Ultrasonography (US) is usually the initial imaging modality for evaluation of pathologic conditions of the scrotum. However, magnetic resonance (MR) imaging can be useful as a problem-solving tool when sonographic findings are equivocal. MR imaging allows characterization of scrotal masses as intratesticular or extratesticular and can demonstrate various types of lesions and tissue, including cysts or fluid, solid masses, fat, and fibrosis. MR imaging may be of value when the location of a scrotal mass is uncertain or when US does not allow differentiation between a solid mass and an inflammatory or vascular abnormality. Gadolinium-enhanced MR imaging can help differentiate between a benign cystic lesion and a cystic neoplasm. Gadolinium-enhanced imaging can also be used to demonstrate areas of absent or reduced testicular perfusion, such as in segmental testicular infarct. Finally, MR imaging can demonstrate an intraabdominal undescended testis, which can be difficult to detect with US, and is superior to US in differentiation between an undescended testis and testicular agenesis.

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Computed tomography (CT) was performed in 50 patients before and after extracorporeal shock wave lithotripsy (ESWL) to determine the effects of ESWL on the kidney and perinephric tissues. Bilateral treatments were performed in three patients. Post-ESWL scans demonstrated subcapsular hematomas in eight (15%) patients (two large, six small, none symptomatic) and intrarenal hematomas in two (4%) patients. In three (6%) patients small subcapsular fluid collections of uncertain cause were seen. Treated kidneys showed a statistically significant mean increase in size (9%) after ESWL, as measured at the axial level of the major stone fragment. Perinephric soft-tissue stranding and fascial thickening were seen in 37 (70%) of 53 treated renal fossae, with the changes ranging from mild to severe. The authors conclude that while most patients undergoing ESWL will show some posttreatment abnormality on CT scans, the procedure appears to be associated with a low frequency of serious renal trauma.

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The signal intensity of the corpora cavernosa of the penis at magnetic resonance (MR) imaging may vary from that of the corpus spongiosum; this difference is dependent on the rate of blood flow within the cavernous spaces that constitute the corporal bodies. Also visible at MR imaging are the layers of fibrous tissue that envelop the corporal bodies, the deep arteries and veins, subcutaneous connective tissue, tunica dartos, epidermis, and urethra. While the iliac, pudendal, perineal, and common penile arteries can be evaluated with three-dimensional MR angiography, the smaller end arteries of the penis have not yet been reliably demonstrated. MR imaging may be used to detect and stage penile and urethral cancers, identify and characterize benign penile masses, evaluate arteriogenic impotence, identify penile fractures, evaluate penile prostheses, localize periurethral abscesses, and identify plaques of Peyronie disease. With its direct multiplanar imaging capabilities, superb soft-tissue contrast, and excellent spatial resolution, high-field surface coil MR imaging can show the soft-tissue and vascular anatomy of the penis, as well as the appearance of many penile diseases.