Step 1: The gastrointestinal tract begins at the mouth where mechanical digestion begins. Saliva in the mouth functions to moisten and lubricate food before swallowing and to partially digest food particles.

Step 2: Food moves from the mouth, down the esophagus, and into the stomach.

Step 3: In the stomach, glands secrete hydrochloric acid, which helps digest food and destroy bacteria that enter the body with the food. Little nutrient absorption occurs in the stomach. The digested particulate matter, known as chyme, moves from the stomach into the first portion of the small intestine, the duodenum.

Step 4: Small Intestine

It is in the small intestine where most of the digestion and absorption of food occurs. Special enzymes breakdown carbohydrates, fat, and proteins into smaller components that the intestinal cells can absorb and use throughout the body for nutrients. The pancreas and liver also secrete substances into the small intestine to aid in the digestion of substances.

At birth, a normal neonates small intestine is ~240 cm and colon is ~40 cm. Neonatal short bowel is considered <25 cm with ileocecal valve or <40 cm without ileocecal valve.

The small intestine has 3 parts:

1. Duodenum: Main section for absorption of iron and folate. This is also the section that bile and pancreatic enzymesenter the intestine to aid in digestion.

2. Jejunum: Major section of nutrient absorption.

3. Ileum: Major section of nutrient absorption. This is the only section of intestine that can absorb vitamin B12. If your child does not have his or her ileum, which is common in short bowel patients, they will require vitamin B12 supplementation.

Step 5: Food passes from the ileum through the ileocecal valve and enters the colon. The colon serves two main roles:

1. Acts as a storage chamber for undigested material.

2. Functions to reabsorb water.

Step 6: When initiated, contractions of the rectum and relaxation of the anal sphincter cause defecation, and stool is deposited.

Digestion and absorption rely on many components of proper contractions, enzymes, and cell function. If any of these functions are impaired, then the process may not proceed as planned, as seen in patients with intestinal failure.

For a handy graphic and overview of this process, find our 'Overview of Digestion' in our Topic of the Month Resources.

Short bowel syndrome may lead to intestinal failure.

Intestinal Failure (IF) develops when your child's small intestine does not provide the necessary long term nutrition needed to sustain a normal life. This results in the need for additional long term nutrition to be delivered through large veins in the body. This is called "Parenteral Nutrition" or "PN."

Intestinal rehabilitation is the process of restoring nutritional autonomy. This means weaning from parenteral nutrition (PN) and onto oral feedings. This allows your child to live free from PN and its associated complications.

Enteral (i.e. passing through the intestine either via the mouth or tube feeding) is critical to maintain normal intestinal structure and function. In order to transition your child from parenteral to enteral nutrition (EN), the intestinal epithelium (lining) must adapt to optimize nutrition absorption.

Your team of surgeons, gastroenterologists, and dieticians will work with you and your child to determine the optimal formula and diet to help the intestine adapt.

In general, carbohydrates may be poorly tolerated by intestinal failure patients as they are broken down by the gastrointestinal tract bacteria into small, osmotically (water) active organic acids that can cause a large amount of water to be drawn into the distal small intestine and colon, causing large fluid losses. Moderate amounts of fat are usually tolerated in the short bowel syndrome diet as well as protein.

Your child may also become dehydrated quickly due to large fluid losses from a high output ostomy, persistent secretory diarrhea, or pseudo-obstruction resulting in large gastric and duodenal losses. In cases like these, an oral rehydration solution containing glucose and sodium may be recommended. You may be required to monitor your child’s urine and stool output to assess the hydration status of your child.

If your child has short bowel syndrome or persistent diarrhea and is requiring tube feedings, a continuous feed through a nasogastric (NG) tube or gastrostomy tube may be recommended. This permits constant saturation of the carrier proteins, thus taking full advantage of the limited absorptive area of the intestine.

It is important to understand that the transition from intestinal failure to adequate intestinal function and the ability to wean from parenteral nutrition to full enteral feeding can take weeks, months, and even years.

1. Diet modification

2. Oral Rehydration Therapy

3. Vitamin and Mineral Supplements

4. Medications

5. Surgical Procedures

At an intestinal rehabilitation center, your child will have a team of clinicians to support them through their journey. Typically on an intestinal rehabilitation clinical team, you will find a:

• Surgeon

• Gastroenterologist

• Nutritionist or Dietician

• Social Worker

• Child Life Specialist

• Clinical Nurse Coordinator

• Advanced Practice Nurse

• Mid-Level Providers

• Pharmacist

• Speech-Language Pathologist

• Occupational Therapist

Intestinal adaptation is the bowel's ability to 'adapt' or adjust to the changes that have occurred within the intestine. The intestine compensates for lost function in one area of the intestine by adapting at another site. Intestinal adaptation is a slow process and can take up to two years to complete.

In what ways does the bowel adapt in children with short bowel syndrome or intestinal failure?

1. The villi (little finger-like projections that line the intestine) in the remaining intestine increase in both number and size. This increases the surface area of the intestinal wall, increasing the area in which food and nutrients can be absorbed.

2. Decrease in motility. This allows for increased contact time with the intestinal wall, which allows for increased nutrient absorption.

Predictors of intestinal adaptation and the ability to wean from parenteral nutrition include:

• The length of the bowel remaining.

• The anatomical section (i.e. location/ portion) of bowel that is remaining.

• Presence or absence of the ileocecal valve.

• Presence or absence of the colon.

Since different parts of the bowel absorb different types of nutrients, depending upon which section your child is lacking, will determine the nutritional deficiencies he or she will have and the extent of his or her intestinal failure.