The anus and rectum are the final portions of the gastrointestinal tract in relation to digestion and excretion of food products, and are subject to numerous problems. However, many patients are reluctant to ask or speak about these problems with their physician or gastroenterologist. Some anal and rectum problems can become quite serious if they are not treated.

The rectum is at the end of the large intestine, between the sigmoid colon and the anus. It is lined with tissue that contains glands that secrete mucus to protect and lubricate the rectum.

The anus is located at the end of the rectum. It is the opening where stool exits the body. The anal tissue includes both surface skin layers and intestinal tissues. The nerves in this area are very sensitive to pain.

Rings of muscles called anal sphincters keep the anus closed between bowel movements. The interior sphincter is located closer to the rectum and is controlled subconsciously. The exterior sphincter is closer to the skin and can be controlled voluntarily.

Stool that passes through the digestive system is stored in the descending colon. When this becomes full, the stool moves through the sigmoid colon into the rectum, which stretches as it fills. As the rectum senses the presence of stool, it causes an urge to defecate. Older children and adults can hold stool in the rectum until an appropriate time and place for a bowel movement. However, infants and younger children do not have the necessary muscle control and cannot withstand the urge to defecate.

Bowel patterns vary greatly from person to person. Further, a person will generally have different bowel patterns at different times. Factors such as diet, stress, medications and disease can affect bowel patterns. Regular frequency of bowel movements in Western societies may range from two or three a week to two or three a day. In most cases, it is easiest to defecate in the morning, particularly 30 minutes to an hour after the first morning meal.

Chronic or sudden changes in the frequency, consistency or volume of bowel movements may signify a gastrointestinal problem. The presence of blood, mucus, pus or excessive oil or grease in the stool may be warning signs of a problem anywhere in the gastrointestinal tract. Problems that originate in the rectum or anus are usually related to abnormal structures, improper function or infections or inflammations. Some problems may fall into more than one category. For example, an anal fissure (tear) originates as a structural problem, but if left untreated may affect anal function.