An enema, also known as a clyster, is an injection of fluid into the lower bowel by way of the rectum. The word enema can also refer to the liquid injected, as well as to a device for administering such an injection.
In standard medicine, the most frequent uses of enemas are to relieve constipation and for bowel cleansing before a medical examination or procedure; also, they are employed as a lower gastrointestinal series (also called a barium enema), to treat traveler's diarrhea, as a vehicle for the administration of food, water or medicine, as a stimulant to the general system, as a local application and, more rarely, as a means of reducing body temperature, as treatment for encopresis, and as a form of rehydration therapy (proctoclysis) in patients for whom intravenous therapy is not applicable.
The principal medical usages of enemas are:
As bowel stimulants, enemas are employed for the same purposes as orally administered laxatives: to relieve constipation; to treat fecal impaction; to empty the colon prior to a medical procedure such as a colonoscopy. When oral laxatives are not indicated or are not sufficiently effective, enemas may be a sensible and necessary measure.
A large volume enema can be given to cleanse as much of the colon as possible of feces. However, a low enema is generally useful only for stool in the rectum, not in the intestinal tract.
Such enemas' mechanism consists of the volume of the liquid causing a rapid expansion of the intestinal tract in conjunction with, in the case of certain solutions, irritation of the intestinal mucosa which stimulates peristalsis and lubricates the stool to encourage a bowel movement. An enema's efficacy depends on several factors including the volume injected and the temperature and the contents of the infusion. In order for the enema to be effective the patient should retain the solution for five to ten minutes, as tolerated. or, as some nursing textbooks recommend, for five to fifteen minutes or as long as possible.