enema(redirected from contrast enema)
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Related to contrast enema: barium enema
the injection of fluids into the rectum through the anus in order to clear the intestine of retained stool or to administer medicinal liquids or diagnostic agents.
Enemas are classified as purgative, laxative, medicinal, and diagnostic. Purgative, or evacuative, enemas involve the injection of 1–1.5 liters of water or soap solution at 25–30°C in order to stimulate peristalsis by irritating the intestinal mucosa and to soften a hard stool. A variation of the purgative enema is the siphon enema, in which a half-liter or liter of water is injected repeatedly and rhythmically by the siphon principle. The siphon enema is used with intestinal pareses to promote the restoration of peristalsis. Laxative enemas involve the injection of 50–200 ml of vegetable oil or 50–100 ml of a hypertonic solution of table salt, magnesium sulfate, and sodium sulfate; it is used when strain is undesirable in evacuating the bowels. Medicinal enemas involve the introduction of medicinal substances to act directly on the intestinal mucosa or to be absorbed through the intestinal walls (for example, in cases of intractable vomiting). Proctoclysis, or the rectal drip method, is used when the introduction of large quantities of fluid into the body is necessary (fluid injected by drops being better absorbed). The injection of glucose solution or physiological saline by enema is extremely uncommon. Diagnostic enemas involve the introduction of contrastive substances for subsequent X-ray examination.