Venous Thromboembolism in Neonates, Children, and Adolescents: A Comprehensive Narrative Review of Risk Factors, Diagnosis, Treatment, and Prevention.

Venous thromboembolism (VTE) was once considered rare in the young, but it has become an increasingly important complication of contemporary pediatric care, driven by the improved survival of children with complex chronic illness and by the expanding use of central venous catheters. This narrative review synthesizes current evidence on VTE across the entire pediatric age range, from the critically ill neonate to the injured adolescent. We first examine noncerebral VTE in children beyond the newborn period, describing an incidence that is far lower than in adults yet rising among hospitalized patients, the multifactorial risk factors dominated by central venous catheters, and the age-dependent protection conferred by developmental hemostasis. We outline a diagnostic approach centered on compression ultrasonography and computed tomography pulmonary angiography, and a treatment paradigm that increasingly favors direct oral anticoagulants and shorter, six-week courses for low-risk provoked events. Dedicated sections address the distinct biology, presentation, and management of neonatal thrombosis, including renal vein thrombosis, portal vein thrombosis, and purpura fulminans, for which low-molecular-weight heparin is preferred and warfarin is generally avoided. We review the heightened, malignancy-specific risk of cancer-associated thrombosis, the difficulty of anticoagulating the thrombocytopenic child, and the consistent evidence against routine primary thromboprophylaxis. Cerebral sinovenous thrombosis is considered in depth, emphasizing its age-dependent triggers, the central role of magnetic resonance venography, and the safety of anticoagulation. Finally, we summarize the comparatively low but age-graded risk of VTE after major pediatric trauma and the puberty-based approach to prophylaxis. Throughout, we highlight the continued reliance on extrapolated adult data, the emergence of pediatric randomized trials and multicenter registries, and the unmet need for prospectively validated risk-prediction tools. The review offers clinicians an integrated, contemporary framework for recognizing, diagnosing, treating, and preventing thrombosis from the neonate to the adolescent.