Материал: Advanced Imaging of the Abdomen - Jovitas Skucas

FEMALE REPRODUCTIVE ORGANS

include imaging, especially MRI. The latter offers additional data on stromal invasion and lymph node involvement. Postcontrast MRI, in particular, appears very useful. In a number of practices, a barium enema and IV urography are no longer obtained in staging these tumors. Ultrasonography, including endovaginal US, has achieved only limited acceptance.

Clinical FIGO staging is somewhat inaccurate, especially with nodal involvement and advanced stages, more often underestimating rather than overestimating tumor spread. In fact, lymph node involvement is not assessed in clinical FIGO staging. Nevertheless, clinical FIGO staging is the primary factor guiding treatment decisions. Imaging also has limitations, as discussed below; nevertheless, imaging is widely employed for both prognosis and therapeutic decisions.

General Imaging Findings: Relative imaging accuracy in staging early cervical carcinoma is not settled. Computed tomography has low staging accuracy. It cannot evaluate size or stromal invasion because it does not differentiate tumor from surrounding normal cervical tissue. Parametrial invasion is difficult to define. Computed tomography is useful, however, in suspected advanced disease, and CT detects ureteral invasion and the resultant hydronephrosis as well as rectosigmoid invasion. Comparison studies of CT versus MRI show MRI to be superior in staging these tumors (95) and, in general, CT has been largely supplanted by MRI (Fig. 12.29). Both sagittal and coronal views are useful.

Endovaginal Doppler US in women with locally advanced cervical carcinoma reveals significantly lower RI and PI values for the uterine arteries than in healthy women; no differences exist between tumor stages, and this information appears of limited use in staging.

In distinction to some other tumors, dynamic contrast enhanced MR of cervical carcinomas does not aid in treatment decisions in those considered for radical hysterectomy (96). T2weighted sequences appear superior to contrast enhanced and fat-suppressed images. A phased array coil and a body coil achieve similar accuracies in local staging of invasive cervical cancer.

T2-weighted MRI reveals a hyperintense cervical tumor with an adjacent hypointense

stromal ring (assuming the tumor is sufficiently large to be visible). Preservation of this hypointense stroma surrounding the tumor on T2-weighted images argues against parametrial invasion. Stromal disruption without visible parametrial tumor invasion is often considered an indeterminate finding, although the extent of stromal invasion detected varies on the sequences used. Magnetic resonance imaging can correctly predict myometrial invasion and identify cancer extension in relation to the internal os (97).

Regions of increased MR contrast enhancement consist mainly of cancer cell fascicles, while poorly enhancing regions are composed mostly of fibrous tissue containing scattered cancer cells (98) (Fig. 12.30). Contrastenhanced dynamic MRI assesses tumor angiogenesis and appears to have prognostic significance. MR time versus signal-intensity curves of tumor contrast enhancement reveals that high-grade tumors have earlier MR contrast enhancement than lower grade ones, presumably due to their increased vascularity (99).

Vaginal invasion is usually evaluated clinically. Early vaginal invasion is difficult to detect with MRI, although MRI aids in detecting forniceal invasion. Rectal or bladder wall invasion is identified either on T2-weighted images or postcontrast. Magnetic resonance imaging suggests bladder invasion if an irregular bladder wall outline is evident or tumors protrude into the lumen.

Lymph Node Involvement: The ability to detect pelvic lymph node metastases is of obvious importance for staging gynecologic cancers, yet a high false-negative rate is evident with all imaging modalities. Thus in patients with various gynecologic cancers, the sensitivities were CT, 48%; MRI, 54%; and PET, 24% (100). The specificities, as expected, were high: CT, 97%; MRI, 91%; and PET, 77%. Other studies have achieved higher CT and MRI sensitivities (101), but otherwise these findings are typical. The poor PET results are due primarily to urinary FDG making the evaluation of pelvic lymph nodes difficult. A typical imaging definition of a metastatic node is a rounded soft tissue structure >10mm in diameter or a node containing central necrosis. Central necrosis had a positive

Local spread eventually encases and eventually obstructs the ureters. Metallic stents, at times augmented by J-endostents, are useful to maintain ureteral patency.

Adenoma Malignum

Adenoma malignum (minimal deviation adenocarcinoma) of the uterine cervix is a rare neoplasm suggested by cytologic atypia but not detected by cervical biopsy or Papanicolaou smears. Most authors separate it from the more conventional cervical adenocarcinoma. Pathologically, it tends to have a benign, cystic appearance and mimics endocervical glandular hyperplasia or cervical nabothian cysts, which are filled with mucus. This tumor has a poor prognosis. It tends to spread to the peritoneal cavity early in its course and is relatively resistant to radiotherapy and chemotherapy. Interestingly, this tumor often develops in patients with Peutz-Jeghers syndrome.

Endovaginal Doppler US showed extensive small vessels surrounding one such cystic tumor (102).

Magnetic resonance reveals multiple cysts deep in the cervical stroma. T1-weighted images shows them to be either isointense or slightly hyperintense relative to uterus and markedly hyperintense on T2-weighted images. These tumors contain solid components, with both the cystic and solid portions best identified on postcontrast images.

Whether MR can differentiate adenoma malignum from more benign cervical cystic lesions is debatable.

Other Cervical Tumors

An adenosarcoma is a rare tumor, most often occurring as a polyp in the endometrial cavity. Less often it originates in the cervix, mimics a benign cervical polyp, and is resected, and only histology identifies both he benign epithelial cells and the sarcomatous stroma.

A rare cervical neoplasm differentiates into a small cell neuroendocrine carcinoma. Lymph node metastases are common.

Vaginal Tumors

Many primary vaginal neoplasms are epidermoid in origin. They tend to have a polypoid

ADVANCED IMAGING OF THE ABDOMEN

or superficial ulcerating appearance, and most occur in the upper half of the vagina.

Carcinoma

A clear cell carcinoma of the vagina is associated with past exposure to diethylstilbestrol (DES). These tumors range from polypoid to infiltrating. Radiology has a limited role in their diagnosis but MR is useful in gauging spread.

Sarcoma

Vaginal rhabdomyosarcomas are found almost exclusively in young children, with only a few reported in postmenopausal women. Imaging is limited in their evaluation, except in outlining surrounding anatomy. Ultrasonography reveals a solid, mostly hypoechoic tumor.

An angiosarcoma infiltrates the surrounding soft tissues. These highly vascular tumors often are amenable to preoperative angiographic embolization.

Melanoma

Primary vaginal melanoma is rare. Most develop in postmenopausal women and occur in the lower third of the vagina. A bleeding exophytic tumor is not uncommon. Primary melanomas tend to infiltrate early, often involve the lymphatics, and have a poor prognosis. Melanoma metastasis to the vagina is also rare.

Fat-saturated T1-weighted MRI appears more useful than more conventional sequences in establishing the extent of tumor spread.

Metastasis/Invasion

Occasionally a mole invades the vagina. Women with these hypervascular tumors are at significant risk for major hemorrhage. Selective angiography with embolization can be lifesaving.

Paravaginal Cysts

Paravaginal cysts can be either inflammatory or developmental in origin (Table 12.10). They tend to be well defined and ovoid in shape. Their content of clear fluid, pus, or blood determines their imaging characteristics. Similar to other simple cysts, most paravaginal cysts are

FEMALE REPRODUCTIVE ORGANS

Table 12.10. Paravaginal cysts

Inflammatory

Bartholin’s gland cyst

Epithelial inclusion cyst

Mucous cyst

Developmental Urogenital sinus cyst Mesonephric cyst

Wolffian duct Gartner’s duct

Paramesonephric cyst (Urethral diverticulum)

hypointense on T1and hyperintense on T2weighted MRI. Some have a fluid–fluid level; the dependent fluid is hypointense and the nondependent fluid hyperintense on T2weighted images. These cysts show no contrast enhancement; the presence of a solid component or any enhancement should suggest a neoplasm.

Lymph node metastasis is not uncommon at initial presentation. Computed tomography and MR reveal a well-marginated tumor with peripheral enhancement. The bladder base becomes elevated.

The rare periurethral sarcoma or carcinosarcoma also presents with acute urinary retention; imaging should suggest a urethral tumor.

Obstruction

Fallopian Tubes

The most common etiology for fallopian tube obstruction is pelvic inflammatory disease (discussed earlier in this chapter).

Hysterosalpingography is generally considered to be the gold standard in detecting fallopian tube occlusion in infertile patients. False-positive diagnoses of obstruction are caused by inspissated mucus, tubal diverticula in the distal ampulla in otherwise patent tubes, or insufficient pressure during contrast injection.

Urethral Tumors

Most nephrogenic adenomas originate in the urinary bladder, with only an occasional one originating in the urethra or even in a urethral diverticulum. Most mimic other anterior vaginal wall tumors. Magnetic resonance imaging is useful in defining their extent.

An inverted papilloma of the female urethra is rare.

Primary urethral melanomas usually involve the distal portion. Most tend to be polypoid (103). Most of these tumors contain melanin, although prominent melanin is found only in a minority.

Urethral leiomyomas are very rare. Initial presentation is either acute urinary retention or hematuria, with an occasional stress incontinence.

The proximal one third of the female urethra is lined by transitional epithelium, and thus most proximal urethral carcinomas are transitional cell carcinomas, while distal ones tend toward adenocarcinomas.At initial presentation most have already spread to periurethral tissues and have a poor prognosis. Urethral carcinomas typically manifest with acute urinary retention.

Hydrosalpinx

Fallopian tube obstruction due to any cause can result in a hydrosalpinx. Some patients undergoing in-vitro fertilization develop a hydrosalpinx, believed to be secondary both to an obstruction and increased secretions due to hormonal stimulation. The hydrosalpinx can be followed to resolution with serial US.

Magnetic resonance imaging identifies most dilated fallopian tubes and differentiates them from other adnexal tumors.

A primary megaureter can mimic a hydrosalpinx on US.

Recanalization

With lack of contrast spill into the peritoneal cavity during hysterosalpingography, selective salpingography differentiates between spasm and anatomic obstruction, and, if necessary, fallopian tube recanalization clears an obstruction (104); successful recanalization can be achieved in most women. On a long-term basis a number of these women again develop tubal obstruction.