Short bowel syndrome

You are the gastroenterology registrar and have been referred a neonate from the NICU. He was born at 30 weeks of gestation, but unfortunately developed fulminant sepsis secondary to necrotising enterocolitis. He underwent a laparotomy and had 15 cm of dead gut removed.

He is now being referred to you for long-term management of short bowel syndrome.

Bottom line

Short bowel syndrome is a malabsorptive state which occurs due to congenital disease or when a significant portion of the small bowel is removed due to surgery

The amount and anatomy of the remaining gut determine the outcome of enteral and parenteral nutrition

Intestinal failure is when a child is dependent on parenteral nutrition

Structural and functional adaptation occurs with the remaining small bowel

Management requires a multidisciplinary team approach

Complications include: growth failure, parenteral nutrition-associated liver disease, small bowel bacterial overgrowth, sepsis and nutritional deficiencies

What is short bowel syndrome or short gut?

This is the malabsorptive state, which occurs due to surgical resection or congenital disease of a significant portion of the small intestine. The amount and anatomy of the remaining bowel influence the tolerance for enteral nutrition (EN) and the need for parenteral nutrition (PN).

What are the common causes of short gut?

Children who have undergone procedures for necrotising enterocolitis, volvulus, atresia, and gastroschisis.

This makes ex-premature babies, and children with chromosomal anomalies, one of the larger cohorts presenting with short gut – something to keep in mind during clinical examinations!

What is intestinal failure?

Intestinal failure (IF) in a child with short gut is defined as a dependence on parenteral nutrition to maintain minimal energy and fluid requirements for growth.

What is intestinal adaptation?

Intestinal adaptation is the process by which the remaining bowel attempts to increase fluid and nutrient absorption. Structural adaptation involves an increase in the size of the intestinal villi and the absorptive surface area, while functional adaptation refers to a slowing of bowel transit time, thereby increasing the time available for nutrient reabsorption.

How does the remaining anatomy influence the outcome?

The jejunum is the primary absorptive site for most nutrients. Jejunal resection thus leads to a deficiency of nutrients at least in the short term. Adaptation here is primarily functional.

The ileum is the primary site for B12 and bile acid absorption, and so resection here may lead to B12 and fat malabsorption.

Loss of the ileocecal valve has been associated with the need for longer-term PN.

How is it managed?

Management requires a multidisciplinary team approach.

Medical management

This focuses on the provision and monitoring of calories, micronutrients, fluids, electrolytes and growth. This is often provided for by a combination of parenteral (PN) and/or enteral nutrition. Although patients often require PN, including home PN, for an extended period, the ultimate goal is successful weaning from PN to achieve complete enteral nutrition, with sustained growth and maintenance of normal nutrition.

To normalise life for the child, parents and caregivers of children on PN are often trained in the hospital to administer PN at home. PN bags are premixed and delivered weekly to their home. Home PN training is managed by a dedicated nursing team, and PN delivery is coordinated by the pharmacist. Growth velocity and weight are reviewed by the dietician.

The medical team monitors nutrient levels, treats any complications that arise, and reviews the ratio of enteral to parenteral nutrition based on the child’s progress.

Some hospitals have specialised nutrition teams comprising nurses, pharmacists, dietitians, and doctors to ensure the child reaches his or her growth potential.

Surgical intervention

Long-term parenteral nutrition is administered through central venous catheters, which are placed by surgeons. Complications of central venous catheters include line sepsis, thrombosis and migration.

Surgical intervention is also required for placement of feeding stomas, such as a gastrostomy or jejunostomy. These feeding tubes allow the administration of enteral feeds, either continuously or as boluses.

Enteral feeds help reduce dependence on long-term parenteral nutrition and its associated complications.

What are the complications related to short bowel syndrome?

Growth failure

Parenteral nutrition-associated liver disease (PNALD)

Long term use of parenteral nutrition results in liver disease, which occurs in 40-60% of infants on PN. PNALD involves changes in liver histology, including fibrosis, and can progress to cirrhosis and failure.

Strategies to prevent PNALD include early introduction and grading up of enteral feeds, cycling of PN and prevention of infection. Fish oil-based lipid emulsion has been shown to reverse PNALD when compared to standard soybean-based lipid emulsions. Oral ursodeoxycholic acid may also improve cholestasis.

Small bowel bacterial overgrowth (SBBO)

This occurs due to impaired bowel motility and bacterial reflux from the colon (with ileocecal valve resection or incompetence).

The loss of the terminal ileum is also a risk factor for bacterial overgrowth. SBBO can result in further malabsorption with failure to thrive, bacterial translocation causing sepsis, and D-lactic acidosis, which occurs when the GI tract is colonised by D-lactate-producing organisms, leading to toxic blood levels, ataxia, and delirium.  Symptoms include abdominal pain, cramps, distension and diarrhoea. SBBO may also cause deficiencies of fat-soluble vitamins and vitamin B12.

Treatment may include cycling antibiotics such as metronidazole, trimethoprim-sulfamethoxazole, or rifaximin.

Sepsis

This is either due to bacterial translocation from the bowel or catheter-related infections. It is for the latter reason that home PN training to caregivers emphasises strict aseptic techniques. Some centres have begun trialling ethanol locks for tunnelled catheters to reduce the incidence of catheter related blood stream infections.

Micronutrient deficiencies

Patients are particularly susceptible to deficiencies in fat-soluble vitamins and zinc, calcium, selenium, copper and magnesium. 

When would we consider intestinal transplantation?

Indications for intestinal transplantation include:

• Impending and overt liver failure due to PNALD
• Thrombosis of 2 or more central veins
• 2 or more episodes per year of catheter-related sepsis requiring hospitalisation
• Line-related fungaemia, septic shock or ARDS
• Frequent episodes of dehydration despite optimal fluid supplementation

References

Uko V, Radhakrishnan K, Alkhouri N. Short bowel syndrome in children: Current and potential therapies. Pediatr Drugs 2012;14(3):179–188.

Duro D, Kammin D, Duggan C. Overview of Pediatric Short Bowel Syndrome. JPGN 2008 47:S33–S36.