Ultrasound of the Acute Scrotum

Phebe Chen, MD, Susan John, MD

Disclosures

Appl Radiol. 2006;35(3):8-17. 

In This Article

Inflammation

Inflammatory causes of scrotal pain predominate in all age groups. Epididymitis usually results from descending infection, frequently associated with urinary tract infection. Genitourinary anomalies (such as ectopic ureter, ectopic vas deferens, or urethral stricture) may predispose a child to epididymitis. In pubertal boys and young adults, epididymitis most commonly results from sexually transmitted diseases. Less commonly, epididymitis may result from hematogenous infection, trauma, idiopathic granulomatous disease, and vasculitides, such as Henoch-Schönlein purpura and Kawasaki disease. Chemical epididymitis from amiodarone hydrochloride, an antiarrhythmic agent, has been described.[5] With infectious epididymitis, the process begins in the tail and proceeds cephalad. On US, the epididymis is enlarged and hypoechoic or heterogeneous in echotexture[7] (Figure 6). Often there is a reactive hydrocele and scrotal wall thickening. Associated orchitis is seen in 20% of cases and may be diffuse or focal, characteristically seen as a crescentic hypoechoic lesion within the testicle, located at the periphery near the inflamed epididymis.[1] Isolated orchitis is rare, and is usually a result of postviral or posttraumatic inflammation (Figure 7). On color Doppler, epididymitis is seen as diffuse or focal areas of increased color signal (Figure 6B). Hyperemia is the only US finding in 20% of patients with epididymitis and 40% of patients with orchitis.[3,7] Focal hyperemic areas may mimic testicular mass, hypervascular epididymal tumors, or spontaneous detorsion of testis with hyperemia.[5,7] Testicular ischemia may occur secondary to venous outflow obstruction.[3,4] Fournier's gangrene is a polymicrobial necrotizing fasciitis of the scrotum that can extend to the lower abdominal wall.[4] The diagnosis of Fournier's gangrene is made when soft tissue air is seen as echogenic foci with shadowing within the scrotal tissues. Such air can be differentiated from bowel within an inguinal hernia by demonstration of peristalsis of intestinal loops. The scrotal skin is usually thickened and hyperemic in scrotal fasciitis. Other complications of epididymitis include infarction, abscess, and pyocele formation.[5,7] Idiopathic scrotal edema can occur in boys 4 to 7 years of age. The scrotal skin is edematous, but the testis and epididymis are normal.[3]

Epididymitis. (A) The inflamed epididymis is enlarged and hypoechoic (arrows). (B) Note the increased vascularity within the inflamed epididymis and a small reactive hydrocele.

Epididymitis. (A) The inflamed epididymis is enlarged and hypoechoic (arrows). (B) Note the increased vascularity within the inflamed epididymis and a small reactive hydrocele.

Orchitis. (A) The inflamed testis is inhomogeneous in echotexture, not unlike that seen with acute torsion, (B) but abnormal hypervascularity supports the diagnosis of orchitis. Note a small hydrocele.

Orchitis. (A) The inflamed testis is inhomogeneous in echotexture, not unlike that seen with acute torsion, (B) but abnormal hypervascularity supports the diagnosis of orchitis. Note a small hydrocele.

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