Although the incidence of venous thromboembolism (VTE) during childhood is remarkably lower than that seen in adults, VTE is increasingly recognized in the pediatric population as a complication of improved treatment strategies for previously lethal childhood diseases. This review summarizes the available information on the incidence, pathogenesis, and clinical manifestation of VTE in children beyond the neonatal period, excluding the central nervous system.
Diagnostic and therapeutic strategies for VTE in infants and children are discussed separately. VTE in the newborn is also discussed separately. (See "Diagnosis and treatment of venous thrombosis and thromboembolism in infants and children" and "Pathogenesis, clinical features, and diagnosis of thrombosis in the newborn" and "Management of thrombosis in the newborn".)
The incidence of VTE in children is not precisely known because only a few prospective studies of this subject exist [1,2]. In a first analysis of Canadian registry data, the incidence of documented VTE in the upper or lower venous system was 5.3 per 10,000 hospital admissions or 0.07 per 10,000 children aged 1 month to 18 years, with a peak incidence in infants younger than 1 year of age, and a mortality rate of 2.2 percent . The mortality rate was predominantly due to associated conditions, which were identified in 96 percent of children; a central (indwelling) venous line was the single most important predisposing factor for VTE, being present in 33 percent of cases.
The annual rate of VTE in children in the United States, calculated from data from the National Hospital Discharge Survey (1979-2001), was 0.49 per 10,000 children per year . The rate of diagnosis was higher in children younger than 2 years and in those older than 15 years compared to those between 2 and 14 years of age (1.05, 1.14, and 0.24/10,000 children per year, respectively). In teenagers, but not in younger children, the rate was greater in girls than boys (1.49 versus 0.81/10,000 children per year) and pregnancy accounted for the difference. For all age groups, the rate of VTE was approximately two times greater among blacks than whites.
A study that sampled more tertiary care hospitals in the United States reported substantially higher rates of VTE and that rates rose from 34 cases per 10,000 children in 2001 to 58 per 10,000 children in 2007 . This represents a 70 percent increase in the diagnosis of VTE over the seven-year study period. The study was not able to determine whether this increase was due to a true increase in the frequency of VTE versus an increase in the detection of previously undiagnosed VTE, and did not have information about the proportion of VTE that were associated with central venous lines (CVL). A separate study reported similar rates in freestanding children’s hospitals (40 per 10,000), and much lower rates in community hospitals (7.9 per 10,000); nearly 80 percent of the episodes of VTE were associated with an underlying chronic condition .