The pathogenesis of constipation.

The pathogenesis of the constipation that is commonly experienced by cancer patients, especially those with advanced disease, is the result of multiple influences on the control of intestinal motility and fluid handling. These factors include the direct effects of malignancy on gut structure, paraneoplastic neural impairment, biochemical disturbance, and adverse effects of cancer treatments. In addition, the debility and reduced oral intake associated with cancer also contribute, as, perhaps, might the older age of many cancer patients. A detailed understanding of the mechanisms of constipation, especially in association with illness, is lacking, and most treatments remain nonspecific.