The Small Bowel's Big Secret: A Case of Hidden Adenocarcinoma Unmasked by Capsule Endoscopy

Small bowel adenocarcinoma (SBA) is an uncommon gastrointestinal malignancy that frequently presents with vague or nonspecific symptoms, leading to delayed diagnosis and poor outcomes. Because the small bowel is largely inaccessible to standard endoscopy, many patients endure prolonged abdominal pain, iron deficiency anemia, and weight loss before the underlying pathology is identified. Capsule endoscopy can reveal lesions that are often missed on upper or lower endoscopy and cross-sectional imaging, but its use remains limited in many centers due to issues of availability, cost, or delayed clinical consideration. We report the case of a 79-year-old man with a history of ischemic heart disease and paroxysmal atrial fibrillation who presented with one year of post-prandial abdominal pain, vomiting, and significant weight loss. Initial investigations, including gastroscopy, colonoscopy, and computed tomography of the abdomen and pelvis, were unrevealing. Capsule endoscopy subsequently identified a small bowel mass, and surgical resection confirmed moderately to poorly differentiated adenocarcinoma with negative margins and no nodal involvement. Following surgery, the patient recovered well and remains symptom-free on follow-up imaging. This case highlights the diagnostic challenge of SBA and reinforces the importance of considering capsule endoscopy early in patients with persistent, unexplained gastrointestinal symptoms, especially in elderly individuals with iron deficiency anemia. It also underscores the need for wider access to small bowel imaging in resource-limited settings and calls for further research into optimal post-resection surveillance strategies for small bowel malignancies.