Small bowel metastasis from colorectal cancer in patients with inflammatory bowel disease: a diagnostic challenge

Small bowel metastasis from colorectal cancer (CRC) is rare and difficult to diagnose, especially in patients with inflammatory bowel disease (IBD). We report two cases with two different presentations. The first, a male in his 80s known to have ulcerative colitis in remission, presented with an elevated CA 19-9 tumour marker one year after laparoscopic anterior resection for CRC. Positron emission tomography and subsequent enteroscopy revealed a duo-jejunal lesion, histologically confirmed as consistent with metastatic CRC. The second patient, a man in his 60s with stricturing Crohn's disease, presented acutely with small bowel obstruction eight months after hemicolectomy for stage IIIc CRC. Imaging and enteroscopy identified a jejunal mass, also confirmed as consistent with metastatic CRC. Both patients underwent resection but later developed peritoneal spread, with both undergoing palliative chemotherapy and immunotherapy. These cases highlight the need to consider small bowel metastasis in IBD patients with previous CRC.