Материал: Advanced Imaging of the Abdomen - Jovitas Skucas

FEMALE REPRODUCTIVE ORGANS

when present, represents engorged follicles. Some hemorrhage is common and, if untreated, eventual necrosis ensues.

Echogenicity of a torsed ovary varies considerably.A US finding of a twisted vascular pedicle is suggestive of ovarian torsion but this is not always present. Doppler US suggests the degree of viability of a torsed ovary. With a nonviable ovary, Doppler US shows absent arterial and venous flow centrally, low-velocity arterial flow in the periphery, or absent or even reversed diastolic arterial flow. The lack of blood flow within a twisted vascular pedicle implies a nonviable ovary. The presence of internal arterial flow has prognostic implications because some of these can be treated successfully with laparoscopic untwisting.

Occasionally US detects an engorged fallopian tube. Cul-de-sac fluid is a common but nonspecific finding. Ultrasonography is not foolproof, however. Transabdominal US in two girls with abdominal cysts revealed a “double wall”sign, and duplication cysts were diagnosed (11); surgery revealed ovarian cysts, torsion, and hemorrhage within the cyst wall.

In addition to detecting engorged blood vessels in ovarian torsion, MR often also detects uterine deviation to the twisted side. The lack of CT or MRI contrast enhancement of the involved ovary signifies arterial compromise.

The wall of any associated cystic tumor is edematous and thickened. Any superimposed hemorrhage modifies the imaging appearance.

A rare finding with torsion involving an ovarian tumor is presence of intravascular gas within the tumor. This gas probably represents oxygen released from trapped oxyhemoglobin.

Fallopian Tube

Isolated fallopian tube torsion can develop in the absence of prior surgery or infection, but it is rare. Prior adhesions, inflammation, or ovarian disease predisposes to torsion. Possible congenital associations include a long mesosalpinx or mesovarium. Clinically, these patients have severe lower abdominal pain and signs of peritoneal inflammation.

Ultrasonography reveals an adnexal tumor and also a hydrosalpinx.

Uterus

Uterine torsion consists of the long uterine axis being rotated more than 45 degrees. Some of these torsions involve a uterine myoma.

Torsed uterine leiomyomas tend to be hyperintense on T2-weighted MRI once ischemia develops.

Infection/Inflammation

Pelvic Inflammatory Disease

Pelvic inflammatory disease (PID) is most often bacterial in origin and most often bilateral. Clinically, it mimics an acute abdomen and suggests appendicitis or bowel perforation. Acute salpingitis typically manifests as a pyosalpinx or hydrosalpinx. The infection spreads and evolves into either peritonitis or a tubo-ovarian abscess. Peritonitis ranges from diffuse to focal, occasionally localizing around the liver (Fitz-Hugh Curtis syndrome is discussed in Chapter 14). Gonococcal ovarian infection is rare. The clinical presentation is nonspecific.

Hysterosalpingography is contraindicated during suspected acute salpingitis. Endovaginal US often identifies free fluid in the cul-de-sac but endovaginal US has a low sensitivity in identifying fallopian tube intraluminal fluid or even a developing tuboovarian abscessees. Either CT, US, or MRI should detect a tuboovarian abscess or hydrosalpinx once it is established. A hydrosalpinx is common, usually bilaterally. Superficially, the imaging appearance of a pyosalpinx or hydrosalpinx mimics a dilated loop of bowel. The wall of a pyosalpinx tends to enhance considerably with contrast. Endovaginal Doppler US reveals a low resistive index in presence of severe infection.

Magnetic resonance imaging is not often performed for suspected PID but it has considerable potential. MRI findings include a fluid-filled tube, pyosalpinx, tubo-ovarian abscess, polycystic-appearing ovaries, and pelvic fluid. In one study, MRI sensitivity in detecting PID was 95% and specificity 89% and, for comparison, endovaginal US sensitivity was 81% and specificity 78% (12).

One sequela of scarring during healing is tubal obstruction and resultant hydrosalpinx formation.

Abscess

Among less common causes of a tubo-ovarian abscess is endovaginal oocyte retrieval for in vitro fertilization. Clinically, these patients present with pain and often a palpable tumor.

The CT and US findings of a tubo-ovarian abscess, regardless of cause, are similar to those

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of other intraabdominal abscesses. Often an abscess consists of a complex, thick-walled, cystic adnexal tumor having no specific characteristics. Some abscesses are associated with a hydrosalpinx. The presence of gas, although uncommon, is almost pathognomonic of an abscess. Most of these abscesses form discrete tumors, with an occasional one being diffuse and having an appearance similar to focal peritonitis.

Ovarian abscesses range from hypointense to hyperintense on T1-weighted images. A thin hyperintense rim is common. Most abscesses are hyperintense on T2-weighted images. Many contain linear stranding.

Some of these abscesses obstruct an adjacent ureter,and imaging should thus also evaluate for any hydroureter. The presence of adenopathy is variable.

The imaging appearances of a tubo-ovarian abscess and a necrotic tumor overlap. The differential often also includes an appendiceal or Crohn’s abscess.

Pelvic abscesses are drainable using an endovaginal US-guided trocar and catheters (13).

Tuberculosis

Adnexal involvement with tuberculosis is uncommon. A typical pattern of spread in affected individuals is from fallopian tubes to the uterus, with resultant infertility.

Tubal calcifications develop with tuberculous involvement. These are seen as linear or somewhat nodular calcifications along the fallopian tubes. Generally both tubes are involved. The presence of such calcifications, regardless of how they are detected, should suggest tuberculosis.

Hysterosalpingography identifies fallopian tube occlusion or narrowing, with the tube lumen having an irregular, beaded appearance. Outpouchings tend to mimic salpingitis isthmica nodosa. Any contrast spilled from the fimbriated tubal ends is loculated. A hydrosalpinx develops in some. Extensive fistulas are not common. Endovaginal US reveals fallopian tube wall thickening. Any hydrosalpinx is readily detected.

Uterine involvement leads to synechiae varying in size and extent; these synechiae can

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be identified if intrauterine fluid is instilled. An eventual decrease or even obliteration of the uterine cavity ensues. Endovaginal US reveals a thickened and inhomogeneous endometrium. Occasionally endometrial aspiration biopsy in a woman with bleeding yields necrotic debris with focal granulomas and even acid-fast bacilli.

Cervical tuberculosis can mimic a carcinoma; a biopsy should be diagnostic.

Actinomycosis

Pelvic actinomycosis is a chronic infection with the anaerobic gram-positive bacteria Actinomyces israelii. This commensal is found in normal body cavities; its growth is promoted by the presence of an intrauterine device. When invasive, it causes a chronic, indolent infection consisting of a soft tissue tumor mimicking a neoplasm. Histology identifies characteristic actinomyces granules.

The imaging findings are often more extensive than the symptoms suggest. A characteristic of this infection is extensive fistulization extending into surrounding structures. Occasionally one of the ureters becomes obstructed.

Two examples serve to illustrate the great mimicry of this infection: Pelvic actinomycosis with secondary liver involvement in a 50-year- old woman initially suggested a pelvic neoplasm with liver metastases (14). Computed tomography and US in a 37-year-old nulliparous woman with an intrauterine device revealed a large right adnexal mass adherent to the uterus and compressing the bladder, a preoperative diagnosis of ovarian cancer was made, and she underwent bilateral salpingo-oophorectomy and total abdominal hysterectomy (15); the resected specimen revealed actinomycosis.

Endometritis/Cervicitis

Among rarer causes of endometritis is infection with Trichinella spiralis, at times resulting in small calcifications with trichinella infiltrating the basal endometrium. A rare endometritis evolves into pyometra, perforation, and an acute abdomen.

Most syphilitic cervicitis is evident both clinically and pathologically. Rarely, syphilis presents with a cervical tumor mimicking a carcinoma.

Rarer Infections

Especially in the tropics, colorectal amebiasis can evolve into an amebic rectovaginal fistula. These fistulas heal after definitive therapy.

In endemic areas fallopian tube involvement with Schistosoma haematobium infection should be considered. Infected patients have an increased incidence of ectopic pregnancies and eventually develop infertility. Schistosoma eggs are found in the fallopian tubes, resulting in hydrosalpinx and PID.

Ovarian echinococcal infection is rare even in endemic regions, although adnexal involvement is not. Imaging reveals a pelvic cyst, with some cysts containing internal septa or even having an onion skin appearance. With active disease, color Doppler reveals increased peripheral vascularity. In endemic regions a check for hydatid serology appears reasonable.

Salpingitis Isthmica Nodosa

Salpingitis isthmica nodosa is an inflammatory disorder affecting the fallopian tubes and associated with infertility and an increased risk of ectopic pregnancy.

Hysterosalpingography reveals multiple diverticulum-like outpouchings adjacent to the tubal lumen, most often in the proximal isthmic portion of the tube, with the distal isthmus and tubal segments adjacent to uterine cornua less often involved. Fallopian tubes tend to be more convoluted than usual, a difficult subjective finding. Associated hydrosalpinx and tubal occlusion are common. Selective salpingography establishes whether fallopian tubes are patent.

Uterine Synechiae

Intrauterine adhesions, or synechiae, range from focal to diffuse involvement of the uterine cavity. Synechiae are associated with infertility (Asherman’s syndrome). Most common causes

of Asherman’s syndrome are postpartum uterine surgery and termination of pregnancy. Rare causes include infections such as tuberculosis and even schistosomiasis.

Hysterosalpingography identifies synechiae as irregular fixed filling defects within the uterine cavity. A severity grading system is reported (Table 12.2), although the hysterographic findings do not always reflect the hysteroscopic appearance. Most synechiae can be differentiated from polyps because the latter have a smooth round or oval configuration and synechiae are irregular in outline. Occasionally extensive adhesions obliterate the endometrial cavity to the point of preventing filling during hysterosalpingography.

Synechiae are identified with endovaginal US. Sonohysterography reveals synechiae as bridging bands in the fluid-distended uterine cavity.

The fibrous synechiae have a low signal intensity on T2-weighted MRI and are not visualized directly, but MRI is useful in evaluating the uterine cavity above adhesions for the presence of endometrial tissue. A normal endometrium and endometrium-to-myometrium junctional zone are absent on T2-weighted MRI in women with severe Asherman’s syndrome.

Operative hysteroscopy consisting of the surgical division of synechiae is the therapy of choice. Video-enhanced endoscopic hysteroscopy is further aided by intraoperative US; such US allows hysteroscopic lysis of adhesions at equivalent distances from the uterine wall, especially in the uterine cornua.

Table 12.2. Hysterographic classification of Asherman’s syndrome

Grade Description

1Single uterine defect less than one tenth of

uterus in size

2One or more defects occupying less than one

fifth of uterus

No gross uterine cavity deformity

3About one third of uterus involved Uterine cavity deformed by adhesions

4All or most of uterus involved Severe deformity

Source: Adapted from Dykes et al. (16).

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An endometrial carcinoma can develop in a setting of intrauterine synechiae.

Pregnancy Related

Normal Pregnancy

Hysterosalpingography is contraindicated during pregnancy. If performed, it reveals an early intrauterine pregnancy as a small sessile tumor.

Ultrasonography

The ability of US to visualize normal ovaries decreases from the first trimester to the second and from the second trimester to the third.

Early US signs of an intrauterine pregnancy include a chorionic rim sign, consisting of a hyperechoic rim around an intrauterine fluid collection, and the presence of a double decidual sac. Sensitivities of these two signs for an intrauterine pregnancy are about 60–80%, and specificity approaches 100%.

Endovaginal US can assess the corpus luteum during early pregnancy. Corpus luteum ranges from macrocystic, to microcystic, to noncystic. No correlation exists between corpus luteum size and pregnancy failure, although a decrease in volume between two examinations is associated with a greater risk of nonviable outcome.

A hyperechoic, thick-walled sac within a thickened endometrium suggests an intrauterine pregnancy, although it is insensitive in detecting an early pregnancy. With a positive pregnancy test and endovaginal US evidence of intrauterine fluid but without an embryo or yolk sac, follow-up US is necessary.

Doppler US of the uterine arteries can be obtained by either endovaginal and transabdominal techniques. During early pregnancy, the intrauterine arterial peak systolic velocity and resistive index values recorded transabdominally are lower than the endovaginal ones, but after 28 weeks of gestation the differences narrow.

An abnormal uteroplacental circulation, detected by Doppler US, suggests a spontaneous preterm delivery. An abnormal color Doppler

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study of a viable early pregnancy is associated with an increased risk of miscarriage. A uterine artery systolic/diastolic ratio significantly higher than normal later in pregnancy is often found with preterm delivery.

Transperineal US is often used to monitor cervical effacement at the start of labor. Ultrasonography reveals progressive cervical canal shortening and the opening of a funnel-shaped internal os, which gradually extends to the lower cervix and leads to effacement.

Magnetic Resonance Imaging

Magnetic resonance imaging offers a number of advantages in the pregnant patient and fetus. It is used for pelvimetry, because aside from the lack of ionizing radiation, MRI readily outlines the maternal bony pelvis and related soft tissues together with the fetus. A number of MR pelvimetry techniques have been described, most having the goal of decreasing image acquisition time.

Magnetic resonance is a viable alternative for differentiating hydronephrosis of pregnancy from hydronephrosis due to an obstructing stone. Only limited studies are available on the use of gadolinium in pregnancy. Current evidence points to no obvious harm.

Ectopic Pregnancy

An ectopic pregnancy implants either within the fallopian tube or in other locations in the pelvis or abdomen. Intraabdominal pregnancy is discussed in Chapter 14.

Etiology for ectopic implantation is unknown. Previous infection appears to play a role. Women on progestin-only pills are more prone to extrauterine pregnancies than those on combined oral therapy.

A human chorionic gonadotropin (hCG) of >2000mIU/mL and no US evidence of an intrauterine pregnancy is suggestive of an ectopic pregnancy, although some of these women do have a normal pregnancy. In early pregnancy small amounts of intrauterine fluid detected by US should be interpreted with caution; it is found with both an intrauterine and an ectopic pregnancy.

Some ectopic pregnancies resolve spontaneously. A longer time from the last menstrual

period, decreasing b-hCG levels, the absence of gestational sac, and a high ectopic pregnancy resistive index are predictors of spontaneous resolution (17).

Tubal

Clinical

Tubal rupture due to an ectopic tubal pregnancy is treated by salpingectomy. On the other hand, an ectopic tubal pregnancy detected prior to tubal rupture is amenable to laparoscopic microsurgery or other therapy.

An ectopic pregnancy manifests as pain, vaginal bleeding, and an adnexal mass. These findings are nonspecific and are found in a number of other conditions both in the pregnant and nonpregnant woman.A pregnancy test differentiates between these two groups. A tubal pregnancy results in hemosalpinx, bloody ascites, and a complex adnexal mass, findings identified by imaging with varying success rates. A bilateral tubal ectopic pregnancy is extremely rare.

A ruptured ovarian neoplasm in a pregnant woman mimics a ruptured ectopic pregnancy.

Imaging

Transabdominal US is generally performed as an initial examination for a suspected ectopic pregnancy. With a positive pregnancy test, the primary role of US is to detect an intrauterine pregnancy. The significance of not detecting an intrauterine pregnancy is limited, although an ectopic pregnancy is then considered. A definite diagnosis of an ectopic pregnancy is sonographic detection of a live embryo in an extrauterine location, a finding not often made.

Endovaginal US provides additional information in a setting of both an ectopic pregnancy and an intrauterine pregnancy. It is possible to detect an intrauterine pregnancy within several weeks after conception. The intradecidual sign consists of a hyperechoic endometrial region in the thickened decidua. This sign, in those with a b-hCG level >2000mIU/ml, achieved a sensitivity of 88% for diagnosing an intrauterine pregnancy (18). In a typical clinical setting sonographic evidence of an intrauterine

pregnancy essentially excludes an ectopic pregnancy (see Heterotopic Pregnancy, below). An ectopic pregnancy can be missed with endovaginal US, and some practices perform both transabdominal US for an overview and endovaginal US for its higher resolution; occasionally an ectopic pregnancy is detected with transabdominal US but not endovaginal US.

The ovary is a useful landmark when searching for an ectopic pregnancy. With endovaginal US an ectopic tubal pregnancy appears as a ring-like tumor having an anechoic center and

ahyperechoic periphery—an adnexal ring sign. Although often sought, this sign is not pathognomonic for an ectopic pregnancy. In some patients with a subsequently proven ectopic pregnancy, US will not detect any adnexal tumor or tubal ring. The reverse is also true, namely, the sonographic findings of an ectopic pregnancy can be mimicked by other conditions, for instance, a ruptured ovarian hemorrhagic cyst (19). The presence of intrauterine fluid does not exclude an ectopic pregnancy because such a pregnancy may be associated with a pseudosac.

Published sensitivities and specificities of US in detecting an ectopic pregnancy vary depending on specific criteria used. In general, with

apositive pregnancy test and no detectable intrauterine pregnancy, the presence of fallopian tube rings or extraovarian complex tumors has a high specificity and sensitivity for a tubal pregnancy.

In symptomatic pregnant women, an US three-layer endometrial appearance has been described in some women with ectopic pregnancy, but this sign is also seen in other conditions. Small endometrial decidual cysts are also identified in some ectopic pregnancies, but their significance is questionable.

Color Doppler US is believed to add little to a diagnosis of an ectopic pregnancy. Nevertheless, only an occasional ectopic pregnancy has arterial endometrial blood flow, and the presence of endometrial arterial blood flow aids in excluding an ectopic pregnancy.

In general, the presence of an adnexal tumor or intraperitoneal fluid should not be used as

acriterion for diagnosing tubal rupture. With a distended tube, blood and an amniotic sac of a tubal pregnancy have different MR signal intensities; bloody ascitic fluid has varying hyperin-

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tensity on T1-weighted MR images. An adnexal tumor has a complex signal intensity on both T1and T2-weighted images.

The therapy of an ectopic pregnancy generally is surgical. As alternate therapy, tubal pregnancies can be managed with local methotrexate injection using abdominal or endovaginal US for guidance. Nevertheless, methotrexate therapy has its own complications, including an acute abdomen and bleeding. Of interest is that hysterosalpingography after methotrexate therapy shows bilateral tubal patency in some of these women.

Cornual

A cornual ectopic pregnancy is rare, occurring in about 2% to 4% of all ectopic pregnancies. Rupture at the implantation site occurs at an advanced gestational age, and resultant severe bleeding is associated with increased maternal morbidity and mortality.

A cornual pregnancy has been successfully treated with methotrexate injection; US and laparoscopy are used for guidance.

Ovarian

An intraovarian ectopic pregnancy is rare. Surgical findings range from a hematoma, to an ovum, to placenta and fetus. Most often implantation is superficial and the ovary can be preserved.

Ultrasonography usually shows a complex nonspecific tumor. Some of these consist of a double hyperechoic structure surrounding a hypoechoic region. Endovaginal US aids in localization.

In the rare combined intrauterine and ovarian pregnancy, the ovarian pregnancy consists of a rapidly growing adnexal tumor and intraperitoneal hemorrhage, and it is not surprising that US cannot distinguish between an intraovarian pregnancy and an ovarian cancer.

Cervical

It has been said (20):

The majority of obstetricians will never see a cervical pregnancy; the minority who has to treat this pathology wishes to have never seen one.