Advances in the treatment of common childhood illnesses have led to an increase in the number of thromboembolisms (TEs) in children. Premature infants as well as children with congenital heart disease and cancer are at highest risk of having a TE, related to the use of central venous lines (CVLs) and other commonly used interventional therapies. CVLs account for most of TEs in children and are the reason childhood TEs are more common in the upper extremity vasculature than the lower extremity. Table 162.1 lists common causes of TE in children. The incidence of TE is highest in two age groups: neonates, who have the highest rate, and adolescents, who have the highest incidence of spontaneous TE.

Physical exam findings are related to the location of a TE. Extremity clots are usually evidenced by localized painful edema and discoloration. Inferior vena cava or renal vein thromboses present with renal dysfunction or an abdominal mass associated with hematuria and thrombocytopenia. Pulmonary embolism classically presents with acute chest pain and respiratory distress. Common symptoms of stroke are hemiparesis in adolescents and seizures in neonates. CVL clots usually present with loss of patency or superior vena cava syndrome.

Imaging remains the gold standard in making the diagnosis of TE. The best imaging modality depends on the location of the TE. For example, an extremity TE is best detected by Doppler ultrasound, although a venogram may be required if a CVL-associated TE in the upper extremity is suspected. Suspected PE would warrant a spiral chest computed tomography scan or ventilation/perfusion scan. No laboratory test can confirm the presence of TE. However, in the last decade, numerous prothrombotic factors have been discovered. Unfortunately, little is known about the need for TE prophylaxis in the pediatric population based on these test results. Inherited prothrombotic factors can be divided into three groups: factors in the coagulation cascade, their natural inhibitors, or metabolic factors (Table 162.2).