Ultrasound in Pediatric Emergencies

Gaurav Saigal, MD, Jennifer Runco Therrien, MD, and Frank Kuo, BS

Disclosures

Appl Radiol. 2014;43(8) 

In This Article

Scrotal Pathology

US is the primary imaging modality for evaluating the acute scrotum in children. Common pediatric scrotal diseases seen in the ED include testicular torsion, testicular appendage torsion, epididymitis, orchitis, hernia, hematocele and abscess. Familiarity with ultrasound technique, characteristics and common pitfalls is essential to differentiate these conditions, establish an accurate diagnosis, and initiate treatment.

Testicular Torsion

The principle objective in imaging the child with acute scrotal pain is to promptly detect testicular torsion. Testicular torsion results when an abnormally mobile testis twists on the spermatic cord, obstructing its blood supply. Testicular torsion is a surgical emergency since ischemia can lead to testicular necrosis and nonviability if not corrected within 6 hours of onset of symptoms.[13] Severe testicular pain is the most common presenting symptom.

On color Doppler, complete absence of intratesticular blood flow and normal extratesticular blood flow is diagnostic (Figure 8).[13,14] The presence of flow within the testis does not exclude torsion, since incomplete vascular obstruction can sometimes occur from intermittent torsion. Using a linear-array high-frequency (7–14 MHz) transducer, the asymptomatic testis is scanned to optimize settings for low flow, resistance and velocity. Once a satisfactory image of the asymptomatic side is obtained, the painful symptomatic side is studied without changing machine settings.[15]

Figure 8.

A 9-year-old boy presenting with right testicular pain for the past 12 hours. Gray-scale (A) and color Doppler (B) ultrasound images of both testes demonstrate an altered echogenicity of the right testicle compared to the left. Doppler image of both testes side to side demonstrates absence of flow in the right testicle with preserved flow in the left, using the same ultrasound settings. Right-sided testicular torsion was noted at surgery and right sided orchiectomy was performed.

Gray-scale sonography has no role in diagnosing torsion, but can effectively display the sequelae of testicular ischemia and predict viability.[13] During the first 6 hours after symptom onset, when the testis is salvageable, normal architecture and echogenicity is typically preserved. Over the next 24 hours, the testis becomes enlarged, susually hypoechoic or inhomogeneous, associated with edema of the epididymis and scrotal wall. These alterations indicate decreased likelihood of viability. Imaging both testes simultaneously in transverse orientation is the optimal technique to identify subtle sonographic differences (Figure 8).[16]

Testicular torsion can be a diagnostic challenge because blood flow is often difficult to detect in normal small prepubertal testes. Torsion may be partial or intermittent so arterial flow is not necessarily absent. The testis can also undergo spontaneous detorsion and ischemia may be secondary to other conditions (vasculitis, trauma, epididymitis-ochitis).[13,16] Hydrocele and scrotal skin thickening are common findings in the majority of these conditions and thus nonspecific.

Torsion of Testicular Appendage

In a child with an acute scrotum, torsion of a testicular appendage represents the most common cause of scrotal pain.[17] Testicular appendages are remnants of the paramesonephric duct and are usually located at the superior testicular or epididymal head.[18] Patients are typically under 13 yrs. of age and the onset of pain is more gradual than that seen with testicular torsion; thus, patients often present days after symptoms develop. An avascular structure in an area of increased vascularity, separate from the typically enlarged testis and epididymis is the characteristic appearance of testicular appendage torsion (Figure 9).[17] Torsion can lead to increased vascularity in the epididymis and testis and thus may mimic epididymitis and/or orchitis. The torsed appendage becomes more echogenic with time and can eventually calcify or slough off as a calcified loose body between the layers of the tunica vaginalis; referred to as a "scrotal pearl."

Figure 9.

A 10-year-old with right scrotal pain. US of the scrotum-transverse (A) and longitudinal (B) images demonstrate enlargement of the right scrotum with underlying heterogeneously enlarged and hypervascular epididymis (white arrows). There is increased flow in the right epididymis and the testis compared to the contralateral side. A heterogeneous, centrally hyperechoic avascular structure is noted within the area of the increased vascularity (black arrows), consistent with a torsed testicular appendage.

Epididymitis

Epididymitis is more common in young adults secondary to sexually transmitted pathogens. However, it also occurs in children and is usually idiopathic, due to retrograde urinary tract infection or may be related to an underlying urogenital anomaly.[18] In the acute setting, the epididymis appears enlarged and heterogeneous on gray-scale US and demonstrates increased flow on color Doppler (Figure 10).[14,16] The adjacent testis is concurrently involved in 20% of cases, occurring more commonly in adults.[14,18] A heterogeneous, enlarged and hyperemic testis is characteristic of orchitis. Orchitis without epididymitis is typical of infection by the paramyxovirus, which causes mumps.[15] Complications include abscess and infarction, both of which can be easily mistaken for torsion.[19]

Figure 10.

A 14-year-old boy presenting with right scrotal pain. Longitudinal (A) Color Doppler image of the right scrotum demonstrates marked increased vascularity (white arrows) in an enlarged and heterogeneous-appearing right epididymis, consistent with epididymitis. Transverse image (B) with the left side for comparison shows normal minimal flow (black arrow) in the left epididymis.

Testicular Trauma

In the setting of trauma, accurately diagnosing testicular rupture is important, since treatment involves urgent surgical repair. On gray-scale US, the testicle appears heterogeneous with irregular contours and the tunica albuginea is disrupted (Figure 11A, B).[18,20] Hematocele is the most common finding following trauma, which initially appears echogenic becoming hypoechoic as it evolves. The hematocele is avascular on color Doppler.[19]

Figure 11.

A young adult male presented with trauma to his scrotum and scrotal pain following a motorcycle accident. Testicular ultrasound (a, b) demonstrates a heterogeneous, predominantly echogenic left testis (solid white arrow) with markedly irregular and lobulated contours and no color flow compared to the normal right testis (red arrow). A large left scrotal hematoma was also present with scrotal edema (dotted white arrow). At surgery, tunica albuginea lacerations and a large scrotal hematoma were found.

Hernia

Intrascrotal inguinal hernia occurs through the patent processus vaginalis. Imaging should begin with the patient supine and then standing. The bowel or omentum is visualized separately from the normal testis and epididymis. Absence of peristalsis on real-time scanning is worrisome for incarceration, another cause of acute scrotal pain.

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