Материал: Advanced Imaging of the Abdomen - Jovitas Skucas

rectal examination and monitoring PSA levels. A rising PSA should prompt bone scintigraphy. If scintigraphy is positive, no further workup is needed. Magnetic resonance imaging has a role in a setting of an indeterminate bone scan. A rising PSA level and negative bone scintigraphy suggests local recurrence and transrectal USguided biopsy and CT or MR for adenopathy appear appropriate.

In men with inoperable prostate cancer, radionuclide bone scans, serum PSA, and serum prostatic acid phosphatase levels monitor progression, although some investigators believe that serum PSA level by itself is sufficient to follow disease progression. Men with untreated prostatic cancer or those refractory to endocrine therapy have an exponential increase both in PSA level and in prostatic acid phosphatase level; tumor marker doubling time is a useful guide in estimating cancer growth rates and in determining prognosis after relapse.

Urinary PSA levels are not useful for posttherapy follow-up because PSA is also secreted by periurethral glands.

Imaging: Postoperative recurrence is either local or metastatic. Computed tomography sensitivity in detecting local recurrence is low, with postoperative deformity making evaluation difficult. Endorectal US is more sensitive but less specific than digital rectal examination for detecting local recurrence although both provide only limited information (58). Adding Doppler US improves both sensitivity and specificity. With an elevated serum PSA level and a negative bone scan, US-guided prostate fossa biopsies should be considered, especially of any hypoechoic foci detected by endorectal US. Negative biopsies, however, are of limited significance.

For detecting local recurrence, an endorectal coil MRI study is superior to a body coil MRI study. Endorectal surface coil MRI sensitivities and specificities close to 100% have been enthusiastically reported in detecting local recurrence and some authors believe that endorectal MRI has a place in those who have had a prostatectomy and local recurrence is suspected (59). Nevertheless, one study found poor accuracy, and solid tumor foci were detected only if they were >1cm in diameter, while diffuse tumor infiltration was not detected (60). The authors also found that contrast-enhancement provided no additional information, and they concluded

ADVANCED IMAGING OF THE ABDOMEN

that in this setting MRI cannot replace follow-up biopsy. When seen, recurrence is identified as a soft tissue tumor in the prostatic bed, which is hypoto isointense on T1and hyperintense on T2-weighted images. A fibrotic peripheral zone is hypointense.

Monoclonal antibody radioimmunoscintigraphy with In-111–capromab pendetide shows promise in detecting occult recurrence. This antibody conjugate localizes to a glycoprotein found primarily on prostate tissue cell membranes. In men with an elevated serum PSA at least 3 months after therapy, monoclonal antibody imaging was superior to PET scanning in identifying recurrent cancer; most common sites of recurrence are prostatic fossa and lymph nodes.

Small Cell/Anaplastic Carcinoma

A nondifferentiated small cell prostatic carcinoma is rare. These are aggressive tumors associated with a poor prognosis. These tumors often exhibit morphologic and functional neuroendocrine characteristics. Superficially, some mimic a lymphoma. The CEA levels tend to be normal.

Computed tomography often detects metastatic disease in men presenting with an anaplastic prostate carcinoma; bone metastases are associated with a more modest PSA level compared to a typical prostatic carcinoma.

Lymphoma/leukemia

Primary non-Hodgkin’s lymphoma of the prostate is rare. Clinically, these lymphomas can mimic acute prostatitis.

Secondary hematologic malignancies involving the prostate and adjacent lymph nodes range from chronic lymphocytic leukemia to lymphoma. Transrectal US–guided prostate biopsies should be diagnostic.

An occasional outlet obstruction is the first manifestation of a leukemic or lymphomatous prostatic infiltrate.

Mesenchymal Neoplasms

Prostatic leiomyomas are rare. These tumors can be quite large and imaging findings nonspecific. A diagnosis is established with a biopsy.

MALE REPRODUCTIVE ORGANS

Of clinical importance are postoperative spindle cell nodules and pseudosarcomatous fibromyxoid tumors; pathologically, these tumors may be misidentified as sarcomas.

Most prostatic sarcomas occur in children under 10 years of age, thus allowing differentiation from carcinoma. Most of these are rhabdomyosarcomas. In adults about 25% of prostatic sarcomas are leiomyosarcomas. Previous pelvic radiation, such as for a seminoma, is occasionally associated with a prostate sarcoma. These tumors tend to be large at initial presentation.

Ultrasonography identifies most prostatic sarcomas as heterogeneous tumors having decreased attenuation, probably due to focal necrosis.

These sarcomas are hyperintense on T2weighted MRI, with the surrounding fibrosis being hypointense.

Wolffian Duct Structures

Endorectal US appears to be a reasonable first study in evaluating the distal male reproductive tract for potentially correctable causes of infertility. Cysts and duct obstructions are detected.

Seminal Vesicle Disorders

Seminal vesicle cysts can be either congenital or acquired. They are located posterolateral to the bladder in the general location of the seminal vesicles. An occasional one is more midline in location and inhomogeneous in appearance. Most cysts are unilateral and more frequent on the right side. A cyst can obstruct an adjacent seminal vesicle.A rare cyst is huge. Most of these cysts are discovered incidentally. An association exists between seminal vesicle cysts and absence or dysplasia of the ipsilateral kidney. An ectopic ureteral insertion into the seminal vesicle is found in some of these patients; the presence of a seminal vesicle cyst thus warrants further imaging; both structures originate from a common embryologic mesonephric duct.

Multiple, bilateral seminal vesicle cysts develop in men with autosomal-dominant polycystic kidney disease.

Computed tomography density tends to be >40 Hounsfield units (HU) in seminal vesicle cysts. Endorectal US readily identifies these

retrovesically located cysts. Magnetic resonance imaging is also very useful in detecting seminal vesicle cysts, which are hyperintense on both T1and T2-weighted images.

Transperineal puncture under endorectal US guidance fills a cyst with contrast and establishes the diagnosis. Most seminal vesicle cysts are resected; a minority undergo transurethral marsupialization using endorectal US guidance.

In temperate climates the most common cause of seminal vesicle calcifications is diabetes mellitus. Schistosomal calcifications are encountered in the Near East. Less often calcifications are secondary to tuberculosis. Seminal vesicle calculi are associated with painful ejaculation. Endorectal US detects duct obstruction by stones or fibrosis. Calcifications are hypointense on both T1and T2-weighted MRI.

Seminal vesicle hydatid cysts are rare. CT reveals thin wall water-density cysts (61); some also develop daughter cysts.An infected cyst can evolve into an abscess. These abscesses can be drained percutaneously.

An infected cyst can evolve into an abscess. These abscesses can be drained percutaneously.

Most seminal vesicle neoplasms are reported anecdotally. A rare cystadenoma mimics a cyst.

Rarely, amyloidosis infiltrates the seminal vesicles.

Ejaculatory Duct Disorders

An ejaculatory duct cyst adjacent to the duct can occlude the duct lumen. Some of these cysts are associated with infertility. These cysts are identified and treated using endorectal US guidance. Their aspirate contains spermatozoa, thus distinguishing these cysts from müllerian duct cysts.

Occasionally identified is urethroseminal reflux into the ejaculatory ducts.

Endorectal US–guided opacification of the seminal tracts with contrast is useful in men with suspected ejaculatory duct obstruction and dilated seminal vesicles. Most ejaculatory duct obstructions are bilateral.

Hemospermia

Causes of hemospermia include prostatitis, seminal vesicle or ejaculatory duct calcifications, cysts, and vascular anomalies. End-

orectal gray-scale and Doppler US determine the cause of hemospermia in most in men. Detected are periurethral calcifications, prostatic inflammation, seminal vesicle ectasia, and various cysts. Magnetic resonance using an endorectal coil is probably more sensitive. Hyperintense seminal vesicles on T1-weighted images suggest hemorrhage, and hypointense ones both on T1and T2-weighted images consist of fibrosis due to chronic inflammation.

Penis

Urethra

Extravasation/Fistula

Unusual causes of anterior urethral fistulas are involvement by Crohn’s disease and infection by tuberculosis and schistosomiasis. An occasional primary adenocarcinoma originates in a urethrorectal fistula.

Most catheters inserted through a urethral perforation are readily apparent on a contrast study. A urethroscrotal fistula leads to massive scrotal enlargement. These are readily apparent with imaging; bone scintigraphy reveals an appearance similar to a scrotal bladder.

Obstruction

In adult men the most common cause of bladder outlet obstruction is BPH. Less common are prostate, bladder and related structure neoplasms, inflammation, urethral strictures, and a neurogenic bladder. Urethral valves as a cause of obstruction are of more importance in the pediatric age group.

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called sonourethrography) also appears to have a role. Sonourethrography evaluates both length and severity of a stricture. It visualizes not only strictures but also associated corpus spongiosum fibrosis which ranges from isoto hyperechoic to the corpus spongiosum.

With recurrent posterior (bulbar) urethral strictures, initial balloon angioplasty followed by insertion of an expandable metallic stent appears worthwhile; short-term results are satisfactory, but some men develop an exuberant fibrotic reaction requiring either a urethrotomy or urethroplasty.

A bioabsorbable self-expandable reinforced poly-l-lactic acid spiral stent shows promise. Inserted immediately after urethrotomy in men with recurrent urethral strictures, all but one stent was epithelialized at 6 months and degraded in all at 12 months (62).

Urethral Valves

Posterior urethral valves were discussed earlier (see Congenital). Anterior urethral valves rarely result in obstruction. Similar to posterior urethral valves, they are usually detected with a voiding cystourethrogram.

Calculi

Urethral calculi are either primary or secondary. Primary calculi develop in a diverticulum, proximal to a stricture,or in the presence of a foreign body. Secondary calculi pass from the bladder.

Urethral calculi are best detected by conventional radiography; they can be missed during a contrast study if only contrast-filled images are obtained.

Stricture

Distal to the prostate, the most frequent acquired abnormality of the male urethra is a benign urethral stricture. An uncorrected stricture eventually leads to hydronephrosis, chronic pyelonephritis, vesicoureteral reflux, and renal failure. These complications often are irreversible.

A rare cause of urethral obstruction is primary amyloidosis of the penile urethra these strictures are amenable to urethral dilation.

Urethral strictures are studied by a retrograde urethrogram. Ultrasonography (also

Verumontanum Hyperplasia

Hyperplasia of verumontanum mucosal glands is a rare cause of urethral obstruction. Occasionally a prostatic biopsy suggests a low grade adenocarcinoma, but in reality it represents hyperplasia of verumontanum mucosal glands.

Functional Obstruction

The clinical role of endorectal US while voiding is yet to be established. It has been used to study suspected dysfunctional voiding when more obvious causes are excluded; voiding US detects

MALE REPRODUCTIVE ORGANS

abnormal motion of the posterior urethra during voiding.

Occasionally voiding cystourethrography detects extreme posterior urethral ballooning and a disproportionate caliber between the posterior and penile urethra; in some individuals a kink is identified between the two segments, but in others no obvious obstruction is identified.

Diverticulum

Urethral diverticula are rare in males. Congenital ones predominate in young boys, while in adults most are secondary either to previous trauma or an adjacent abscess rupturing into the urethra. Urethral diverticula develop in men with spinal cord injuries. Stones tend to form within these diverticula, presumably due to stasis. Diverticula close to the fossa navicularis are associated with meatal stenosis.

Neoplasms, including a nephrogenic adenoma, can develop in an urethral diverticulum.

Diverticula are detected by US, CT, and MRI. More proximal ones mimic a müllerian duct cyst or a dilated utricle and are midline in position. These outpouchings are readily identified with a voiding cystourethrogram, which reveals a diverticulum filling and compressing the urethra during voiding and then emptying at the end of micturition. Differentiation from an anterior urethral valve is difficult in some individuals; keep in mind that the pathogenesis of some urethral diverticula and anterior urethral valves appears similar.

Tumors

Urethral

Polyps in the male urethra are rare; most are not neoplastic and tend to occur in the posterior urethra. Some fibroepithelial polyps are pedunculated and at times reflux into the bladder at rest. Schistosomiasis also results in urethral polyps. Obstruction is the most common presentation.

Either a voiding cystourethrogram or retrograde urethrogram should detect a polyp. The differential diagnosis for a polyp detected with a urethrogram includes an ectopic ureterocele; US should differentiate between these two con-

ditions because a polyp is hyperechoic while a ureterocele is anechoic.

Condyloma acuminata is seen as multiple intraluminal urethral tumors. They tend to have a shaggy, irregular appearance.

A urethral hemangioma is a benign vascular tumor. Hematuria is a typical presentation. At times postejaculation hematuria or clotinduced urinary retention develops. Treatment is surgical, although depending on the size and number of lesions, selective arterial embolization may be worthwhile.

Primary urethral adenomas and carcinomas are uncommon. They tend to evolve in a setting of superimposed chronic disease. The histology of these tumors varies; posterior urethral cancers tend to be transitional cell carcinomas, anterior urethral ones often are squamous cell carcinomas, and Cowper’s or Littre’s gland tumors are adenocarcinomas. A rare transitional cell carcinomas develops in the fossa navicularis; some of these are associated with synchronous or metachronous more proximal transitional cell carcinomas. An occasional adenocarcinoma in situ is detected in a villous adenoma. Chronic strictures predispose to cancer, generally a squamous cell carcinoma; these cancers tend to be irregular in outline. The rare urethral epidermoid carcinoma is also associated with a prior urethral stricture and related complications.

Smaller transitional cell carcinomas often present as intraluminal urethral nodules; with growth they infiltrate the adjacent structures. A rare transitional cell carcinoma is occasionally detected in the fossa navicularis. Squamous cell carcinomas infiltrate and often ulcerate. At times a blood clot mimics a malignancy, although blood clots tend to be more irregular and elongated in appearance. Sinus tracts developing in some cancers mask the underlying tumor, which is often detected by finding marked progression between examinations.

Primary malignant melanoma is more common in the distal urethra and tends to be polypoid in appearance. The histopathology is similar to that of melanomas at other sites. Occasionally confusing the pathologic diagnosis is an amelanotic appearance. An occasional one mimics a urethral carcinoma.

Non-Hodgkin’s lymphoma involving the urethra is rare. Urethral obstruction is a typical presentation.