Anomalies of the Female Reproductive System Embryology

The internal genital organs, as well as the lower urinary system, originate from two paired urogenital structures that develop in both sexes, the mesonephric ducts (Wolffian ducts) and the paramesonephric ducts (Mullerian ducts).

In female development the Mullerian ducts are divided into two segments. The distal segments move towards the midline and soon fuse into a single tube, the uterovaginal canal. The resulting septum that divides the uterovaginal canal disappears soon after. Failure of lateral fusion of the Mullerian ducts results in a wide variety of abnormalities of the uterus, cervix and vagina. The development of the vagina is induced by the fusion of the uterovaginal canal with the urogenital sinus (transversal fusion). Due to the close developmental relationship between the genital and the urinary tract, association of anomalies in both systems are common [4].

Normal Appearance and Ultrasound Techniques

During normal growth and development the uterus and ovaries undergo a series of changes in size and configuration.

Under the influence of maternal and placental hormones, the neonatal uterus is remarkably prominent with a thick myometrium and a definable endometrial lining [5].

At two to three month of age, the uterus regresses to its prepubertal size and tubular configuration. The endometri-um is usually not visualised, making it rather difficult to evaluate uterine anomalies in infants and older children.

The post-pubertal uterus has the adult pear-shape appearance and the echogenicity and thickness of the en-dometrial lining varies according to the menstrual cycle [6].

High-resolution, real-time sonography has become the first-step imaging technique for the evaluation of the pelvis in infants, children and adolescents. Using the filled bladder as an acoustic window, the internal genital organs and the lower urinary tract are easily evaluated. In infants and young children who are not able to maintain a full bladder, filling of the bladder with sterile saline solution via a 5 to 8 French feeding tube might be necessary [7]. The same principle can also be used to outline the vagina (water vaginog-raphy), the rectum (water enema) or the urogenital sinus in complex congenital anomalies of the genitourinary tract. A transperineal sonographic approach should always be considered in cases of anomalies of the lower pelvis, since it allows an excellent documentation of the urethra, the peri-urethral soft tissue, the rectum and the distal genital tract.

Mullerian Duct Anomalies

Based upon the embryological development of the female genital system, uterovaginal malformations are classified as Mullerian agenesis in cases of a developmental defect of the caudal portion of the Mullerian ducts (Mayer-Rokitansky-Kuster-Hauser syndrome), disorders of the lateral fusion resulting from failure of the two Mullerian ducts to fuse and disorders of the vertical fusion that are caused by faults in the union between the Mullerian tubercle and derivatives of the urogenital sinus (transverse vaginal septum, cervical agenesis, disorders of the hymen).

Mayer-Rokitansky-Kuster-Hauser Syndrome

The Mayer-Rokitansky-Kuster-Hauser syndrome is characterised by the absence of the entire or, more frequent ly, the proximal two thirds of the vagina, absence or abnormalities of the uterus and malformations of the upper urinary tract. The most frequently found subtype of the syndrome consists of two rudimentary uterine horns located on a higher level than expected and normal Fallopian tubes, ovaries and kidneys.

Sonographic evaluation aided by instillation of fluid into the bladder as well as the rectum may demonstrate the absence of vagina and uterus. MR imaging is frequently needed to clearly document the ovaries and the rudimentary uterus.

Uterus Didelphys (Fig. 4)

Disorders of the lateral fusion of the distal segments of the two Mullerian ducts include septate, bicornuate, didelphys and unicornuate uterus. In the absence of obstruction, these malformations are asymtomatic during

Fig. 4. Bicornuate uterus. 6-day-old newborn female newborn with congenital segmental dilatation of the colon (C). Transverse image through the pelvis shows two separate uterine horns (arrows), B = bladder. (Reprinted with permission from [4])

childhood or at puberty. A uterus didelphys or bicornuate uterus can readily be documented on sonographic evaluation of the newborn.

Imperforate Hymen (Fig. 5)

Although the hymen membrane is entirely of urogenital sinus origin, imperforate hymen is commonly listed together with defects of the vertical fusion of the Müllerian ducts. Imperforate hymen may either be symptomatic in the newborn period or after onset of puberty when development of hydrocolpos/hydrometrocolpos or hematocol-pos/hematometrocolpos, respectively occurs. Sonographic evaluation shows the cystic dilatation of the vagina with the less distensible uterus attached to it. Internal echoes reflect cellular debris. Fluid may also be found in the peritoneal cavity due to spillage of genital secretion via the Fallopian tubes. Larger hydro- or haematocolpos may obstruct one or both ureters resulting in hydronephrosis.

Association of Lateral and Vertical Fusion Anomalies (Case no. 2 on CD-ROM)

The frequent association of vertical with lateral fusion anomalies means that it is useful to consider vaginal anomalies according to the presence or the absence of obstruction. Nonobstructive vaginal anomalies encompass bifid vagina, longitudinal vaginal septum and incomplete transverse septum. Among the obstructive vaginal anomalies are imperforate hymen, complete transverse vaginal septum, unilateral obstructive longitudinal vaginal septum, obstruction of a unilateral rudimentary horn and atresia of the uterine cervix or the vagina. Sometimes obstructive disorders already present at birth due to accumulated genital secretion. More commonly, however, the

Fig. 5. Imperforate hymen with hydrometrocolpos and ascites due to spillage of genital secretions via the fallopian tubes into the peritoneal cavity. a, b Sagittal scans. The vagina (V) as well as the uterus (U) are dilated, with broad communication through the cervical ostium (open arrowheads). The vagina shows a fluid-debris level (closed arrowheads). c Distended, fluid-filled abdomen. The air-filled loops of bowel cluster in the center of the abdomen. The lateral edge of the liver (arrowheads) is visible. (Reprinted with permission from [4])

Fig. 5. Imperforate hymen with hydrometrocolpos and ascites due to spillage of genital secretions via the fallopian tubes into the peritoneal cavity. a, b Sagittal scans. The vagina (V) as well as the uterus (U) are dilated, with broad communication through the cervical ostium (open arrowheads). The vagina shows a fluid-debris level (closed arrowheads). c Distended, fluid-filled abdomen. The air-filled loops of bowel cluster in the center of the abdomen. The lateral edge of the liver (arrowheads) is visible. (Reprinted with permission from [4])

patient seeks medical advice at puberty with cyclic abdominal pain and a pelvic mass is found. The whole spectrum of Mullerian duct anomalies from the obstructed hemivagina in association with an uterus didelphys to the unicornuate uterus, which reflects the extreme end of the spectrum, are almost always associated with severe ipsi-lateral renal anomalies (renal agenesis, renal dysplasia, ectopia, ipsilateral ectopic ureter, and hydronephrosis).

This strong association should urge the physician to evaluate always both systems when a malformation is detected in one of them.

Urogenital Sinus Malformation

Urogenital sinus is suspected during physical examination of a newborn with a normally placed anus in association with either ambiguous genitalia or normal female external genitalia but only a single opening within the vestibulum. It is either found isolated or in association with chromosomal and hormonal abnormalities or as a cloacal variant.

Female Hypospadia

In female hypospadias the urethral meatus is positioned in the anterior wall of the vagina. Proximal hypospadias often show a narrowing of the urethra with signs of urinary outflow obstruction and are commonly associated with cloacal anomalies and female pseudohermaphroditism. Diagnostic evaluation will, therefore, be discussed below.

Distal hypospadia is more likely to have a urethra of normal diameter with no meatal stenosis and is frequently asymptomatic. In these girls the urethral meatus is on the roof of the vagina just inside the introitus and the urethra has to be catheterised blindly.

Congenital Adrenal Hyperplasia

In most instances, female pseudohermaphroditism results from the exposure of a female fetus to excessive andro-gens. The most common causes are congenital adrenal hyperplasia (an autosomal recessive disorder of adrenal steroidogenesis). The increased level of androgens within the foetal bloodstream causes virilisation of the external genitalia, which may vary from minimal phallic enlargement of the clitoris to almost complete masculinisa-tion. At birth these patients present with marked clitoral enlargement, a variable degree of labioscrotal fold fusion and rugation. The opening of the urogenital sinus at the clitoral base may mimic penile hypospadia. Urinary tract anomalies are common and encompass renal agenesia, ectopia, and cystic dysplasia as well as uni- and bilateral hydronephrosis, vesicoureteral reflux and signs of urinary outflow obstruction.

The primary task of the radiologist is to demonstrate the level of communication between the vagina and the urethra, the anatomy of the internal genitalia, to rule out kidney anomalies and to document adrenal gland hyperplasia.

Sonographic evaluation of the patient is usually the first-step imaging technique, followed by conventional radiology using contrast material. Transabdominal ultrasound will demonstrate the internal genitalia, the kidneys and adrenal glands, and show any obstructions such as hydrocolpos and hydrometrocolpos [8]. Demonstration of enlarged adrenal glands with wavy limb configuration, however, is highly indicative of congenital adrenal hyperplasia [6].

Fluoroscopic studies with water-soluble contrast material are required to examine the exact anatomy of the malformation.

Cloacal Malformation

The cloacal malformation, the most complex type of im-perforate anus, is a complex congenital malformation with a common outflow of the urinary, genital and intestinal tract into a urogenital sinus. Cloaca is exclusively seen in phenotypic females.

The diagnosis of cloacal malformation is made when, in addition to an absent anus, only one perineal orifice is found between the labia. Every newborn girl with imperforate anus should be considered to have a cloacal malformation until proven otherwise.

Associated anomalies include uterus didelphys [9], renal anomalies, ectopia of the ureter, bladder diverticula, lower spinal cord abnormalities, anomalies of the pelvic osseous structures such as sacral agenesis or hypoplasia, dysraphism and pubic diastasis.

Obstruction of the cloaca may occur at any level and determines whether the proximal distended urinary and/or genital system is filled solely with genital secretions or contains urine and/or meconium as well.

Ultrasound is the most efficient first-step imaging technique in the diagnostic work-up of these patients. Performed early after birth, no or only little intestinal gas will be present and a clearer documentation of the in-trapelvic structures can be obtained. An abdominal mass in the neonate with cloacal malformation is almost always a distended vagina and/or uterus filled with urine and/or meconium because the path of least resistance for their egress was into the vagina instead of the cloaca. Obstruction of the common outlet can lead to retrograde flow via the fallopian tubes and accumulation of intraabdominal fluid. In cases where urine enters the rectum and colon, the meconium may calcify in utero and intra-luminal calcification can be documented sonographically as well as radiologically. The distance between the blind end of the rectum and the perineum should be measured by transperineal ultrasound, and the kidneys should be evaluated, as well as the spinal cord [6].

Sonographic features of spinal anomalies, occurring with a frequency of nearly 50% in patients with cloacal malformations, are either a high lying plump conus or a tethered cord with a thickened filum terminale.

The next step in the imaging process are fluoroscopic studies using water-soluble contrast material to visualise the often unpredictable and erratic courses of the communication between the multiple structures, and to provide functional information about reflux and competence of the urinary sphincter.

MR imaging is gaining acceptance in imaging congenital abnormalities of the genital tract, but should be used in conjunction with other imaging modalities.

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