Recognition and diagnosis of abnormal anogenital anatomy require the examiner to first master knowledge of normal male and female anatomy, including the variations that present during the process of child physical development. This has sometimes been a challenge in the field of child abuse pediatrics because use of high-grade magnification (colposcopy or digital imaging) typically reveals details that can mistakenly be attributed to trauma or disease. Studies of newborns and children selected for nonabuse provide important data that has defined normal anatomy. This chapter describes aspects of anogenital embryology and major anatomical structures assessed during child sexual abuse medical evaluations. This information provides a basis for accurate interpretation of injuries and diseases that can be associated with sexual abuse.
Genital Embryology
Early in development, the genital system is undifferentiated and has the capability of forming either male or female anatomy. Three primary structures evolve to form the genital system: primordial germ cells, two sets of paired indifferent ducts, and the cloaca. Primordial germ cells from the embryonic endoderm migrate to a midregion, the urogenital ridge, becoming the “indifferent” gonads. By gestational week six, two symmetrical sets of paired ducts form near the urogenital ridge, the wolffian (mesonephric) ducts and the müllerian (paramesonephric) ducts. The ducts lengthen, descending into the future pelvis to join the cloaca (primitive bladder-rectum) at a cloacal protuberance called the müllerian tubercle. During this time, the ureteric buds form off the mesonephric (wolffian) ducts, eventually becoming the kidneys and ureters. If the fetus is male, the gonads become testes and produce AMH (anti-müllerian hormone), causing the müllerian ducts to regress and disappear. The testes produce testosterone, which maintains the growth of the wolffian ducts and promotes their further differentiation to form the spermatic ducts (vas deferens, epididymis).
Female gonads differentiate into ovaries. The ovary does not produce testosterone or AMH. In the absence of testosterone, the wolffian ducts regress. Wolffian duct remnants may remain as “rests” of tissue (epithelial inclusions). Paravaginal or paracervical wolffian remnants may form cysts called Gartner duct cysts. Without AMH, the müllerian ducts flourish, fuse in the midline near the junction to the cloaca, and differentiate further to become the uterus, fallopian tubes, and upper (proximal) two thirds of the vagina.
The cloaca is the precursor for the external genitalia, the bladder, urethra, and the rectum. The urorectal septum forms by gestational week seven to separate the cloaca into two parts, the rectum and the urogenital sinus. In females, the müllerian tubercle (cephalic end of the urogenital sinus) joins to the fused müllerian ducts (now a primitive uterovaginal canal). The caudal side of the müllerian tubercle forms the vaginal plate and two sinovaginal bulbs, which elongate to reach the perineum. The perineal surface of the urogenital sinus is the urogenital membrane, flanked by swellings that form the urogenital folds, outer labioscrotal swellings, and the genital tubercle (different from the müllerian tubercle).
At this point, the external genitalia are “indifferent” genitals. With further growth and differentiation, the genital tubercle becomes either the glans penis (male) or the clitoris (female), the urogenital folds become the body of the penis (male) or the labia minora (female), and the labioscrotal swellings become the scrotum (male) or the labia majora (female). In males, the urogenital membrane first becomes a groove, then the penile urethra as the urogenital folds encircle it. In females, the urogenital membrane becomes the vestibule. The urogenital sinus separates into urethral and vaginal canals. The central cells of the solid vaginal canal break down caudally to form the vaginal lumen, extending to canalize the hymen.
The hymen contains fibrous connective tissue that is part elastic and part collagenous in nature. The inner surface of the hymen contains cells from the vagina (embryological vaginal plate) and the external surface of the hymen contains cells derived from the urogenital sinus. , Incomplete canalization of the hymen results in an imperforate, microperforate, or septated hymen. Using animation, this embryological process is well illustrated on the Web site of The Hospital for Sick Children, Toronto, Canada, called “Sick Kids Child Physiology. ”
Recent studies challenge the accepted concept that the upper vagina is müllerian in origin and the lower vagina originates from the urogenital sinus (cloaca). Studies of wolffian structures in rat embryos demonstrate that the entire outer vagina is formed from wolffian duct cells and lined internally with müllerian tubercle (urogenital sinus) cells. , No studies have challenged the origin of hymenal tissues from the urogenital membrane (cloaca).
Variants in Female Genital Anatomy
Hymenal Configurations
The hymen has several distinct anatomical configurations that are influenced by the child’s age and physical maturation. The three most common configurations are annular, crescentic, and fimbriated. An annular hymen has hymenal tissue present circumferentially and forms a doughnutlike appearance ( Figure 10-1 ). A crescentic hymen has no definable hymenal tissue between approximately the 11 and 1 o’clock positions anteriorly ( Figure 10-2 ). A fimbriated hymen has multiple folded areas of tissue along the hymenal edge ( Figure 10-3 ). These redundant projections of tissue frequently overlap and obscure the hymenal orifice. A sleevelike hymen is a redundant or thickened hymen seen typically in infants with residual maternal estrogen ( Figure 10-4 ). As estrogen resolves, annular hymens become more common. Crescentic hymens occur most commonly in girls aged 4 through 9 years. ,
Other hymenal configurations such as septate and cribriform occur less frequently. A septate hymen has one or more nonrigid bands of hymenal membrane that cross the orifice and essentially create two (or more) separate openings ( Figure 10-5 ). The septum often resolves as the child develops, or ruptures spontaneously. Septate hymens do not usually cause any problems, though if the septum persists at the time of menses, the use of tampons might be problematic.
Examination should differentiate a septate hymen from a vaginal septum. Vaginal septa divide the vaginal canal into two vaginal sections ( Figure 10-6 ). The vaginal septum can be transverse or longitudinal. Differential diagnosis of a transverse septum includes imperforate hymen, vaginal atresia, or vaginal agenesis. Importantly, a longitudinal vaginal septum (which divides the vagina lengthwise) can occur in association with other genitourinary anomalies, especially uterine didelphys (duplication) or bicornuate uterus. A vaginal septum or complete vaginal duplication (with uterine didelphys) is thought to occur during fetal development when the müllerian ducts fail to fuse completely. Urological anomalies are found in 20% to 30% of females with uterine anomalies and in 50% with vaginal agenesis because ureteric bud formation (kidney and ureter development) occurs at the same stage of development. MRI is recommended as the optimal test to differentiate müllerian agenesis, cervical agenesis, transverse vaginal septum, imperforate hymen, and longitudinal septum.
A cribriform (sievelike) hymen is defined by multiple small openings in the hymenal membrane. The hymen may have only a very small opening (microperforate) or no opening at all (imperforate) ( Figure 10-7 ). Careful examination (with positioning to improve relaxation, application of saline drops, or use of a small swab) can differentiate a truly imperforate hymen from a normal one with adherent edges. An imperforate hymen should be followed yearly, but if it persists at the onset of puberty (sexual maturity level 2), the child should be referred to a gynecologist. Septate, cribriform, and imperforate hymenal variations result from failure of the urogenital membrane to completely canalize/perforate during embryogenesis. ,
A number of variables affect the appearance of the hymen, particularly the child’s developmental stage (sexual maturity rating) and presence of estrogen. Extrinsic factors such as examination position (supine versus prone knee-chest), the child’s comfort and relaxation during the examination, and the examiner’s experience and technique have been shown to affect the observed hymenal configuration and morphology. In one study of 93 prepubertal girls selected for nonabuse (ages 10 months to 10 years), hymens were more frequently characterized as crescentic when examined in the prone knee-chest position (54%) than the supine position with either labial separation (41%) or labial traction (44%). This study also found that examination position and technique affected the relative redundancy, vascular patterns, and size of the hymenal orifice. Additional variables such as a child’s comfort level and ability to cooperate with the anogenital examination often markedly affect the appearance of the hymen and surrounding structures.
The Newborn Hymen
The question of whether there is a congenital condition of “absent hymen” is sometimes raised when a child is examined for suspected sexual abuse. To address this question, Jenny et al examined 1311 female newborns before discharge from their birth hospital; all had hymens. Jenny concluded “… in the absence of major genitourinary anomalies, one could expect hymenal tissue to be present in young female children.” In addition, Mor and Merlob reported examinations of more than 25,000 female newborns. All had hymens, effectively disproving the idea of congenital absence of the hymen in otherwise normal females. Several other studies have examined this question and all have confirmed that newborn females are born with hymens. ,
Girls born with vaginal agenesis or atresia (for example Mayer-Rokitansky-Küster-Hauser syndrome) have normal external genitalia ( Figure 10-8 ). Their condition develops from müllerian agenesis, resulting in absence or rudimentary formation of müllerian structures (uterus, fallopian tubes, and proximal vagina). This condition is the most common cause of primary amenorrhea (15%) and may be associated with renal and skeletal anomalies. – Abnormalities/absence of the hymen might be expected with significant cloacal anomalies, such as persistent cloaca (confluence of rectum, vagina, and urethra), imperforate anus with fistula, or cloacal extrophy. However, absence of the hymen associated with these or any other disorders has not been reported.
Developmental Changes to the Hymen
The hymenal configuration changes during different stages of growth and development, particularly with exposure to estrogen. Estrogen effect on the hymen is first apparent at birth due to maternal estrogen crossing the placenta during gestation. A newborn hymen appears thickened and pale, often associated with labial and clitoral prominence ( Figure 10-9 ). Estrogen exposure produces a thick, white vaginal discharge, and in some cases, withdrawal vaginal bleeding occurs in the neonatal period as estrogen levels decrease. Once maternal (or exogenous) estrogen is eliminated, the hymen gradually becomes thin and less redundant with sharp, well-defined edges. The labia also appear less prominent. This transition usually occurs within months after birth, but the effects of maternal estrogen can persist for 2 to 3 years in some cases. ,
Hymenal changes in early childhood have been well documented by several longitudinal studies by Berenson et al. They initially examined 468 female newborns and found that 80% had annular hymens, 19% had fimbriated hymens, and 1% had septate or cribriform hymens. None of the newborns had crescentic hymens. In a follow-up study, Berenson reexamined 57 of these infants and noted that by 1 year of age, 42% of them had undergone a change in hymenal morphology since birth. At 1 year, 28% of subjects now had a crescentic hymenal configuration while 7% were fimbriated and only 54% remained annular. Many infants progressing from an annular to a crescentic hymen by age 1 had a hymenal notch at 12 o’clock (anterior) as a newborn. This finding lends support to the idea that crescentic hymens begin as annular or fimbriated configurations with a superior midline notch that widens to fill the 11:00 to 1:00 o’clock positions. Berenson also noted that by 1 year, 58% of subjects had a marked decrease in tissue redundancy, correlating with the expected decrease in serum estrogen levels after birth.
In a subsequent study, Berenson examined a group of 134 female infants between birth and 2 months old and again at 3 years old. (Forty-two of these subjects were also examined near 1 year of age). At 3 years old, a majority of subjects (55%) now had crescentic hymens and 38% had annular configurations. Berenson observed that hymenal configuration changed in 65% of subjects between birth and 3 years of age, largely because of the increasing numbers of crescentic hymens. Maternal estrogen effects also resolved in 75% of 3-year-old subjects. As a result, hymenal edges transformed from thickened and redundant to sharp and well-defined.
Subsequent examinations were conducted at 5, 7, and 9 years of age. The percentage of hymens in the crescentic configuration continued to increase as prepubertal girls aged. By 9 years old, 90% of the 61 subjects had a crescentic hymen and only 10% remained annular ( Table 10-1 ).
| Newborn n = 468 | 1 Year n = 62 | 3 Years n = 42 | 5 Years n = 93 | 7 Years n = 80 | 9 Years n = 61 | |
|---|---|---|---|---|---|---|
| Hymenal Configurations | ||||||
| Annular | 80% | 54% | 38% | 23% | 18% | 10% |
| Crescentic | 0% | 28% | 55% | 77% | 82% | 90% |
| Fimbriated | 19% | 7% | 2% | 0% | 0% | 0% |
| Variations | ||||||
| Clefts/notches | 35% * | 29% | 12% | 7% | 9% | 11% |
| Tags | 13% | 11% | 10% | 13% | 10% | 10% |
| External ridges | 93% | 14% | 6% | 3% | 1% | 0% |
| Longitudinal intravaginal ridges | 56% | 53% | 81% | 86% | 90% | 92% |
| Vestibular bands † | – | 95% | 100% | 100% | 100% | 100% |
| Redundant/thickened ‡ | 100% | 42% | 25% | |||
* Not recorded in newborns with fimbriated hymens.
† Not quantified for newborns due to difficulty with visualization; also includes periurethral bands.
Like the effects of maternal estrogen at birth, increased serum estrogen during puberty causes a second period of change in hymenal morphology. In general, as girls develop secondary sexual characteristics, their hymens transition from a thin, translucent appearance to a redundant, elastic, and thickened hymen ( Figure 10-10 ). The hymenal tissue also becomes less sensitive to touch, such that adolescents are better able to tolerate examination aids, such as a swab or Foley catheter balloon.
Yordan and Yordan conducted a cross-sectional study of 168 girls ages 7 to 17 years (sexual maturity ratings I-V) to determine if progressive genital changes could be correlated to sexual maturity ratings of the breasts. Subjects with sexual maturity rating (SMR) I breast development were noted to have very thin hymenal rims with small, thin, smooth labia minora. These girls also had a network of fine blood vessels in the fossa navicularis that extended to the hymenal rim. In SMR II subjects, there was a less pronounced vascular pattern and the hymenal rim remained thin. SMR III subjects demonstrated the beginnings of true estrogen effects on the genitals with hymenal thickening and still less prominence of superficial blood vessels. Clear vaginal secretions (physiological leukorrhea) appeared during this stage. SMR IV breast development was associated with hymens with thick, redundant projections and without visible blood vessels in the hymen or fossa navicularis. These subjects also had enlargement and darker pigmentation of the labia minora. SMR V subjects had further changes to the labia minora with elongation and development of rugae. While this cross-sectional study provides an important description of the hymen and surrounding tissues at different sexual maturity ratings of the breast, a longitudinal study further describing hymenal and genital tissue changes associated with progress through puberty would be an important contribution.
Longitudinal Intravaginal Ridges
Longitudinal intravaginal ridges are narrow, thickened ridges on the vaginal wall that often extend from the inner surface of the hymen into the vaginal vault ( Figure 10-11 ). At the point where an intravaginal ridge attaches to the inner surface of the hymen, there is frequently a hymenal mound (bump). Intravaginal ridges have been noted to occur in 61% of newborns and appear to become more common with age. Intravaginal ridges have been described in 89% to 94% of prepubertal females. Children often appear to develop multiple intravaginal ridges as they age. Intravaginal columns are prominent intravaginal ridges that occur along the anterior and posterior vaginal walls.
