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Genital Findings in Prepubertal Girls Evaluated for Sexual Abuse
A Different Perspective on Hymenal Measurements
Perry A. Pugno, MD, MPH
Arch Fam Med. 1999;8:403-406.
ABSTRACT
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Objective To evaluate the usefulness of the horizontal transhymenal diameter as a screening parameter to differentiate between prepubertal girls with and without other definitive signs of sexual abuse.
Design Case comparison study using transhymenal measurements as a diagnostic screening test referenced against prior publications of criterion standards.
Setting A primary care (family practice) clinic in association with an academic program in northern California.
Patients A consecutive, referred sample of 1058 prepubertal girls aged 6 months to 10 years who were examined as allegedly having been sexually molested between 1987 and 1994.
Results Girls with no definitive signs of genital trauma exhibited a mean transhymenal diameter of 2.3 mm and in general showed an increase of approximately 1 mm per year of age. Girls with definitive signs of genital trauma exhibited a mean transhymenal diameter of 9.0 mm and no significant variance with age. Correcting for age differences, the transhymenal diameter was highly significant as a differentiating factor (F=1079, P<.001). When compared against the criterion standard, the transhymenal measurement is 99% specific and 79% sensitive as a screening tool.
Conclusion Although not independently diagnostic of sexual molestation, the transhymenal diameter, when compared against the criterion standard for age, is a useful screening parameter for primary care physicians evaluating children of potential sexual abuse.
INTRODUCTION
DURING the past 2 decades, the number of children suspected to have been sexually abused has increased dramatically.1 The attention given to this societal problem is measured by the rising number of media reports focused on it. Despite increased attention and its obvious importance, however, the diagnosis of sexual abuse remains difficult to establish in most cases. This state of affairs poses a challenge to the medical profession to support the needs of the judicial system and child protective agencies to make a determination as to the presence or absence of physical signs of sexual molestation. Although this has also prompted the medical profession to determine with some sense of assurance the "normal" developmental anatomy of children's genitalia, multiple investigators2-5 have reported on the occurrence and perceived significance of physical signs correlated with localized trauma to the genitalia. Some studies6-8 have even attempted to identify the parameters of "normalcy" through detailed screening of pediatric patients, but results vary widely. The most difficult variable to control for the abused child is the variable of unreported sexual abuse.9
One physical parameter that received substantial attention in recent years is the horizontal transhymenal diameter measured in prepubertal girls. Previous studies8, 10-11 have documented the high degree of correlation between examiners recording such quantitative measurements. For this parameter, multiple authors have suggested a benchmark threshold of "normal" for prepubertal girls of 4 to 10 mm,12-16 some noting enlargement with age11, 17 and others not.5, 18
There is also good consensus among physicians who perform evidentiary examinations on a regular basis that no single parameter should be used as a criterion for the establishment of the diagnosis of sexual abuse.4 Still, it remains important to clarify whether the parameter of transhymenal measurement has a role in lending further credence to other physical findings currently associated with sexual abuse. To do so, however, demands the identification of a reliable "control" population with which these findings can be compared.
The purpose of this project was to evaluate the transhymenal diameter measurement from a somewhat different perspective, specifically from within a population of children referred for examinations for suspected sexual molestation. The main question, therefore, became, "Is the horizontal transhymenal diameter of prepubertal girls, with definitive evidence of penetration trauma to the genitalia, significantly different from that of alleged victims who show no definitive physical signs of acute or chronic penetration trauma to genital tissues?"
SUBJECTS AND METHODS
SUBJECTS
From calendar years 1987 through 1994, a total of 1839 children were referred to the Mercy Family Health Center, Redding, Calif, for evidentiary examinations as potential victims of sexual abuse. They included 403 boys and 1436 girls. The children were referred by either social service or law enforcement agencies from a total of 14 northern California counties. For the purposes of this study, 1058 prepubertal girls (maturational level, Tanner I) were identified within an age range of 6 months to 10 years 9 months.
DATA ANALYSIS
All children referred for evidentiary examinations were evaluated in accordance with the California Medical Protocol for the Examination of Sexual Assault and Child Sexual Abuse Victims,19 and physical findings were documented on the mandated California Child Sexual Abuse Reporting Form (OCJP 925). Historical information was obtained from all available sources, including family members, social workers, and law enforcement personnel. As part of the evaluation process, each child underwent a complete general physical examination. These examinations were conducted at a leisurely pace to ensure the child's cooperation and maximum state of relaxation. Any child refusing or resisting the examination was eliminated from the study (n=5). In all cases, genital examinations were conducted by myself with the child in the supine "frog leg" position, and used the labial separation technique. Briefly, this technique involves gentle separation of the labia just sufficient to permit visualization of the introitus.11 The horizontal transhymenal diameter was measured with no traction, since traction obviously enlarges the orifice and would be impossible to quantify accurately (force, vector, etc). The measurements were made repeatedly when the child being examined was "relaxed and cooperative"; this was believed to be a reproducible end point, identifiable to any health professional who frequently examines children.
The horizontal transhymenal diameter was defined as the width of the orifice in the hymenal membrane between the 3- and 9-o'clock positions as viewed in the coronal plane. Transhymenal diameters were directly measured macroscopically using both a precision millimeter scale and a comparison of the opening with precision illustrations of circular and elliptical figures. In addition, genitalia were reexamined using the labial traction technique11 with the child in either the knee-chest or lateral recumbent position to ensure as comprehensive an examination as possible and to identify the presence or absence of other physical signs. In each case, visualization of the genital tissues was augmented by the use of a lighted, handheld magnifier, a colposcope, or both. Data tabulation was abstracted directly from the reporting form, and an audit of tabulation precision was conducted to ensure an error rate of less than 0.004%.
For 149 cases (14.1%) the examiner was able to compare his measurements of individual children with those reported by other physicians who examined those same individuals. As previously noted, the documented measurements between examiners were virtually identical and in no case varied by more than 1 mm. This provided assurance of the children's cooperativeness with the examinations and the reliability of the measurements' accuracy.
Criteria for the examiner to determine that an individual examination exhibited evidence consistent with the genital trauma of sexual assault were identified by a review of recent literature and the selection of those criteria generally accepted among the relevant medical community to be reliable indicators.3-4,20 These criteria included abrasions, lacerations, contusions, hymenal transections, obvious scarring, and marked narrowing of the hymen itself. For the purposes of this study, minor irregularities of the hymenal ring, septal remnants, bumps, notches, or variations in the vascular pattern were considered sufficiently "nonspecific" to preclude their use in this study as definitive indicators of genital trauma. In addition, since it would be a basis for circular reasoning, the measurement of the hymenal opening itself was eliminated as an indicator of genital trauma.
Statistical analysis was performed using the publicly available software package Epi Info produced by the National Institutes of Health.21 The analysis of variance and  2 tests for statistical significance were calculated using the method of Yates correction.
RESULTS
POPULATION CHARACTERISTICS
The age distribution for the study population is represented in Figure 1. Although many of these children were examined with little or no history available regarding the specifics of the allegations (n=331), a history from the child of genital penetration was noted to be predictive of definitive physical signs of genital trauma (n=299, relative risk=1.84).
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Figure 1. Age distribution of the study population (N=1058).
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TRANSHYMENAL MEASUREMENT
Table 1 summarizes the results of horizontal transhymenal measurements using the supine labial separation technique among prepubertal girls selected by the presence or absence of definitive physical signs of genital trauma. Girls with no definitive signs of trauma (negative examinations) demonstrated a mean transhymenal diameter of 2.3 mm (average age, 5.0 years). Prepubertal girls whose examinations revealed the presence of definitive physical signs of genital trauma (positive examinations) exhibited a mean horizontal transhymenal measurement of 9.0 mm (average age, 6.2 years). Despite correcting for the difference in average age of the 2 populations, the difference in mean transhymenal diameter was highly significant (F=1079, P<.001).
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Transhymenal Diameters by Age and Examination Findings
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The study population with negative examinations was further subdivided into the 3 groups of early childhood (ages 2-5 years), midchildhood (ages 5-8 years), and preadolescence (ages 8-10 years). When compared with the results of other investigators' transhymenal measurements for prepubertal girls selected for nonabuse, the girls with negative examinations in this study exhibited similar values.9 For example, in the age group of 5 to 8 years, this study population of girls with negative examinations exhibited a mean transhymenal diameter of 3.3 mm compared with the mean of 4.2 mm of the study population of McCann et al.9 This supports the perspective that the population with negative examinations is a valid and reliable representation of "normal" genital anatomy.
To further assist in the evaluation of these data from a normative viewpoint, scatter diagrams of individual measurements were plotted against a reference guideline for maximal normal transhymenal diameter by the age of the child. Figure 2 and Figure 3 demonstrate the relationship of individual measurements with a reference guideline for the upper limit of "normal" transhymenal diameters as included in the Informational Guide to the California Medical Protocol for the Examination of Sexual Assault and Child Sexual Molestation Victims.22 The guideline is based on an expected increase in transhymenal diameter of approximately 1 mm per year of age during the prepubertal period (after 5 years of age, the maximum diameter equals 1 mm per year of age).
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Figure 2. Horizontal transhymenal diameter findings in prepubertal girls (n=685) with physical examinations negative for definitive signs of genital trauma, plotted against a reference guideline for maximal "normal" hymenal measurements.
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Figure 3. Horizontal transhymenal diameter findings in prepubertal girls (n=373) with physical examinations positive for definitive signs of genital trauma, plotted against a reference guideline for maximal "normal" hymenal measurements.
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This guideline is consistent with the findings of other investigators.17, 23 When compared with the reference guideline, the results of this study demonstrate a very low incidence of false-positive findings (specificity, 99%) and a reasonably low incidence of false-negative findings (sensitivity, 79%). In other words, this study shows that the horizontal transhymenal diameter measurement, when compared with a commonly used reference guideline, is a potentially useful parameter for the screening of children suspected to have been molested.
COMMENT
With a study of this type it is important to recall that, in the case of sexual assault, the most important elements of the evaluation are the history of the event, that the results of most examinations for suspected abuse are normal, and that penetration of the hymen is not necessary for a diagnosis of sexual assault or abuse.5 However, a goal of this project was to determine whether an objective measurement of genital anatomy in the prepubertal girl could be used to assist an examining physician in assessing the significance of other physical findings under consideration when performing an evidentiary examination for suspected sexual abuse of a child. The results of this study, when compared with other investigators' observations and a reference guideline offered to assist physicians in evaluating this parameter, lend credence to the usefulness of the horizontal transhymenal diameter measured by the supine labial separation technique as a valuable adjunct to the assessment of other physical signs.
As has been acknowledged in previous publications,24-25 there will always be overlap in physical findings secondary to the naturally occurring variations and physical changes among individuals in a given population. Likewise, clinicians must consider all the information available to assess any single individual, and no single physical finding should be used as the sole basis for establishing that a child has been sexually abused. The findings of this study do provide, however, a potentially useful guide to assist in the identification of children who may need a more extensive or detailed expert evaluation. This may find its greatest utility among less experienced examiners faced with the challenge of that decision.
Numerous authors26-28 have stated that, ideally, evidentiary examinations for sexual abuse should be conducted by individuals and in settings where there is the opportunity for a broad experience and ongoing sharing of information and education to both maintain and upgrade the skills of the examiners. The reality is, however, that community providers, including pediatricians, emergency physicians, and family physicians, are commonly called on to evaluate children who are suspected to have been sexually abused. It is hoped that the findings of this study will assist them in their efforts to provide the best possible care to the children they serve.
AUTHOR INFORMATION
Accepted for publication September 24, 1998.
I thank John McCann, MD, for his valued review and insightful comments during the preparation of the manuscript.
Corresponding author: Perry A. Pugno, MD, MPH, Methodist Hospital Family Practice Residency, 7500 Hospital Dr, Sacramento, CA 95823.
From the M.H.S. Family Practice Residency Program, Methodist Hospital of Sacramento, Mercy Healthcare, and Department of Family and Community Medicine, University of California at Davis Medical Center, Sacramento.
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