Testicular Torsion

The testis and epididymis attach to the inner scrotal wall by a broad attachment. When this attachment is too narrow, it may function as a pedicle around which the testis may twist. This twisting, or torsion, compromises the blood supply to the testis, which may lead to infarction of the testis. Acute scrotal pain is often the presenting complaint in males with testicular torsion, a condition that requires emergent treatment to maintain viability of the affected testis. Testicular salvage rates are greatest when surgery is performed within 6 hours of the onset of symptoms. After 24 hours the testis is usually no longer salvageable. Patients with the “bell clapper” deformity, where the tunica vaginalis joins high on the spermatic cord, are more prone to testicular torsion than the general population.

Sonography is the preferred imaging examination for the diagnosis of testicular torsion because of its high sensitivity and specificity. Gray-scale ultrasound findings are often completely normal when torsion is present, and the testes may appear symmetric with respect to both size and echogenicity. A small hydrocele may be present on the affected side. Within a few hours of the onset of symptoms, the scrotal wall will appear thickened, and the testis and epididymis will appear enlarged and hypoechoic secondary to inflammation and/or hemorrhage. Color Doppler is crucial for the diagnosis of torsion. The lack of demonstrable blood flow to the affected testis, assuming appropriate ultrasound settings are used, is virtually pathognomonic for torsion (Fig. 10-1). In prepubertal patients it is often difficult to demonstrate the presence of blood flow even in normal testes. Two potential false negative scenarios need to be considered when evaluating for torsion. First, a torsed testis may untwist spontaneously with resultant hyperemia on color Doppler, thus mistaking testicular torsion for epididymo-orchitis; and second, incomplete torsion may result in venous occlusion without arterial occlusion, which may result in arterial flow being detected in the testis despite torsion being present.

Figure 10-1 Sonographic image of a 19-year-old patient with testicular torsion. No flow is identified in the left testis.

Testicular scintigraphy is often used as an adjunct to ultrasound when a diagnosis of torsion cannot be made with certainty. Given the added delay of scintigraphic examinations, however, some surgeons operate on the basis of an equivocal ultrasound. The treatment for testicular torsion is de-torsion of the affected testicle, and orchiopexy, where the testis is affixed to the scrotal wall to prevent torsion from recurring in the future.

Torsion of the Testicular Appendages

While there are four testicular appendages, only two are commonly visible at ultrasound: the appendix testis and appendix epididymis. These appendages are remnants of embryonic ducts and serve no real function. Because they are attached by a small pedicle, they are prone to torsion. Torsion of these appendages is one of the most common causes of acute scrotal pain in children. The appendix testis is more commonly affected than the appendix epididymis, although it is often difficult to identify the offending appendage. Patients are usually young, prepubertal males who complain of acute onset scrotal pain. On clinical examination there may be a bluish discoloration of the skin at the site of pain, which is called the “blue dot” sign and is pathognomonic. At ultrasound the torsed appendix is often identified as a round, extratesticular, extra-epididymal mass lacking color Doppler flow (Fig. 10-2). A reactive hydrocele may be present, as well as scrotal wall skin thickening.

Figure 10-2 Sonographic image of the testis of a 9-year-old patient showing torsion of the testicular appendix. The arrows show an enlarged swollen appendix testis.

Epididymitis and Orchitis

Epididymitis or epididymo-orchitis is an infection of the epididymis and/or testis and is a common cause of acute onset scrotal pain. Typically, scrotal pain associated with epididymitis or epididymo-orchitis is relieved when the testes are elevated over the symphysis pubis, a maneuver called the Prehn sign. In contradistinction, the pain associated with testicular torsion is not relieved by this maneuver. While the causative agent in epididymitis is usually not identified in young children, the infection usually originates in the prostate gland or bladder and spreads to the epididymis and testis via the vas deferens and spermatic cord lymphatics. A congenital anomaly of the urinary tract may be present. In adolescents the cause is most often a sexually transmitted infection.

Ultrasound examination of a patient with epididymitis demonstrates enlargement of the epididymis, primarily the head, with heterogeneous echotexture. On color Doppler evaluation there is increased blood flow to the epididymis and/or testis (Fig. 10-3). A reactive hydrocele may be an associated finding. When the entire testis is involved, it is often enlarged and has altered echogenicity. On gray-scale imaging findings alone, the appearance of the testis may mimic a diffusely infiltrative disease such as leukemia or lymphoma, although the clinical presentation should suggest the correct diagnosis. Untreated epididymo-orchitis may progress to scrotal abscess formation or may result in testicular infarction, which may lead to testicular atrophy. In patients with epididymo-orchitis, a follow-up sonogram performed 4 to 6 weeks following the initial event is advised in all cases to ensure complete resolution of the imaging findings following appropriate interval therapy. This is important in order to exclude an underlying tumor as the cause for the patient’s symptoms. It is uncommon for a testicular tumor to present with acute scrotal pain; the accepted figure is less than 10% of tumors. It may occur and is usually due to acute hemorrhage or infarction of the testis that contains the tumor. Orchitis secondary to infection with mumps occurs in approximately 25% of patients that contract the disease. The sonographic findings include an enlarged hypoechoic testis, a small hydrocele, and sometimes thickening of the scrotal wall. Infertility may occasionally result following mumps orchitis. Severe scrotal infection may result in the rare condition called Fournier gangrene. This is a fulminant infectious process involving the scrotal wall and skin of the perineum that is in essence a fasciitis. The severe infection may result in gas formation along the fascial planes of the scrotal wall. Sonographic findings include the findings of epididymo-orchitis along with small echogenic ill-defined foci within the scrotal wall. These foci represent gas, and this finding requires urgent communication to the referring physician as surgical débridement may be required. In questionable cases, CT may be performed, which will clearly show the presence of any gas as hypoattenuating foci within the scrotal wall (Fig. 10-4).

Figure 10-3 Sonographic image of a 32-year-old patient with acute epididymitis of the contralateral epididymis. The epididymis is swollen and shows increased vascularity with color Doppler.

Figure 10-4 CT image of a 65-year-old male patient with Fournier gangrene. The image shows gas within the scrotum with a hydrocele and extensive subcutaneous edema.

Inguinal Scrotal Hernia

An uncommon cause of acute scrotal pain is incarceration of an inguinal hernia that extends into the scrotum. Indirect inguinal hernias are not uncommon; however, extension into the scrotal sac is rare. The clinical findings are usually obvious with a large swelling in the scrotum, although the mass may not be easily reduced. Sonographically, the appearance may be nonspecific with a heterogeneous mass identified in the scrotum. It is usually easy to identify the mass as separate from the testis, although following the mass along the inguinal canal may not be easy. The presence of bowel may be detected if the two walls and lumen are clearly visible; however, it is not always clear that the mass represents bowel, and often the mass may merely be omental fat that has herniated into the scrotum. The presence of peristalsis may confirm the diagnosis. In cases where doubt exists, a CT scan could be performed, and this would show the hernia and its contents extending into the scrotum. Signs of incarceration on sonography include the absence of color flow on color Doppler evaluation. Although this may be easy to elicit in identifiable bowel wall, if the hernia consists of omental fat alone, it may be an unreliable sign. On CT, signs of incarceration include edema of the adjacent fat around the hernia, and possibly decreased enhancement of the bowel wall of any bowel loops that may be present in the hernia.

Testicular Trauma

Trauma to the testis may be either penetrating or blunt. Penetrating trauma to the testis, like many other locations, usually requires immediate surgical exploration. Blunt trauma to the testis in a hemodynamically stable patient should be evaluated with sonography. The key diagnosis to make following testicular trauma is the presence or absence of testicular rupture. A ruptured testicle requires immediate surgical repair, and early diagnosis is required to maximize the chances of testicular salvage. A ruptured testicle that is operated on within 72 hours of the trauma has a salvage rate approaching 80%, but this drops to 30% with subsequent delay. The sonographic findings suggesting testicular rupture include loss of clarity of the margins of the testis and abnormal morphology of the testis; on occasion, testicular parenchyma may be identified protruding beyond the testicular capsule. Sonographic findings seen following trauma to the testes that does not result in testicular rupture include altered echogenicity with loss of the normal homogeneity and alternating foci of either increased or decreased echogenicity. Depending on the degree of trauma, the heterogeneity may be focal or more generalized. A focal area of heterogeneity may be mistaken for epididymo-orchitis or even tumor, so an accurate history of testicular trauma is required to help differentiate from these conditions. Despite an accurate history, when focal heterogeneity is seen resulting from trauma, a follow-up scan is advised in 4 to 6 weeks to ensure complete resolution. As with many testicular conditions, a secondary hydrocele is commonly seen following trauma to the scrotum. This appears as a hypoechoic fluid collection within the scrotum. There may be an associated scrotal hematoma, which may also appear as a hypoechoic fluid collection when hyperacute. As this resolves, more complex elements may develop within the scrotum, and the presence of complex fluid in the scrotum following trauma represents resolving hematoma. The long-term sequelae of testicular trauma include complete or incomplete infarction with a resultant smaller testicle, chronic fibrosis, and even calcification.

Cryptorchidism

The arrest in the descent of the testis along its normal path is one of the most common disorders of the genitourinary tract. It occurs in up to 3% of term infants, although the majority of these will descend naturally over the first few months of life. Nearly four out of five maldescended testes in adults are located at or below the level of the inguinal canal. Although maldescended testes are associated with a host of congenital syndromes, this is not always the case and the condition may occur in isolation. The most damaging consequence of maldescended testes is infertility; infertility rates in unilateral maldescent are reported to be close to 20%, but this rises to 75% in cases where the maldescent is bilateral. There is a high rate of germ cell tumors in maldescended testes, and this risk extends to the contralateral descended testis as well. Maldescended testes are also at increased risk of both torsion and trauma and hence should be considered in any patient presenting with pelvic or scrotal pain in which both testes are not clearly palpable. Since the majority of maldescended testes are found in the inguinal canal, the testis may usually be identified by sonography. Maldescended testes appear as small, usually hypoechoic, rounded or oval structures along the line of the inguinal canal (Fig. 10-5). Care should be taken not to confuse the small testis with a lymph node. Any focal areas of heterogeneity within the testis could represent malignant degeneration. The sensitivity of sonography for detecting maldescended testis varies between 75% and 97% and depends on whether the testis is palpable or not. Once the maldescended testis lies higher than the inguinal canal, it becomes difficult for sonography to locate it. Other imaging modalities that may be used to locate the testis include CT and MR. With multidetector CT, the small soft tissue mass of the maldescended testis is usually identifiable, a situation that was not always the case in the era of large slice thickness CT. T2-weighted MR imaging may be useful to locate the high signal testis, which may be best identified using coronal plane imaging along the plane of the gonadal vessels.

Figure 10-5 CT image of a 22-year-old patient with bilateral maldescended testes. These are seen as bilateral oval soft tissue masses in the inguinal canals.

Prostatitis