Материал: Advanced Imaging of the Abdomen - Jovitas Skucas

Extratesticular Fluid

Bowel in an inguinal hernia can mimic the cystic structures outlined below. Bowel is identified with US by peristalsis. Some bowel in a hernia can often be reduced manually.

An epidermal scrotal inclusion cyst, cutaneous in location, is probably due to abnormal embryonal closure of the median raphe. These cysts range from cystic to mostly solid structures, most are hypoechoic but their echogenicity varies considerably.

Spermatocele

The seminiferous tubules merge and connect with tubuli recti, which then enter the mediastinum testis and form the rete testis. Efferent ductules from the rete testis form the head of the epididymis. Dilation of the efferent ductules within the epididymis is believed to result in spermatoceles and epididymal cysts. Spermatoceles are filled with thick, debris-laden fluid.

Ultrasonography reveals spermatoceles as unilocular or multilocular epididymal cysts. Debris within the spermatocele usually makes it hyperechoic. Uncommonly, a spermatocele has an appearance of a solid tumor. Sonographically spermatoceles, hydroceles, and epididymal cysts have a similar appearance. Their MRI appearance varies depending on fluid content.

Epididymal Cyst

Epididymal cysts are common; some are multiple and often are an incidental finding. Their etiology is unknown, but they appear to be congenital in nature. Some adolescents present with an uncomfortable scrotal tumor.

These serous fluid-filled cysts have a typical imaging appearance of an epididymal cyst as described above.

Symptomatic epididymal cysts and hydroceles are treated either surgically or with sclerotherapy. Multiple sclerotherapy treatments achieve a high success rate.

Hydrocele

Increased serous fluid in the tunica vaginalis sac represents a hydrocele. It is either congenital

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and is detected early in life or develops later and manifests as painless scrotal swelling. The scrotum is most often involved, although occasionally a focal hydrocele develops in the spermatic cord.

The processus vaginalis is an inferior outpouching of the peritoneal cavity. Failure of the tunica vaginalis to close off from the peritoneal cavity results in communication between these two structures and fluid accumulates. Partial closure results in a cyst-like structure within the spermatic cord. Spermatic cord hydroceles present as firm inguinal tumors; US identifies a focal, anechoic, and avascular tumor superior to and separate from the testicle.

Abdominoscrotal hydroceles are rare; even rarer are bilateral ones. Most occur in the pediatric age group, enlarge rapidly, and tend to be quite large at initial presentation. Most congenital hydroceles in neonates resolve spontaneously and do not require imaging studies. If a hydrocele does not resolve and therapy is contemplated, imaging helps define the underlying anatomy and detects whether a hydrocele extends into the pelvis.

In a rare newborn a meconium-hydrocele results in an acute scrotum.

Most acquired hydroceles are idiopathic or related to trauma. Some are associated with an underlying disorder such as epididymitis, orchitis, trauma, torsion, or even a neoplasm. In particular, a small hydrocele should raise suspicion of an underlying neoplasm. Most are unilocular, although an occasional multilocular one is encountered. Calculi within hydroceles are not uncommon; US reveals hyperechoic, movable foci in the fluid. Multiple calcifications within a hydrocele should raise suspicion of tuberculosis.

Either US or MRI can be used to evaluate hydroceles, which tend to be mostly anechoic by US and provide an acoustic window for evaluating the underlying testis. Less common is a hyperechoic hydrocele, due to the presence of cholesterol crystals. Hydroceles are homogeneous and hypointense on T1and hyperintense on T2-weighted images, characteristic of fluid. Occasionally septations are identified within a hydrocele, although prominent septations should suggest a hematocele or pyocele.

A rare hydrocele becomes infected and is a surgical emergency.

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After aspirating all fluid, some sclerotherapies have resulted in hydrocele disappearance. On the other hand, an attempt to treat testicular hydroceles by aspiration and injection of a two component fibrin glue consisting of fibrinogen and human thrombin led to hydrocele recurrences (74).

Hematocele

A hematocele consists of blood within a tunica vaginalis sac (i.e., a hydrocele with blood), while a hematoma is blood within the wall. Most hematoceles are traumatic in origin, with a minority due to neoplasm or a bleeding dyscrasia. Clinically, a hematocele presents as a firm, painful mass that does not transilluminate. An acute hematocele is often associated with testicular rupture. An occasional scrotal hematoma in neonates is associated with adrenal hemorrhage.

Initially US shows a hematocele to be mostly anechoic; with time it evolves into a hyperechoic structure and eventually develops a capsule, septations, and even calcifications; at this stage US of a hydrocele, pyocele, and hematocele reveals similar findings.

During the subacute phase, blood within a hematocele is hyperintense both on T1and T2weighted MRI.

Pyocele

A pyocele consists of pus in the tunica vaginalis, generally secondary to an epididymo-orchitis or rupture of a testicular abscess. A scrotal pyocele can be a sequela of bacterial peritonitis, presumably secondary to a peritoneal communication.

A hematocele and a pyocele have a similar initial US appearance, although an enlarged epididymis or testis is more common with a pyocele. Some pyoceles develop internal septa.

Cystocele

A scrotal cystocele is in the differential diagnosis of a fluid-filled scrotal structure. A cystocele should empty with voiding. At times US does not identify the actual connection between a cystocele and bladder.

Lymphocele

Representing an accumulation of lymph in a cystic structure, most scrotal lymphoceles (lymphocysts) develop after pelvic surgery. It can be difficult to differentiate a lymphocele from other cystic abnormalities.

A hydrocele, cystocele, and a lymphocele have similar US appearances, although the presence of septations suggests the latter. With a nondiagnostic fluid aspirate, a Tc-99m albumin colloid lymphogram may visualize pelvic lymphatic channels and eventual pooling of activity within a scrotal lymphocele.

Lymphangioma

A lymphangioma is a tumor of lymphatic channels, often greatly dilated, and lined by endothelial cells. A chronic painless scrotal swelling is the most common presentation. Lymphangiomas range from solid, cystic, to mixed multilocular ones and are a sequella of congenital lymphatic obstruction. Ultrasonography reveals a complex, septated cystic tumor with a normal testis and cord in most. Their US appearance is similar to a hematocele or a pyocele.At times US suggests multiple cystic tumors adjacent to the testis. Yet a correct preoperative diagnosis is difficult and the differential ranges from hernias to various scrotal cysts. Some lymphangiomas extend into the perineum, inguinal region, pelvis and retroperitoneum. They recur after incomplete excision.

Arteriovenous Malformation

A scrotal arteriovenous malformation is either congenital or traumatic in origin.

Doppler US of an arteriovenous malformation reveals a high-velocity waveform; it can thus be differentiated from a varicocele. Magnetic resonance imaging outlines the extent of the lesion and detects fast flow within the visualized vessels.

Testicular Tumors

Considerable variability exists in classifying testicular tumors. Most authors employ a histologic classification, and one such modified scheme is used here, although from an imaging viewpoint it is not ideal.

Testicular cancer is the most common malignancy of young men. With adequate therapy a 5-year survival of over 90% is achieved. Cancer prevalence is considerably higher in the white population of America and Europe compared to Asia and Africa, and the prevalence is increasing in Western Europe. Testicular tumors are rare in related family members. Those who have had one testicular cancer are at a considerably higher lifetime risk of developing another testicular cancer, either synchronously or metachronously. An increased risk, including bilateral tumors, exists in a setting of cryptorchidism. Testicular carcinomas develop in a setting of known testicular microlithiasis (discussed later; see Calcifications).

Typically a testicular neoplasm first manifests as a painless unilateral nodule. In general, a solid intratesticular tumor is considered to be malignant until proven otherwise.

Most testicular neoplasms are treated by orchiectomy. In a solitary testis an organpreserving resection is often appropriate. The potential role of such therapy as transcutaneous high-intensity focused ultrasound as an alternate to organ-preserving surgery is not clear.

The rare gonadoblastoma contains elements of germ cells and stromal tissue. Most are limited to patients with intersex syndromes.

Germ Cell Tumors

Clinical

Over 90% of testicular neoplasms are of germ cell origin, and in adults almost half of all germ cell tumors are seminomatous in origin. Seminomatous tissue is also often present in mixed germ cell tumors. The prevalence of germ cell tumors is approximately 4 per 100,000. The main reason to differentiate germ cell neoplasms as seminomas and nonseminomas is that they are treated differently. Germ cell tumors are not common in the pediatric age group.

An association appears to exist between prior infection by Epstein-Barr virus and subsequent development of seminomas and embryonal carcinomas. Patients with Down syndrome are at a slightly increased risk for testicular cancer; presumably the multiorgan malformations found in trisomy 21 also affect gonads.

Although not common, testicular germ cell tumors do occur bilaterally and are either syn-

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chronous or metachronous in origin. Men with a testicular cancer who have an atrophic contralateral testis and those presenting at age 30 years or younger are at increased risk for a second germ cell tumor in the contralateral testis.

An association exists between membranous glomerulonephritis and a seminoma, presumably representing a manifestation of paraneoplastic syndrome. Gynecomastia develops in a minority of males both with seminoma and nonseminoma and, in a young adult, should lead to a further workup.

Occasionally a testicular tumor first manifests through metastases, with the primary tumor not palpable, and initially the metastasis is believed to represent an extraperitoneal extragonadal germ cell tumor. Ultrasonography detects some of the underlying silent primary tumors, although a rare primary testicular tumor regresses to the point that only a scar remains. An occasional primary testicular site is detected only years later (called burned-out cancer). Testicular US reveals such a burned-out testicular tumor as a hyperechoic region. Some of these men have undergone chemotherapy, retroperitoneal lymph node dissection, and an ipsilateral orchiectomy, with pathologic examination simply revealing a testicular scar; the hyperechoic focus seen with US probably represents the remains of such a burned-out neoplasm. The etiology of this phenomenon is unknown, although ischemic or immunologic factors are probably involved.

Complicating this issue is that not all germ cell tumors occur only in the testes. For instance, Klinefelter’s syndrome patients have an increased prevalence of extragonadal germ cell tumors.

Among more bizarre tumors were simultaneous germ cell and stromal tumors in the same testis in a 24-year-old man (75); the tumor contained seminoma, embryonal carcinoma, choriocarcinoma, and Leydig cell tumor components.

Doubling rate for many germ cell tumors is measured in days.

Detection

High-resolution US should detect most germ cell tumors. These tumors are mostly hypoechoic to normal testicular parenchyma. In general, although many hyperechoic testicular

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tumors are benign, their US appearance alone cannot be used to exclude a malignancy. Most testicular neoplasms are hypervascular. Doppler US has played a limited role in evaluating these tumors.

A diagnosis of germ cell tumor is typically established by radical inguinal orchiectomy.

Staging

A number of staging systems are in use for seminomas and nonseminomatous germ cell tumors, but the TNM staging system is common (Table 13.6). Most seminomas spread via lymphatics, while nonseminomatous teratomas and

(Extent of primary tumor is classified after radical orchiectomy)

Primary tumor:

N2 Metastasis with lymph node mass more than 2 cm but not more than 5 cm in greatest dimension; or more than 5 nodes positive, none more than 5 cm; or evidence of extranodal extension of tumor

N3 Metastasis with a lymph node mass more than 5 cm in greatest dimension