Carcinoid tumours

90% arise in the ileum and appendix and although they are often silent, abdominal pain is a common symptom. Small bowel obstruction can result from intense desmoplastic reaction around the primary tumour. The syndrome of chronic mesenteric ischaemia has been described, related to elastic vascular sclerosis. Less than 20% present with the carcinoid syndrome which includes:

♦ Bronchial constriction

♦ Right-sided valvular heart disease

A majority of these patients are found to have liver metastases and have elevated urinary 5-HIAA levels and plasma chromogranin A and tachykinins (neurokinin A and substance-P). Approximately 30% of small bowel carcinoids are multiple. Pre-operative diagnostic tests are both biochemical and radiological. Urinary 5-HIAA and chromogranin A are assayed, the latter is particularly useful in earlier stage disease.

The primary tumours and metastases can be seen by somatostatin receptor scintigraphy (Octreoscan); 80% of these tumours express somatostatin receptor subtype 2 that binds this somatostatin analogue. This investigation should be supplemented with CT or MRI scan for detection of lymph node and liver metastases. Sometimes a small bowel contrast enema can be informative in patients with intermittent obstructive symptoms.

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