Congenital absence of the inferior vena cava, a rare cause of deep vein thrombosis in adolescent: Case report.

Deep vein thrombosis (DVT) is rare in pediatric patients. Congenital inferior vena cava (IVC) anomalies are asymptomatic; however, these can cause DVT in younger patients rarely. In this case, a 14-year-old male patient was referred to our hospital for lower abdominal pain. At the first hospital he visited, computed tomography revealed a thrombus in the veins of the abdomen and lower extremities; however, an accurate diagnosis could not be made because the thrombus was thought to be inconsistent with abdominal pain. Close examinations revealed swelling of the lower extremities and pain while walking. Contrast-enhanced computed tomography revealed the absence of IVC (AIVC), resulting in DVT at the external iliac, gonadal, inferior mesenteric, and collateral veins of the right pelvic cavity. The patient received anticoagulation therapy. At a follow-up 6 months later, his symptoms improved, and a thrombus was not found. AIVC could cause DVT. DVT is rare in pediatric patients and is difficult to diagnose when the initial symptoms are vague. Conservative treatments are the most commonly used treatment; long-term follow-up is needed.