S3901 An Unwanted Neighbor: Contiguous Spread of Colonic Adenocarcinoma

Introduction: Colorectal carcinoma remains a global burden despite screening gains. Metastases usually involve liver, lung, and distant nodes; direct small-bowel invasion is rare and portends poor survival. We describe a rectosigmoid adenocarcinoma perforating the jejunum, highlighting diagnostic clues and operative planning. Case Description/Methods: A 66-year-old woman presented with palpitations. Vitals were: heart rate 124, blood pressure 96/54 mmHg. Labs showed hemoglobin 4.4 g/dL, iron-deficiency indices. Digital rectal exam produced bright-red blood. After 6 units packed red blood cells, esophagogastroduodenoscopy (EGD) was normal. Colonoscopy showed grade 4 hemorrhoids and a circumferential rectosigmoid mass >15 cm from anal verge; biopsy: moderately differentiated adenocarcinoma. Computed tomography (CT) chest/abdomen/pelvis revealed a 9.4 cm polypoid mass, 8 enlarged regional nodes, and an 8 mm posterior perirectal node. A ureteral stent safeguarded the left ureter. Open rectosigmoidectomy with en-bloc jejunal resection and diverting ileostomy was done after intra-operative perforation into adhered bowel. Post-op sepsis was managed with broad antibiotics. Pathology: T4bN1a stage IIIc adenocarcinoma (1/16 nodes). Adjuvant chemotherapy was planned. Discussion: About 70% of colorectal cancers are sporadic adenocarcinomas. Left-sided tumors present with obstruction and hematochezia; right-sided with occult bleeding and anemia. Small-bowel involvement occurs in <2% of colorectal cancers and is usually metastatic. Direct invasion defines T4b disease, mandates multivisceral en-bloc resection, and worsens prognosis. Severe iron-deficiency anemia plus overt bleeding expedited colonoscopy, allowing diagnosis before complete obstruction. Imaging hinted at jejunal invasion, confirmed only during surgery. Curative therapy depends on radical resection with adequate nodal harvest; adjuvant chemotherapy improves stage III outcomes. Surgeons should anticipate multivisceral resection and coordinate ureteral protection and multidisciplinary care in such advanced cases.