Radiation damage to the rectum and anus: pathophysiology, clinical features and surgical implications.

Radiation kills cancer cells by inducing various degrees of deoxyribonucleic acid fragmentation and disruption of intracellular membranes that lead to either immediate or delayed cell death. Although radiation can be effective in destroying cancer, its usefulness is limited by damage to normal tissues that surround the target tumour or those in the path of the radiation beam. The rectum and anus are damaged frequently during radiotherapy for abdominopelvic malignancy, including preresection therapy for rectal cancer. Such damage is often associated with lesions in the perineal skin, genitourinary tract, colon, and small intestine. Surgical intervention often is required for the most severe forms of these complications.