Patients with carcinoid syndrome often have metastasis to the liver, where serotonin is normally metabolized. This metastasis allows serotonin and other vasoactive substances to bypass hepatic metabolic degradation, resulting in the aforementioned symptoms. Carcinoid syndrome can also occur without hepatic metastasis in the setting of nodal involvement, which enables direct hormone release into the systemic circulation.5
Carcinoid syndrome affects fewer than 10% of patients with carcinoid tumors.6 Therefore, although carcinoid tumor should be suspected in patients with suggestive symptoms, other diagnoses must be considered.
Other disorders to consider on work-up
Chronic diarrhea and colicky abdominal pain are nonspecific features also associated with conditions such as inflammatory bowel disease and celiac disease, necessitating further work-up to elucidate the diagnosis.
Inflammatory bowel disease often involves elevated inflammatory markers, such as increased ESR and C-reactive protein.
Ulcerative colitis can show thickened and inflamed bowel walls on CT, with cross-sectional target appearance due to transmural involvement.
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