Abdominal cramps with recurrent diarrhea occur and are often the patient's major complaint. Malabsorption syndrome has been documented in some cases. Many patients develop right-sided endocardial fibrosis, leading to pulmonary stenosis and tricuspid regurgitation. Left heart lesions, which have been reported with bronchial carcinoids, are rare because serotonin is destroyed during passage through the lung. Diagnosis Nonfunctioning carcinoids can be detected similarly to other space-occupying lesions, eg, by angiography, CT, or MRI, depending on the site.
Definitive diagnosis is made histologically.
Certain drugs, including guaifenesin, methocarbamol, and phenothiazines, also interfere with the test. On the 3rd day, a 24-h urine sample is collected for assay. Provocative tests with calcium gluconate, catecholamines, pentagastrin, or alcohol have been used to induce flushing. These may aid in the diagnosis in some patients but must be performed with care. Localization of the tumor may require an extensive evaluation, including laparotomy.