Sonography of Pediatric Scrotal Swelling Brian D. Coley, MD Sonography is the preferred imaging method for the evaluation of pediatric scrotal swelling. By identifying the site of origin and whether a mass is solid or cystic, the diagnosis is usually readily made, making ultrasound especially valuable in patient management. Scro- tal pathology differs in pediatric patients, especially prior to puberty, making understanding of pediatric conditions essential. This article reviews the common intra- and extratesticular causes of pediatric scrotal swelling and their sonographic appearances. Semin Ultrasound CT MRI 28:297-306 © 2007 Elsevier Inc. All rights reserved. T he discovery of a scrotal mass in a young boy causes great alarm. While the nature of the mass may be apparent on physical examination, imaging is often required for diagno- sis. Most causes of pediatric scrotal swelling are due to benign extratesticular causes, but testicular tumors do occur. Sonog- raphy is the ideal modality for evaluation of the pediatric scrotum and its contents. In evaluating a child with a scrotal mass, ultrasound (US) allows confirmation that a mass is present, whether it is intratesticular or paratesticular, and whether it is solid or cystic. While no imaging test is perfect, sonography is nearly 100% sensitive for the detection of tes- ticular neoplasms, 1-4 with a negative-predictive value of al- most 100%. 1 In general, there is a greater risk for malignancy with intratesticular masses than for extratesticular masses, making the determination of site of origin clinically relevant; US is 90 to 100% accurate in differentiating intratesticular from paratesticular processes. 3-7 While there are some lesions whose histology can be suspected based upon sonographic features, most masses will require tissue sampling or resec- tion for diagnosis. Abnormalities of Testicular Number and Size Polyorchidism is an unusual congenital anomaly character- ized by more than one testis in one hemiscrotum. Testicular duplication probably occurs after 3 months of gestation as an error in the separation and fusion of the genital ridge (pri- mordial testis) and mesonephric ducts (primordial epididy- mis). 8,9 Most cases present with triorchidism 10,11 and there is a marked left-side predominance (Fig. 1). The testes usually share a common epididymis and vas deferens, although each testis may have its own. Patients usually present with an asymptomatic scrotal mass. However, there is associated con- tralateral cryptorchidism in 15 to 50%, inguinal hernia in 30%, and hydrocele in 9%. 12 Torsion of one or both testes within a single hemiscrotum occurs in up to 13% of pa- tients. 13 These testes are also at higher risk for malignancy, with an incidence of up to 5%. 8 Sonographically, the super- numerary testes are smaller than normal. Otherwise they have normal testicular echogenicity and echopattern. This appearance allows for close follow-up as a conservative treat- ment option. 14 Heterogeneity or abnormal vascularity are worrisome features for malignancy and require surgical in- tervention. Testicular size asymmetry can lead to evaluation for a scro- tal mass. Asymmetry may be a normal transient finding dur- ing puberty (Fig. 2) or can be the result of previous cryp- torchidism, testicular torsion, trauma, or as a complication of inguinal hernia repair. Testicular echogenicity is not reliable in ascribing a cause to testicular asymmetry, although in gen- eral damaged testes will be relatively hyperechoic to normal parenchyma. Inflammatory conditions such as epididymo-orchitis and vasculitis can result in a small testis. Varicoceles can result in testicular hypotrophy of the ipsilateral testis, 15,16 and this finding may prompt varicocele repair to promote testicular growth. 17-19 Testicular Neoplasms Primary Testicular Neoplasms Prepubertal primary testicular neoplasms are uncommon, with an incidence of 0.5 to 2 cases per 100,000 children, representing 1 to 2% of solid childhood tumors. 20,21 Prepu- Section of Ultrasound, Department of Radiology, Columbus Children’s Hos- pital, and The Ohio State University College of Medicine and Public Health, Columbus, Ohio. Address reprint requests to: Brian D. Coley, MD, Chief, Section of Ultra- sound, Department of Radiology, Columbus Children’s Hospital, 700 Children’s Drive, Columbus, Ohio, 43205. E-mail: bcoley@chi.osu.edu. 297 0887-2171/07/$-see front matter © 2007 Elsevier Inc. All rights reserved. doi:10.1053/j.sult.2007.05.006