Small-Bowel Lymphoma: The Hidden Cause of Obscure Gastrointestinal Bleeding.

Obscure gastrointestinal bleeding (OGIB) accounts for approximately 5% of all gastrointestinal bleeding cases, with the small intestine being the most common source of origin. Primary small-bowel lymphoma is a rare malignancy that can present as intestinal bleeding in 2% to 22% of cases.  A 67-year-old male presented with a four-day history of diarrhea and melena, accompanied by severe anemia with a hemoglobin level of 5 g/dL. While a colonoscopy only revealed internal hemorrhoids and an ascending colon polyp, a subsequent non-contrast whole-abdomen CT scan demonstrated a 6-cm segmental small bowel wall thickening involving the proximal and distal ileum, accompanied by mesenteric fat stranding and aggressive aneurysmal dilatation. Further evaluation using antegrade enteroscopy identified a mass with central ulceration in the proximal ileum. Histopathological analysis of the ileal biopsy specimens revealed small intestinal mucosa heavily infiltrated by a diffuse, highly cellular tumor with small-to-medium neoplastic cells, confirming a malignant round cell neoplasm highly suspicious for non-Hodgkin lymphoma. This case highlights the critical clinical challenge of managing OGIB and underscores the importance of early diagnostic interventions. Utilizing CT imaging alongside device-assisted enteroscopy is vital for the prompt recognition of hidden small bowel disorders like lymphoma, enabling timely treatment, preventing life-threatening hemorrhagic complications, and improving the overall patient prognosis.