Practice Essentials
A suggested definition for short bowel syndrome (SBS) in pediatric patients is the requirement for intravenous nutrional and fluid supplementation in those with less than 25% of remaining small bowel that is expected for gestational age. [1] This condition results from the alteration of intestinal digestion and absorption that occurs after extensive bowel resection. It is a complex disorder with nutritional, metabolic, and infectious consequences. Bowel obstruction is a potential complication of SBS (see the image below).
Small-bowel obstruction caused by intussusception in a 5-month-old patient is visible on plain radiograph.
Signs and symptoms
Although SBS may rarely be a congenital condition, most patients with SBS have undergone bowel resection for one of the following:
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A congenital anomaly such as an omphalocele, gastroschisis, or intestinal atresia
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Necrotizing enterocolitis associated with prematurity [2]
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Intestinal ischemia from malrotation and volvulus
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Crohn disease (infrequent with current treatment)
Children with cloacal exstrophy do not have SBS in the classical sense but often have all the signs and symptoms associated with functional intestinal failure.
Patients with SBS may present with any of the following:
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Nutritional deficiencies
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Malabsorptive diarrhea
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Dehydration
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Vomiting
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Bloating
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Gastroesophageal reflux
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Failure to thrive
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Drug toxicities
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Sepsis
See Presentation for more detail.
Diagnosis
Children with SBS should undergo standard hematologic and biochemical studies, according to institutional guidelines.
Background
Short bowel syndrome (SBS) is the result of the alteration of intestinal digestion and absorption that occurs following extensive bowel resection. A suggested definition for pediatric patients is the requirement for intravenous nutrional and fluid supplementation in those with less than 25% of remaining small bowel that is expected for gestational age. [1] Short bowel syndrome represents a complex disorder that affects normal intestinal physiology with nutritional, metabolic, and infectious consequences. Few conditions in pediatric gastroenterology pose as great a challenge as short bowel syndrome. [4]
In general, the leading causes of death in affected infants who are being treated with parenteral nutrition are central line sepsis and liver failure with the prolonged use of parenteral nutrition.
Pathophysiology
The small intestine of the neonate is approximately 250 cm in length. By adulthood, the small intestine grows to approximately 750 cm. As a consequence, the infant and the young child have a favorable long-term prognosis compared to an adult in regards to potential intestinal growth after intestinal resection. Intestinal adaptation may take weeks to months to be achieved; in the interim, children who have had intestinal resection need nutritional support through various therapeutic measures, including parenteral nutrition. The duodenum and jejunum are responsible for the absorption of most dietary constituents except vitamin B-12 and bile acids.
The jejunum is characterized by long villi and a large absorptive area. The tight junctions are relatively large, rendering the epithelium more porous to larger molecules and the free and rapid flux of water and electrolytes. In comparison, the ileum has shorter villi and a less absorptive surface area than the jejunum. Furthermore, the tight junctions are tighter, permitting less flux of water and electrolytes from the vascular space into the intestinal lumen and, consequently, the ileum is more efficient in the absorption of water. Although nutrients are less well absorbed in the ileum, it has site-specific receptors for the absorption of bile acids and vitamin B12. Moreover, many GI hormones that affect intestinal motility, including enteroglucagon and peptide YY, are produced in the ileum. The small intestinal sites of nutrient absorption are as follows:
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Duodenum - Iron
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Jejunum - Carbohydrates, proteins, fat, vitamins
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Ileum - Bile acids, vitamin B-12
In general, virtually all digestion and absorption is completed within the first 100-150 cm of jejunum in a healthy individual. In the absence of an intact colon, the minimum length of healthy bowel necessary to avoid parenteral nutrition is approximately 100 cm. Patients who have less than 100 cm of jejunum exhibit significant malabsorption. Although the ileum is limited in its capacity to form chylomicrons compared to the jejunum, studies have shown that the ileum has greater adaptive function as far as improving its absorptive function in the presence of short bowel syndrome. Similarly, studies in animals have shown that intestinal transit time is more likely to improve (ie, increase) in patients with proximal small-bowel resection as opposed to patients with distal small-bowel resection.
The jejunum cannot develop site-specific carriers for the transportation of vitamin B12 and bile salts, and, consequently, these are malabsorbed permanently in patients, following ileal resection. Furthermore, the loss of enteroglucagon and peptide YY cannot be underscored in the regulation of small-bowel motility.
In addition to the effects of long-term parenteral nutrition on the liver, small bowel dilation in children with short bowel syndrome is associated with mucosal damage, bowel-derived bloodstream infections, and cholestatic hepatic injury. [5] The presence of a pathologic small bowel diameter ratio exceeding 2.17 was associated with increased fecal calprotectin and decreased citrulline, and small bowel diameter ratio was greater in the presence of intestinal bloodstream infections. [5]
Etiology
Necrotizing enterocolitis, intestinal atresias, and midgut volvulus are the most common causes of short bowel syndrome in the neonatal period.
Intussusception with ischemic small-intestinal injury is a common cause of short bowel syndrome in older infants and children.
Through innovations in the surgical management of patients with chronic inflammatory bowel disease, Crohn disease is a less frequently associated cause of short bowel syndrome.
Prognosis
The long-term survival of children with very short bowel syndrome appears to be excellent—providing no life-threatening complications requiring transplantation develop. [6, 7] Risk factors for nutritional failure include gastroschisis and delayed ostomy closure. Intestinal rehabilitation may potentially lead to complete weaning of parenteral nutrition before these children reach adulthood. [6] In general, weaning off parenteral nutrition is strongly dependent on the anatomic profile and length of the residual bowel. [8] Nonetheless, for those who survive as well as their family/caretakers, short bowel syndrome has a significant impact on quality of life, including psychosocial and emotional functioning. [9, 10]
Complications
The leading cause of death in infants with short bowel syndrome who are treated with parenteral nutrition is central line sepsis and complications of the liver and biliary tract associated with the prolonged use of parenteral nutrition.
Cholestasis is also a frequent complication of patients on long-term parenteral nutrition. To some extent, bacterial overgrowth and specific nutrition deficiency can lead to worsening cholestasis in patients with short bowel syndrome. The use of a fish-oil based fatty acid emulsion has been shown to decrease cholestasis once established compared with historic controls. [11]
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Small-bowel obstruction caused by intussusception in a 5-month-old patient is visible on plain radiograph.
