Gastroenterology Book


24 hour Urine 5-hydroxyindoleacetic acid

Aka: 24 hour Urine 5-hydroxyindoleacetic acid, 24 hour 5-HIAA
  1. Indications
    1. Carcinoid Syndrome Evaluation
  2. Mechanism
    1. Serotonin (5-Hydroxytryptamine) produced by Carcinoid
    2. Serotonin converted to 5-HIAA for excretion
  3. Interpretation
    1. Normal: Urine 5-HIAA < 9 mg/day
    2. Equivocal: Urine 5-HIAA 9 to 25 mg/day
      1. Possibly consistent with Carcinoid Syndrome
      2. See Other causes of 5-HIAA elevation
    3. High: Urine 5-HIAA >25 mg/day
      1. Diagnostic for Carcinoid Syndrome
  4. Increased Urine 5-HIAA 24 hour Levels
    1. Malignant Carcinoid (>25 mg/day)
    2. Acute Intestinal Obstruction
    3. Celiac Sprue
    4. Excessive Banana or walnut ingestion

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