A 55-year-old man presents with abdominal pain and diarrhea that occurs after eating, leading to fear of eating and subsequent weight loss. He also complains of flushing. What could be the potential diagnoses and next steps?
These symptoms could suggest carcinoid syndrome, especially the flushing and diarrhea that can be provoked by eating. Carcinoid syndrome is caused by a neuroendocrine tumor, typically in the gastrointestinal tract. The next steps would include a 24-hour urine test for 5-HIAA, a breakdown product of serotonin which is often elevated in carcinoid syndrome. If the urine test is positive, imaging studies and endoscopy would be necessary to locate the tumor.