Lethal prognosis of an infant with intraperitoneal large venous malformation

Abstract Intraperitoneal venous malformations are uncommon; therefore, the prognosis of patients has not been determined and appropriate treatments have not been established. Here, we report a neonate with extensive intraperitoneal venous malformation. She did not have developmental disorder nor functional disability; thus, she was observed without treatment. However, the patient died suddenly of obstructive venous return disorder due to thrombosis in a vein draining from the venous malformation, followed by blood pooling in the expanding venous malformation. Intraperitoneal extensive venous malformation is associated with a lethal prognosis due to thrombosis. Anticoagulation therapy should be proactively considered for prophylaxis of thrombotic dysfunction.