1. Indications
   1. Carcinoid Syndrome Evaluation...search this website
2. Mechanism
   1. Serotonin (5-Hydroxytryptamine) produced by Carcinoid...the above website
   2. Serotonin converted to 5-HIAA for excretion...the above website
3. Interpretation
   1. For 48 hours prior to collection...IMPORTANT!!:Patients should discontinue or avoid all medications for a couple days prior to testing (pain medication acetaminophen and cough medication guaifenesin can cause elevated results; likely many other medications do, too) and should not eat avocados, bananas, butternuts, cantaloupe, dates, eggplant, grapefruit, hickory nuts, honeydew, kiwi fruit, melons, nuts, pecans, pineapple, plantain, plums, tomatoes, or walnuts for a 48-hour period prior to start of collection...these contain 5-HIAA-like cross-reacting substances & can cause a "false positive" elevation!!
   2. Normal: Urine 5-HIAA < 9 mg/day (5-HIAA elevation is only 50% sensitive for carcinoid...can miss intestinal carcinoid with 6cm of matted mesenteric mets [CN07-80]as long as normal liver function).
   3. Equivocal: Urine 5-HIAA 9 to 25 mg/day .
      1. Possibly consistent with Carcinoid Syndrome[LMC-03-5303 was 15.2 & had liver mets].
      2. See Other causes of 5-HIAA elevation, above.
      3. can also look for elevations of blood serotonin and chromogranin.
   4. 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); if elevated, an octreatide nuclear medicine scan (Indium-111 pentetreotide scan...Octreascan) can help localize any metastasis for possible resection.
   2. Acute Intestinal Obstruction
   3. Celiac Sprue
   4. Excessive Banana or walnut ingestion

References:

1. FamilyPracticeNotebook.com.....lab

[posted 2/02; latest addition 1 December 2007]