Vomiting and profound weight loss as a clue to the diagnosis of malignant coloduodenal fistula.

Colon cancer generally presents with lower gastrointestinal symptoms, such as diarrhea, constipation, and general abdominal discomfort; it is rare for the primary presentation to have upper gastrointestinal symptoms. We report a patient with coloduodenal fistula secondary to colon malignancy who presented with incessant vomiting and dramatic weight loss as the chief complaint. It is important to consider colon cancer as part of the differential in patients with atypical presentations of upper gastrointestinal symptoms who have known colon cancer risk factors.