Small intestine & ampulla

Other malignancies

Carcinoid syndrome

Last author update: 1 August 2012
Last staff update: 19 November 2020

Copyright: 2003-2024,, Inc.

PubMed Search: Carcinoid syndrome[TI] small bowel

Hanni Gulwani, M.B.B.S.
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Cite this page: Gulwani H. Carcinoid syndrome. website. Accessed July 13th, 2024.
Definition / general
  • Occurs in 1% with carcinoid tumors, 20% with widespread metastases
  • Elevated levels of 5-hydroxyindoleacetic acid (5-HIAA), a metabolite, are found in blood and urine
  • Normally liver deactivates vasoactive amines (serotonin, histamine, bradykinin, others) released from carcinoid tumors
  • Clinical symptoms occur if liver metastases are present or if tumor venous blood flow bypasses the liver
  • Vasomotor disturbances (cutaneous flushes, cyanosis of face and anterior chest, intermittent hypertension), palpitations, intestinal hypermotility (nausea, vomiting, diarrhea, cramps)
  • Also asthmatic attacks with bronchospasm, fibrosclerosis of AV and tricuspid valves, elastotic sclerosis of mesenteric vessels causing ischemia, dermal sclerosis, hepatomegaly
Carcinoid heart disease
  • Right sided focal or diffuse plaques of thickened valvular or mural endocardium that may extend to the great veins, coronary sinus, pulmonary trunk and main pulmonary arteries
  • Tricuspid and pulmonic valves are usually affected by plaque formation
  • Left heart and left sided valves are less frequently affected
  • Endocardial fibrosis is a reaction to serotonin or kinin peptide exposure
  • Plaques are composed of fibroblasts, myofibroblasts and smooth muscle cells embedded in a collagenous matrix, covered by a layer of endothelium
  • No elastic tissue is present within the plaque
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