End-stage Intestinal Diseases: Indications for Intestine Transplantation in Children
The structural indications of SGS result from intestinal failure caused by massive surgical resection or anatomic loss of intestine due to congenital anomalies. Functional indications causing intestinal failure occur as a result of severe motility or absorptive disorders despite a normal intestinal length. Table 1 lists the indications for small bowel transplantation in adults and children.
Structural Indications in Pediatric Intestine Transplantation
The most common indications for intestine transplantation in children are midgut volvulus and gastroschisis.
Volvulus. Volvulus results from a malrotation of the bowel around a fixed point formed by congenital or adhesive bands or when the small intestine becomes twisted around the mesentary, causing vascular compromise leading to necrosis of the intestine. Malrotation with volvulus is often diagnosed in utero or presents within the first 2 months of age, but may occur at any age.
Gastroschisis. Gastroschisis occurs when variable lengths of the intestine and occasionally part of the liver, without a peritoneal sac, herniate through an abdominal wall defect located to the right of the umbilical cord. There is a higher incidence in premature births, and these infants usually have associated stenoses or atresias of the jejunum or ileum.
Atresia and stenosis. Atresias and stenoses are congenital defects of the small intestine, usually diagnosed within 24 to 48 hours after birth. Duodenal atresia results when the lumen fails to recanalize during weeks 8 to 10 of gestation and is associated with prematurity (25%). Infants present with bile-stained vomiting with the first feeding and abdominal x-rays reveal gastric and duodenal distention. Jejunoileal atresias are more common, with most cases involving complete obstruction of the distal ileum or proximal jejunum. The etiology of jejunoileal atresias is thought to be infarction. Presentation includes bile-stained vomiting within 48 hours of birth and abdominal distention. Abdominal films show dilated loops of bile with an absence of colonic gas. An association with common variable immune deficiency has been reported in infants with intestinal atresias.
Necrotizing enterocolitis (NEC). NEC is a disorder that presents in premature infants and is associated with early initiation of hyperosmotic feedings, vascular insufficiency, hypoxia, and early colonization of the gut with gram-negative bacteria.[23,24] Patients presenting with NEC at evaluation for intestine transplantation had the worst prognosis of all indications, with a survival of less than 30% at 1 year. A thorough pulmonary and neurologic evaluation of these premature infants is imperative since they are predisposed to bronchopulmonary dysplasia and intraventricular hemorrhage.
Trauma. Trauma is a rare indication for intestine transplantation in children, but transplantation may be required in cases of extensive bowel resection with inadequate adaptation of the remaining bowel. These patients usually require an isolated intestine if transplantation occurs in a timely manner prior to any hepatic damage from TPN.
Functional Indications in Pediatric Patients
Hirschsprung Disease. Long segment Hirschsprung disease, or congenital megacolon, is a common indication for intestine transplantation in children. In this condition, there is a congenital absence of intramural nerve plexuses or aganglionosis resulting in a functional obstruction of the bowel with colonic dilatation. Patients present in the neonatal period with abdominal distention or minimal or no passage of meconium. Later presentations include severe constipation with recurrent fecal impaction, anemia, and malnutrition. Diagnosis is confirmed through manometry and intestinal biopsy showing aganglianosis. Due to the risk of enterocolitis, the aganglionic portion may be resected with diversion of the ganglionic proximal bowel resulting in minimal residual bowel. It is important to assess motility of the residual bowel and stomach during the transplant evaluation since pseudo-obstruction may be present.
Chronic intestinal pseudo-obstruction (CIP). CIP includes a heterogeneous group of disorders that are characterized by intestinal obstruction in the absence of an anatomic obstruction and are caused by ineffective intestinal contractions. CIP may involve the entire intestinal tract or selectively involve the colon and/or other hollow viscera such as the bladder. It may be neuropathic or myopathic, with most symptoms beginning at birth or by 1 year of age.[30,31] The neuropathic form may cause severe abdominal pain while the myopathic form places the patient at risk for spontaneous bowel perforation as well as megacystitis or megaureter, which may cause repeated urinary tract infections and subsequent renal dysfunction.[17,30,31] Most patients present with bilious vomiting, abdominal distention, and constipation affecting nutritional intake and growth. Antroduodenal manometry is usually abnormal and reveals abnormal smooth muscle or neuronal function. Patients with CIP have a mortality of over 30% in the first year of life, which is associated with other abnormalities such as urinary bladder neuromuscular disease causing renal dysfunction, concomitant intestinal malrotation that increases the risk of volvulus and ischemia, and immunodeficiencies that may result in an increased risk of infection. When patients with CIP are evaluated for transplantation, barium studies are done to determine the length and anatomy of the intestine, manometry of the GI tract is performed to confirm the diagnosis and establish further organ involvement, and a thorough urologic evaluation is obtained to assess for the presence of megacystitis.
When patients present with a diagnosis of CIP that is not supported by history or in whom testing is not definitive, the possibility of Munchausen by proxy (MBP) must be considered. MBP is a critical psychiatric disorder in which a parent, usually the mother, fabricates or intensifies an illness through over-reporting and/or manipulation. Because MBP presents as a group of symptoms that are not easily diagnosed or explained by tests, the child may be given the diagnosis of CIP since it also is a rare disorder without a specific diagnostic test. In CIP, diarrhea may be caused by active secretion or bacterial overgrowth. However, diarrhea in patients with MBP who are diagnosed with CIP may be caused by syrup of ipecac or overuse of laxatives. Cases have also been identified during evaluation for transplantation and following transplantation.[31,34]
Microvillus inclusion disease. Microvillus inclusion disease is a rare autosomal recessive disorder that causes severe secretory diarrhea with an 80% mortality in infancy due to malabsorption and malnutrition. The disease is thought to be caused by disorders of the brush border assembly and differentiation. Diagnosis is confirmed through electron microscopy of intestinal biopsies, which reveal severe villous atrophy without crypt injury and an absence or hypoplasia of the microvilli. TPN has resulted in a longer-term survival in some patients; however, early referral to an intestine transplant center is essential.
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