenosis: often due to atherosclerosis or fibromuscular dysplasia.

Renal Causes

  • Acute tubular necrosis: due to ischemia, nephrotoxins, or rhabdomyolysis.
  • Glomerulonephritis: autoimmune diseases such as SLE, vasculitis, or post-infectious.
  • Interstitial nephritis: often drug-induced or related to infections.
  • Vascular causes: thrombotic microangiopathy, malignant hypertension, or vasculitis.

Post-Renal Causes

  • Obstructive uropathy: due to renal calculi, prostatic hypertrophy, or ureteral strictures.
  • Bladder outflow obstruction: secondary to prostate cancer, bladder tumors, or neurogenic bladder.
  • Bilateral ureteric obstruction: often due to malignancy or severe retroperitoneal fibrosis.

Key Points in History 🥼

Symptoms

  • Oliguria or anuria: suggests acute kidney injury, especially if recent onset.
  • Nausea, vomiting, or anorexia: common in uremia.
  • Confusion or lethargy: could indicate severe uremia or electrolyte imbalance.
  • Back or flank pain: may suggest renal colic, obstruction, or pyelonephritis.

Background

  • Past medical history: diabetes, hypertension, chronic kidney disease, or recent infections may predispose to AKI.
  • Drug history: use of NSAIDs, ACE inhibitors, or nephrotoxic antibiotics.
  • Social history: recent dehydration, reduced oral intake, or exposure to nephrotoxins (e.g., contrast agents).
  • Family history: hereditary conditions such as polycystic kidney disease or Alport syndrome.

Possible Investigations 🌡️

Blood Tests

  • Serum creatinine: elevated levels indicate renal dysfunction.
  • Urea: elevated in renal failure but also in dehydration and high protein intake.
  • Electrolytes: look for hyperkalemia, hyponatremia, or metabolic acidosis.
  • Full blood count: anemia may indicate chronic disease; leukocytosis suggests infection or inflammation.
  • Coagulation profile: to assess for DIC or other coagulopathies.
  • Autoimmune screen: ANA, ANCA, anti-GBM antibodies for vasculitis or glomerulonephritis.

Urinalysis

  • Dipstick: look for protein, blood, leukocytes, nitrites, or glucose.
  • Microscopy: red cell casts suggest glomerulonephritis; white cell casts suggest pyelonephritis or interstitial nephritis.
  • Urine electrolytes: helpful in distinguishing between pre-renal and renal causes.
  • Urine osmolality: low in acute tubular necrosis.

Imaging

  • Ultrasound: to assess kidney size, hydronephrosis, or obstruction.
  • CT scan: may be indicated if there is suspicion of obstruction or renal masses.
  • MRI: useful in cases of suspected renal vein thrombosis or renal artery stenosis.
  • Renal biopsy: indicated if glomerulonephritis or interstitial nephritis is suspected.

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Renal