Approximately 5 of every million US children age 0–9 years are hospitalized for abusive abdominal trauma each year. These numbers include about 15 hospitalizations per million infants (age <1 year) and 10 per million toddlers (age 1–3 years). As the confidence intervals for 2003 and 2006 incidence rates overlap, there is no clear change in incidence during this time period. While these hospitalizations account for a small percentage (~4%) of all child abuse hospitalizations, they represent a significant proportion of hospitalizations for abdominal trauma among infants and toddlers. Therefore, abuse should be strongly considered when infants and toddlers present with abdominal injuries, unless high velocity trauma, such as a motor vehicle crash, is clearly involved or the event is witnessed by a reliable observer.
Only 1 other study, by Barnes et al. (2005)
in the UK, has examined the incidence of abusive abdominal trauma, but not in hospitalized children only. The incidence among children ages 0–4 from the KID data is much higher (~8 per million) than Barnes' calculation of 2.3 cases per million children (95% CI 1.43–3.78). Our data suggest that US children in this age group are much more likely to be victims of abusive abdominal trauma than their British counterparts. The difference in rates between the 2 studies might, however, be due to methodological differences. The Barnes study used an ongoing surveillance program for rare disorders, in which pediatricians returned cards each month noting whether they had identified any children with the listed disorders. Over 2 years, 92% of all cards were returned, suggesting very good ascertainment. However, surgeons were not part of the surveillance program, and the authors do not make clear whether pediatricians were involved in caring for all children with trauma, or only those identified by surgeons as having been abused. If the latter is true, than any instance of abuse that surgeons missed would not be counted. Barnes' data included all children with abusive abdominal trauma, not just hospitalized children, yet still had lower rates than those seen in our US hospitalization data. In addition, our rates are more likely to be underestimates than overestimates, given the known reluctance of physicians to acknowledge and report the possibility of abuse (Flaherty et al., 2006
; Gunn, Hickson, & Cooper, 2005
; Jones et al., 2008
; Sege & Flaherty, 2008
). Differences in these rates do not necessarily reflect overall differences in violence between the 2 countries. While the US has a fourfold higher homicide rate, national statistics indicate that the incidence rates of assault and intimate partner violence are higher in the UK, although, here too, these may involve methodological differences (Coleman, Jansson, Kaiza, & Reed, 2007
; Heron et al., 2009
; MMWR, 2008a
; Rand, 2008
; Tjaden &Thoennes, 2000
; Walker, Flatley, Kershaw, & Moon, 2008
The highest hospitalization rates in our study were seen among infants, males, and children with Medicaid. Data from earlier studies have suggested that toddlers are the most frequent victims of abusive abdominal trauma (Cooper et al., 1988
; Trokel et al., 2006
). While the percentage
of child abuse injuries caused by abdominal trauma is highest among toddlers, our data indicate that the highest rates
of abusive abdominal trauma are seen among infants. The incidence among toddlers is intermediate between that of infants and older children. Therefore, it is important for clinicians to consider the possibility of abuse when evaluating infants with abdominal injuries.
Approximately 25% of abdominal trauma hospitalizations in infants were the result of abuse, according to KID data. While this is a large proportion, it is smaller than the 50% that Trokel et al. (2006)
found in their evaluation of data from the National Pediatric Trauma Registry (NPTR). This difference could be from better diagnosis of child abuse at pediatric trauma centers (usually located within children's hospitals) compared to community hospitals. Another possibility is that because the KID includes both trauma and non-trauma centers, children with more minor injuries are included; these may be more likely the result of injuries other than child abuse.
By far, the most common injury seen in our data was liver trauma (64% of cases). Wood, Rubin, Nance, and Christian (2005)
, in a 10 year single-institution retrospective review of abdominal trauma hospitalizations also noted liver injuries to be the most common (92% of cases). However, Barnes et al. (2005)
identified liver injuries less often (35%). While 12% of our hospitalizations had injuries to the stomach and/or intestines, these injuries were seen more often in other studies (35–65% of cases) (Barnes et al., 2005
; Ledbetter, Hatch, Feldman, Fligner, & Tapper, 1988
; Trokel et al., 2006
; Wood et al., 2005
). Intestinal injuries were, in fact the most common finding in Barnes' et al. (2005)
data. These differences may be explained, in part, by differences in data sources. Inclusion of children who died before they could be hospitalized (Barnes et al., 2005
) and restricting data to trauma centers (Trokel et al., 2006
) would increase the proportion of more severe injuries in the sample. In contrast, data from Wood and the KID database did not include injuries severe enough to result in pre-hospital death, and they included injury hospitalizations that might not necessitate trauma center referral. Because intestinal perforations are more likely to require surgical repair and may more often be fatal; they may be overrepresented in trauma center and mortality data, and underrepresented in general hospitalization data.
Risk factors for abusive abdominal trauma are similar to those seen in other forms of inflicted injury (Keenan et al., 2003
; United States Department of Health and Human Services, 2010
). These risks include young age, poverty, and male gender. Poverty was a particularly pronounced risk factor in our data, with approximately 10-fold higher incidence rates for Medicaid beneficiaries compared to those with private insurance. It is possible that biases in identification of abuse by socioeconomic status account for at least some of the difference in rates by insurance status, as suggested by previous studies (Lane & Dubowitz, 2007
; Hampton & Newberger, 1985
; Jason, Andreck, Marks, & Tyler, 1982
). However, poverty has also been clearly demonstrated as an independent risk factor for maltreatment (Kotch, Browne, Dufort, & Winsor, 1999
Several limitations to our findings should be noted. First, because the number of abusive abdominal injuries was relatively small, some of our rate estimates were imprecise, particularly for smaller age groupings and older age groups. As with any child abuse data, it is highly likely that cases of abuse were misclassified as accidental injury. Likewise, some cases of accidental injury may have been misclassified as abuse, particularly in minority children. In addition, it is possible that some inflicted injuries in the older children were the result of assault by a peer or non-caregiving adult, and not abuse by a caregiver.
Because race data were missing for 1/3 of the sample, we opted not to include incidence rates by race. While CPS data demonstrate higher rates of minority children in the child welfare system (United States Department of Health and Human Services, 2010
), other data suggest that rates of maltreatment are no different for Black than for White children, or that differences that do exist are the result of confounding by poverty (Sedlack & Broadhurst, 1996
; Sedlack, McPherson, & Das, 2010
). We therefore felt that including rates of abusive abdominal trauma by insurance status was far more valuable than including rates by race.
While we anticipate that most children with symptomatic abusive abdominal trauma will be hospitalized for their injuries, the KID data do not include children who died prior to reaching a hospital, or who died in a hospital emergency department. Further, abused children may have abdominal injuries that are asymptomatic or associated with minor or vague complaints (Lindberg et al., 2009
; Coant, Kornberg, Brody, & Edwards-Holmes, 1992
; Lane, Dubowitz, & Langenberg, 2009
). Because screening for occult abdominal trauma is not routine practice in all hospitals, it is likely that many cases of occult abdominal trauma are not identified, and therefore not reflected in KID data (Lane et al., 2009
Despite these limitations, our study is important in that it is the first effort to examine the incidence of abusive abdominal trauma in children in the US. Further, we have demonstrated that infants are at highest risk for abusive abdominal trauma hospitalization, challenging previously held assumptions that toddlers were at greatest risk. Although the incidence of abusive abdominal trauma is lower than in many other maltreatment-related injuries, (e.g., the incidence of abusive head trauma is tenfold higher), it represents a significant proportion of all abdominal trauma injuries. It is therefore important that clinicians consider the possibility of child abuse unless there is a clear history of non-inflicted abdominal injury; missed cases of abuse and failure to protect may lead to escalating trauma and even death (Jenny, Hymel, Ritzen, Reinert, & Hay, 1999
Abdominal injuries may require long hospitalizations, and result in significant costs to the health care system (Trokel, DiScala, Terrin, & Sege, 2004
). The high mortality from abusive abdominal trauma is a substantial problem. Therefore there is a strong need to identify better methods of prevention of abusive abdominal trauma, as well as other forms of maltreatment.