Urogenital ImagingAtrophy, testicular
may affect undescended or normally descended testes. In
cryptorchidism, the testis is generally normal in size and shape up to the time of puberty. After puberty, progressive atrophy develops, with shrinkage and
fibrosis of the testis.
Ultrasound (US) may be able to detect
atrophic undescended testes in the inguinal region and
CT may help in cases where the testis is intra-abdominal. However,
MRI is the most useful study. MR imaging is reliably able to locate remnants of testicular regression (e.g. regressed undescended testis composed of fibrous scar with haemosiderin deposition and
calcification). The diagnosis can be made when an
atrophic cord is seen approaching the bases of the empty scrotum. On T2-weighted images, regressed testes exhibit low signal intensity, which correlates histologically with remnant cord structures and a fibrotic nodule containing haemosiderin deposition and
calcification. There are multiple causes of atrophy of normally positioned scrotal testes, including
atherosclerosis, previous
orchitis, hypopituitarism, malnutrition,
obstruction to outflow of semen, irradiation, and prolonged androgen deprivation therapy.
At imaging by US or MRI, atrophy is recognized when there is a clear reduction in testicular size. An atrophic testis is hypoechoic, and the abnormality can be localized or diffuse. It can often be differentiated from testicular neoplasm by preserved vascular anatomy, by demonstration of normal testicular morphology, and on the basis of clinical findings. The size of the testis is not always helpful in differentiation as in localized atrophy the total testicular size may be normal. Furthermore, cancer can coexist in a small testes.
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