Undescended testis: value of MR imaging.

Magnetic resonance (MR) imaging was performed in 32 male patients, 20 with no abnormalities and 12 with clinically suspected undescended testes. The results were compared with ultrasonographic, computed tomographic, clinical, and surgical findings. The undescended testes were unilateral in eight patients (one had testicular duplication) and bilateral in four. Of 16 undescended testes, 15 were correctly identified on MR images. One intraabdominal testis was not seen. Testis-fat contrast at 0.35 T was optimal with a short repetition time (TR) and a short echo time (TE). At 1.5 T, good contrast was achieved with short TR/TE sequences, but the contrast was even more pronounced with even longer TR/TE parameters. In seven patients with unilateral undescended testes, the undescended and contralateral testes showed symmetrical tissue signal intensity on both T1- and T2-weighted images. In three, the undescended testis was of lower signal intensity, suggesting atrophy. MR imaging promises to become an important diagnostic tool in the detection of undescended testes.