A Case of Sigmoid Colon Cancer with Patent Foramen Ovale and Left-Sided Inferior Vena Cava Initially Detected during the Workup for Cerebral Infarction.

INTRODUCTION: Patent foramen ovale (PFO) is present in approximately 25% of adults, whereas a left-sided inferior vena cava (IVC) is a rare congenital vascular anomaly. Both conditions are associated with thromboembolic risk; however, their coexistence in patients with colorectal cancer has not been reported. We report a rare case of sigmoid colon cancer complicated by PFO and left-sided IVC, initially detected during the diagnostic workup for cerebral infarction.

CASE PRESENTATION: A 69-year-old man was diagnosed with cerebral infarction, and transthoracic echocardiography revealed PFO with a positive bubble test. While receiving anticoagulation therapy, he developed persistent hematochezia, and subsequent investigations revealed sigmoid colon cancer with a solitary liver metastasis. Contrast-enhanced CT demonstrated a left-sided IVC running along the left side of the abdominal aorta and joining the right renal vein. Laparoscopic sigmoidectomy with D3 lymph node dissection was safely performed with careful attention to the aberrant venous anatomy. The postoperative course was uneventful, and anticoagulation therapy was resumed early. The patient subsequently underwent hepatic resection after systemic chemotherapy.

CONCLUSIONS: This case highlights the importance of accurate preoperative anatomical evaluation and careful perioperative thromboembolic management in laparoscopic colorectal surgery involving coexisting PFO and major vascular anomalies.