Carcinoid syndrome

Occurs in 20% to 70% of patients with metastatic midgut carcinoid. Initial symptoms occur once the valves are significantly damaged.

Fibrosis occurs, which predominantly affects the right heart valves and, occasionally, left-sided valves. Management involves care of heart failure. Heart valve surgery should be considered in patients with stable disease. There is greater mortality in patients with midgut tumours and carcinoid heart disease than in those with midgut tumours alone.

Patients often develop recurrent episodes of abdominal pain, which is often worse with large meals.

Mesenteric fibrosis may be a presenting symptom or may present insidiously over many years and occurs independently of progression of liver disease. Approximately 20% of patients develop mesenteric fibrosis. This occurs more commonly in patients in whom the primary tumour is not resected.

Patients often present with episodes of sub-acute bowel obstruction/acute bowel obstruction that may require hospital admission. Bowel resection may be required in addition. Surgical bypass should be considered in patients with recurrent obstruction.

Uncommon but potentially life-threatening event. Can occur at times of stress, especially at times of surgery and interventional procedures (chemotherapy, hepatic embolisations, or medicines) due to release of amines into the circulation. Prior to surgery, patients with carcinoid syndrome should be commenced on octreotide infusion. [Figure caption and citation for the preceding image starts]: Octreotide planar image showing uptake in the liver from tumourFrom the collection of Dr R. Srirajaskanthan and Dr M. Caplin; used with permission [Citation ends].

Features of carcinoid crisis include hypotension, occasionally hypertension, tachycardia, arrhythmias, wheezing, and flushing.

A continuous infusion of octreotide is used to prevent carcinoid crisis. If symptoms persist, intravenous hydrocortisone should be administered.

Features of pellagra include diarrhoea, dermatitis, and dementia. Arises because tryptophan is required to produce niacin. Uncommon, occurring in 7% of cases. Sub-clinical niacin deficiency is more common.

Vitamin B3 deficiency