An enema is a way to clean out the large intestine, which is called the colon or bowel. Various solutions, including the most commonly used mixture of mild soap and warm water, are inserted into the rectum to soften the stool, according to Medicine Online.
While warm water and mild soap is a common enema solution, little is known about its effectiveness. Consequently there is no specific guidance when choosing the best enema for a given patient. In one study, pre-operative patients were given either a tap water or soapsuds enema. Amount of enema instilled into the colon and output were measured. Soapsuds enemas produced significantly greater output than tap water and were equally well tolerated, according to U.S. National Library of Medicine.