Carcinoid syndrome mimicking irritable bowel syndrome: don't fall into the trap

Carcinoid syndrome (CS) is a complex condition caused by the systemic release of bioactive substances from neuroendocrine neoplasms (NENs), particularly small bowel tumors (sbNENs). Its symptoms-flushing, abdominal pain, and diarrhea-often resemble irritable bowel syndrome (IBS), resulting in misdiagnosis and delayed therapy.

This review examines the pathophysiology of CS, especially serotonin overproduction and its effects on gut motility and secretion. The overlap between CS and IBS is analyzed, with emphasis on diagnostic pitfalls and warning signs. Distinctive features include "dry" flushing without sweating, typical of CS, versus "wet" or emotional flushing in IBS or anxiety. Poor response to standard IBS treatments and symptom exacerbation after specific foods or alcohol may also indicate CS. The utility of biomarkers such as 5-HIAA and imaging modalities including intestinal ultrasound and 68 Ga-DOTATATE PET/CT is discussed. A comprehensive literature search was conducted using PubMed, Embase, and the Cochrane Library for English-language studies published between January 2000 and March 2024.

Early recognition of subtle differences and red-flag symptoms, combined with appropriate use of biomarkers and imaging, can minimize misdiagnosis. Timely identification of CS may improve patient outcomes by enabling earlier and more effective interventions.