Материал: Advanced Imaging of the Abdomen - Jovitas Skucas

Occlusion (Sterilization)

Most sterilization procedures belong in the realm of the obstetrician/gynecologist. The role of fallopian tubal occlusion with n-butyl-2- cyanoacrylate is not yet clear.

Cervix

Benign cervical stenosis is an occasional cause of infertility. It is often suspected when difficulty cannulating the cervical canal is encountered. Therapy consists of cannulating the cervix under fluoroscopic guidance and dilating the endocervical canal with balloon catheters or dilators.

Urethra

Bladder outlet obstruction is rare in women. Many of these women have had prior pelvic surgery. An occasional urethral neoplasm is a cause for obstruction.

Diverticula

Fallopian Tube

Salpingitis isthmica nodosa, or diverticulosis, is associated with pelvic inflammatory disease. Mucosal proliferation extends into the muscle layers, and the fallopian tube wall thickens. Infertility is common. An increased risk of ectopic pregnancy is associated with this condition.

Hysterosalpingography reveals diverticulumlike outpouchings in one or both fallopian tubes. These outpouchings range from solitary to multiple. The fallopian tubes tend to be dilated or obstructed, and a diverticulum can mimic distal tubal occlusion.

Fallopian tube recanalization is possible in salpingitis isthmica nodosa and may allow future intrauterine pregnancy.

Urethral

Incontinence and voiding dysfunction, regardless of cause, are discussed in Chapter 11.

Believed to represent sequelae of prior infected, obstructed, and ruptured periurethral glands, most urethral diverticula in women

ADVANCED IMAGING OF THE ABDOMEN

are acquired. Some authors differentiate a true diverticulum from a pseudodiverticulum, with the latter representing mucosal herniation through a periurethral fascial defect. Occasionally multiple, they are periurethral in location, and are most common along the posterolateral wall in the distal two thirds of the urethra.

These diverticula fill during voiding and then empty intermittently. Some larger ones are palpable. The differential diagnosis of a palpable periurethral soft tissue tumor includes a diverticulum, a periurethral cyst, and a soft tissue neoplasm.

Periurethral glands and ducts empty close to the urethral meatus, with the largest ones called Skene’s ducts.A Skene’s duct cyst, a consequence of either a congenital abnormality or a chronic inflammation, is palpable along the anterior vaginal wall. These cysts do not communicate with the urethral lumen, and a urethrogram thus differentiates them from diverticula. Also, MR identifies not only a cystic structure but also a solid, enhancing glandular component.

Adenomas and adenocarcinomas originate in urethral diverticula and paraurethral ducts near the urethral lumen. These are difficult to diagnose.

A radiopaque or lucent calculus forms in some of these diverticula secondary to stasis; it needs to be differentiated from a malignancy, generally an adenocarcinoma.

Urethral diverticula are studied with voiding cystourethrography, double-balloon urethrography, and US using an endovaginal, endorectal, or transperineal approach. False-negative results occur with all of these procedures. Voiding cystourethrography visualized only about three quarters of these diverticula, but due to its simplicity it is often the first test obtained. Urethroscopy has a low yield rate. Traditionally the double-balloon urethrogram has been the procedure of choice, although current US accuracy approaches that of a doubleballoon study. Magnetic resonance occasionally aids in establishing the relationship of a diverticulum to the urethra and in evaluating other etiologies of a palpable tumor in this location. Video urodynamic studies reveal stress incontinence in some of these women, and then both a diverticulectomy and an anti-incontinence procedure are necessary.

Either endovaginal or endorectal US provides useful information about the shape, volume,

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and content of a diverticulum, and about its relationship to the urethra. An endoluminal catheter-based US transducer identifies a diverticulum and aids in evaluating any periurethral inflammation and diverticular wall thickness.

Although currently not often used, MRI both detects these diverticula and outlines the surrounding structures. No bladder catheterization is required. Diverticula are hypointense on T1and hyperintense on T2-weighted images. Currently MR has a role in women with a clinical suspicion of a diverticulum but negative double-balloon urethrography or US study; keep in mind that false-negative studies also occur with MR.

A rare diverticulum recurs postoperatively (105).

Fistulas

The role of imaging is to define the fistulous communications. External fistulas are best studied with fistulography. Magnetic resonance imaging appears superior to other imaging modalities in detecting and outlining the extent of vaginal and uterine fistulas.

An enterouterine fistula is rare. Most are secondary to neoplasms; these do not heal if tumor has grown into the fistula.

Vesicouterine fistulas tend to be secondary to prior cesarean section or abnormal delivery (106); urinary leakage from the vagina or cyclic hematuria is typical presentations. These fistulas are better identified with a cystogram than IV urography; hysterosalpingography also has a high yield rate, provided the study is of high quality.

Most vaginal fistulas are rectoor colovaginal, urethrovaginal, cervicovaginal, or vesicovaginal, with the latter being most common. Most are related to pregnancy or prior hysterectomy. Malignancy, radiation therapy, diverticulitis, inflammatory bowel disease, and even Behçet’s syndrome are less common associated conditions.

Simple urovaginal fistulas extend to the bladder, urethra, or ureter; they are complex if more than two organs are involved. Most of these fistulas are symptomatic.

With a suspected vaginal fistula, vaginography using a water-soluble contrast agent should outline it. A barium enema is an alternative

with a suspected coloor rectovaginal fistula. Some authors have had better success in detecting a fistula with vaginography than with barium enema, although the results depend considerably on the technique of examination and attention to detail. Over the years I have had more success with a barium enema than with vaginography. If either method does not outline a fistula, then the other should be performed.

A rectovaginal fistula-occluding device, containing a nitinol wire and designed for endorectal insertion, successfully occluded several fistulas associated with pelvic irradiation or surgery (107).

Prolapse and Pelvic Floor

Abnormalities

Discussed here is pelvic floor prolapse in a global context only. Cystoceles and urinary incontinence are covered in more detail in Chapter 11, while rectal prolapse is discussed in Chapter 5. The two primary imaging studies used are MR and cystocolpoproctography (or specific components of the latter, such as proctography). Functional MRI is gradually replacing proctography in women suspected pelvic floor dysfunction and pelvic prolapse. Rectal and vaginal opacification (either with water or an enteral MR contrast agent) aids in establishing reference organ positions both at rest and during straining. A high field strength MR magnet using fast gradient echo sequences and an endovaginal coil provides pelvic floor images during relaxation and straining. Sagittal images are most often employed using a pubococcygeal reference line. At times 3D images are useful but they are not essential.

Normally pelvic organs do not descend below a pubococcygeal reference line on straining, and the pelvic floor muscles do not change their position (Fig. 12.31). Normal pelvic organ position is defined in reference to this line, but no universal criteria exist defining the borderland of prolapse. Complex organ prolapse is more common than individual prolapse; at times a cystocele or an enterocele is masked by a rectocele.

Pelvic prolapse is the displacement of pelvic structures due to an endopelvic fascia weakness. To illustrate the often complex interrelated

Figure 12.31. Pubococcygeal tear. Upright (A) and straining (B) views reveal a diverticular-like rectal outpouching (arrows). (Courtesy of Arunas Gasparaitis, M.D., University of Chicago.)

abnormalities found with lax pelvic organs and pelvic floor muscles, in 15 patients with constipation, a single sagittal section with T2weighted gradient echo sequence and dynamic MRI identified rectal prolapse (n = 5), an anterior rectocele (n = 8), pelvic floor descent (n = 5), enterocele (n = 2) and anorectal dyscoordination (n = 3) (108); in 15 patients with incontinence, such a dynamic MR study detected an anterior rectocele (n = 10), pelvic floor descent (n = 11), enterocele (n = 2), rectal prolapse (n = 1), and puborectalis insufficiency (n = 1). Triphasic dynamic MRI and triphasic fluoroscopic cystocolpoproctography using similar amounts of contrast to opacify the bladder, vagina, and rectum achieves similar results (109); although cystoceles and enteroceles tend to be underestimated by MR, pelvic organs and pelvic floor muscles are better identified with this modality. Also, cystoproctography does not reveal peritoneoceles.

From an imaging viewpoint, the pelvic floor can be subdivided into an anterior compartment where urethroceles and cystoceles develop, a middle compartment for uterine prolapse and enteroceles, and a posterior compartment for rectoceles (110); clinical and

B

imaging findings do not, however, always provide similar results, and the role of imaging is not settled. Dynamic cystoproctography reveals that over 90% of women with pelvic floor dysfunction have abnormalities in all three compartments (111); for example, among women with middle compartment (genital) symptoms, 91% had cystoceles, 56% a hypermobile bladder neck, 82% rectoceles, 58% enteroceles, 11% sigmoidoceles, 20% rectoanal intussusception, and 16% anal incontinence. Most rectoceles and cystoceles detected by cystoproctography are also evident on physical examination; the correlation between imaging and physical examination for enteroceles and sigmoidoceles is poor.

Not all widening of the rectovaginal space on straining is due to a rectocele. A peritoneocele should be suspected in women with unexplained widening. Less often is bowel present in this space.

Vaginal vault or cervical prolapse leads to vaginal mucosal eversion. Complete uterine prolapse is called procidentia. Sagittal T2weighted MR images identify not only prolapsing gynecologic structures, but also any associated bladder or bowel prolapse.

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Rarely, the uterus and ovary herniate into an inguinal hernia.

Pneumatosis

Pneumatosis of gynecologic organs is rare. If present, infection with a gas-forming organism or tissue necrosis should be suspected.

Imaging occasionally detects vaginitis emphysematosa, consisting of gas-filled cysts in the vaginal wall (112); this is a benign and selflimiting condition.

Vascular Lesions

Ovarian vein syndrome is discussed in Chapter 10. It usually occurs on the right and is due to compression of the ureter between the external iliac artery and a dilated ovarian vein. Left ovarian vein syndrome is due to ureteric compression between a dilated ovarian vein and the psoas muscle.

Bleeding

Postpartum bleeding was discussed earlier (see Pregnancy Related).

The most common causes of prepubertal vaginal bleeding consist of vaginal foreign bodies, precocious puberty, or tumors such as vaginal rhabdomyosarcoma or hemangioma.

In women with postmenopausal bleeding, US is a useful first step; a combination of endovaginal US without and with saline instilled into the uterus (endovaginal hysterosonography) is often more useful than either study alone. Both US studies achieve higher sensitivities in locating a bleeding site than does a diagnostic hysteroscopy.

Advanced pelvic malignancies not uncommonly result in major bleeding. In many of these women a diagnosis is already established, and surgery is not a viable option. Transcatheter embolization arrests bleeding in a majority of these women.

Ovarian Varicocele/Pelvic

Congestion Syndrome

Ovarian and broad ligament varicoceles, or varices, develop most often due to ovarian vein

incontinence and result in pelvic congestion. Secondary causes include inferior vena caval obstruction, portal hypertension, and other etiologies for increased blood flow in this region, such as an extensive vascular malformation.

Chronic pelvic pain is the most common presentation in these mostly multiparous women.

Imaging reveals serpentine paraovarian structures that enhance postcontrast. Unfortunately,it is difficult to place dilated ovarian veins in a proper perspective. Thus defining an incompetent and dilated ovarian vein as one measuring 7mm or greater, arterial phase helical CT found that 47% of asymptomatic women renal donors had dilated ovarian veins, more often on the left but bilateral in some women (113), a finding questioning the relevance of dilated ovarian veins. Others have found a 10% prevalence of ovarian varices in the general population, with slightly more than half of these having pelvic congestion syndrome and thus possibly benefitting from ovarian vein embolization or ligation (114).

Most of these varicoceles are treated surgically. A percutaneous approach using a sclerosing agent has been employed successfully. Although embolization achieves a high initial technical success rate, complete relief of pain is variable.

Ovarian Vein

Thrombophlebitis/Thrombosis

Most often ovarian vein thrombosis is detected postpartum, yet imaging has detected thrombosis in a variety of other settings, some associated with symptoms, others incidentally. In some women postpartum ovarian vein thrombosis is a sequela of infection. As already mentioned, ovarian vein thrombosis is a common incidental finding in women who have had a hysterectomy and bilateral salpingo-oophorectomy (49). Occasionally pelvic vein thrombosis develops in association with large uterine fibroids. A clinical diagnosis of ovarian vein thrombosis with its associated therapeutic implications should not be made lightly or based on imaging findings alone.

The right vein is affected more often. Some thrombi extend into the inferior vena cava. Clin-

ically, these patients are febrile and an infection is usually suspected. Puerperal ovarian vein thrombophlebitis can mimic renal colic and acute appendicitis. Pulmonary emboli are occasionally an early manifestation.

The diagnosis is suggested by CT,Doppler US, or MRI. A word of caution: at times early-phase postcontrast helical CT reveals retrograde flow in a normal ovarian vein. Therefore,asymmetric ovarian vein density during early-phase helical CT should not be misdiagnosed as a sign of ovarian vein thrombosis. Also, MR angiography shows absent flow in some ovarian veins even if they are patent, but MRI should detect vessel patency.

Ultrasonography reveals a tubular soft tissue tumor in the pelvis, at times extending to the inferior vena cava. A thrombus ranges from hypoto hyperechoic. Adjacent inflammation is common, and right-sided ovarian vein thrombosis can suggest acute appendicitis. Ultrasonography should detect any ureteral involvement. Ultrasonography also can monitor the response to anticoagulant therapy.

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Hemangioma

Ovarian hemangiomas are rare. Magnetic resonance imaging can suggest the diagnosis.

Uterine hemangiomas are also rare. Some of these contain punctate calcifications, aiding identification. Ultrasonography identified extensive uterine hemangiomatosis in a pregnant woman with Klippel-Trenaunay-Weber syndrome (115). Hemangiomas are homogeneous and hyperintense on T2-weighted images, thus distinguishing them from the more common hypointense myomas (Fig. 12.32).

Arteriovenous Malformations

Gynecologic arteriovenous malformations are uncommon but are one of the causes of uterine arteriovenous shunting. Past nomenclature used for these tumors included circoid aneurysm and arteriovenous aneurysm or

fistula. They have been miscalled angiomas and cavernous hemangiomas. These malformations contain proliferating vascular channels, often

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small and capillary-like in appearance. Most of these malformations are believed to be congenital in origin. Most develop in the myometrium.

Metrorrhagia is a common presentation. It is more common in premenopausal women. Uncontrolled bleeding after dilation and curettage should suggest an arteriovenous malformation, a (pseudo)aneurysm, an arteriovenous fistula, or a large vessel trauma.

Gray-scale US in women with uterine arteriovenous malformations is nonspecific, revealing subtle inhomogeneous myometrial tubular structures. Doppler US detects low-resistence flow and signals with flow reversals, suggesting arteriovenous shunting (Fig. 12.33).

Magnetic resonance imaging detects an arteriovenous malformation as a focal uterine tumor containing disrupted junctional zones and, if the tumor is large enough, prominent parametrial blood vessels. Flowing blood in these malformations presents as a serpiginous signal void on both T1and T2-weighted MRI, while stasis results in a hyperintense signal on T2-weighted images. A malformation enhances on postcontrast images, similar to blood vessels. Magnetic resonance angiography shows tortuous, coiled vessels in the pelvis.

Only a few vaginal arteriovenous malformations have been described. These lesions can be suspected with Doppler US, CT, and MRI. They are hypointense on T1and hyperintense on T2-weighted images; contrast-enhanced T1weighted images reveal paradoxical flow-related enhancement in some, possibly caused by turbulent blood flow.

Traditional therapy of massive uncontrolled bleeding was uterine artery ligation or hysterectomy. Pelvic arteriography is diagnostic and also provides access for transcatheter embolization for these often surgically difficult to resect tumors. Selective transcatheter arterial embolization of uterine arteriovenous malformations and other similar vascular abnormalities tends to preserve reproductive capacity.

Uterine Artery Aneurysms

Uterine true aneurysms are rare. (Pseudo)- aneurysms are more common and are a cause of massive bleeding (Fig. 12.34).

Gray-scale US reveals a pulsating, hypoor anechoic structure. True fusiform aneurysms contain an arterial flow pattern. Color and duplex Doppler US identify (pseudo)aneurysms