Purpose: To determine the causes of intrascrotal disease in patients who were sent for scrotal sonography at King Chulalongkorn Memorial Hospital and whether the imaging findings can help differentiate the tumor from infection of the testis.
Material and Method: Retrospective review was performed in 72 cases of extratesticular lesions and 48 cases of the
intratesticular lesions to find out the causes of intrascrotal disease. The sonographic findings in the cases with final
diagnosis of intratesticular infection and testicular tumor were analyzed according to the following criteria including the size of the testis, number, echogenicity, and margin of the mass, diffuse abnormal echogenicity of the testis, presence of fluid
in the scrotal sac, epididymal lesion, scrotal skin thickening and calcification.
Results: Hydrocele was the most common extratesticular lesion (29.87%) and epididymitis was the second most common (14.28%). Infection was the most common intratesticular pathology (54.17%) and tumor was the second most common
(31.25%). Most testicular tumors appeared as a focal mass while testicular infection usually caused diffuse abnormal
echogenicity throughout the testis (p = 0.008). Epididymal lesions and skin thickening were usually detected together with
intratesticular infection while they were not present in the cases of tumor (p = 0.000061 and 0.017). The number, echogenicity, margin of the mass, presence of testicular enlargement, fluid in the scrotal sac and calcification did not differ between testicular infection and tumor.
Conclusion: Hydrocele was the most common cause of extratesticular disease, followed by epididymitis. Most of the
extratesticular pathology was benign entities. For intratesticular disease, the most common cause was infection, followed by intratesticular tumor. Findings of a solitary intratesticular mass without epididymal lesion or skin thickening prefered malignant entity, while diffuse abnormal echogenicity of the testis with epididymal lesion and skin thickening prefered infectious process.

Keywords: Scrotal sonography, Scrotal disease, Testicular lesions