The Scrotum and Testes
The testes are located in the scrotum in 90% of full-term infants. When not in the scrotum, they are usually to be found within the inguinal canal. Rarely, they are intra-abdominal. Testicular size varies with age and with the onset of puberty. US is the gold standard for evaluating the testis and epididymis as it can demonstrate changes in size and texture, as well as assessing blood flow using spectral and color Doppler. NM (99m Tc pertechne-tate) has been used in cases of suspected torsion, but as it uses radiation it is not usually recommended. MRI can also assess the testis but is rarely indicated because of the cost.
On US, the normal testis is primarily of homogeneous echo-genicity ( Fig. 3.59 ). A not uncommon finding is microcalcification within the testicular parenchyma ( Fig. 3.60 ) and is usually of no clinical significance.
An undescended testis, seen in 0.5% of boys prior to puberty, is the most common abnormality seen. Congenital aplasia of one testis is rare, and bilateral aplasia is very rare. US is the modality of choice to search for the testes, but if they are not within the inguinal canal they may be diff cult to see within the abdomen due to bowel gas; in that case, MRI may be useful.
If there is scrotal swelling without pain or inflammation, the most common cause is a hydrocele ( Fig. 3.61 ). If there is pain and/or evidence of inflammation, then testicular torsion has to be the first consideration, as this is a surgical e mergency. Testicular torsion is indicated if there is disorganization of the echo texture, usually enlarged and hypoechoic, ( Fig. 3.62 ) with loss of blood flow within the testis on color Doppler; however, this is not always reliable, particularly if the torsion is intermittent. The most common radiologic diagnosis with an acutely tender testis is epididymitis (with or without orchitis). Seeing marked increase in blood flow to a swollen epididymis on color Doppler can make the diagnosis ( Fig. 3.63 ). If the testis is involved with increased blood flow, then it is orchitis as well as epididymitis. Torsion of the testicular appendage is the other diagnosis to be considered and is seen as a swollen appendage separate from the epididymis. Torsion is the most common cause in infants and adolescents, and 50% of boys with torsion of the testicular appendage are between 9 and 12 years old.
Trauma can result in testicular hematomas. These can remain for an extended period of time and hence be mistaken for a more sinister lesion ( Fig. 3.64 ). If there is a patent processus vaginalis, herniation of bowel loops or fluid from the perito-neal cavity can occur and extend into the scrotum. This can also happen with meconium peritonitis resulting in calcification.
Tumors are rare before puberty. The most common involvement of the testis by tumor is in leukemia.