Short Bowel Syndrome

Short bowel syndrome, or SBS, is also sometimes called short gut. It refers to a collection of health issues faced by people who have problems absorbing nutrients from food. SBS usually occurs in people whose small intestines have been affected by injury, surgery, or other issues that reduce their function. SBS can affect people of all ages. The small intestine may be impaired by a birth defect, illness or injury later in life, or surgery required to treat another condition. The condition is relatively rare, affecting about three of every one million people. An estimated twenty thousand people in the United States are affected by SBS in any given year.

Background

The human body has two types of intestines, small and large. They are also referred to as the small and large bowels. The large intestine reaches a length of about five feet in adults. It performs the final digestive functions, removing excess water and some nutrients and changing digested food into stool that is excreted as waste. While this is an important function, people can live without a large intestine. This is because most of the essential digestive functions occur in the small intestine.

The small intestine is a long tube-shaped organ that reaches about twenty feet in length in an adult human. Its key function is to absorb nutrients from food. The small intestine has three parts, each of which is responsible for absorbing specific nutrients. The first part of the small intestine, the duodenum, absorbs crucial minerals, such as iron. The second part, the jejunum, takes in protein, carbohydrates, fats, and many vitamins. The final part, the ileum, absorbs bile acids from the digestive process and vitamin B12.

The process of digesting food and removing nutrients begins in the mouth when food is chewed. Chewing and digestive juices in saliva begin breaking down food, which then moves down the esophagus to the stomach. There, stomach acid and the action of the stomach further break down the food to form a substance called chyme, which enters the small intestine. In fully functioning intestines, the chyme moves along and nutrients are removed. In people with SBS, however, at least part of the small intestine is missing or does not function properly, resulting in poor absorption of nutrients. The severity and symptoms experienced by a person with SBS depend in part on what portion of the small intestine is affected, since different nutrients are absorbed in different areas of the intestine.

Overview

In some cases, SBS is caused by a birth defect that leaves an infant with a damaged or non-functioning section of bowel. Other times, poor function develops later in life as a result of an injury or illness that damages a portion of the intestine. Most cases, however, result from surgical removal of the intestine. To treat some illnesses, such as cancer, Crohn's disease, a hernia, or a birth defect caused by improper placement of the intestines within the body, the decision might be made to remove half or more of the small intestine and a large portion or all of the large intestine. This treats the problems from the original illness, but it leaves the patient with insufficient intestines to properly digest food, resulting in SBS.

The first symptom of SBS is usually diarrhea, or watery, soft stools. Diarrhea by itself can cause dehydration and a number of related health problems that can result in malnutrition and death. Dehydration occurs because too much of the water and electrolytes ingested pass through the body without being absorbed; malnutrition results from the failure of the intestines to absorb nutrients, leaving the body without the things it needs to create energy and function properly. Both dehydration and malnutrition can be fatal; this is especially true of infants, whose smaller size increases the impact of these conditions.

As a result of dehydration and the lack of nutrients, the patient may also experience weakness, fatigue, and other problems as various systems struggle to function without necessary nutrition. In addition, the patient could experience bloating, cramping, foul-smelling stools, gas, vomiting, and heartburn caused by under-digested food. People who have SBS often develop food-related allergies because their bodies are not equipped to properly digest certain foods, such as milk. They may experience ulcers, or raw spots in the digestive system caused by too much stomach acid, or have too much bacterial growth in the small intestine. Some patients may develop kidney stones, or small but often painful collections of matter in the kidneys and urinary tract.

The first steps in diagnosing SBS include taking a family and personal medical history and performing a physical exam. Blood tests are usually ordered to determine how the body is functioning and to look for indicators of mineral and vitamin deficiencies. A fecal fat test will be done; a sample of stool is collected and tested to determine how well the intestines are processing ingested fat. Other diagnostic tests commonly used include an X-ray to look for physical abnormalities in the intestines; an upper gastrointestinal series, during which the patient has an X-ray while drinking a substance called barium as a contrast agent that helps to outline the intestines to reveal problems; or a computerized tomography scan, which uses a different imaging technique and possibly a contrast agent to provide more detailed views of the intestines and their function.

The first form of treatment for a patient with SBS is nutritional help to replace the fluids and nutrients lost due to the condition. This may be done by increasing the amount of liquids taken orally and through feeding supplements administered through the bloodstream (parenteral nutrition) or through a feeding tube in the nose or mouth (enteral nutrition). The patient will be placed on a special diet plan that involves frequent small meals that avoid fatty foods and other foods known to create a problem.

Other treatments may include medications to treat the various problems related to SBS, such as drugs to curb diarrhea, proton pump inhibitors and H2 blockers to reduce acid production, and drugs that slow the function of the intestine to keep the nutrients there longer and increase the odds of absorption. Some patients may have small intestine transplant surgery to treat SBS.

Bibliography

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