AUTHOR AND EDITOR INFORMATION

Section 1 of 11  

• Authors and Editors
• Introduction
• Frequency
• Embryology
• Clinical
• Diagnostic Evaluation
• Treatment
• Complications
• Conclusions
• Multimedia
• References

INTRODUCTION

Section 2 of 11  

• Authors and Editors
• Introduction
• Frequency
• Embryology
• Clinical
• Diagnostic Evaluation
• Treatment
• Complications
• Conclusions
• Multimedia
• References

Bowel obstruction in the newborn is one of the most common newborn surgical emergencies. Successful management of a newborn with a bowel obstruction depends on timely diagnosis and prompt therapy. The diagnosis can usually be made based on history and physical examination and corroborated by simple radiographic studies. Physicians who evaluate infants for intestinal obstruction must also consider catastrophic events such as volvulus, in which the intestine twists around its blood supply. This may involve the entire midgut or the apex of an "apple peel" atresia, in which the intestine distal to the obstruction winds around the ileocecal vessels, or a loop of intestine may twist around a congenital band or other fixed point, such as in intestinal duplication. In these instances, early surgical intervention may mean the difference between intestinal salvage and crippling short-gut syndrome, but such cases are uncommon. The typical case of neonatal bowel obstruction is straightforward in diagnosis and treatment, and the outcome is usually excellent.
 
In contrast to proximal bowel obstruction, patients with distal small bowel or colonic obstruction present with abdominal distention, delayed passage of meconium, and absence of transitional stools (meconium mixed with normal stool content). Imperforate anus and other anorectal anomalies may be readily diagnosed by inspection of the perineum. Plain radiographic findings often suggest distal obstruction by revealing a pattern of dilated small-bowel proximally with no air in the distal colon and rectum. In these patients, a diatrizoate (Gastrografin) enema may be both diagnostic and therapeutic (in cases of meconium plug syndrome).
 
Intestinal obstruction can be complete (atresia) or incomplete (stenosis). Atresias are frequently accompanied by mesenteric defects. In stenosis, the bowel and mesentery appear normal. Stenosis typically occurs in the small bowel or anus. Congenital hypertrophic pyloric stenosis is an acquired rather than congenital disorder. Atresias occur in the esophagus, the antrum of the stomach, the duodenum, the jejunum, the ileum, the colon, and the rectum (where a shelflike partition above a normal anal canal may be observed), or the rectum may end blindly and the anus may be unformed (imperforate).

The intestine may also be obstructed by intraluminal contents, as in meconium ileus or meconium plug syndrome. Aganglionic megacolon (Hirschsprung disease) is a functional obstruction. The intestine appears completely normal; however, because of the absence of ganglioncells, it can only contract. Peristalsis depends on sequential contraction and relaxation.

FREQUENCY

Section 3 of 11  

• Authors and Editors
• Introduction
• Frequency
• Embryology
• Clinical
• Diagnostic Evaluation
• Treatment
• Complications
• Conclusions
• Multimedia
• References

The incidence rate of malrotation of the midgut with clinical symptoms is 1 case per 6000 newborns. As many as 1 in 100 newborns have some asymptomatic anomaly of fixation, rotation, or both. It also occurs with congenital diaphragmatic hernia, gastroschisis, and omphalocele. Malrotation causes duodenal obstruction by 2 different mechanisms: extrinsic compression by Ladd bands, which are the abnormal peritoneal attachments of the right colon, and midgut volvulus, which twists the duodenum. Obstructive symptoms usually manifest during the first month of the life (50% of cases), and 90% of cases occur before the end of first year; however, in many instances, diagnosis is delayed until adulthood.¹

Duodenal obstruction from an atresia or web affects as many as 1 in 6,000-10,000 infants. Duodenal atresia is present in 4% of infants with trisomy 21.  In this context, a congenital heart defect is often present. Atresia of the jejunum or ileum occurs more frequently (1 case per 1500 births). 

Cystic fibrosis, which occurs in 1 infant per 3000 live births, is reported in 10-20% of babies with meconium ileus.² It is the most common genetic disease in people of European origin.

Hirschsprung disease affects 1 in 4500-7000 newborns; it is more common in white infants and affects males 4 times more frequently than females. Hirschsprung disease is hereditary in approximately 12.5% of patients; this subset of patients typically has involvement of the entire colon (total colonic aganglionosis).

Isolated imperforate anus has an incidence of 1-3 cases per 10,000 births, and a female predominance is observed. Administration of folic acid during pregnancy has been shown to reduce the incidence of imperforate anus to 1 case per 10,000 births.

EMBRYOLOGY

Section 4 of 11  

• Authors and Editors
• Introduction
• Frequency
• Embryology
• Clinical
• Diagnostic Evaluation
• Treatment
• Complications
• Conclusions
• Multimedia
• References

The GI tract arises from the yolk sac. At 3-4 weeks' gestation, it becomes a distinct entity; however, a connection, the vitelline (omphalomesenteric) duct, may persist as a Meckel diverticulum. The alimentary tube is divided according to its blood supply into the following:

• Foregut
• • Esophagus, stomach, and duodenum: These are vascularized by multiple sources
  • Thyrocervical, intercostal, celiac axis, and superior mesenteric vessels
• Midgut
• • Jejunum and ileum
  • Ascending and proximal transverse colon: These are supplied by the superior mesenteric vessels
• Hindgut 
• • Distal colon: This is supplied by the inferior mesenteric vessels 
  • Rectum: This is supplied by the internal iliac vessels.

Aberrations of foregut formation include duodenal stenosis, duodenal atresia, and annular pancreas. Maldevelopment of the midgut includes malrotation and jejunal and ileal atresia. Meconium ileus involves the distal ileum. Hirschsprung disease (aganglionic megacolon), meconium plug syndrome, and imperforate anus involve the hindgut. Enteric duplications occur in all 3 locations.
 
Foregut anomalies
 
Duodenal atresia is caused by a mechanism different than the mechanism that causes atresias in other parts of the intestine. Duodenal atresia is believed to occur from a failure of canalization of the duodenum’s lumen. Prior to 8 weeks' gestation, the duodenum is solid; vacuoles then form and coalesce to create a lumen. If this process is incomplete, an atresia or a web may develop.

A duodenal web is a band of mucosa that obstructs the duodenal lumen. Usually, webs have perforations; thus, the obstruction is incomplete. Occasionally, they may stretch distally within the lumen of the duodenum like a windsock. A surgeon must guard against assuming that the web originates where the duodenum changes in caliber. A tube pushed through a gastrostomy into the duodenum tents the duodenal wall at the site of the web’s origination; this is where the duodenum should be opened to excise the web.

Duodenal atresia may be associated with an annular pancreas, in which a band of pancreatic tissue encircles the duodenum. Congenital anomalies, such as trisomy 21 (40% of patients), imperforate anus, and congenital cardiac disease, are present in 50% of babies with duodenal atresia. 
 
Midgut anomalies
 
At 6-10 weeks' gestation, growth of the midgut outstrips the capacity of the abdominal cavity, and the midgut is extruded into the extracoelomic space. When the peritoneal cavity has sufficiently grown, the midgut returns and rotates around the axis of the superior mesenteric vessels; the duodenum passes under the superior mesenteric vessels, and the colon passes over them. This establishes the C loop of the duodenum and the rectangular course of the colon. Malrotation results when the GI tract fails to complete this process.³

The portions of the intestine that are fixed to the retroperitoneum include the duodenum and the ascending colon as well as the hepatic flexure, the splenic flexure, and the descending colon. This arrangement maximizes the base of the midgut mesentery, extending from the left upper quadrant (ligament of Treitz) to the right lower quadrant (ileocecal valve). Without rotation of the intestine, the colon remains medial to the duodenum and the peritoneal bands; attaching the ascending colon to the retroperitoneum obstructs the duodenum. These are called Ladd bands in honor of the surgeon who developed the operation to correct this anomaly. Without fixation of the mesentery to the retroperitoneum, the superior mesenteric vascular pedicle retains a narrow base; hence, it is liable to twist during peristalsis, causing midgut volvulus.
 
Jejunoileal atresia is a condition acquired during fetal development and not a preprogrammed embryonic anomaly. In their classic work on fetal dogs in 1955, Louw and Barnard elucidated the pathophysiology of jejunoileal atresia.⁴ The extent of intestinal loss and the appearance of the atretic intestinal segment varied according to the timing and degree of the disruption of the mesenteric blood supply. Atresias may be single or multiple. Interruption of the main superior mesenteric blood supply results in atresia of the jejunum and proximal ileum; the distal ileum is preserved because of retrograde blood flow from the ileocolic vessels. Other abdominal conditions occurring in utero, such as gastroschisis or intussusception, may be associated with intestinal atresia due to kinking, stretching, or otherwise disrupting the blood flow to the fetal bowel. Chromosomal anomalies are rare (<1%) in babies with jejunoileal atresia.
 
Meconium ileus is the earliest manifestation of cystic fibrosis, an autosomal recessive condition characterized by abnormalities in cellular membrane physiology and chloride ion transport that contribute to progressive respiratory failure, derangements in cellular secretory patterns, and diminished mucosal motility. Of newborns with cystic fibrosis, 10-20% present with meconium ileus, an association first described by Landsteiner in 1905.⁵ The gene for cystic fibrosis is carried by as many as 4% of Ashkenazi Jews and 1% of people of Asian descent.

In 1988, the genetic mutation that causes cystic fibrosis was localized to q31.2 locus on chromosome 7; subsequently, over 1400 mutations have been identified in this gene, which contains 230,000 base pairs and codes for a protein called cystic fibrosis transmembrane conductance regulator (CFTCR).⁵ Abnormalities in the CFTCR disrupt membrane ingress and egress of the chloride ion, which subsequently affects sodium transport as well. The meconium of affected babies is thick and sticky; this, coupled with the poor motility of an immature intestine, leads to intraluminal obstruction of the terminal ileum. A contrast enema reveals the characteristic finding of microcolon due to the proximal obstruction. 
 
Meconium plug syndrome refers to inspissated meconium that obstructs the colon; it may denote Hirschsprung disease but not cystic fibrosis. Conditions that predispose to dysmotility of the neonatal bowel (eg, maternal preeclampsia, maternal diabetes mellitus, maternal administration of magnesium sulfate, prematurity, sepsis, hypothyroidism) may be responsible for the formation of the meconium plug.  A contrast enema can be both diagnostic of and therapeutic for this condition.
 
Hirschsprung disease, first described in 1886 by the Danish physician Harold Hirschsprung, is a disorder of the neuroenteric pathways in the distal colon that results in a bowel that is tonically contracted. The normal bowel, in response to an antegrade peristaltic wave, reflexively relaxes downstream, allowing propagation of the peristaltic wave. This relaxation phase reflex is controlled by neuroenteric ganglion cells, which are present in the submucosal layer of the intestine and migrate from the neural crest distally along the bowel to reach the rectum at about 7-10 weeks’ gestation. Hirschsprung disease is congenital absence of neuroganglion cells; consequently, the peristaltic relaxation phase is not distally conducted to the affected intestine, which does not appropriately relax, causing a functional obstruction. 
 
Because of the antegrade embryonic migration of ganglion cells, Hirschsprung disease usually affects a continuous segment of bowel that extends from the rectum proximally to the level of normal ganglionated bowel. This is termed the “transition zone." The extent of the aganglionic segment varies with each patient.
 
The genetic defects responsible for Hirschsprung disease consist of abnormalities on more than one chromosome (termed oligogenic inheritance) and include the RET protooncogene, located at chromosome 10q11.21. In Hirschsprung disease, RET interacts with a protein termed EDNRB, encoded by the gene EDNRB, which is located on chromosome 13. Six other genes are associated with Hirschsprung disease, including GDNF on chromosome 5, EDN3 on chromosome 20, SOX10 on chromosome 22, ECE1 on chromosome 1, NTN on chromosome 19, and SIP1 on chromosome 2. Variations in RET and EDNRB must coexist for Hirschsprung disease to develop; however, the specific mechanism is not yet clear.  

Recently, syndromic cases of Hirschprung disease (associated with other defects of the autonomic nervous system) were shown to be caused by mutations in the homeobox gene PHOX2B. Mutations in RET and related signaling pathways and modifier genes on 3p21, 9q31, and 19q12 may lead to a failure of migration of the enteric neural crest cells during fetal development. Hirschsprung disease may be a model for understanding other disorders of bowel motility. 
 
Hindgut abnormalities

At 4-6 weeks' gestation, the hindgut separates into the urogenital sinus and the anorectum, which then undergoes canalization. The distal third of the anus develops from ectoderm and becomes the anal pit, whereas the proximal portion of the anal canal is derived from mesoderm. An anal membrane covers the canal until 8 weeks’ gestation, when it perforates and becomes a patent anus. Imperforate anus results if this sequence of events improperly occurs.

CLINICAL

Section 5 of 11  

• Authors and Editors
• Introduction
• Frequency
• Embryology
• Clinical
• Diagnostic Evaluation
• Treatment
• Complications
• Conclusions
• Multimedia
• References

General

Prenatal Diagnosis and Evaluation

• Duodenal atresia: Polyhydramnios is present in as many as 50% of fetuses with duodenal obstruction. Frequently, the stomach and proximal duodenum are fluid-filled and dilated. The image on fetal ultrasonography is similar to the double-bubble sign observed on radiography of the infant after birth (ie, air fills the dilated stomach and duodenum). See Media file 3. 
• Malrotation: No specific prenatal evaluation reveals the presence of intestinal malrotation, although Molvarec et al (2007) reported 2 cases that were prenatally diagnosed with good outcomes.⁹ Malrotation is an anatomic malformation that only predisposes to obstruction. 
• Jejunoileal atresia: Small bowel obstruction due to jejunoileal atresia may also lead to polyhydramnios. This may be detected on prenatal ultrasonography.

Distal obstructions

• Meconium ileus, Hirschsprung disease, and imperforate anus
• • A distal bowel obstruction may develop in utero without fetal ultrasonography detecting any abnormality. An abnormally dilated loop of small bowel may be mistakenly identified as colon, which normally fills with meconium and dilates, as parturition approaches. 
  • In meconium ileus, the bowel proximal to the obstruction may dilate and perforate in utero, causing intense inflammation (ie, meconium peritonitis) around a pseudocyst, in which the extruded meconium is contained by the adherence of the adjacent loops of intestine.
  • In other instances, the perforation may seal after releasing only a small amount of meconium. Extraluminal meconium calcifies, and these scattered calcifications can be seen with fetal ultrasonography and, subsequently, with abdominal radiography.

Postnatal Presentation in the Newborn

• Duodenal atresia: Vomiting, upper abdominal fullness, and the classic double-bubble abdominal radiography sign are consistent features of duodenal atresia. In duodenal stenosis, small amounts of distal bowel gas may be observed on plain radiography. An infant with duodenal atresia may present with bilious or nonbilious vomiting, depending on the location of the obstruction with respect to the ampulla of Vater. In 85% of patients with duodenal atresia, the obstruction lies distal to the ampulla, and these patients have bilious vomiting. The abdomen is usually distended by the dilated stomach and proximal duodenum but becomes scaphoid when the contents of the distended stomach and duodenum are aspirated. Patients with duodenal atresia should be evaluated for trisomy 21 (Down syndrome). 
• Malrotation with volvulus: The initial presentation of a newborn with volvulus of the midgut is often bilious vomiting. Immediately after acute volvulus of the midgut, the abdomen is soft and scaphoid and may or may not be tender. As blood flow in the superior mesenteric pedicle is compromised, the bowel becomes ischemic and dilates, and the baby’s abdomen becomes increasingly distended and firm. Hypotension and shock may develop from sequestration of fluid within the obstructed bowel. Passage of frank blood per rectum may also occur. Prompt surgical intervention is required. 
• Jejunoileal atresia: Infants with jejunoileal atresia may present with abdominal distention, vomiting, and obstipation. A hugely dilated (thumb-sized) loop of intestine denotes intestinal obstruction (ie, "the rule of thumb"). In 12% of newborns with jejunoileal atresia, intra-abdominal calcifications, which represent sites of extraluminal meconium, are observed on plain radiography. This association occurs because interruption of blood flow to the atretic bowel is followed by sterile necrosis and perforation of the intestine with extrusion of meconium.

• Meconium ileus: This condition usually presents with abdominal distention and obstipation. Bowel loops with varying diameters are seen with plain radiography. The diagnosis is confirmed by Gastrografin enema, which may be therapeutic as well. Patients who present with meconium ileus should be evaluated for cystic fibrosis.
• Meconium plug syndrome: This relatively benign condition usually occurs in healthy appearing term infants. Abdominal distention and failure to pass meconium within the first 24 hours of life are the presenting signs.
• Hirschsprung disease: Babies with Hirschsprung disease may have an indolent clinical course, with delayed or infrequent stooling and abdominal distension that occurs following the initiation of feeds. No abdominal tenderness is noted, unless the baby develops enterocolitis, which is not uncommon.
• Imperforate anus: Routine inspection of a newborn perineum should include notation of the position and patency of the anus. Anorectal malformations range from anterior displacement of the anal opening to a completely imperforate anus. Many infants with imperforate anus have an abnormal sacral progression (seen on pelvic radiographs), as well as a fistula between the rectum and the genitourinary tract, demonstrated by finding meconium in the urine. A newborn with imperforate anus should undergo plain radiography 12-24 hours after birth in the cross-table, prone, "jack-knife" position to assess the distal progression of gas within the rectum; this clarifies whether a colostomy or primary anoplasty is indicated.

DIAGNOSTIC EVALUATION

Section 6 of 11  

• Authors and Editors
• Introduction
• Frequency
• Embryology
• Clinical
• Diagnostic Evaluation
• Treatment
• Complications
• Conclusions
• Multimedia
• References

Physical Examination

Imaging Studies

• Duodenal atresia
• • Plain radiography of the abdomen reveals a classic double-bubble sign (see Media file 3). Air is an excellent contrast medium and may be introduced into the baby’s stomach if duodenal obstruction is suspected. The double-bubble sign is not nearly so impressive in cases of incomplete obstruction; also, gas bubbles are present in the distal intestine.
  • Incomplete duodenal obstruction mandates urgent radiographic imaging, laparotomy, or both to differentiate duodenal atresia from malrotation with volvulus. 
• Malrotation with volvulus
• • Radiographic imaging is used to confirm the clinician’s suspicion that the baby has malrotation with volvulus. When the baby’s predominant symptom is bilious vomiting, an upper GI series is obtained.
  • Findings that corroborate this diagnosis include incomplete obstruction caused by torsion of the jejunum (see Media file 1) or by extrinsic compression.
  • The ligament of Treitz may be abnormally located to the right of the vertebral column or below the level of the pylorus. 
  • If the baby presents with abdominal distension, tenderness, and hematochezia, a barium enema is more definitive because it differentiates malrotation with volvulus from Hirschsprung enterocolitis, which it may mimic. Radiographic signs of malrotation include absence of the splenic and hepatic flexures and a cecum positioned in the right upper quadrant; in volvulus, colonic obstruction is observed.
  • Ultrasonography can also be used in the diagnosis of malrotation with or without volvulus. Normally, the superior mesenteric artery lies to the left of the superior mesenteric vein. A superior mesenteric artery that lies to the right or anterior to the superior mesenteric vein at some location along its course suggests malrotation (see Media file 2). Because a 360º twist can occur, visualizing the orientation of these vessels along their full course is important in order to minimize the risk of a false-negative finding.
• Jejunoileal atresia
• • Plain radiography of the abdomen reveals distention of the stomach and small bowel proximal to the obstruction.
  • Occasionally, in proximal atresias with a large mesenteric defect, the distal bowel obtains its blood supply from the ileocecal vessels. The unused, microintestine spirals around these vessels.  This is the so-called “apple peel” or “Christmas tree” deformity. The tip of the “Christmas tree” (the proximal end of the preserved distal intestine) may kink or volvulize, adding urgency to the evaluation and surgical correction of this condition because the length of the intestine is already shortened by the atresia.

Distal obstruction

Plain radiography may be diagnostic of a distal intestinal obstruction if a pattern of dilated proximal loops of intestine without any distal air is noted. A contrast enema confirms the diagnosis and, in cases of meconium plug syndrome, may be therapeutic.

• Meconium ileus
• • On the plain radiography of the abdomen, a “soap bubble” or “ground glass” appearance of the inspissated meconium may be observed.
  • Calcification on scout radiography suggests bowel perforation in utero.
  • A contrast enema with hyperosmolar Gastrografin may be both diagnostic and therapeutic.
  • A water-soluble contrast agent is preferable to barium, and contrast enemas should not be administered in the presence of bowel perforation or compromise.
  • A pseudocyst may develop around bowel that perforated and leaked meconium in utero. In these patients and in patients whose initial management with enemas was unsuccessful, an exploratory laparotomy is indicated.
• Meconium plug syndrome
• • A contrast enema should be performed in all infants and may be diagnostic (a normal-appearing colon laden with meconium-filling defects) as well as therapeutic (successfully loosening the meconium plug and promoting evacuation).
  • Hirschsprung disease may be associated with meconium plug syndrome in 4% of patients; therefore, some clinicians perform a rectal biopsy in patients who present with meconium plug syndrome.
• Hirschsprung disease
• • The most common history associated with Hirschsprung disease of a term newborn is either failure to pass meconium in the first 24 hours of life or chronic constipation following discharge from the nursery.
  • A high index of suspicion for Hirschsprung disease should be maintained in all neonates with delayed passage of meconium. Failure to recognize Hirschsprung disease in a timely fashion may eventuate in toxic megacolon and death.
  • Hirschsprung disease may be suggested by the finding of a “transition zone” on contrast radiography; this is an abrupt change in the diameter of the narrow aganglionic rectum and distal colon and the proximally dilated normal bowel.
  • Failure to evacuate the contrast 24 hours following the enema is another characteristic finding.
  • Anal manometry in patients with Hirschsprung disease reflects the failure of the rectum to relax following inflation of the balloon. However, the study is difficult to perform in an uncooperative patient.
  • If these studies suggest Hirschsprung disease, they should be followed by a confirmatory rectal biopsy. Suction rectal biopsy may be performed at the bedside with a specially designed instrument inserted through the baby’s anus. Suction is applied through a side hole, and a knife amputates a small piece of rectal mucosa and muscularis mucosa. The specimen is examined for ganglion cells, which, if present, effectively eliminate Hirschsprung disease from consideration. In addition, acetylcholinesterase staining of the submucosa can reveal abnormal hypertrophic nerve fibers that are characteristic of Hirschsprung disease. False positives may occur, because the absence of ganglion cells may simply mean that an inadequate amount of tissue was submitted; hence, the criterion standard, full-thickness rectal biopsy, should be performed to corroborate the diagnosis before definitive surgery is performed.
• Imperforate anus
• • The preoperative workup of imperforate anus is focused on determining which operation is most appropriate, primary anoplasty or colostomy, to attain the ultimate goal of continence. Determining the proximity of the distal rectum to the anal skin and determining whether the rectum passes through the levator muscle sphincter complex is crucial to making the correct decision.
  • Lateral abdominal radiography with the child in the prone jack-knife position or invertography with the baby held upside down yields helpful information.
  • Newborns with low imperforate anus have a fistula to the skin; in those with high imperforate anus, the fistula ends in the genitourinary system (the bladder or urethra or vagina). Low lesions may be primarily repaired by perineal anoplasty. A colostomy is opened in newborns with intermediate or high imperforate anus.

TREATMENT

Section 7 of 11  

• Authors and Editors
• Introduction
• Frequency
• Embryology
• Clinical
• Diagnostic Evaluation
• Treatment
• Complications
• Conclusions
• Multimedia
• References

Preoperative treatment

• Duodenal atresia
• • Preoperative treatment includes fluid resuscitation and nasogastric decompression.
  • The baby should be evaluated for trisomy 21.
  • Duodenal atresia is considered a midline defect, and evaluation for associated anomalies should include echocardiography, head and renal ultrasonography, and vertebral skeletal radiography. 
• Malrotation with volvulus
• • Preoperative treatment is focused on urgent relief of the intestinal obstruction.
  • In addition to nasogastric decompression and fluid resuscitation, these infants may require intubation and mechanical ventilation and inotropes for cardiovascular support.
  • Broad-spectrum antibiotics should be administered because of the likelihood of ischemic or gangrenous bowel.
  • A delay in surgical intervention in a patient with malrotation and volvulus prolongs the period of bowel ischemia and may lead to catastrophic loss of intestine.
• Jejunoileal atresia
• • Immediate preoperative nasogastric decompression limits distention of the intestine proximal to the atresia.
  • Appropriate intravenous fluids should be started. 
  • A contrast enema corroborates the diagnosis and is useful in excluding a second, more distal obstruction.
  • Parenteral nutrition, as well as respiratory, cardiovascular, and hemodynamic support, may be necessary postoperatively.
• Meconium ileus
• • Nasogastric decompression and intravenous fluids and antibiotics are initially administered.
  • The Gastrografin enema may be effective in loosening the meconium impaction, but the enema fluid must be refluxed into the terminal ileum. A recent review suggested that this procedure in low-birthweight infants may require special techniques.¹⁰
  • Attention must be paid to the weight of the affected neonate and to the volume of the instilled fluid.
  • Gastrografin diluted with N-acetylcysteine may be administered by nasogastric tube from above to further loosen the meconium.
  • Hyperosmolar solutions (10% acetylcysteine) may be effective in drawing fluid into the lumen of the bowel, thereby loosening the thick meconium; however, this may cause electrolyte disturbances due to intracellular and extracellular fluid realignment with risk of hypovolemic shock.
  • Hyperosmolar enemas may increase the risk of perforation with enteric bacteremia. The risk of perforation is reportedly 3-10%. 
• Meconium plug syndrome: The infant should be on a nothing-by-mouth (NPO) restriction and should receive intravenous fluids until the problem is resolved and the infant can begin enteral feeding (meconium plugs have been passed). Surgery is not usually indicated. 
• Hirschsprung disease: As with other types of distal obstruction, the infant should be made NPO, the stomach should be decompressed, and parenteral nutrition should be provided until the infant has surgical intervention (either colostomy or primary pull-through) and enteral nutrition can be provided. 
• Imperforate anus: The infant should receive parenteral nutrition until surgery is performed (either colostomy or anoplasty). With resolution of the obstruction, the infant may begin feedings.

Operative therapy

• Duodenal atresia: Surgery involves identification of the point of obstruction and determination of the most appropriate means of relieving the obstruction. This depends on the cause of the obstruction (ie, primary atresia, annular pancreas, or a web). A severely dilated proximal duodenum usually requires tapering to facilitate its emptying into the much smaller caliber distal segment. 
• Malrotation with volvulus
• • Malrotation with midgut volvulus is a true surgical emergency in the newborn. Delay in operation may result in catastrophic loss of the bowel and death.
  • In patients with irreversible ischemia, the entire midgut is forfeit, and the child cannot survive.
  • Surgical treatment for malrotation is the Ladd procedure, which includes evisceration of the midgut and immediate counterclockwise derotation of the torsed intestine to release the volvulus and to re-establish flow of blood to the bowel. The duodenum is then followed, dividing the bands that attach it to the colon and opening the leaves of the mesentery like the pages of a book, revealing the superior mesenteric vessels, which are comparable to the book’s binding.
  • The bowel is returned to the abdomen in a manner that spreads out the mesentery as much as possible. Whereas the normal axis extends from the ligament of Treitz (left upper quadrant) to the cecum (right lower quadrant), the Ladd procedure reverses the malposition of the duodenojejunal junction (right lower quadrant) and the cecum (left upper quadrant). The mesentery is spread out over the retroperitoneum where it becomes adherent; this prevents recurrent volvulus. The appendix is removed because it often ends up in the left upper quadrant, which could impede the diagnosis of appendicitis in the future.
• Jejunoileal atresia: Surgery for jejunoileal atresia involves resection and primary anastomosis of the proximal and distal segments. A diverting ostomy is avoided if possible. As with surgery for duodenal atresia, resection or tapering of the proximal dilated segment is occasionally necessary to limit the dysmotility that occurs in grossly dilated bowel. The ileocecal valve is preserved if possible because this prevents egress of bacteria from the colon into the small intestine with resultant bacterial overgrowth and malabsorption.
• Meconium ileus
• • Calcification on scout radiography indicates that an intestinal perforation occurred in utero and spontaneously sealed; if not, the extruded meconium is walled off by adjacent intestine to form a pseudocyst.
  • These babies have meconium peritonitis and their appearance is unmistakable; a baby who is born with (as opposed to those who develop) a distended, erythematous abdomen is obvious. 
  • A laparotomy is undertaken with drainage of the meconium pseudocyst and identification of the site of the perforation, which is converted to an enterostomy.
  • In uncomplicated meconium ileus, an enterotomy with irrigation of the bowel contents may successfully loosen the meconium and permit its evacuation and closure of the enterostomy or appendicostomy. In other patients, an ostomy for diversion and access for proximal and distal irrigation with N-acetyl-cysteine (Mucomyst) may be necessary.
• Meconium plug syndrome: Operative intervention is indicated only if Gastrografin enemas are unsuccessful in loosening the meconium plug (the appearance of which is white), which permits the baby to evacuate the meconium, which is black and tarry.
• Hirschsprung disease
• • The treatment of Hirschsprung disease is primarily surgical, except in instances of enterocolitis.
  • Patients with Hirschsprung disease are treated with a colostomy which expeditiously decompresses the bowel and allows the baby to resume feedings. A colostomy remains the best procedure of choice in these patients.
  • A pull-through procedure is performed at age 3-6 months. The pull-through procedure is being performed at younger and younger ages; currently, it is performed during the newborn period in appropriate patients. Results are excellent, provided the baby does not have a history of enterocolitis, in which case recurrent enterocolitis is probable.
  • Also, not all patients with Hirschsprung disease can be decompressed and given an adequate bowel prep allowing a primary pull-through to be safely performed; a colostomy and subsequent pull-through procedure is the better option.
  • The most recent innovations include minimally invasive techniques, such as the transanal pull-through using laparoscopy in cases in which the transition zone is not located in the distal sigmoid colon.
• Imperforate anus
• • Low lesions with fistulous connections to the perianal skin or perineal body can be repaired primarily by perineal anoplasty. 
  • If the distal rectum is several centimeters above the anus or if a fistula runs from the rectum to the vagina or urethra or urinary bladder, the imperforate anus is classified as intermediate or high, and the infant should undergo a colostomy.
  • Definitive repair of the imperforate anus is by posterior sagittal anorectoplasty, in which the rectum is situated within the striated muscle complex (levator sling) and anal sphincter; this procedure allows the muscles of continence to properly function.¹¹ The ultimate outcome depends on the precision of the surgery, the presence or absence of the sacroperineal musculature, and the degree of colonic dysmotility.

Medical Therapy
 
To minimize mortality and morbidity, attention must be paid to treating the life-threatening symptoms of the obstruction while simultaneously identifying and treating the underlying cause. Intestinal obstruction generally causes fluid loss and an electrolyte imbalance, either from vomiting, in cases of proximal obstruction, or third-space sequestration of fluid within the intestine’s lumen, in more distal obstructions. Treatment begins with assessment and correction of intravascular depletion and electrolyte imbalance. Gastric intubation and decompression are performed. Intravenous antibiotics are administered because, as the bowel distends in response to increased intraluminal pressure, perfusion to the wall of the intestine diminishes (ie, the law of LaPlace), and, concomitantly, its resistance to bacterial invasion diminishes. In addition, respiratory and cardiovascular support is provided to maintain hemodynamic stability.  

Abnormalities with anatomic discontinuity obviously require surgery. Although Hirschsprung disease is a functional obstruction, it also requires surgery to relieve the obstruction. Other functional obstructions, such as meconium ileus and meconium plug syndrome, respond favorably to medical intervention. Unless a clear contraindication is noted, medical therapy should attempted in all infants prior to proceeding with surgery. A Gastrografin enema should be performed. Contrast radiography is diagnostic, and the Gastrografin enema has remarkable efficacy in loosening the sticky meconium and facilitating evacuation (>50% of cases).

Multiple enemas may be required, and the fluid must be refluxed into the terminal ileum. Gastrografin and N-acetylcysteine may also be administered by nasogastric tube to help loosen the impacted meconium. Hyperosmolar solutions (10% acetylcysteine) draw fluid into the lumen of the bowel and enhance their efficacy in expelling the thick meconium; however, they may increase the risk of perforation (reportedly 3-10%).

General postoperative care          

In the postoperative period, derangements in fluid balance, glucose metabolism, and respiratory status are common. Most infants have third-space fluid sequestration following laparotomy, and the intravenous fluid requirements are at least 1.5-times normal. By checking the patient’s heart rate and systemic blood pressure, peripheral perfusion, and urine output, the adequacy of fluid resuscitation can be determined. Serum electrolytes should be closely monitored because fluid shifts between body compartments are common and require a prompt response.

Replacement of fluid due to third-space fluid sequestration should consist of 0.5-to-normal saline. Gastric decompression decompresses the proximal bowel and facilitates healing of an intestinal anastomosis until the resumption of normal peristalsis. Respiratory support depends on the length of the surgical procedure, the depth of the anesthetic, the degree of postoperative bowel distention, which may prevent normal movement of the diaphragm, and the need for postoperative analgesia and resultant respiratory depression. The duration of antibiotics depends on the underlying bowel problem and whether fecal contamination of the peritoneal cavity has occurred. 

Following surgery for bowel obstruction, a transient ileus is invariably present, possibly prolonged by narcotic analgesia. Early initiation of total parental nutrition is indicated until bowel function permits delivery of adequate enteral nutrition. 

Cardiovascular and coagulation complications, such as shock and disseminated intravascular coagulation, may complicate the presentation of patients with intestinal ischemia or necrosis. Management of these complications may continue to challenge the clinician during the postoperative period. Also, despite resumption of peristalsis, these infants may not tolerate enteral feedings because their intestinal mucosa must regenerate before it is able to absorb nutrients. A period of trophic feeding may stimulate mucosal regeneration, and a predigested or elemental formula may be better tolerated. If the terminal ileum is resected, derangements in folate metabolism and in the enterohepatic circulation may occur. Wound care is usually straightforward, and antibiotics are not generally required beyond the immediate preoperative period.

COMPLICATIONS

Section 8 of 11  

• Authors and Editors
• Introduction
• Frequency
• Embryology
• Clinical
• Diagnostic Evaluation
• Treatment
• Complications
• Conclusions
• Multimedia
• References

Complications include the following:

• Total parenteral nutrition cholestasis and hyperalimentation hepatitis
• • When total parenteral nutrition (TPN) is required to support an infant's recovery, numerous complications may occur due to the catheter or the intravenous solution. These include problems in obtaining central venous access, migration of the catheter, and sepsis.
  • Percutaneously inserted catheters can be used successfully in this population, but have the disadvantage of inability to infuse blood products and obtain blood samples.
  • Problems caused by the TPN solution include cholestasis, liver damage, and nutritional deficiencies. Meticulous attention to the composition parenteral nutritional may minimize these long-term complications.
  • A fish-oil lipid emulsion is under investigational use in the United States; it appears to minimize the liver toxicity that is seen with traditional soybean oil lipid formulations.¹² Normal oropharyngeal activities such as sucking should be encouraged or oral aversion may develop.
• Postoperative stricture and adhesions
• • Postoperative adhesions occur between loops of intestine and between the intestine and the peritoneal surface of the abdominal cavity. They may be caused by peritonitis or by the surgical procedure. Anastomotic stricture may be at the suture line.
  • A recent study of 1541 children who had intestinal surgery showed an adhesion rate of almost 10% in the operative site and a rate of approximately 5% elsewhere.¹³
  • Gentle manipulation of the bowel, limiting contamination of the peritoneal cavity, and meticulous technique in creating an intestinal anastomosis may limit postoperative strictures and adhesions.
• Decreased gut motility
• • Poor motility is often observed following bowel resection for intestinal obstruction.
  • Chronic dilatation of the intestine proximal to the obstruction may alter normal peristalsis across that segment of bowel, even after the obstruction has been relieved.
  • Interruption of vagal neuroenteric pathways by an atresia or surgical anastomosis may also contribute to abnormal intestinal motility.
  • Two promotility pharmacologic agents are used in this age group (ie, metoclopramide and erythromycin). Randomized controlled trials of these agents have produced variable results compared with placebo, and each has side effects that may render them unacceptable choices. Many clinicians use one or the other based on anecdotal reports or personal experience. 
• Malabsorption
• • Short-gut syndrome results when the length of intestine that remains postoperatively cannot sustain normal absorption of nutrients.
  • The normal length of the small bowel in a term infant is approximately 250 cm; in adults, the normal length is 600-800 cm. The estimated minimum jejunoileal length for sufficient bowel function in a term infant is 75 cm.
  • Resection of more than 60% of the small bowel or resection that removes crucial anatomic segments such as the ileocecal valve predisposes the infant to malabsorption, resulting in failure to grow and failure to develop normally.
  • Bacterial overgrowth in the remaining intestine can also contribute to malabsorption and subsequent failure to thrive. 
  • Every effort is made intraoperatively to preserve bowel length.
  • Some children with short-gut syndrome manage to survive with the aid of parenteral nutrition, predigested formulas, and pharmacologic agents used to slow motility.
  • Probiotics have been shown in some studies to normalize bowel flora and improve outcomes.
  • Bowel-lengthening procedures, creation of intraluminal valves, and manipulation of bowel recovery with nutritional and hormonal treatments can help wean the patient with short-gut syndrome from dependence on parenteral nutrition.
  • Newer techniques, such as the serial transverse enteroplasty (STEP) procedure, may offer improved bowel function and length in some patients.
  • Patients with volvulus and infarction of the entire midgut or with multiple intestinal atresias may not have enough bowel length to survive. Difficult ethical decision must be made whether to proceed with intestinal resection and whether to continue life-support.
  • Small-bowel transplant, with or without other viscera such as liver and pancreas, is being performed in select centers in the United States, with varying results.

Complications associated with specific conditions are as follows:

• Malrotation
• • Complications depend on the condition of the bowel at the time of presentation and surgery.
  • The most feared complication is necrosis of the entire bowel and death. 
  • Reducing the volvulus and performing the Ladd procedure before closing the abdomen is helpful, as is planning a second-look procedure the following day.
  • Sometimes, bowel that appeared necrotic proves viable.
  • If a massive small bowel resection is performed, a high jejunostomy is created, which results in the loss of large volumes of fluid and electrolytes and makes formulation of TPN solutions more complex.
  • After a few weeks, the ostomy can be closed, which places the remaining colon into the intestinal stream and simplifies fluid and electrolyte management; however, the baby then experiences diarrhea and its attendant complications.
• Duodenal atresia: In straightforward cases repaired with an end-to-end anastomosis, the most frequent complication is delayed emptying of the proximal duodenum. Only patience is required because the anastomosis usually functions normally by the third postoperative week. Revising the anastomosis is rarely necessary.
• Jejunoileal atresia
• • In uncomplicated small bowel atresia, as in duodenal or jejunoileal atresia obstructions, complications are very uncommon. 
  • The intestinal atresia occurs as a result of intrauterine ischemia and necrosis of a segment of intestine.
  • The ends of the intestine heal but are no longer in continuity. 
  • If the bowel is in good condition at birth, a primary repair is possible. 
  • Small bowel atresia may occur in conjunction with gastroschisis. 
  • If the exposed bowel is thick and matted, then the atresia may not be apparent for several weeks after surgical repair of the gastroschisis. 
  • Failure of normal bowel motility and function by 4 weeks should prompt a contrast study to look for evidence of obstruction and atresia.
  • Meconium ileus and plug syndrome: Complications of treating babies with meconium plug syndrome are extremely rare. Babies with meconium ileus and cystic fibrosis may require enzyme replacement, although predigested or elemental formulas are used.
• Hirschsprung disease
• • Infants with Hirschsprung disease who are not diagnosed and treated during the newborn period may present with enterocolitis; this is suggested by abdominal distention and explosive diarrhea, especially following a rectal examination with dilatation of the anal sphincter.
  • Sepsis may also occur due to compromise of the integrity of the massively dilated proximal bowel, which allows bacterial mucosal translocation and invasion into the intestinal vascular supply.
  • Management of Hirschsprung enterocolitis includes intravenous fluids and antibiotics, along with irrigation of the distal colon using a rectal tube inserted through the anus.
  • Stool studies may be positive for the Clostridium difficile toxin, mandating the use of oral vancomycin or metronidazole.
  • A diverting colostomy may be necessary, if rectal irrigations fail to control recurrent episodes. 
• Imperforate anus
• • Babies who have low imperforate anus typically suffer from constipation, although the anus is widely patent.
  • The major complication in babies with high imperforate anus is incontinence, which occurs either because the rectum is improperly situated within the striated muscle complex or because the muscle complex is deficient.
  • Other minor complications may occur, such as prolapse of rectal mucosa through the neoanus, but this is easily repaired surgically.
  • Depending on the motility of the colon, babies with high imperforate anus may suffer from either diarrhea or constipation.
  • Pena has devised a bowel-training program that is extremely helpful in the management of these patients.¹¹

Prognosis

• Malrotation
• • The morbidity and mortality from malrotation and midgut volvulus are directly related to the magnitude of bowel loss.
  • The mortality rate may be as high as 65% if 75% or more of the small bowel is found to be necrotic.
  • Survivors may develop short-gut syndrome, with the attendant complications of malabsorption and malnutrition.
  • The Ladd procedure corrects the partial duodenal obstruction and prevents midgut volvulus but does not change the intestinal dysmotility, which may be associated with malrotation; hence dysmotility symptoms such as constipation may persist. 
• Duodenal atresia: This has a good prognosis for normal bowel function.
• Jejunoileal atresia: Long-term outcomes are generally excellent if sufficient bowel is present for absorption and growth. 
• Meconium ileus: The long-term outlook depends on whether or not the infant has cystic fibrosis. If the infant does have cystic fibrosis, bowel function and nutritional status depend on the severity of the cystic fibrosis and the effectiveness of its management. If cystic fibrosis is not present, outcome is excellent.
• Meconium plug syndrome: Most patients with meconium plug syndrome have an excellent outcome following relief of the obstruction, and no further intervention is required. If laparotomy is necessary to evacuate the meconium, another diagnosis should be considered, such as Hirschsprung disease, which is associated with meconium plug syndrome in 4% of patients. A rectal biopsy should be performed in these cases.
• Hirschsprung disease
• • The outcome for most patients with Hirschsprung disease is good both in terms of continence and stool frequency; however, bowel dysmotility, manifested by refractory constipation or recurrent episodes of enterocolitis, may persist despite removal of the aganglionic colon and rectum.
  • A recent report of 26 patients in a case-controlled investigation suggests that Doppler-flow studies of the splanchnic circulation prior to surgery may predict the likelihood of normal bowel function postoperatively.¹⁴
  • Long-term complications may include bowel obstruction from adhesions or internal hernia, acquired aganglionosis, disordered motility in the proximal colon or small bowel, internal sphincter achalasia, or functional megacolon caused by stool-holding behavior. The latter children require complex interdisciplinary care to ensure an adequate quality of life, even after a successful pull-through procedure.¹⁵
  • Imperforate anus: Outcome depends on the precision of the surgery, the severity of the sacral and perineal musculature deficiency, and the degree of colonic dysmotility.

CONCLUSIONS

Section 9 of 11  

• Authors and Editors
• Introduction
• Frequency
• Embryology
• Clinical
• Diagnostic Evaluation
• Treatment
• Complications
• Conclusions
• Multimedia
• References

Additional educational resources may be obtained by accessing eMedicine’s Esophagus, Stomach, and Intestine Center and eMedicine’s patient education article Constipation in Children.

MULTIMEDIA

Section 10 of 11  

• Authors and Editors
• Introduction
• Frequency
• Embryology
• Clinical
• Diagnostic Evaluation
• Treatment
• Complications
• Conclusions
• Multimedia
• References

Media file 1:  Malrotation.
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Media file 2:  Malrotation with volvulus of the proximal small intestine coiled around superior mesenteric vessels.
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Media file 3:  Duodenal atresia. Note double-bubble sign and narrowing in second portion of the duodenum.
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Media file 4:  Jejunal atresia. Note the sharp transition between proximal dilated jejunum and distal unused intestine at point of atresia.
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Media file 5:  Jejunal atresia. Ischemic compromise of proximal segment.
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Media file 6:  Meconium plug. Contrast enema reveals dilated colon proximal to plug and can be therapeutic to relieve obstruction.
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Media file 7:  Imperforate anus.
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Media file 8:  Algorithm for the diagnosis of neonatal intestinal obstruction.
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REFERENCES

Section 11 of 11

• Authors and Editors
• Introduction
• Frequency
• Embryology
• Clinical
• Diagnostic Evaluation
• Treatment
• Complications
• Conclusions
• Multimedia
• References

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