The genitourinary system

Female genital organs

 

Anatomy

The uterine cervix is only partially available for visual inspection. Transvaginal ultrasonography can show the border between the cervix and the parametria. On T2-weighted MR images of the cervix two to three zones are often seen (Fig. 102); it has for the major part a low signal intensity because of its high fibrous structure. The cervical canal containing mucus and epithelial glands is seen as a central high signal intensive stripe. On T1-weighted images the structure is homogenous and it is possible to demarcate it from its surroundings.

Figure 103. Ovaries. Abdominal and transvaginal ultrasonography of a normal ovary. Transvaginal ultrasonography gives more details.

The size of the uterus depends on the hormonal state of the female. At ultrasonography its echogenicity is homogenous with an echo rich centreline (the endometrium). On T2-weighted images the uterine body has a typical zonal structure (Fig. 102). The central high signal intensity area represents the endometrium. The myometrium has two different zones: a thick outer zone with an intermediate signal intensity and a narrow inner zone with a low signal intensity, called a junctional zone. On T1-weighted images the uterus has a homogenous medium signal intensity structure and the outer surface is more clearly demarcated from the surroundings than on T2-weighted images. The uterus is often located anterior-superiorly to the vagina, but it may be even more anteflexed. It may also be retroflexed or retroverted.

Visualization of normal salpinges requires direct injection of contrast media. (Fig. 8). Sometimes the isthmic part is seen in the uterine comua at ultrasonography and MRI.

The ovaries may be located anywhere in the pelvic part of the abdomen. Their size depends on the hormonal cycle. Following external hormonal stimulation they may become very large. At ultrasonography (Fig. 103) performed late in the menstrual cycle echo poor areas (follicles) are seen in the ovaries, which already are somewhat hypoechoic. It is often difficult to see normal ovaries at abdominal ultrasonography, whereas at transvaginal ultrasonography is often possible to identify one or two non-enlarged ovaries. MRI is able to demonstrate normal ovaries in most women of reproductive age. They appear as slightly heterogeneous masses, and they are well delineated on axial, sagittal and coronal images. On T1-weighted images they have a low to medium signal intensity difficult to distinguish from the surrounding bowel loops; on T2-weighted images they are often indistinguishable from the surrounding fat.

 

a	Figure 104. Cervical cancer. a) Transverse T2-weighted image demonstrating tumor invasion into the right parametrium (arrow). b) T2-weighted image demonstrating that the cervical tumor extends into the uterine body, where three leiomyomas (arrowheads) were also present.
b

Pathology

Transvaginal ultrasonography has become an important supplement to the traditional gynecological examination of the uterus and its adnexae. Structures larger than 6 cm may be overlooked at transvaginal ultrasonography. Therefore both transvaginal and transabdominal ultrasonography should always be performed.

Cervix
Correct staging of cervical cancer is of utmost importance because it is decisive for the choice of treatment. A patient with stage Ib cancer (confine d to cervix) can undergo surgery, whereas a patient with stage Ila is better treated with radiotherapy. Radiotherapy of a recently operated

	Figure 105. Multiple cervical ovula nabothi in a patient with stage I endometrial cancer of the uterine body.
	Figure 106. Bicornuate uterus. T2-weighted image showing two areas with high signal intensity.

region results often in complications. Neither ultrasonography nor CT have proved to be better than manual palpation during general anesthesia for staging, whereas MRI seems to be more accurate than manual examination. In some patients T2-weighted images give a good outline of the cancer whereas in other patients contrast enhanced images are necessary to delineate the cancer (Fig. 104). MRI can also be used for demonstration of ovula nabothi, a kind of retention cyst, (Fig. 105), which occurs more frequently with increasing age.

Uterus
Uterine anomalies have been reported to be best delineated on MR-images (Fig. 106). They can best be evaluated with a combination of T2-weighted axial and sagittal images. The diagnostic capability of MRI

	Figure 107. Uterine calcifications in patient with recurrent ovarian cancer
a	Figure 108. Endometrial cancer stage Il. Total disappearance of the zonal structure and occurrence of necroses. a) T2-weighted image. b) T1-weighted image after administration of gadodiamide .
b

seems to be better than ultrasonography regarding size and number of uterine leiomyomas (Fig. 104 b); CT can only show calcifications and prominent changes on the surface of the uterus (Fig. 107). T2-weighted MRI is optimal for the diagnosis of submucosal and intramural lesions, since the contrast between the leiomyoma and the myometrium or endometrium is high. T1-weighted images are needed for determining the extent of subserosal leiomyomas. Neither ultrasonography nor MRI are able to distinguish between benign cystic leiomyoma and leiomyosarcoma. Adenomyosis produces diffuse and smooth uterine enlargement, which can be seen on both ultrasonography, CT and MRI. At MRI the junctional zone is thickened. Changes in the endometrial echopattern are indicative of endometrial cancer. At MRI endometrial carcinoma has a

	Figure 109. Benign ovarian tumor. T1weighted image after administration of gadodiamide. Large, thin walled, low signal intensity process behind the uterine body. No solid component was demonstrated.
	Figure 110. Malignant ovarian tumor. T1weighted image after administration of gadodiamide. Solid mass (arrows) whose signal intensity increased after application of contrast medium and a major cystic part which had a moderate signal intensity unchanged after administration of contrast medium.

higher signal intensity than that of the myometrium and cervix. The overall accuracy of MRI for stage I and Il is higher than that for clinical examination and CT. The use of MR-contrast medium improves the accuracy of staging (Figs. 105, 108). As regards stage III and IV MRI is not more accurate than CT. MRI seems also to be useful to control the effect of chemotherapy. With the use of MRI (and CT) intravenous urography and bowel X-ray for indirect demonstration of invasion are no longer indicated.

Ovaries
A torsed ovary can be diagnosed with Doppler ultrasonography demonstrating absence of blood flow in the ovary. Ovarian tumors - even the malignant ones - are often asymptomatic for a long time. Normally it is possible by ultrasonography to measure the size of the ovaries (the larger, the higher the risk for malignancy) and determine whether the process is solid and/or cystic. The flow pattern determined by color Doppler can give some indications about whether the mass is benign or malignant. The MRI appearance of ovarian tumors (Figs. 109, 110) can vary

	Figure 111. Recurrent ovarian tumor (arrow) dose to the enhancing uterus.
	Figure 112. Peritoneal carcinomatosis. T1-weighted image after administration of gadodiamide demonstrating high signal intensity tissue around the bowel (arrow) and ascites (arrowhead). The bladder is displaced to the right.

considerably. Primary MRI criteria indicating a malignant lesion are 1) size greater than 4 cm, 2) solid mass or large solid component, 3) wall thickness greater than 3 mm, 4) septa greater than 3 mm thick and/or presence of vegetations or nodularity, and 5) necrosis. Ancillary criteria are 1) involvement of pelvic organs or sidewall, 2) peritoneal, mesenteric, or omental disease, 3) ascites, and 4) adenopathy. A lesion can be classified malignant when at least two of the primary criteria are present and benign when either none or of the criteria are present. Ovarian tumors are still in many centres not biopsied due to the risk of peritoneal seeding. CT can be used for diagnosis of recurrence (Fig. 111) but a normal CT does not exclude recurrence. The ability of MRI with and without intravenous contrast to detect recurrence (Fig. 112) makes it is possible to obviate the need for second look operations in up to 75% of the patients.

	Figure 113. Tubo-ovarial abscess. Ultrasonography shows an echo poor septated process dose to the uterus (U).
	Figure 114. Endometriosis. T2-weighted image showing signal intensive and signal poor cystic processes.

Adnexa
In the adnexae fluid collections, hematomas, abscesses (Fig. 113) and endometriosis (Fig. 114) may occur. Transvaginal ultrasonography is excellent for the diagnosis (mainly echo-poor areas) and treatment of the three first diseases. Abscesses from bowel diverticula and inflammatory bowel diseases may be difficult to differentiate ultrasonographically from diseases in the adnexae. In case of an uncertain ultrasonography primarily MRI and secondarily CT should be performed. At MRI infected cystic masses have longer T1 and T2 relaxation times than hemorrhage. On T2-weighted images they have a high signal, but their appearance can vary considerably. Endometriosis presents various types of lesions. Large endometrial cysts or endometriomas have very variable features. They undergo cyclic bleeding during the menstrual cycles. Neither ultrasonography nor MRI can exclude the occurrence of endometriosis, but the sensitivity of MRI is higher than that of ultra sonography.

	Figure 115. Extra pulmonary small cell cancer occupying the pelvis and displacing a normal cervix and uterine body cranial. T2-weighted image. The anatomy is well demonstrated on this sagittal image.
	Figure 116. Hydrosalpinx. Hysterosalpingography demonstrating a closed and dilated right ampullary end.

In rare cases tumors like extrapulmonary small cell cancer and sarcomas may arise from the connecting tissue. MRI is superior compared to both CT and ultrasonography in the work-up of these rare malignancies (Fig. 115).

Infertility
For evaluation of infertility primarily ultrasonography and secondarily MRI should be performed to exclude anomalies and cystic ovaries. The next step is hysterosalpingography, which can demonstrate congenital anomalies, processes in the uterine cavity and postinflammatory changes of the salpinges and the peritoneal cavity. A typical finding is bilateral sactosalpinx (hydrosalpinx) (Fig. 116), in which case the ampulary ends

Figure 117. Anatomic relations of the adrenal glands and arterial supply.

are closed and dilated; sometimes minor adhesions may be broken during the examination.

Intervention

Biopsy and diagnostic puncture are performed under imaging guidance. Included is also oocyte aspiration for in-vitro insemination. It should be remembered that transvaginal punctures nearly always are very painful. Selective catheterization of the salpinges can be performed through the uterine cavity. Thereby, some occlusions of the isthmic part of the salpinges can be reopened. The technical success rate is between 80 and 90% and the pregnancy rates are around 30%. Also balloon dilatation of stenotic portions of the salpinges is possible.

 

Henrik S. Thomsen and Howard M. Pollack