Synchronous Sigmoid Colon and Small Bowel Adenocarcinomas: A Rare Case of Dual Primary Malignancies Presenting With Acute Bowel Obstruction.

Synchronous colorectal and small bowel adenocarcinomas are exceptionally rare. This case report presents a 65-year-old male patient with acute bowel obstruction who underwent an emergency laparotomy. Intraoperative findings revealed synchronous sigmoid colon and small bowel tumors with peritoneal metastases. The patient underwent sigmoidectomy, small bowel resection, and metastasectomy. Histopathology confirmed two distinct primary adenocarcinomas. Postoperative management included KRAS mutation-guided chemotherapy. At the two-year follow-up, the patient remained disease-free. This case highlights the importance of thorough intraoperative exploration in emergency presentations and demonstrates the potential for favorable outcomes with aggressive multimodal treatment in synchronous gastrointestinal malignancies.