1. George W. Kaplan, MD* 1. 2. *Clinical Professor of Surgery and Pediatrics, University of California at San Diego School of Medicine; Chief of Urology, Children’s Hospital, San Diego, CA. After completing this article, readers should be able to: 1. Determine when to treat hydroceles. 2. Describe the primary difference between testicular tumors and hydroceles. 3. Delineate the treatment of torsion of the testis. 4. Describe the abnormalities that frequently are associated with epididymitis. 5. Explain the best method of detecting varicocele. Scrotal enlargement is seen with some frequency in children and adolescents. There are a number of lesions in the differential diagnosis whose import varies from mundane to life-threatening. Recognizing these lesions and making the diagnosis can enhance the efficacy of any practicing clinician. Lesions can be divided into chronic (or at least subacute) and acute, and the differential diagnosis of each category is substantially dissimilar. ### HYDROCELE Hydroceles are seen very frequently in children and with some regularity in newborn males. A hydrocele is a collection of fluid between the layers of the tunica vaginalis surrounding the testis. In children, hydroceles usually appear because the processus vaginalis is patent between the peritoneal cavity and the scrotum. During the first year of life, the processus vaginalis often closes spontaneously, and the hydrocele usually resolves. However, if the patent processus vaginalis is sufficiently enlarged, it is unlikely to close spontaneously, and a hernia (a viscus that protrudes into the patent processus vaginalis) is likely to be present. Hydroceles are easily recognized as swelling in the scrotum, either unilaterally or bilaterally (Table 1⇓ ). They may cast a bluish hue to the overlying scrotal skin, especially in infants and younger children. Transillumination of the hydrocele, if positive, will establish the presence of fluid. If the hydrocele collapses with gentle pressure, a hernia component is likely. In general, hydroceles in infants younger than 1 year of age are allowed to resolve spontaneously; even very large noncommunicating hydroceles in infants often resolve spontaneously (Table 2⇓). Hydroceles that …