Материал: Advanced Imaging of the Abdomen - Jovitas Skucas

guishing this abnormality from a bicornuate uterus.

Magnetic resonance imaging is helpful in identifying this condition (Figs. 12.8 and 12.9). Nevertheless, both US and MRI most often misdiagnose a septate uterus as either a normal or bicornuate uterus. The MR septal signal intensity varies depending on its composition and often is not a reliable indicator in differentiat-

ing a septate from a bicornuate uterus; on T2weighted images a fibrous septum is seen as a hypointense region, while a myometrial septum has a signal intensity similar to myometrium.

Generally hysteroscopic metroplasty is performed for a septate uterus, with preservation of future vaginal delivery.

Diethylstilbestrol-Related Abnormalities

Patients who have been exposed in utero to DES develop a number of gynecologic abnormalities, including cervical stenosis, various uterine

Figure 12.6. Didelphys in a 13-year-old. Right uterus (arrow) is hypointense due to blood and left uterus (arrowhead) hyperintense due to fluid and secretions. (Source: Burgener FA, Meyers SP, Tan RK, Zaunbauer W. Differential Diagnosis in Magnetic Resonance Imaging. Stuttgart: Thieme, 2002, with permission.)

Figure 12.7. Endometrial carcinoma in a bicornate uterus. A transverse oblique MR image identifies an intrauterine tumor (arrow). (Source: Burgener FA, Meyers SP, Tan RK, Zaunbauer W. Differential Diagnosis in Magnetic Resonance Imaging. Stuttgart: Thieme, 2002, with permission.)

Figure 12.8. Septate uterus. Transverse T2–weighted image identifies a septum in the uterine cavity (arrow). The external uterine outline is normal. (Source: Imaoka I, Kitagaki H, Sugimura K. MR imaging associated with female infertility. Nichi-Doku Iho 2000;45:440–450, with permission from Nihon Schering K. K.)

development abnormalities, and distorted fallopian tubes. Clinically, DES exposure is associated with subsequent infertility and ectopic pregnancies.

Hysterosalpingography in these patients shows a narrow irregular cervix and a small irregular uterine cavity. The uterus may have a T-shape. Currently hysterosalpingography is the preferred imaging modality in evaluating DESrelated abnormalities.

Figure 12.9. Septate uterus (arrow) identified on T2-weighted transverse oblique MR image. (Source: Burgener FA, Meyers SP, Tan RK, Zaunbauer W. Differential Diagnosis in Magnetic Resonance Imaging. Stuttgart: Thieme, 2002, with permission.)

Sex Differentiation Abnormalities

These abnormalities are usually subdivided into genetic disorders, gonadal disorders, and phenotypic sex differentiation disorders. Unless testicular tissue is present, a fetus develops into a female or a variant of a female. Genetic and hormonal evaluations are needed to define the underlying abnormalities in many of these infants and imaging has a limited role. Ultrasonography is helpful in outlining internal genital anatomy, although MRI provides better resolution.

Gonadal Disorders

Gonadal disorders include true hermaphroditism and gonadal dysgenesis (Turner’s syndrome). Both ovarian and testicular tissue is present in true hermaphrodites. For instance, an ovotestis can contain spermatogenesis in testicular tissue.

Patients with Turner’s syndrome have their gonads replaced by connective tissue. The incidence of malignancy is increased in this tissue.

Phenotypic Differentiation Disorders

Phenotypic abnormalities develop in a setting of several endocrine disturbances. Female pseudohermaphrodites have a normal female XX karyotype and normal internal female genitalia, but have virilizing external genitalia due to excess androgen from a number of sources. The most common etiology is congenital adrenal hyperplasia. Ultrasonography or MRI should confirm normal internal genitalia.

Male pseudohermaphrodites have a normal male XY karyotype, and testicular tissue is present, but the internal or external genitalia is ambiguous. Imaging should exclude the presence of ovaries and uterus.

Testicular feminization is a rare sex-linked disorder caused by androgen receptor gene mutations. Peripheral insensitivity to androgen leads to female external genitalia, undeveloped müllerian duct structures, androgen-producing testes, and a male genotype.As a result, the proximal third of the vagina, cervix, uterus, and fallopian tubes are either absent or rudimentary. The sexual orientation is female. Testes are undescended. Ultrasonography identifies a blind-ending vagina and no uterus or adnexal

FEMALE REPRODUCTIVE ORGANS

structures; MRI also diagnoses uterine agenesis and detects undescended testes, often within or just below the inguinal canal; the testes are smaller and more hypointense than normal on T1-weighted images and isointense on T2weighted images.

Testicular feminization should be suspected in girls having ambiguous genitalia and an inguinal hernia. Later these patients have primary amenorrhea. In distinction to male cryptorchidism, the incidence of testicular neoplasms in patients with testicular feminization begins to increase only after the age of 30 years. Thus in the complete form of testicular feminization gonadectomy can be delayed.

Cloacal Malformation

In a cloacal malformation the rectal, urinary, and genital tracts communicate and exit through a common perineal opening, or cloaca. This rare anomaly occurs only in girls, develops early in the embryo, and varies in appearance depending on how the connecting tracts join.

A diverting colostomy is generally performed initially. A contrast study of the cloaca helps define the underlying anatomy. Using this study as a guide, a catheter can be advanced into the bladder and a cystogram performed. Injection into the distal limb of the colostomy should define the rectal communication.

Diastasis of the symphysis pubis is common in these girls. Sacral and spinal chord abnormalities are common.

McCune-Albright Syndrome

A combination of café-au-lait spots, fibrous dysplasia, and precocious puberty is found in McCune-Albright syndrome. Ovarian follicular cysts are a common finding.

Vagina and Urethra

Gartner’s duct cysts originate from mesonephric (wolffian) duct remnants that fail to reabsorb. Most occur parallel and anterolateral to the vagina and are small and asymptomatic, although occasionally a large cyst is encountered. An occasional one visualizes during hysterosalpingography if it communicates with the uterus.

Figure 12.10. Pyometra secondary to an obstructed cervix. Sagittal T2-weighted MR image reveals a greatly distended uterus (arrows). Blood and debris account for the slightly hyperintense appearance. (Source: Burgener FA, Meyers SP, Tan RK, Zaunbauer W. Differential Diagnosis in Magnetic Resonance Imaging. Stuttgart: Thieme, 2002, with permission.)

Vaginal obstruction results in hemato (metro)colpos or hydrocolpos. At times the obstruction evolves into a large pelvic soft tissue tumor, evident both clinically and with imaging. Obstructions range from imperforate hymen to a vaginal septum. With hematometra, cervical dysgenesis is also in the differential. Both US and MR are useful in detecting these abnormalities (Fig. 12.10). Endorectal US is a viable alternate for suspected vaginal abnormalities if endovaginal US is not feasible. Transperineal US should detect a vaginal septum.

Magnetic resonance imaging of hematocolpos reveals a high signal intensity blood collection on both T1and T2-weighted images and helps establish whether the distention extends into the fallopian tubes.

Congenital urethral valves are rare in female infants, with most distal urethral obstructions being secondary to a mucous membrane. Urethral duplication is also rare.

Trauma

Blunt abdominal trauma results in uterine rupture, especially during pregnancy. Most are seat-belt injuries; traumatic rupture involves the

fundus, and fetus and placenta extrude into the maternal abdomen. Uterine rupture during the second or third trimester of pregnancy should be diagnostic with US; an empty uterus is identified. Computed tomography can also detect uterine rupture and an intraabdominal fetus.

Uterine rupture during labor is associated with prior hysteroscopy, prior repeated curettage, and perforation. Spontaneous uterine rupture during pregnancy is a complication of Ehlers-Danlos syndrome type IV.

Urethral rupture due to pelvic fracture is rare in women (9). If present, an associated vaginal tear is often also found.

Ultrasonography can detect vaginal foreign bodies in young girls. The echogenicity and acoustic shadowing of a foreign body varies. At times US detects an indentation of the posterior bladder wall.

Acute Gynecologic Conditions

Imaging of acute gynecologic conditions are discussed in more detail in their respective sections in this chapter. Not uncommonly these conditions are in a differential diagnosis of an acute abdomen (discussed in Chapter 14).

Computed tomography in 100 consecutive nonpregnant women suspected of having appendicitis or an acute gynecologic condition achieved a 100% sensitivity and 97% specificity in diagnosing appendicitis and 87% sensitivity and 100% specificity for acute gynecologic condition (10).

ADVANCED IMAGING OF THE ABDOMEN

would label as volvulus for an equivalent condition in the gut).

Ovarian torsion occurs most often in girls and young women but has developed in neonates. Depending on the degree of twist, the onset of pain ranges from gradual to sudden. Severe pain is a common presentation of complete torsion. Clinically, acute right ovarian torsion mimics appendicitis. A not uncommon scenario consists of acute appendicitis being suspected in a young girl, but subsequent laparotomy detects a torsed and necrotic ovary.

Chronic partial ovarian torsion is rare. Intermittent venous obstruction and edema result in massive ovarian enlargement.

Neglected amputated ovaries secondary to ovarian torsion can evolve into calcified cystic tumors which became attached to adjacent structures by a pedicle containing vessels.

Salpingo-oophorectomy is often performed for ovarian torsion. Occasionally prophylactic oophoropexy or even laparoscopic shortening of the uteroovarian ligament is feasible for intermittent torsion.

Imaging

Imaging shows a large, irregular adnexal tumor ranging from solid to thick-walled and cystic (Figs. 12.11 and 12.12). Any cystic component,

Torsion

Ovary

Clinical

Torsion, or a twist of the ovary around its pedicle, leads to venous stasis, edema, and eventual ischemia. Although isolated ovarian torsion does occur, usually it is associated with fallopian tube torsion. It can occur during pregnancy. An ovarian cyst or other tumor, regardless of etiology, predisposes to torsion (gynecologists and urologists prefer the terms severe torsion or even simply torsion to what gastroenterologists

Figure 12.11. Ovarian torsion in an 11-year-old girl with pelvic pain. Computed tomography reveals a retrovesical tumor. Normal gynecological structures were not identified. An appendiceal abscess was initially suspected. (Courtesy of Luann Teschmacher, M.D., University of Rochester.)