IMAGING FEATURES OF RADIATION-INDUCED CHANGES IN THE ABDOMEN

After external-beam radiation therapy, radiation-induced changes may b e observed in abdominal and pelvic organs at imaging. In the liver, an area of low attenuation corresponding to the radiation port (or an ar ea of hyperattenuation if the underlying liver tissue shows fatty chan ge) can be seen at computed tomography (CT) performed within 3-6 month s after therapy. Later, the liver may be fibrotic and contracted. In t he stomach, small intestine, and colon, wall thickening and edema are early manifestations. Ulcers may also be observed. Long-term complicat ions include strictures and fistulas. After irradiation of the kidneys , altered attenuation of the renal parenchyma may be seen at CT. Urete ral strictures, typically involving the distal ureter, may be observed after pelvic irradiation. The bladder may be small and contracted wit h a thickened wall after radiation exposure. Fistulas between the blad der and other pelvic organs sometimes occur. Typical musculoskeletal c hanges include growth abnormalities in skeletally immature patients, f atty replacement of bone marrow, and radiation osteitis. Radiation-ind uced neoplasms are also recognized after therapy.