Книги по МРТ КТ на английском языке / Advanced Imaging of the Abdomen - Jovitas Skucas

Prior hypospadias repair and urethral reconstruction using bladder mucosa, appears to predispose to urethral nephrogenic adenoma formation either at the anastomosis or the graft. Their gross appearance mimicks a carcinoma.

Nonurethral

A corpus cavernosum hemangioma is rare. Some of these have an atypical appearance, are inhomogeneous and even MRI does not distinguish between benign and malignant disease.

A squamous cell carcinoma is the most common penile tumor. Phimosis or human papilloma virus infection are often present. Nodal metastases are common at initial presentation. Tumor stage, lymph node metastasis, and tumor differentiation are independent prognostic factors for survival. Computed tomography often detects inguinal adenopathy at initial presentation, but it should be kept in mind that inflammatory causes for adenopathy are common. Magnetic resonance T2-weighted images are more useful than T1 images in evaluating penile cancers.

Metastases to the penis are uncommon. Among other tumors, prostatic carcinoma has metastasized to the penis. Magnetic resonance imaging is helpful in establishing the extent of invasion.

Cowper’s Glands

Paired Cowper’s glands and ducts are located along the ventral surface of the bulbous urethra. Not uncommonly these ducts fill during an urethrogram or, rarely, on IV urography after voiding. Normal ducts are readily differentiated from fistulas and contrast extravasation.

Duct obstruction results in a retention cyst, which, if large enough, produces a soft tissue impression along the ventral surface during voiding cystourethrography. An occasional one enlarges sufficiently to obstruct the urethra. These glands are also occasionally involved by neoplasms, infection, or stones.

Priapism

Priapism is a sustained erection caused by an abnormal process. It can be partial. In adults, most are idiopathic, with an occasional one a

ADVANCED IMAGING OF THE ABDOMEN

direct result of trauma or a posttraumatic arteriovenous fistula. Rarely, priapism is associated with drug therapy, thromboemboli, sickle cell disease, malignant infiltration of surrounding structures, an adjacent abscess, or a neurologic condition. In pediatrics, aside from trauma, priapism is most often secondary to sickle cell disease or a hematologic malignancy.

Priapism is classifications into low-flow (venous) and high-flow (arterial) states. The low-flow or ischemic type occurs with perineal trauma–induced venous thrombosis, hematoma, or edema of adjacent tissue. The resultant vascular stasis within the corpora leads to a delay in penile venous drainage. Highflow priapism is due to persistent blood inflow, such as with a cavernosal artery laceration (arteriocavernosal fistula).

Doppler US aids in distinguishing the two types of priapism. Arteriosinusoidal fistulas result in pulsatile, high-flow corpora cavernosa signals. Perineal duplex Doppler US achieves almost 100% sensitivity in detecting high-flow arterial priapism, but false positives do occur and limit the specificity.

In low-flow priapism, pudendal arteriography opacifies the dorsal and bulbar arteries, but not cavernosal arteries because of decreased inflow and stasis.

In selected individuals both CT and US are useful in excluding an underlying neoplasm or abscess as the etiology for the priapism.

High-flow priapism, generally related to trauma, can be treated with selective bulbocavernosal artery embolization.

Peyronie’s Disease

Peyronie’s disease consists of excessive fibrosis and plaques in the sheath covering the corpora cavernosa. It is probably caused by a vasculitis or inflammation. Calcified plaques develop eventually, and if sufficiently extensive, they are visible with conventional radiography. Soft tissue radiography using a mammography technique detects calcifications but does not detect plaques without calcification. Calcifications are also detected with US and CT.

Palpation and US are the examinations of choice in detecting plaques. Plaques vary in size from less than 1cm to several cm in length and from 2 to 4mm in thickness. Ultrasonography reveals more extensive plaques than does clini-

MALE REPRODUCTIVE ORGANS

cal evaluation. Ultrasonography detects tunica albuginea thickening. Some investigators consider inflammation to be present if hypoechoic foci are identified around a central hyperechoic region.

Doppler US after intracavernosal papaverine injection in these patients reveals decreased peak systolic flow velocity and increased end diastolic flow velocity. Contrast enhanced color and power Doppler US identifies vascularity around plaques in about one-third of patients with established Peyronie’s disease. Doppler US shows that penile cavernosal-spongiosal communications near plaques remain patent with low resistance flow, providing a pathway for blood leakage (63); these findings are difficult to place in proper perspective.

Whether MRI detects more plaques than does US is debatable. Some plaques show postcontrast enhancement, suggesting active inflammation, and MR appears superior in monitoring the progression of the inflammation.

Peyronie’s disease has been treated with local injection of interferon-alfa-2b into plaques. Noncalcified plaques respond best. Extracorporeal shock-wave lithotripsy (ESWL) has been used to treat symptomatic plaques believed to be of recent origin. The preliminary results appear encouraging (64).

Impotence

Vascular causes of impotence are most common, followed by diabetes mellitus and others. Vasculogenic impotence is usually divided into insufficient arterial inflow (arteriogenic) and excessive venous leakage (venogenic).

Arteriogenic

Internal iliac arteriography has been considered the gold standard in detecting arteriogenic impotence, and although numerous studies over the years have established its usefulness, it is little used today. An erection developing after intracavernosal injection of papaverine is presumed to be evidence that the arterial and venous pathways are intact. Following papaverine injection, diabetic individuals have a significantly lower cavernosal artery peak blood flow velocity than do nondiabetics.

Color Doppler US evaluates arteriogenic impotence by measuring peak systolic velocity and systolic rise time of deep arteries supplying the corpora cavernosa. Following papaverine injection, a systolic rise time of 110msec or greater appears to be a good discriminant for arterial disease. A peak systolic velocity in the cavernosal arteries of greater than 25 to 30cm/ sec is a normal response to papaverine or prostaglandin B1 injection. These values should be accepted with caution because they are lower if penile arterial communications exist. Marked differences in velocity between the two cavernosal arteries suggest unilateral disease. Reversal of systolic flow implies proximal penile artery obstruction.

Extensive vascular connections exist between the penile dorsal artery and cavernous arteries, but the dorsal artery function in impotence is not clear. Normally dorsal artery color Doppler US reveals an increase both in systolic and diastolic velocities after intracavernous papaverine injection. Flow is decreased or even absent in the dorsal artery in men with arteriogenic impotence.

Venogenic

The gold standard in diagnosing venogenic impotence is pharmacologically aided cavernosometry and cavernosography. Role of color Doppler US after cavernosal papaverine injection in diagnosing venous dysfunction is not clear; published sensitivities have ranged from 50% to 100% in detecting venous dysfunction.

The cavernous artery resistance index (RI) is obtained from Doppler US data by:

RI = (peak systolic velocity - end diastolic velocity)/peak systolic velocity

After intracavernous injection of prostaglandin, Doppler US in men with suspected venogenic impotence found RI values in those with corporal leakages to be significantly lower than in those with previously normal cavernosometry and cavernosography, although some overlap exists (65); men with an RI >0.9 were not venogenic impotent and those with an RI <0.75 had corporal leakages, while in those with an RI between 0.75 and 0.9, cavernosometry and cavernosography were necessary for diagnosis.

Thrombophlebitis

Anecdotal reports of thrombophlebitis of the penile superficial dorsal vein have been reported. Etiologies include trauma associated with sexual intercourse, penile strangulation, penile injection, infection, neoplasms, and prior surgery.

Scrotum and Spermatic Cord

Acute Scrotum

Acute onset of scrotal swelling and pain should be approached as an emergency. The most common etiologies are testicular torsion, testicular appendage torsion, acute epididymitis, acute epididymo-orchitis, and trauma. Less common are vasculitis, hematoma, and a strangulated hernia. Both a perforated appendicitis and laparoscopic appendectomy can result in an abscess, even in the scrotum. Some of these conditions mimic testicular torsion on scrotal US. Testicular torsion is most common in infants under 1 year, while in older individuals testicular appendage torsion predominates. Epididymoorchitis increases in frequency with age. A differential diagnosis based on age should be used with caution, however, because considerable overlap exists.

Especially in pediatric patients, Doppler US is often the study of choice to differentiate conditions associated with decreased blood flow, such as torsion, from inflammatory disorders where blood flow is often increased. Scrotal scintigraphy is also sensitive in differentiating ischemic conditions from inflammation, realizing that a choice of imaging modality is often based on relative availability and local expertise.

Dynamic contrast-enhanced subtraction MRI evaluates testicular perfusion and relies more on functional rather than anatomic criteria. Dynamic MRI has better spatial resolution than scintigraphy. It aids in differentiating testicular from extratesticular disorders. One limitation is the need for sedation for younger boys.

Testicular Torsion

Testicular torsion (or spermatic cord torsion) occurs at all ages of childhood, but with two

ADVANCED IMAGING OF THE ABDOMEN

peaks: one in newborns where presumably it represents continued evolution of an intrauterine condition, and another during puberty and adolescence. It is uncommon after the age of 35 years.

Newborn

Spermatic cord torsion occurs both prenatally and postnatally. In the newborn, torsion manifests as a testicular tumor. Occasionally a neonate is found with bilateral testicular torsion.

Gray-scale US shows an enlarged testis. A hydrocele is present in some. Color Doppler US is useful in detecting testicular torsion, although the small testicular size in newborns makes evaluation difficult; intratesticular blood flow is lacking on the affected side and normal on the contralateral side.

Delayed therapy or tight torsion consisting of several turns is associated with a poor prognosis. Yet a case can be made for conserving even a necrotic testes found at surgery; some partially necrotic testes retain normal long-term function.

Children and Adults

Clinical

Testicular torsion occurs primarily in postpuberty boys and young men. Torsion of the testicular appendage should be suspected in younger boys. Simultaneous bilateral testicular torsion has been reported. The incidence of torsion increases after orchiopexy for an undescended testis.

Torsion is treated as an emergency. Torsion obstructs venous blood flow and leads to congestion, swelling, hemorrhage, and eventual ischemia. The time frame for ischemia to develop varies depending on the degree of torsion and the resultant vascular obstruction. A delay of 6 to 12 hours increases testicular loss rate considerably. Without therapy, torsion eventually progresses to testicular atrophy.

Nausea and vomiting are common in boys with testicular torsion, findings uncommon in those with testicular appendage torsion or those with epididymoorchitis. Some surgeons consider that older boys with acute scrotal pain less

MALE REPRODUCTIVE ORGANS

than 12 hours in duration, especially if associated with nausea or vomiting, have testicular torsion, imaging is not necessary and exploration is performed. Although currently diagnostic imaging prior to surgical correction is often performed, an occasional publication still maintains (66):

. . . physical examination is sufficient to manage patients with torsion of the spermatic cord.

In view of more recent sonographic refinements, some institutions have modified their previous policy of surgical intervention for all those with an acute scrotum; one approach is to operate when a surgeon has a high degree of suspicion for torsion and perform emergency Doppler US in the rest; those having a normal or increased testicular blood flow are presumed not to have testicular torsion and are treated medically. Such an approach assumes ready availability, on an emergency basis, of experienced sonographic personnel and equipment.

Intermittent testicular torsion results in recurrent testicular pain that remits either spontaneously or after self-manipulation. Imaging is often noncontributory in this condition. In one such 12-year-old, color Doppler detected bilateral flow but pulsed Doppler revealed asymmetric high-impedance flow with an increased resistive index on the involved side (67).

Imaging

With testicular torsion, gray-scale US shows testicular enlargement, varying testicular echogenicity, and often a hydrocele. At times US also detects any related complications requiring surgical intervention. When performed for testicular torsion, a US finding of an inhomogeneous or hypoechoic testis suggests a nonviable testis, and a normal homogeneous, isoechoic appearance suggests a viable testis. Nevertheless, these findings are often not clearly identified; overlap exists, and gray-scale US alone often cannot be relied on during the immediate decision-making time frame.

The primary role of color Doppler US is to differentiate acute testicular torsion from other acute conditions such as acute epididymitis, sequelae of trauma, or a neoplasm. Ideally, normal blood flow and a cord compression test should exclude torsion in most individuals.

Figure 13.5. Testicular torsion. Transverse Doppler image of both testes shows completely absent flow to left testis. (Courtesy of Deborah Rubens MD, University of Rochester.)

Torsion results in no perfusion and thus no Doppler signal on the affected side (Fig. 13.5). A potential pitfall in a Doppler US diagnosis of testicular torsion includes the occasional spontaneous testicular detorsion; Doppler US reveals normal or even increased testicular blood flow with detorsion. In some studies, Doppler US reaches a sensitivity and specificity of >90% in detecting testicular torsion, although in one study Doppler US identified no blood flow in the symptomatic testis in 61% of individuals with proven testicular torsion, but in the other 39% Doppler US was unreliable (intratesticular perfusion was present or no signal was obtained in either testis) (68); in all individuals with testicular torsion, however, high-resolution US detected a spiral twist of the spermatic cord at the external inguinal canal. A twisted spermatic cord in the scrotum is identified as a round or oval extratesticular mass connecting superiorly with a normal inguinal cord.

Nevertheless, imaging and diagnostic problems remain. One should keep in mind that Doppler US also detects the lack of perfusion in some normal prepubertal testes. At times Doppler US identifies blood flow in a setting of partial necrosis. Operator experience, use of appropriate Doppler US equipment, and knowledge of study limitations play a role.

An MRI of testicular torsion shows a twisting spermatic cord, described as a whirlpool

appearance. The twist has a hypointense signal. Currently, however, MRI is limited in evaluating torsion, often due to logistic problems.

Considerable literature exists for radionuclide scrotal imaging with Tc-99m- pertechnetate for suspected testicular torsion, although this examination has been supplanted by Doppler US in some institutions. Among individuals presenting with acute scrotal pain, published scintigraphy specificities and sensitivities approach 100% in detecting testicular torsion. A photopenic region in the hemiscrotum is compatible with testicular torsion, although cysts such as hydroceles and spermatoceles are also photopenic, and care is necessary to distinguish these entities. An inguinal testis needs to be excluded. Also, early torsion may not show asymmetry.

Color Doppler US and scintigraphy achieved similar statistical significance in detecting testicular torsion in boys with acute scrotal symptoms and clinically equivocal clinical presentations, except that scintigraphic specificity was greater (69); scintigraphy appears to prevent unnecessary surgery in some of those with equivocal findings on Doppler US. Which modality to employ often evolves into relative imaging availability for this acute condition.

Testicular Appendage Torsion

A distinction of testicular torsion and torsion of the testicular appendages is of clinical importance because the latter does not require emergency surgery.

Ultrasonography of appendix testis torsion shows an enlarged, homogeneous appendix testis medial or posterior to the head of the epididymis; some US scans reveal varying echogenicity. A hydrocele may be identified. Scrotal wall thickening and an enlarged epididymis head can develop. Color Doppler US reveals normal or increased flow, a finding that usually excludes testicular torsion.

A scintigraphy finding of a normal radionuclide angiogram and a localized focus of increased tracer activity suggest testicular appendage torsion, but keep in mind that increased tracer uptake is not present during the first several hours after onset of symptoms and radionuclide scrotal imaging may be falsely negative for testicular appendage torsion during this time.

ADVANCED IMAGING OF THE ABDOMEN

Infection/Inflammation

Epididymitis

Acute

Acute epididymitis is the most common cause of acute scrotal pain and swelling in teenagers and young men. It is usually due to retrograde spread of infection from either the bladder or prostate, and it tends to be unilateral. Most acute scrotal infections originate in the epididymis rather than the testis and result in isolated epididymal involvement (epididymitis). Less common is both epididymal and testicular involvement (epididymo-orchitis). Especially in infants and children, associated congenital anomalies are common and they should undergo full urologic evaluation.

Amiodarone, an antiarrhythmic agent, induces a sterile epididymitis; it is treated by lowering the drug dosage. Hemorrhagic epididymitis occurs in Henoch-Schönlein purpura. Acute unilateral epididymitis with an abscess developed in a patient after bacillus CalmetteGuérin therapy for superficial bladder cancer (70).

Acute testicular segmental infarction is a complication of epididymitis (Fig. 13.6). In addition to findings of epididymitis, gray-scale US reveals a testicular infarct as a discrete hypoechoic testicular tumor that has little or no flow detected with color Doppler US. An occa-

Figure 13.6. Magnetic resonance imaging of segmental testicular infarction (arrow). [Courtesy of Gabriel Fernández, M.D.,Vigo (Pontevedra), Spain.]

MALE REPRODUCTIVE ORGANS

sional epididymitis evolves into an epididymal abscess.

Spermatic cord vascularity is increased in acute epididymitis, while testicular blood flow is normal or increased. This increased cord vascularity helps differentiate acute epididymitis from torsion, which has a similar clinical presentation but decreased spermatic cord vascularity.

High-resolution gray-scale US most often reveals an enlarged hypoechoic epididymis. A hydrocele is apparent in some. The testis is also abnormal with an associated orchitis (epididymo-orchitis). With epididymal hemorrhage the epididymis assumes a heterogeneous appearance. Still, some individuals with acute epididymitis have a normal gray-scale US examination and only Doppler US is abnormal. Doppler US detects epididymal hyperperfusion in epididymitis and establishes testicular peak systolic blood velocities in the right and left side (Fig. 13.7). Peak systolic velocity is increased in acute orchitis and epididymitis.

T2-weighted MR signal intensity ranges from hyperto hypointense with acute epididymitis. Use of IV contrast enhancement aids in accentuating changes bilaterally.

Testicular scintigraphy with Tc-99m-pertech- netate discloses varying blood flow patterns. Inflammation results in hyperemia, and any asymmetry should be viewed as abnormal.

In general, an enlarged epididymis and a testicular tumor point to infection rather than neoplasia; most often orchitis extends from epididymitis, while testicular neoplasms involve the epididymis mostly during their later stages. Likewise, scrotal skin thickening and a hydrocele suggest infection.

Chronic

Occasionally acute epididymitis evolves into chronic inflammation and a painless tumor indistinguishable from other scrotal tumors. At times chronic epididymitis leads to fibrosis and an enlarged epididymis having a heterogeneous echo appearance. Other complications of epididymitis include abscess, pyocele, and infarct.

Epididymal tuberculosis has developed into a hard, nontender tumor, at times containing calcifications. Testicular involvement is common. Chlamydial epididymitis has also presented as a solid scrotal tumor. Occasionally encountered is an epididymal Candida abscess. Leukemic infiltration can mimic epididymoorchitis.

Involvement by Behçet’s disease led to recurrent epididymo-orchitis (71).

Figure 13.7. Epididymitis. Transverse Doppler image of right testis and epididymis shows enlarged hypervascular epididymis (arrows) compared to testis (T). (Courtesy of Deborah Rubens MD, University of Rochester.)

Orchitis

Most episodes of orchitis result from extensions of acute epididymitis. In isolated orchitis a viral infection, such as mumps, should be suspected. Neglected testicular torsion or an infected neoplasm are less common causes of orchitis and possible abscess.

An early US finding of orchitis is increased vascularity in the inflamed testis. With progression, the testis enlarges, becomes hypoechoic, and is covered by a thickened, echogenic tunica albuginea. Ultrasonography of focal orchitis shows a mixed or hypoechoic tumor mimicking a neoplasm. A focal region of hypervascularity detected by Doppler US may represent either inflammation or a neoplasm; follow-up US of an inflammation should show return to normal.

Magnetic resonance imaging shows either a focal region or a diffuse heterogeneous decrease in signal intensity on T2-weighted images.

Technetium-99m-pertechnetate scintigraphy of an inguinal hernia can mimic the appearance of orchitis.

Severe infection evolves into suppuration, abscess, or testicular infarction. In general, the imaging findings of a testicular abscess are similar to those of a neoplasm. Often clinical findings and response to therapy distinguish these conditions.

Granulomatous Epididymo-Orchitis

Grouped under granulomatous epididymoorchitis are tuberculosis, brucellosis, syphilis, some fungi, and a rare idiopathic inflammation. From a clinical viewpoint little purpose is served in attempting to differentiate epididymal involvement from orchitis or the more common epididymo-orchitis.

Tuberculosis

Scrotal tuberculosis develops from either hematogenous spread or extension from prostate and seminal vesicle infection. Initial involvement is generally an epididymitis, extending to an epididymo-orchitis and occasionally orchitis, most often unilateral. A common clinical presentation consists of a painless chronic epididymal nodule, and the presence of such a nodule, especially in a setting of infertility, should suggest tuberculous epididymitis. A neoplasm is often in the differential diagnosis of a tuberculoma. An occasional tuberculoma arises as an asymptomatic inguinal spermatic cord nodule. A tubercular pyocele tends to be more heterogeneous than a typical abscess. Some contain internal septations.

Epididymal involvement ranges from nodular to diffuse. A heterogeneous, hypoechoic pattern is most common, followed by a mixed pattern, with a hyperechoic pattern being the least common. Most other infections result in a homogeneous US appearance, and thus an enlarged heterogeneous epididymis should suggest tuberculosis. Testicular involvement ranges from an enlarged hypoechoic testis, to a hypoechoic focus, to multiple small hypoechoic nodules in an enlarged testis. A hydrocele is

ADVANCED IMAGING OF THE ABDOMEN

common. Sinus tracts and calcifications occasionally develop.

Brucellosis

Brucellosis is implicated in 10% to 15% of men with epididymo-orchitis in brucellosis endemic regions of Turkey and Spain. Most involvement is unilateral and ranges from heterogeneous epididymis, to diffuse orchitis, to focal hypoechoic testicular tumors. Doppler US detects increased vascularity. Scrotal wall and tunica albuginea thickening, and a hydrocele are associate findings.

Idiopathic Granulomatous

Idiopathic granulomatous orchitis is a rare inflammatory condition, possibly due to sperm extravasation and resultant reaction. It is rarely bilateral. Imaging findings tend to mimic a testicular cancer. Ultrasonography reveals a solid testicular mass. Calcifications develop within some of these tumors. The diagnosis is usually made after orchiectomy.

Filariasis

Infection with Wuchereria bancrofti (filariasis) is common in some parts of the tropics. Microfilariae from the blood are ingested by mosquitoes, and with further development they eventually evolve into larvae, which are then injected into humans. The nematode resides in human lymphatics, where it incites a lymphangitis and eventual lymphatic obstruction. Occasionally dead nematodes calcify, and imaging reveals small thin, linear strands.

Not all lymphedema is on an infective basis. Occasionally seen is congenital lymphedema. It also develops after surgical dissection and due to lymphatic obstruction by tumors.

Lymphatic obstruction leads to dilated, thinwalled, fluid-filled structures. At times a superimposed bacterial infection develops. Lymphatic rupture leads to lymphoceles, while lymphatic sinuses drain into surrounding tissues, some even forming external sinuses. Eventually extravasated lymph, resultant fibrosis, and other reactive changes lead to a hard, thickened infiltrate mimicking a neoplasm.

Filarial epididymo-orchitis and spermatic cord lymphadenitis are often bilateral. Initially

MALE REPRODUCTIVE ORGANS

the involved spermatic cord enlarges and has a homogeneous, hypoechoic US appearance. Ultrasonography detects dilated lymphatics even in those patients who are still asymptomatic. Associated hydroceles initially are anechoic, but with fibrosis and debris result in a more heterogeneous appearance and tend to mimic a pyocele. At this stage calcified granulomas and surrounding capsular calcifications are common.

Other Infections

Amebiasis involving the scrotum is rare. A hydatid cyst can develop in an undescended testes.

Similar to epididymitis, fungal orchitis is typically encountered in debilitated or diabetic patients. Even scrotal aspergillosis has developed.

Mumps orchitis is not common but should be suspected with a preceding parotitis. These individuals have marked scrotal swelling, fever, and significantly elevated serum C-reactive protein levels.

Some instances of mumps orchitis progress to testicular atrophy.

Fournier’s Gangrene

A necrotizing fasciitis, known as genitoperineal gangrene, perineoscrotal gangrene, necrotizing fasciitis, or Fournier’s gangrene, is a fulminant infective obliterative endarteritis involving the perineum and external genitalia and resulting in progressive necrosis and systemic sepsis. Named after the French dermatologist who first described it in 1883, some authors limit the use of the term Fournier’s gangrene only to a primary infection and not to the more common secondary infections of the genitalia or perineum. Men are primarily affected.A urethral or anorectal source is found in about half; in the other half no cause is identified. Debilitated and diabetic individuals are more often affected, with Fournier’s gangrene occasionally being the initial clinical manifestation of unsuspected diabetes.

Conventional radiography and CT identify subcutaneous emphysema in about half of these individuals. Asymmetric fascial thickening and fat stranding are common imaging findings,

occasionally seen even before subcutaneous emphysema is apparent, and these findings should suggest Fournier’s gangrene. The differential diagnosis includes a scrotal abscess and extension of gas from a more superiorly located source, such as diverticulitis.At times Fournier’s gangrene coexists with an abscess.

These patients represent urologic emergencies. Debridement, antibiotics, and hyperbaric oxygen are the current therapies employed. Mortality remains high despite broad-spectrum antibiotics and aggressive surgical debridement.

Granuloma

Some solid, painful epididymal or vas deferens tumors represent granulomas. A number of these have developed after vasectomy and probably are a tissue reaction to sperm extravasation into surrounding tissues; an occasional one is caused by a foreign-body reaction. Ultrasonography reveals these granulomas to be solid and either isoor hypoechoic. An occasional one eventually calcifies. Some enhance on postcontrast MRI.

Malacoplakia

Malakoplakia of the testis is rare. Occasionally it manifests as painless testicular enlargement. Some men have had a preceding urinary tract bacterial infection.

A testicular cancer is often suspected.

Sarcoidosis

Even in a setting of systemic sarcoidosis, genital involvement is uncommon, although sarcoidosis and inflammatory nodules have presented as extratesticular scrotal tumors. The epididymis tends to be involved more often than the testis. Some affected individuals develop signs and symptoms mimicking epididymitis. A painless tumor develops in others.

Imaging findings are similar to those seen with epididymitis or a testicular neoplasm.

Tumors

Clinical

An extensive differential diagnosis exists for the infant or boy presenting with a scrotal tumor

Table 13.4. Etiology of a painless scrotal tumor in the pediatric age group

Testicular

Neoplasm

Cyst

Congenital malformation

Posttraumatic

Infection/inflammation

Extratesticular

Neoplasm

Cyst

Hematocele

Infection/inflammation

Pachyvaginalitis testis

Sebaceous cyst

Splenogonadal fusion

Source: Adapted from Aragona et al. (72).

(Table 13.4); two peak age groups exist: 0 to 1 year and 13 to 14 years. In adults, most intratesticular tumors are malignant, while most extratesticular tumors tend to be benign.

The most often encountered epididymal tumors are adenomatoid tumors, leiomyomas, and cystadenomas. Men with von HippelLindau disease are at increased risk for epididymal cystadenomas, similar to the increased incidence of broad ligament cystadenomas found in women with this disease. Anyone presenting with bilateral epididymal cystadenomas should be investigated for this disease.

Imaging

Testicular US readily differentiates intratesticular from extratesticular tumors. In further differentiating between benign and malignant tumors in pediatrics, the imaging modality chosen is often US, but the literature provides conflicting data; some authors achieve sensitivities and specificities over 90% in detecting testicular malignancies, but others find poor specificity and believe that the role of US is limited in this differential.

Currently MRI is limited in differentiating among various scrotal tumors.

Cystic Nonneoplastic Conditions

Cysts originate in the epididymis, spermatic cord, tunica vaginalis, and tunica albuginea (Table 13.5). Most are of unknown etiology. One

ADVANCED IMAGING OF THE ABDOMEN

of the tasks of US is to differentiate between intratesticular and extratesticular cysts. The latter are more common.

Testicular Fluid

In addition to the differential diagnoses listed in Table 13.5, fluid is also present in dermoid cysts and mature teratomas with a cystic component, although often these latter have an associated soft tissue component. These cysts vary in size up to several centimeters in diameter. They are smooth and homogeneous in appearance.

Not all testicular cysts are benign. Some testicular neoplasms develop cystic components. In general, a simple, nonpalpable intratesticular cyst is usually followed clinically. If, on the other hand, US detects a solid component, there is internal echogenicity, septa are present, or if a thick cyst wall is detected, a malignancy is more likely.

Simple Testicular Cyst

Simple intratesticular cysts tend to be small and are filled with serous fluid. Ultrasonography

Table 13.5. Scrotal cystic structures

Intratesticular

Testicular neoplasm containing cysts

Simple testicular cyst

Tunica albuginea cyst

Epidermoid cyst

Rete testis dilatation

Abscess

Cystic dysplasia

Extratesticular

Spermatocele

Epididymal cyst

Hydrocele

Hematocele

Cystocele

Lymphocele

Lymphangioma

Epididymal papillary cystadenoma

Abscess

Pyocele

Amebiasis

Vascular

Varicocele

Hemangioma

Arteriovenous malformation

MALE REPRODUCTIVE ORGANS

detects many simple testicular cysts and also aids in differentiating a simple cyst from a neoplasm. These cysts are anechoic, and they have a thin wall and no solid component.

A simple testicular cyst is hypointense on T1and hyperintense on T2-weighted images. The high T2-weighted signal intensity makes some of these cysts isointense to normal surrounding parenchyma.

Typically these cysts are excised without performing an orchidectomy.

Tunica Albuginea Cyst

Tunica albuginea cysts develop within the tunica. Most are small and solitary, and are discovered incidentally. Some are palpable. They contain either serous fluid or blood.

At times due to prior trauma, tunica vaginalis cysts develop between the visceral portion of the tunica vaginalis and the tunica albuginea. Some indent the testis, thus aiding in distinguishing them from a hydrocele.

Ultrasonography suggests a benign cyst if it is unilocular. If the cyst is multilocular and complex, a malignancy is in the differential. Ultrasonography cannot differentiate between tunica albuginea cysts and tunica vaginalis cysts.

Epidermoid Cyst

Epidermoid cysts are believed to be of germ cell origin, possibly representing a teratoma variant differentiating along ectodermal lines. They are benign, occur at any age, and can be bilateral and large. Clinically, they tend to be detected as painless testicular tumors. Some epidermoid cysts are extratesticular in location.

Because these cysts contain cholesterol crystals and other residual debris, US reveals a hypoechoic, well-marginated tumor with a hyperechoic wall. Some have a laminated or concentric ring-like alternating hypoand hyperechoic appearance (73), and some contain calcifications.

Magnetic resonance imaging of a scrotal epidermoid cyst tends to show similar findings to those of an intracranial epidermoid cyst; namely, most are hypointense on T1and hyperintense on T2-weighted images. Some have a peripheral hypointense region on both T1and

T2-weighted images, giving them a bull’s-eye or onion ring appearance.

These are avascular tumors; Doppler US reveals no flow, and they do not enhance postcontrast MR (73).

Although epidermoid cysts can be treated by simple enucleation, with a newly discovered tumor the differential diagnosis often includes a teratoma or a malignancy; imaging cannot differentiate between these entities, and histologic study of surrounding tissue is necessary.

Rete Testis Dilatation (Tubular Ectasia)

Some men develop dilation and possible cysts in the rete testis, at times bilaterally. Most men with this benign condition are over 55 years old, with only a rare case reported in a child; in the latter this condition can be associated with other congenital urinary anomalies and an embryonic malformation is the most likely cause.

Physical examination detects a scrotal tumor typical of a spermatocele.

Ultrasonography reveals a testicular tumor containing multiple small spherical or tubular anechoic or hypoechoic structures with coarse internal echoes without an associated solid component. Cysts, if present, are located in the periphery, in the region of the mediastinum testis. Coexisting epididymal cysts, epididymitis, and spermatoceles are often present. The US appearance, location, and frequently coexisting epididymal abnormality suggest that this condition represents rete testis dilation, probably in association with epididymal obstruction. The rare rete testis adenocarcinoma probably has a similar appearance. Cystic dysplasia of the testis also has a similar US appearance, although cystic dysplasia occurs mostly in children. Dilation of the rete testis is differentiated from a varicocele by the lack of flow, shown by Doppler US.

Magnetic resonance imaging also detects these tumors. They are hypointense on T1and isoto hyperintense on T2-weighted images, in distinction to most testicular tumors, which are hypointense on T2 weighted images. They do not enhance after IV gadolinium.

In some men this condition can be differentiated from a testicular neoplasm on the basis of clinical, US, and MRI findings, and orchiectomy is not necessary to establish the diagnosis.