Female Genital Tract

Sonography remains the imaging study of choice for the initial evaluation of most abnormalities of the pediatric pelvis, including the assessment of gynecologic masses, pelvic pain, ambiguous genitalia, and disorders of puberty (1,2,3). Computed tomography (CT) and magnetic resonance imaging (MRI) are helpful when the origin of a mass cannot be established by sonography or when evaluation of the full extent of a lesion is required (4,5,6,7). This chapter reviews the sonographic, CT, and MRI findings of the common pelvic abnormalities in children.

NORMAL ANATOMY

OVARIES

Ovarian morphology and size vary with patient age and pubertal status (8,9). Ovarian size is usually expressed as a volume (length × width × anteroposterior dimension × 0.5)(Table 10.1). The volume of the neonatal ovary is relatively large, due to in utero stimulation by maternal hormones. After the neonatal period, ovarian volume decreases, related to a decrease in maternal hormone levels. In infancy and early childhood, the ovaries are quiescent. Growth begins again around 8 years of age, with the ovary increasing at least four times in size by the onset of puberty.

Figure 10.1 Normal prepubertal ovary. Longitudinal sonogram of the right ovary of a 2-year-old girl shows multiple small follicles (arrowheads), measuring less than 9 mm in diameter (B, bladder).

Table 10.1: Ovarian Volume Measurements

	Age	Mean Ovarian Volume cm³ (±1 SD)
Premenarchal
Neonate	1 day-3 mo	1.1 (1.0)
Infant	4-12 mo	1.1 (0.7)
	13-24 mo	0.7 (0.4)
Early childhood	2-8 years	0.8 (0.4)
	3 years	0.7 (0.2)
	4 years	0.8 (0.4)
	5 years	0.9 (0.2)
	6 years	1.2 (0.4)
	7 years	1.3 (0.6)
	8 years	1.1 (0.5)
Late childhood	9 years	2.0 (0.8)
	10 years	2.2 (0.7)
	11 years	2.5 (1.3)
	12 years	3.8 (1.4)
Puberty	13-14 years	4.2 (2.3)
	>14 years	9.8 (0.6)
SD, standard deviation. From: Baltarowich OH. Female pelvic organ measurements. In: Goldberg BB, Kurtz AB, eds. Atlas of ultrasound measurements. Chicago: Year Book Medical Publishers, 1990;190-242; Cohen HL, Shapiro MA, Mandel FS, et al. Normal ovaries in neonates and infants: a sonographic study of 77 patients 1 day to 24 months old. AJR 1993;160:583-586; Orsini LF, Salardi S, Pilu G, et al. Pelvic organs in premenarcheal girls: real-time ultrasonography. AJR 1984;153:113-116.

In general, the ovaries can be seen on sonography in virtually all girls in the first two decades of life. The ovaries in prepubertal girls are often not seen on CT, but they should be visualized by onset of puberty.

The ovaries in the prepubertal girl contain unstimulated (primordial) follicles, most measuring between 4 and 9 mm in diameter (Fig. 10.1) (10). The ovaries of the pubertal girl will contain both stimulated and unstimulated follicles (Figs. 10.2, 10.3, and 10.4). In the first half of the cycle, virtually all the follicles are in an unstimulated state. By day 10 of the cycle, the stimulated follicle destined to ovulate increases to approximately 15 mm in diameter. The other follicles remain less than 1 cm in diameter. By midcycle, the
stimulated follicle can attain a size of 20 to 30 cm, before it ruptures and releases its ovum. The ruptured follicle involutes and becomes a corpus luteum, unless the ovum is fertilized. Corpus luteum follicles range between 10 and 30 mm in diameter. Of note, the diameter of a physiologic cyst should be 3 cm or less.

Figure 10.2 Normal pubertal ovary. A. Estrogen phase. Longitudinal sonogram on day 10 of the menstrual cycle shows multiple follicles less than 10 mm in diameter (arrowheads). B. Progesterone phase. Longitudinal sonogram on day 20 of the menstrual cycle shows a dominant cyst (arrow), measuring 18 mm in length. This likely represents a corpus luteum cyst.

Figure 10.3 Normal pubertal ovaries. CT scan of a 15-year-old girl on day 12 of the menstrual cycle demonstrates a stimulated follicle (arrows) measuring 25 mm in diameter in the right ovary. A normal low attenuation left ovary (L) is seen. (U, uterus).

Figure 10.4 Normal pubertal female pelvis, MRI. A. Coronal T2-weighted fat-saturated MR image of a 14-year-old girl demonstrates multiple bright follicles in the cortex of the ovaries (arrowheads). Some normal intermediate signal stromal tissue also can be noted (U, uterus). B. T2-weighted MR of another adolescent girl on day 10 of the menstrual cycle shows a high-intensity cyst, measuring 20 mm in diameter, in the left ovary (arrow), representing a developing follicle (U, uterus; arrowhead, right ovary).

Table 10.2: Normal Uterine Diameters and Volume

Age	Length (cm), mean (± 1 SD)	AP Dimension of Corpus (cm), Mean (± 1 SD)	AP Dimension of Cervix (cm), Mean (± 1 SD)	Volume (cm³)
2 years	3.3 (0.4)	0.7 (0.3)	0.8 (0.2)	2.0 (02)
3 years	3.4 (0.4)	0.6 (0.1)	0.8 (0.2)	1.6 (0.08)
4 years	3.3 (0.3)	0.6 (0.2)	0.9 (0.2)	2.1 (0.06)
5 years	3.3 (0.6)	0.8 (0.3)	0.8 (0.2)	2.4 (0.1)
6 years	3.2 (0.4)	0.7 (0.3)	0.8 (0.2)	1.8 (0.2)
7 years	3.2 (0.4)	0.8 (0.2)	0.8 (0.3)	2.3 (0.1)
8 years	3.6 (0.7)	0.9 (0.3)	0.8 (0.2)	3.1 (0.2)
9 years	3.7 (0.4)	1.0 (9.3)	0.9 (0.2)	3.7 (0.2)
10 years	4.0 (0.6)	1.3 (0.5)	1.1 (0.3)	6.5 (0.4)
11 years	4.2 (0.5)	1.3 (0.3)	1.1 (0.3)	6.7 (0.3)
12 years	5.4 (0.8)	1.7 (0.5)	1.4 (0.6)	16.2.(0.9)
13 years	5.4 (1.1)	1.6 (0.5)	1.5 (0.2)	13.2 (0.6)
AP, Anteroposterior; SD, standard deviation.
From: Orsini LF, Salardi S, Pilu G, et al. Pelvic organs in premenarcheal girls: real-time ultrasonography. AJR 1984;153:113-116.

Figure 10.5 Normal neonatal uterus, sonogram. Longitudinal sonogram shows prominence of the uterine fundus (arrowheads) and a thin, hyperechoic endometrial stripe, as a result of in utero hormonal stimulation.

UTERUS AND VAGINA

The uterus, similar to the ovary, has characteristic changes in size and appearance with age and pubertal status (Table 10.2) (8,9). The neonatal uterus is relatively prominent and the fundus is slightly larger then the cervix (fundus-to-cervix ratio of 1.2), reflecting in utero stimulation by maternal hormones (Fig. 10.5). At 2 to 3 months, the uterus decreases in size, acquiring a tubular shape with the size of the cervix equal to that of the corpus (Fig. 10.6). The prepubertal uterus remains small until about 8 to 9 years of age, when it begins to enlarge as puberty approaches. By puberty, the corpus again has become larger than the cervix, producing the adult pear-shaped uterus, and the endometrial stripe is again identifiable.

In the newborn female, the endometrial lining is thickened and a brightly echogenic endometrial stripe can be identified, caused by in utero maternal stimulation (see Fig. 10.5). With this exception, the endometrial stripe is usually not visualized in the prepubertal uterus on any imaging study (see Figs. 10.6 and 10.7).

Zonal anatomy is again noted at puberty. The hyperechoic endometrial stripe reappears. At sonography, it measures 2 to 3 mm in thickness in the early menstrual phase (days 1 to 5), approximately 8 mm in thickness in the proliferative phase (days 6 to 14), and approximately 15 mm in the secretory phase (days 15 to 28) (Fig. 10.8). On contrast-enhanced CT scans, the central endometrial canal, which contains low-attenuation blood or secretions, can be differentiated from myometrium and endometrium, which enhance intensely. The
myometrium and endometrium cannot be differentiated from each other (Fig. 10.9). Three distinct zones can be seen within the fundus on T2-weighted MR images: the high signal intensity endometrium, low signal intensity inner myometrium, and intermediate signal intensity outer myometrium (Fig. 10.10).

Figure 10.6 Normal prepubertal uterus, sonogram. Longitudinal sonogram of a 2-year-old girl. The uterus (arrows) is small and tubular with no differentiation between fundus and cervix. Zonal anatomy is indiscernible. There is no recognizable endometrial stripe.

Figure 10.7 Normal prepubertal uterus, CT. CT scan of a 5-year-old girl. The uterus (arrow) appears as a small homogeneous, oval soft-tissue structure posterior to the bladder. Neither ovary is visualized.

CONGENITAL UTERINE ANOMALIES

Congenital uterine anomalies occur in about 0.5% of females. Two paired müllerian ducts ultimately develop into the structures of the female reproductive tract. During development
of the female reproductive tract, the lower segments of the paired müllerian ducts fuse to form the uterus, cervix, and upper vagina. After the lower müllerian ducts fuse, a central septum is present, which eventually resorbs to form a single uterine cavity and cervix. Uterine anomies result when there is an error in development or fusion of the ducts or resorption of the midline septum. Patients may present with primary amenorrhea, mass (hematocolpos), or delayed onset of menarche. Coexistent renal ectopia or agenesis occurs in 20% to 30% of patients. Ultrasonography and MRI are the studies of choice to detect and characterize müllerian duct anomalies (11,12). The most common anomalies are discussed below.

Figure 10.8 Normal pubertal uterus. Three different patients. A. Early menstrual phase. Longitudinal sonogram shows a 3-mm thick echogenic endometrial stripe (cursors). B. Proliferative phase. Longitudinal sonogram near the time of ovulation shows an 8-mm-thick endometrial stripe (arrowheads). C. Secretory phase. Longitudinal sonogram shows an endometrial stripe thickness of 15 mm (arrowheads). Note in all three patients that there is pear-shaped uterus, with a fundus that is larger than the cervix.

Figure 10.9 Normal pubertal uterus. Contrast-enhanced CT scans of a 15-year-old girl shows a low-attenuation right ovary (R) and the uterine fundus (arrow). The higher attenuation myometrium and endometrium can be differentiated from the lower attenuation endometrial canal, but they cannot be differentiated from each other.

Figure 10.10 Normal pubertal uterus. Zonal anatomy is well seen on a sagittal T2-weighted image from a 12-year-old girl. The high-intensity endometrial complex (e) is surrounded by the low-intensity signal of the junctional zone (arrow) and the outer intermediate signal intensity myometrium (m).

Figure 10.11 Mayer-Rokitansky-Kuster-Hauser syndrome (uterine hypoplasia), 15-year-old girl with amenorrhea. Sagittal T2-weighted image shows a small uterus with fluid within the uterine canal (U) and upper one-third of the vagina (V). There was atresia of the lower two-thirds of the vagina (arrow) documented at surgery. Note the poor zonal definition of the uterus, and a normal ovary (arrowhead).

ERRORS IN MÜLLERIAN DUCT DEVELOPMENT

Uterine agenesis or hypoplasia (often termed Mayer-Rokitansky-Kuster-Hauser syndrome) is the result of absent or arrested development of both müllerian ducts. Findings of agenesis include absence of the uterus, cervix, and/or upper two thirds of the vagina. In uterine hypoplasia, the endometrial cavity is small and the zonal anatomy is poorly differentiated (Fig. 10.11).

Unicornuate uterus results when there is complete, or almost complete, arrest of development of one müllerian duct. Complete absence of one mullerian duct leads to a
banana-shaped uterus (fusiform uterine cavity with lateral deviation) with normal zonal anatomy. Partial arrest in development of one duct results in a rudimentary uterine horn, which may or may not connect to the opposite cornua (Fig. 10.12). If the rudimentary horn is obstructed and contains functioning endometrium, it may be distended by blood or blood products. Unicornuate uterus does not require treatment unless there is hematometra.

Figure 10.12 Unicornuate uterus with a noncommunicating rudimentary horn. A coronal T2-weighted image shows a hypoplastic right uterine horn (arrow), which does not communicate with the normal left uterine horn (U). The left uterine horn is deviated laterally and has differentiated zonal anatomy.

Figure 10.13 Müllerian duct fusion anomalies. A. Uterus didelphys: two uteri, two cervices, two vaginas. B. Uterus duplex bicollis: two uteri, two cervices, one vagina. C. Uterus duplex unicollis (bicornuate uterus): two uteri, one cervix, one vagina. D. Uterus septus: a single uterus divided by a septum. (Adapted from Colodny AH. Disorders of the female genitalia. In: Kelalis PP, King LR, Belman AB, eds. Clinical pediatric urology. Philadelphia: W.B. Saunders, 1985;888-903.)

FUSION ANOMALIES (FIG. 10.13)

Uterus didelphys results from complete nonfusion of both müllerian ducts. Two separate normal-sized uteri, cervices, and vaginas are seen (Fig. 10.14). The two uterine horns are wisely splayed and fully developed with normal endometrial and myometrial zonal widths. There is no effective surgical repair for uterus didelphys.

Bicornuate uterus results from partial nonfusion of the müllerian ducts. Two uterine cavities are seen with normal endometrium. Myometrium separates the two horns (Fig. 10.15). The uterine fundus is markedly concave (fundal depression or cleft >1 cm). There may be one or two cervices depending on whether the central myometrium extends to the level of the internal cervical os (bicornuate unicollis) or the external cervical os (bicornuate bicollis). Treatment is transabdominal surgical resection of the muscular wall between the two uteri (metroplasty).

Arcuate uterus is the mildest fusion anomaly. It has a single uterine cavity with a convex or flat uterine fundus. The endometrial cavity demonstrates a small fundal impression or cleft. This anomaly is not considered clinically significant, since it is not associated with symptoms.

FAILURE OF RESORPTION OF THE MIDLINE SEPTUM

Septate uterus results from failed resorption of the septum between the two uterine horns. There is a single cervix and vagina and a single uterine horn that is divided by a septum. The outer fundal contour is convex, flattened, or mildly concave (fundal cleft <1 cm) (Fig. 10.16). The septum may be composed of muscle or fibrous tissue and is not a reliable means of distinguishing septate and bicornuate uteri. The most reliable means to distinguish
bicornuate uterus from septate uterus is the fundal contour. Differentiation is important because septate uteri are treated with transvaginal hysteroscopic resection of the septum, while an abdominal approach is required for the bicornuate uterus.

Figure 10.14 Uterus didelphys. A. Oblique coronal T2-weighted fat-saturated MR image demonstrates two uterine horns (H) and two cervices (arrows). B. Axial fast spin-echo (FSE) T2-weighted fat-saturated image shows two vaginas (V).

Figure 10.15 Bicornuate uterus. Fat-saturated T2-weighted MR image shows two uterine bodies (arrows). There is a deep cleft (> 1 cm) in the uterine fundus. Each uterine horn is of similar size and has differentiated zonal anatomy. The two bodies fused just above a single cervix.

Only gold members can continue reading. Log In or Register to continue