Definition

Short bowel syndrome (SIC) is a disease of the digestive tract defined by severe malabsorption occurring following extensive resection of the small intestine. A small intestine is called short when it measures less than 200 cm. Since the majority of nutrients (carbohydrates, fats and proteins) are absorbed in the first 150 cm of the intestine, this explains the malabsorption associated with SIC. This malabsorption results in the presence of diarrhea and / or steatorrhea and can lead to malnutrition and metabolic changes which can be fatal. Finally, SIC generally requires the use of parenteral and / or enteral nutrition, because following surgery, the intestine often cannot maintain adequate levels of various nutrients and hydration.

Etiology

There are many causes of CIS in adults. These include, among others, surgical resection of a large section of the small intestine, Crohn's disease, cancer, mesenteric ischemia (the interruption of blood flow to the intestine), volvulus ( coiling of the intestine) and radiation enteritis (inflammation of the intestine caused by radiation therapy).

Symptoms

The main symptoms of SIC are diarrhea and nutritional deficiencies caused by malabsorption. However, the symptoms of SIS depend on the anatomy and function of the remaining small intestine.

Resection (surgical removal) of the small intestine and malabsorption

The small intestine is a section of the digestive tract comprising the duodenum, jejunum, and ileum. Depending on the part of the small intestine that has been removed, the effects on absorption vary.

With the resection of the jejunum, the number of disaccharidases, the enzymes responsible for the digestion of disaccharides (certain sugars, chemically composed of the union of two types of sugars), decreases. The reduction of these enzymes leads to a decrease in the breakdown of disaccharides, a type of carbohydrate of which lactose is a part. As undecomposed disaccharides are not absorbed, this can lead to lactose malabsorption and diarrhea.

With resection of the ileum, the movement of intestinal contents is accelerated and the absorption of vitamin B₁₂ and bile salts is reduced. Malabsorption of bile salts, involved in the digestion of lipids, leads to a decrease in the absorption of lipids and liposoluble vitamins (A, D, E and K). In addition, unabsorbed lipids and bile salts from the large intestine increase and can be altered by the action of intestinal bacteria. Altered bile salts can lead to malabsorption of fat and can lead to steatorrhea. Finally, removing the ileum also causes a decrease in the absorption of water and electrolytes by the large intestine, which can lead to diarrhea and steatorrhea.

Intestinal adaptation

The gut of people with CIS usually undergoes adaptation following surgical resection. The degree of bowel adaptation depends on various factors including the length of bowel resection, the section of bowel that was removed, the condition of the remaining small bowel, bowel continuity, underlying disease, malnutrition and patient age. Usually, intestinal adaptation occurs when the ileum and large intestine are present, but there is little or no adaptation in the jejunum. Intestinal adaptation includes various modifications such as an increase in the number of intestinal cells, an increase in the size of the ileum villi, an elongation of the intestine, and changes in motility and hormonal changes. All its modifications have the effect of increasing the absorption of nutrients and thus limiting malabsorption. Intestinal adaptation usually takes more than a year and is supported by various elements such as enteral nutrition.

The case of oxalates

Oxalates are compounds that occur naturally in some foods and are normally eliminated by the body. However, when the ileum has been removed, the oxalates are no longer eliminated and are absorbed by the large intestine. This increases the presence of these compounds in the urine and promotes urinary stones. Oxalates are found in foods like beets, spinach, nuts, tea, chocolate, strawberries, rhubarb, and wheat bran. People who have had ileum resection generally need to eat a diet restricted in oxalates, ensure adequate hydration, and take calcium supplements, which bind to the oxalates and allow their elimination.

Nutritional approach

The nutritional approach for CIS in adults is to prevent water and electrolyte loss and to initiate parenteral nutrition providing all the necessary macronutrients and micronutrients (carbohydrates, fats, proteins, vitamins and minerals). This is because immediately after surgery, diarrhea is often very severe and people need to be fed intravenously (parenteral nutrition) to replace the losses. The fluids are then gradually reintroduced orally as the patient stabilizes and the amount of stool decreases. Finally, people whose bowel resection has left less than 100 cm of jejunum, as well as those who continue to have excessive losses of nutrients, water and electrolytes often need to receive parenteral nutrition throughout their lives. For people whose remaining jejunum measures more than 100 cm, oral feeding may be resumed.

Nutritional recommendations

Nutritional recommendations for CIS in adults who can resume oral feeding include:

• Eat small, frequent meals. This helps reduce the risk of diarrhea.
• Drink fluids between meals.
• Have higher intakes of protein, which is generally well absorbed, and lower in simple sugars, which promote diarrhea.
• Observe a diet low in oxalates after the ileum has been removed.
• Consumemultivitamin according to nutritional needs (e.g .: magnesium, calcium, iron, vitamin B₁₂, etc.).

Short bowel syndrome is a disease of the digestive tract that can have a huge impact on people with it. In addition, these individuals can have very different profiles depending on the anatomy of the remaining small intestine and the intestinal adaptation which varies from person to person. Therefore, each individual has different needs and professional monitoring for short bowel syndrome is essential.

References 

1. Bouthillier, Lise. January 2019. Diseases of the digestive tract. NUT 2047 Clinical nutrition 2. Montreal: University of Montreal.al.
2. D’Aoust, Louise. January 2019. Hail is short. NUT 2047 Clinical nutrition 2. Montreal: University of Montreal.al.
3. https://www.merckmanuals.com/fr-ca/professional/troubles-gastro-intestinaux/syndromes-de-malabsorption/syndrome-du-gr%C3%AAle-court
4. https://www.merckmanuals.com/fr-ca/accueil/troubles-digestifs/malabsorption/syndrome-de-l-intestin-court

Article written by:

Marie-Noël Marsan, Nutritionist