Carcinoid tumours are neuro-endocrine tumors commonly occur in appendix, other GIT parts and less commonly in bronchus, testis and ovary. In the small intestine, most often, carcinoid tumors are found in terminal two feet of ileum. They are found in crypts of Lieberkuhn and arise from the enterochromaffin cells. They comprise of the cells that secrete vasoactive peptides and are capable of APUD. APUD is abbreviation of amine precursor uptake and decarboxylation. Appendix carcinoid tumor is usually single. They cause luminal obstruction and thus patients present with the features of appendicitis. Small intestinal carcinoid tumors are multiple in 40% cases. Rectal carcinoids are more common than colon carcinoids.
Types of small bowel carcinoidsForegut carcinoids: These include bronchial, thymic, gastroduodenal and pancreatic carcinoids. These produce low levels of serotonin.
Midgut carcinoids: These include jejunal, ileal, appendiceal and right colic carcinoids. These have potential to secrete high levels of serotonin.
Hindgut carcinoids: These include distal colon carcinoids and those which involve the rectum.
- Most often they are asymptomatic
- They may present with abdominal pain, features of intestinal obstruction.
- Hind gut or colon carcinoids present with symptoms of constipation, bleeding per rectum and rectal tenesmus.
- When secodaries are developed in the liver, forty percent patients develop carcinoid syndrome. Carcinoid syndrome results due to the release of 5HT, kinins, prostaglandins, histamine and indoles. Features of carcinoid syndrome include diarrhoea, flushing, cyanosis, asthmatic attacks, hepatomegaly and cardiac lesion on right side.
Investigations for carcinoid tumors
- High urine levels of 5-hydroxyindoleacetic acid.
- 111In-octreotide scintigraphy is used to detect the tumor.
- CT scan is also useful in the evaluation of carcinoid tumors.
- I-131 MIBG scan may also be done.
- If carcinoid tumor is in the tip of appendix, appendicectomy and regular follow up with urine 5HIAA is sufficient.
- If carcinoid tumor is in the base of appendix, right hemicolectomy is needed to be done.
- If tumor is in small intestine and the primary lesion is less than 1 cm, with no lymph nodes, then
- If the secondaries have been developed in the liver, surgical debulking plus hepatic resection, hepatic artery ligation or embolisation may be done.
- Symptomatic treatment
- Long acting somatostatin analogue octreotide may be given.
- Serotonin antagonists, antihistamines, alpha methyl dopa and 5-fluorouracil can be tried.
- Radio-labelled somatostatin analogue
- Indium 111 labelled pentetreotide is also useful.