Gynecologic Sonography in the Pediatric and Adolescent Patient

Technique

The pediatric vagina, uterus, and ovaries are best imaged with transabdominal ultrasound when the patient's bladder is full. All girls are encouraged to drink fluids and not to void in the hour prior to imaging. Teenagers are asked to drink 16 ounces.

Curvilinear, sector, and linear-array ultrasound transducers are usually sufficient for most pelvic ultrasound examinations. In young girls with urogenital malformation, hydrometrocolpos, a labial mass, or anal atresia, a transperineal approach is often useful ( Fig. 34-1 ). A transvaginal approach is used to complement the transabdominal examination in sexually active adolescents. In the patient with a complex congenital anomaly, genitography performed with water-soluble contrast material along with ultrasound examination is frequently helpful in identifying and characterizing the vagina, urogenital sinus, or cloaca.

Normal Anatomy

Uterine and ovarian size and shape are age-dependent and under hormonal influence. Maternal and placental hormonal stimulation lead to a relatively large neonatal uterus and ovaries compared to their size in later infancy, at which point they remain relatively stable in size until a growth spurt occurs at approximately 7 to 8 years of age ( Figs. 34-2 and 34-3 ). Mature ovarian follicles can be identified at all ages owing to the secretion of follicle-stimulating hormone (FSH). The prepubertal cervix is greater than or equivalent in thickness to the uterine fundus, and the endometrium is relatively inconspicuous in this age group ( Fig. 34-4 ). Cervical length is approximately twice that of the fundus in the neonate. During childhood, relative cervical length and thickness decrease but uterine fundal length and thickness increase. Average uterine length varies from approximately 2.5 to 4 cm, with thickness less than or equal to 1 cm. Ovarian volume is slightly less than 1 mL. The uterine fundus elongates and thickens during puberty, outstripping the cervix; the endometrium also thickens and undergoes cyclic changes associated with the menstrual cycle.

Normal Gonadal and Reproductive Tract Development

Development of the female reproductive tract is a complex process that involves cellular differentiation, migration, fusion, and canalization with probable apoptosis (programmed cell death). This integrated sequence of events is associated with many opportunities for abnormal development and structural anomalies. Anomalies of the reproductive tract may present at different time points. Most abnormalities of the external genitalia are obvious at birth, whereas obstructive and nonobstructive lesions of the female reproductive tract may be apparent at birth or only later in childhood, at puberty, in adolescence, or during adulthood.

In the first 3 months of embryonic life, the primordia of both the female and male reproductive tracts are present and develop together. The gonads arise after migration of germ cells to the genital ridge, whereas the genital tract evolves from the formation and reshaping of the müllerian (paramesonephric) ducts, urogenital sinus, and vaginal plate.

Biologic differences between males and females are determined genetically during embryonic development. Sex development can be divided into two processes: sex determination , the developmental decision that directs the undifferentiated gonad to develop as a testis or ovary; and sex differentiation , which occurs once the gonad has developed and is induced by the products of the gonad to establish the phenotypic sex. Factors that affect gene expression influence sex determination, whereas factors that influence sex differentiation include hormones and their receptors.

External Genitalia and Reproductive Tract

External genital development in the male occurs between the 8th and 12th weeks of life and requires high levels of circulating testosterone, the conversion of testosterone to dihydrotestosterone (DHT) by 5α-reductase in the target organs, and functional androgen receptors. Under the influence of DHT, in the male the urogenital sinus gives rise to the prostate gland; the genital tubercle forms the glans penis; the labiourethral folds form the urethra and ventral shaft of the penis; and the labioscrotal folds fuse to form the scrotum. In the female, or in the absence of testicular tissue secreting biologically active testosterone, functioning androgen receptors, or 5α-reductase, the genital tubercle forms the clitoris; the labiourethral folds form the labia minora; and the labioscrotal folds form the labia majora ( Fig. 34-5 ).

The cell layers involved in the formation of the female reproductive tract include the mesoderm, endoderm, and ectoderm. The mesoderm gives rise to the mesonephros and metanephros. In normal development, the mesonephros involutes, leaving only the wolffian ducts, and the metanephros eventually matures into the kidney. A defect within or insult to these mesodermal structures may ultimately result in congenital anomalies of the gonads, kidneys, and associated ducts. The urogenital sinus arises from the endoderm and gives rise to the bladder and urethra in males and females. In females it also forms the vestibule. The urethral and paraurethral glands in girls and the prostate gland in boys develop as outpouchings of the urethra. Nervous tissue, including sensory epithelium, arises from the ectoderm. Fusion of endoderm and ectoderm is involved in the canalization process; defects lead to fusion failure or obstructive lesions.

During the “indifferent” stage of development, two pairs of genital ducts develop from mesodermal tissue in both males and females: the mesonephric (wolffian) and paramesonephric (müllerian) ducts. The paired wolffian ducts connect the mesonephric kidney to the cloaca. The ureteric bud arises from the wolffian duct at about the 5th week of life and induces differentiation of the metanephros, which eventually becomes the functioning kidney; the mesonephric kidney involutes at 10 weeks. The paramesonephric (müllerian) ducts are identified in both sexes at 6 weeks of life. As they grow, the müllerian ducts lie lateral to the wolffian ducts until they reach the caudal end of the mesonephros where they extend medially to nearly touch in the midline near the cloaca. The urorectal septum forms by the 7th week, separating the urogenital sinus from the rectum. In males, regression of the müllerian ducts begins at 8 weeks of life and is almost complete by 10 weeks. In females, the müllerian ducts extend caudally, reaching the urogenital sinus by 9 weeks to form the uterovaginal canal, which inserts into the urogenital sinus at the müllerian tubercle. By the 12th week, the two ducts have completely fused into a single tube, the uterovaginal canal. Two solid evaginations of urogenital sinus origin, the sinovaginal bulbs, grow from the distal müllerian tubercle. Proximal to the sinovaginal bulbs, outgrowths from the distal müllerian ducts result in formation of the vaginal plate. The upper portion of the vagina is formed by vacuolization of the vaginal plate, whereas the lower portion is formed by vacuolization of the sinovaginal bulbs. Canalization begins caudally and proceeds proximally; it is complete by the 5th month of gestation. The distal-most portions of the sinovaginal bulbs form the hymenal tissue which perforates prior to birth ( Figs. 34-5 and 34-6 ). The upper portions of the müllerian ducts form the fallopian tubes.

Structural Anomalies of the Reproductive Tract

Abnormalities related to lateral fusion, vertical fusion, or resorption, agenesis and/or hypoplasia result in structural anomalies of the reproductive tract. A number of classifications of these anomalies have been proposed, although none is complete. The American Society for Reproductive Medicine (ASRM) system identifies groups with similar clinical manifestations and prognosis, although vaginal anomalies are not included ( Table 34-1 , Fig. 34-7 ). The Vagina Cervix Uterus Adnexa–Associated Malformations classification describes abnormalities not covered by the ASRM classification ( Table 34-2 ).

Vaginal and uterine anomalies may be detected in the neonatal period in children undergoing investigation of multiple congenital anomalies; or in adolescents, during workup of amenorrhea, pelvic or abdominal pain, or mass. An initial ultrasound study is usually sufficient in early childhood, with MRI performed at puberty for a more detailed evaluation. In the patient who first presents in adolescence, MRI is usually done following an abnormal ultrasound examination for a comprehensive assessment of the genitourinary tract.

During development of the uterus, failure of septal resorption between the two embryologic müllerian ducts leads to a septate uterus with two endometrial cavities. The septum can be partial or complete, with extension to the internal cervical os. A single cervix is usually present. The outer fundal contour of the uterus is either normal ( Figs. 34-7 and 34-8 ) or flat and broad. A bicornuate uterus results from incomplete fusion of the müllerian ducts. Leave out the part about incomplete development of the uterine horns. The central myometrium may extend to the level of the internal cervical os (bicornuate unicollis) or external cervical os (bicornuate bicollis), and the external surface is indented, typically by more than 1 cm ( Fig. 34-9 ). Complete nonfusion of both müllerian ducts leads to a didelphys uterus ( Fig. 34-10 ). Both horns are fully developed and nearly normal in size. There are always two cervices. There may be a transverse or longitudinal vaginal septum. Although a transverse vaginal septum may occur in association with all of the müllerian duplication anomalies, the greatest association is with didelphys uteri. When there is complete or near-complete arrested development of one müllerian duct, a unicornuate uterus develops with a single horn, an ipsilateral round ligament, and fallopian tube. The unicornuate uterus communicates with a single cervix and a normal vagina. In most patients, arrest is incomplete, and a contralateral rudimentary horn with or without functioning endometrium is present ( Fig. 34-11 ). The rudimentary horn may or may not communicate with the developed uterine horn. Sonography may demonstrate two uterine horns of different sizes. Unless functional endometrium within a noncommunicating horn leads to hematometra or endometriosis, no treatment is generally required. However, because of the potential risk of an ectopic pregnancy developing within a rudimentary noncommunicating horn, some advocate surgical resection.

Failure of fusion and canalization of the müllerian ducts and embryologic urogenital sinus lead to a transverse vaginal septum. Septa are generally less than 1 cm in thickness and extend completely or incompletely across the vagina ( Fig. 34-12 ). There is often a small central or eccentric perforation. A complete vaginal septum may occur in the upper (46%), middle (40%), or lower (14%) vagina. The vagina is short or is a blind-ending pouch. The external genitalia appear normal. Girls may present with mucocolpos in infancy or childhood, hematocolpos in adolescence, or pyohematocolpos from ascending infection through the small perforation. On imaging studies, it is critical to document the presence of a cervix in order to differentiate between a high vaginal septum and cervical atresia, because treatment and prognosis are very different.

Cervical atresia is rare and occurs in association with absence of the upper vagina. Patients may present with primary amenorrhea, cyclic or chronic abdominal or pelvic pain, or a pelvic mass ( Fig. 34-13 ). The usual treatment is hysterectomy.

Vaginal agenesis (müllerian aplasia, Mayer-Rokitansky-Küster-Hauser syndrome) occurs in approximately 1 in 5000 female births and results in congenital absence of the upper vagina in association with variable müllerian duct anomalies. There is usually associated cervical and uterine agenesis, although approximately 10% of patients have a rudimentary müllerian structure with or without functional endometrium. Skeletal, renal, and auditory anomalies are common. Affected individuals have a normal female 46,XX karyotype with normal oocyte and ovarian hormonal function. Patients exhibit normal secondary sexual characteristics and a normal perineum on physical examination. Because the hymen and distal vagina are both derived embryologically from the urogenital sinus, the hymen is usually present, along with a small distal vaginal pouch or vaginal dimple. Ultrasound examination is done to identify and characterize any müllerian tissue; to determine renal presence, position, and morphologic appearance; and to confirm the presence of normal ovaries ( Fig. 34-14 ).

When the lower portion of the vagina fails to develop from the urogenital sinus, distal vaginal atresia occurs and fibrous tissue replaces the absent distal vagina. The upper vagina, cervix, and uterus are normal. Primary amenorrhea is the usual clinical presentation. As the upper vagina becomes distended with blood and secretions, patients may develop cyclic or chronic pain and a pelvic or abdominal mass. Affected individuals have normal secondary sexual characteristics, although a vaginal orifice is absent. Transperineal ultrasound can be used to document absence of the distal vagina and to measure the distance between the proximal vagina and the perineal surface. This technique is especially useful intraoperatively ( Fig. 34-15 ).

An imperforate hymen is the most common anomaly of the female reproductive tract. There are usually no other associated abnormalities. The diagnosis can be made at birth, when a bulge from the associated hydrococolpos or mucocolpos is present, as a result of vaginal secretions related to maternal estrogen stimulation. If not diagnosed at birth, the mucus will eventually be resorbed, and the bulge will resolve. After the onset of menarche, the adolescent patient may be asymptomatic or have a history of cyclic abdominal or pelvic pain. An imperforate hymen can usually be diagnosed by physical examination alone. However, in many patients, a complete physical examination is not performed at birth, and cases in symptomatic adolescents are often initially misdiagnosed. Ultrasound imaging depicts distention of the vagina and uterus with fluid. Echogenic debris within the fluid is due to mucous secretions in infants ( Fig. 34-16 ) and blood in postmenarcheal girls. Ascites may develop following spillage of secretions through the fallopian tubes.

Ambiguous Genitalia

Birth of a child with ambiguous genitalia is rare. However, the substantial risk of psychological damage to the patient and family caused by an incorrect or delayed diagnosis necessitates the need for familiarity on the part of health care providers with the various causes as well as approach to diagnosis and management. Any deviation from the normal appearance of the genitalia, such as clitoromegaly or labial fusion, should lead to immediate evaluation.

An International Consensus Conference on Intersex was organized by the Lawson Wilkins Pediatric Endocrine Society and the European Society for Paediatric Endocrinology in 2006 that resulted in a consensus statement proposing the term disorders of sex development (DSD) to encompass congenital conditions with atypical development of chromosomal, gonadal, or anatomic sex. The DSDs are classified as sex chromosome DSD (karyotype is not the usual 46,XX or 46,XY); 46,XX DSD (chromosomally female); and 46,XY DSD (chromosomally male) ( Table 34-3 ). Karyotyping, hormonal analysis, and imaging are necessary for adequate delineation of these disorders.

Sonography is used to locate the gonads, to determine the presence or absence of a uterus, and to evaluate the adrenal glands for diffuse enlargement or masses. Retrograde genitography, obtained by injecting contrast material through the urogenital orifice, or voiding cystourethrography will characterize the anatomy of the urethra, vagina (if present), urogenital sinus, and occasionally the cervix. In the presence of a cloacal anomaly, the connections of the genital, urinary, and gastrointestinal tracts to the cloaca can be determined.

The most frequent sex chromosome DSD is 45,X (Turner syndrome), which is due to absence of all or part of one of the X chromosomes. Monosomy X is the most common. Characteristic physical features include short stature, low-set ears, webbed neck, and a broad chest. Gonadal dysfunction results in amenorrhea and sterility. The ovaries may not be detected by sonography, and the uterus has a juvenile appearance ( Fig. 34-17 ). Associated conditions include Hashimoto thyroiditis, congenital heart disease, renal anomalies, skeletal abnormalities, and diabetes.

Most cases of 46,XX DSD result from congenital adrenal hyperplasia. The adrenal glands are enlarged, and there is masculinization of the lower urogenital tract ( Fig. 34-18 ). In patients with a urogenital sinus, reflux of urine into the vagina and uterus can result in hydrometrocolpos ( Fig. 34-19 ). The ovaries and uterus are normal. Rarer causes of a masculinized but chromosomally normal female include a masculinizing ovarian tumor and maternal androgen ingestion in early pregnancy.

A cloacal malformation occurs when there is interruption of the normal differentiation of the genital, urinary, and gastrointestinal tracts. Cloacal malformations occur only in females, with an incidence of 1 in 40,000 to 50,000 newborns. Failure of the urorectal septum to form or fuse appropriately during embryologic development leads to incomplete separation of these tracts with a common confluence, the cloaca, and a single perineal opening. There is usually concomitant failure of müllerian duct fusion resulting in uterine and proximal vaginal duplication. The urogenital sinus persists, and the lower vagina and hymen do not form normally. In order to prevent bladder outlet obstruction, drainage of pooled urine through the vagina is usually required. A colostomy is performed to decompress the gastrointestinal tract. Many of these children have additional congenital anomalies necessitating multiple reconstructive operations. Accurate delineation of anatomic abnormalities usually requires genitography or voiding cystourethrography ( Figs. 34-20 and 34-21 ), as well as contrast material–enhanced examination of the distal colostomy limb.