Intestinal atresia

INTRODUCTION — An atresia is a congenital defect of a hollow viscus that results in complete obstruction of the lumen. Intestinal atresia is one of the most frequent causes of bowel obstruction in the newborn and can occur at any point in the gastrointestinal tract. Approximately one-half of the cases involve the duodenum.

The outcome of intestinal atresia following surgical repair is very good. In general, morbidity and mortality depend upon associated medical conditions such as prematurity or cystic fibrosis, other congenital anomalies, the complexity of the lesion, and surgical complications.

Atresia and stenosis of the small and large intestine are reviewed here. Esophageal atresia and anorectal malformations, including rectal atresia, are discussed separately. (See "Functional constipation in infants, children, and adolescents: Clinical features and diagnosis", section on 'Other causes'.)

INCIDENCE — The reported incidence of intestinal atresia ranges from 1.3 to 3.5 per 10,000 live births [1-4], of which approximately 20 percent are associated with a chromosomal anomaly. The incidence and associated anomalies vary by anatomical site:

●Duodenal atresia occurs in approximately 1 infant per 10,000 births, and represents up to 60 percent of small intestinal atresias [1,5]. Approximately 30 percent of infants with duodenal atresia have a chromosomal anomaly, primarily Down syndrome. (See "Down syndrome: Clinical features and diagnosis".)

●Jejunal or ileal atresia occurs in approximately 0.7 per 10,000 births, each representing approximately 20 percent of small intestinal atresias [1].

●Colonic atresia is the least common type; the incidence is approximately 0.25 per 10,000 births, or 7 to 10 percent of cases [6,7].

CLASSIFICATION AND PATHOGENESIS — Interruption of the normal development of the gastrointestinal tract may result in intestinal atresia. The mechanism varies with the segment of bowel that is affected.

Duodenal atresia — The duodenum is derived partly from the embryonic foregut and partly from the midgut. During early gestation (weeks six and seven), portions of the intestinal tract become occluded as the endodermal epithelium proliferates. Patency is restored as recanalization occurs during weeks eight to ten. Duodenal atresia is thought to result from failure of the bowel to recanalize during this period. (See "Overview of the development of the gastrointestinal tract".)

Jejunal and ileal atresia — Jejunoileal atresia has been classified into four types based upon anatomic characteristics [8-10]. Type III is the most common, and type I is the least common form (figure 1) [11].

Jejunal and/or ileal atresia typically is an acquired lesion thought to result from vascular disruption leading to ischemic necrosis of a segment of the fetal intestine. In general, the more proximal the vascular disruption, the more extensive the defect in the bowel (figure 1). Because the fetal bowel is sterile, the necrotic tissue is resorbed, leaving blind proximal and distal ends, often with a gap in the mesentery. This type of atresia has been reproduced in experimental animals by ligation of mesenteric blood vessels [8,12,13]. Causes of the vascular disruption in the human fetus include segmental or midgut volvulus, intussusception, internal hernia, and interruption of the segmental mesenteric blood supply [14].

Some cases are caused by underlying intestinal pathology, which interrupts the blood supply to the gut during fetal life. Additionally, processes that contribute to thrombosis may also contribute to compromise of fetal intestinal vascular supply. Thus, risk factors include:

●Cystic fibrosis – A fetus with cystic fibrosis is predisposed to segmental volvulus due to inspissated meconium, and this may develop into a jejunal or ileal atresia [15].

●Gastroschisis – Gastroschisis is frequently complicated by intestinal atresias, 11 percent of cases in one series [16]. The extent ranges from a simple localized lesion to the rare occurrence of atresia of the entire herniated bowel [17,18]. The atresia is thought to be caused by strangulation of the intestine by the anterior abdominal wall fascial defect or by volvulus of the herniated bowel [18,19]. As the necrotic bowel is resorbed, the proximal bowel seals off, forming an atresia that is usually in the proximal jejunum. The abdominal wall defect may also close as the herniated bowel disappears. The prognosis of this variant is poor because the loss of almost the entire small bowel results in severe short gut syndrome. (See "Gastroschisis".)

●Midgut volvulus – Type IIIB or apple peel atresia (figure 1) may result from a volvulus of all or part of the midgut during gestation [7]. As a result, much of the gut supplied by the superior mesenteric artery disappears, leaving a high jejunal or occasionally even a distal duodenal atresia. The distal ileum winds around a thin vascular stalk, which usually consists of the left branch of the ileocolic artery. A large gap in the mesentery is present along with intestinal malrotation and a microcolon. (See "Intestinal malrotation in children".)

●Medications – Maternal use of vasoconstrictive medications may contribute to interruption of mesenteric blood flow. This was illustrated by a case-control study in which combined exposure to vasoconstrictive drugs (including methylenedioxymethamphetamine, pseudoephedrine, and ephedrine) and cigarette smoking in the first trimester of pregnancy nearly tripled the risk of small intestinal atresia (odds ratio 2.8) [20]. The risk was increased 4.2 times in women who used vasoconstrictive drugs and smoked ≥20 cigarettes per day.

●Inherited thrombophilia leading to spontaneous thrombosis — In one study, the factor V Leiden mutation and a polymorphism of the factor VII gene, both of which are risk factors for thrombosis, occurred more often in newborns with intestinal atresia than in the general population [21]. However, heterozygous mutations in these genes are unlikely to predispose to fetal arterial thrombosis, and there is no correlation between the incidence of intestinal atresias and these thrombophilias across populations [22]. Thus, there is no evidence to support routine screening for thrombophilias in infants with intestinal atresia or their mothers. Other thrombophilias such as antithrombin deficiency have stronger associations with thrombosis risk, but this is uncommon, and an association with intestinal atresia has not been explored. (See "Thrombophilia testing in children and adolescents".)

●Genetic factors – Genetic factors may play a role in a few cases. Although most cases of intestinal atresia are sporadic, familial cases of apple peel atresia have been reported, suggesting a genetic component [23]. A rare familial syndrome of multiple intestinal atresias (Type IV) has been described (MIM #243150). Some cases are associated with either mild or severe combined immunodeficiency (SCID), and are attributable to mutations in the TTC7A gene [24-26]. Another familial syndrome consists of jejunal atresia with ocular chamber abnormalities and microcephaly (Strømme syndrome, MIM #243605) [27].

Colonic atresia — The mechanism of colonic atresia is unknown, but most authorities believe it is the same as for small bowel atresia. Colonic atresia may occur in combination with Hirschsprung disease [28].

CLINICAL FEATURES — Intestinal atresia may present with suspicious findings on prenatal ultrasound, or with clinical symptoms that develop shortly after birth.

Prenatal findings — Less than one-half of infants with intestinal atresias are identified by prenatal ultrasound examination, based on signs of intestinal obstruction. If an abnormality is detected in prenatal ultrasound, this knowledge enhances clinical care because infants can be treated promptly after birth, reducing the risk of complications of poor feeding and vomiting, including volume depletion, electrolyte imbalance, and aspiration pneumonia. However, routine prenatal ultrasound has low sensitivity for detecting gastrointestinal atresias, especially because sonographic signs of obstruction may not become evident until the late second trimester, after the typical time of a fetal anatomic survey. The sensitivity tends to decrease for more distal lesions: in one study, prenatal ultrasound detected approximately 50 percent of duodenal obstructions, 40 percent of jejunal or ileal obstructions, and 30 percent of colonic obstructions [29]. In addition to low sensitivity, ultrasound is not able to accurately identify the number and location of obstructions and has limited ability for assessing the viability of unobstructed distal bowel, and many of the findings are nonspecific [30]. Plain radiographs and contrast examinations should be obtained after birth to confirm the diagnosis and better define the atresia, if present. (See "Prenatal diagnosis of esophageal, gastrointestinal, and anorectal atresia", section on 'Diagnostic performance of ultrasound imaging'.)

Duodenal atresia usually has the characteristic double bubble appearance on prenatal ultrasound (image 1), which is similar to the postnatal abdominal radiograph (image 2). This finding is due to dilation of the stomach and the first part, and often the second part, of the duodenum. Polyhydramnios develops in up to 50 percent of cases, probably because the intestinal obstruction interferes with the gastrointestinal absorption of amniotic fluid swallowed by the fetus [31]. These findings typically develop in the mid- to late second trimester. Duodenal atresia may be difficult to distinguish from choledochal cyst by antenatal ultrasonography but may be further delineated by fetal magnetic resonance imaging. Intestinal atresia associated with gastroschisis is characterized by bowel dilation (>10 mm) on antenatal ultrasound and is associated with increased rates of preterm delivery and overall mortality [19]. (See "Prenatal diagnosis of esophageal, gastrointestinal, and anorectal atresia", section on 'Duodenal atresia' and "Gastroschisis".)

Jejunal and ileal atresias may present with polyhydramnios, ascites, dilated bowel loops, and increased bowel echogenicity [32-34]. Lesions in the proximal small bowel (jejunum) are more likely to be detected compared with distal lesions (ileum) because they result in more severe dilation of the proximal bowel due to continuing fetal swallowing of amniotic fluid, which outpaces intestinal absorption [35]. (See "Prenatal diagnosis of esophageal, gastrointestinal, and anorectal atresia", section on 'Jejunal and ileal atresia'.)

Colonic atresias are unlikely to be detected on prenatal ultrasound unless they are associated with additional more proximal atresias or other congenital anomalies. (See "Prenatal diagnosis of esophageal, gastrointestinal, and anorectal atresia", section on 'Colonic atresia'.)

Postnatal presentation and associated anomalies — Intestinal atresia presents with symptoms and signs of intestinal obstruction, including abdominal distension and vomiting. Many patients fail to pass meconium, which is a nonspecific sign that varies depending on the level of the intestinal obstruction. Vomiting usually begins in the first 24 to 48 hours after birth. Most infants with intestinal atresia are born at or near term. Those with duodenal atresia or other proximal obstruction tend to be small for gestational age [36].

The type and timing of these symptoms vary with the location of the obstructing lesion:

●Duodenal atresia – Infants with duodenal atresia or stenosis typically have gastric distension and vomiting that is often but not always bilious. Affected infants may pass meconium. In approximately 10 to 20 percent of cases, duodenal atresia is associated with malrotation [7,37].

Duodenal atresia is an isolated finding in one-third to one-half of cases. In approximately 30 percent of cases it is associated with Down syndrome, or occasionally with another genetic anomaly [36]. Conversely, approximately 2.5 percent of patients with Down syndrome have duodenal atresia or stenosis [6,38]. (See "Down syndrome: Clinical features and diagnosis".)

Even among infants with a normal karyotype, duodenal atresia is often associated with other structural malformations, including cardiac, gastrointestinal (biliary atresia, agenesis of the gallbladder, esophageal atresia, annular pancreas [39]), renal, limb, and vertebral anomalies. In one study, among infants with duodenal atresia and a normal karyotype, 12 percent had cardiac anomalies, 8 percent had gastrointestinal anomalies, and 7 percent had urinary system anomalies [1].

●Jejunal and ileal atresia – Affected infants typically develop abdominal distension and vomiting within the first two days after birth [7]. Emesis usually is bilious. Most infants with bowel obstruction fail to pass meconium. However, meconium may remain in the distal bowel beyond the obstruction. As a result, newborns with jejunal or ileal atresia may pass meconium.

A minority of infants with jejunal or ileal atresias have associated chromosomal anomalies (<5 percent) [1]. Jejunal atresia is sometimes associated with other major malformations (eg, cardiac malformations, 10 to 20 percent, and other gastrointestinal malformations such as gastroschisis), but this is rare in ileal atresias [36,40]. Jejunal or ileal atresia is also associated with cystic fibrosis (10 of 83 infants in one series) [40], due to inspissated meconium and volvulus during fetal life, as discussed above. (See 'Jejunal and ileal atresia' above and "Cystic fibrosis: Clinical manifestations and diagnosis".)

Some children with jejunal or ileal atresia have underlying immune dysfunction, including mild or severe combined immunodeficiency (SCID) [26]. In a small case series from a referral center, approximately one-half of children with single or multiple atresias had lymphopenia/low cluster of differentiation (CD) counts, more than one-third had hypogammaglobulinemia, and infectious complications were common [41]. (See 'Jejunal and ileal atresia' above.)

●Colonic atresia – Like other types of bowel obstruction, colonic atresia presents with marked abdominal distension, failure to pass meconium, and bilious vomiting. Because the obstruction is distal, symptoms may appear later than with more proximal lesions, although usually within the first three days after birth.

Colonic atresia typically affects otherwise normal newborns. In rare cases, it may be associated with gastroschisis, skeletal abnormalities, other intestinal atresias, and Hirschsprung disease [28,42]. Cases have been reported with congenital varicella syndrome [43].

In infants with partial intestinal obstruction (stenosis or web), the presentation may be more insidious, with obstructive symptoms developing days or weeks after birth. This is most common in children with Down syndrome and duodenal stenosis, who sometimes present later in infancy or later with poor feeding and failure to thrive. In some cases the symptoms are intermittent, causing further delay in diagnosis.

Intestinal obstruction reduces enteric excretion of bilirubin and often results in jaundice. Serum bilirubin concentration frequently is higher with small than with large bowel obstruction. (See "Unconjugated hyperbilirubinemia in neonates: Etiology and pathogenesis".)

POSTNATAL EVALUATION — Intestinal atresia should be suspected in a newborn with signs of intestinal obstruction. These include abdominal distension, bilious vomiting, and failure to pass meconium.

History — A complete prenatal history should be obtained. This should include gestational age, family history, medications, drug use, and pregnancy complications. For infants presenting with signs or symptoms of intestinal obstruction, important elements include:

●Detailed results of prenatal screening, especially:

•Sonographic signs of obstruction such as polyhydramnios and dilated bowel loops. A variety of conditions are associated with fetal polyhydramnios, including small intestine atresias and other congenital anomalies and maternal diabetes mellitus. (See 'Prenatal findings' above and "Polyhydramnios: Etiology, diagnosis, and management in singleton gestations", section on 'Conditions associated with polyhydramnios'.)

•Evidence of any other congenital anomalies, including maternal screening tests or sonographic signs of Down syndrome. (See 'Postnatal presentation and associated anomalies' above and "Down syndrome: Overview of prenatal screening", section on 'Choice of screening test in singleton pregnancies'.)

●Family history of cystic fibrosis, congenital anomalies (especially gastrointestinal anomalies), or fetal loss.

●Perinatal history:

•Any problems with the labor or delivery

•Infant's gestational age

•Timing of onset of abdominal distention and vomiting, if the emesis was bilious or nonbilious, and whether the infant was fed

•Whether and when the infant has passed meconium

Physical examination — A complete physical examination should be performed, including an assessment of severity of illness. (See "Assessment of the newborn infant", section on 'Physical examination'.)

Important elements for infants presenting with signs and symptoms of intestinal atresia are:

●Respiratory compromise (eg, due to aspiration or massive abdominal distension, causing elevation of the diaphragm).

●Signs of volume depletion (eg, oliguria, dry mucus membranes, poor skin turgor, and sunken fontanelle). Vomiting in a newborn infant can quickly lead to dehydration, and may require intravenous fluid replacement.

●Jaundice – This is a consequence of a small intestinal atresia, and may be exacerbated by dehydration.

●Congenital anomalies – In particular, signs of chromosomal abnormalities such as Down syndrome and congenital heart defects. Infants with intestinal atresias often have a chromosomal abnormality or other congenital anomalies, especially for proximal atresias. (See 'Postnatal presentation and associated anomalies' above.)

●Perineum – Examine for location and patency of the anus since anal atresia is sometimes associated with more proximal atresias.

●Abdomen – The appearance of the abdomen may suggest the location of the atresia. If the obstruction is distal, the abdomen is often markedly distended, with visible or palpable loops of bowel. Proximal obstruction may result in little distention. The abdomen should be palpated to detect the presence of a mass. Abdominal tenderness may indicate peritonitis. The presence or absence of bowel sounds should be noted. The inguinal area should be examined for signs of an inguinal hernia.

Imaging — Conventional (without contrast, or "plain") radiographs of the abdomen should be obtained in all infants with signs of bowel obstruction, as outlined in this appropriateness criteria table for newborns with bilious vomiting.

If intestinal obstruction was diagnosed prenatally on ultrasound, plain radiographs should be performed after birth to confirm the diagnosis. If the plain films show signs of obstruction, contrast studies usually should be performed to help localize and establish the cause of the obstruction before proceeding to surgery, unless urgent intervention is indicated because of pneumoperitoneum or signs of shock or peritonitis. (See 'Contrast radiographs' below.)

Abdominal radiograph — A supine antero-posterior abdominal radiograph and either upright, lateral decubitus, or cross-table lateral films should be obtained in all cases of suspected neonatal intestinal obstruction (algorithm 1). The main purpose is to confirm the presence of obstruction, estimate the segment affected (ie, proximal or distal bowel), and assess for perforation as evidenced by pneumoperitoneum. In some cases, the radiograph gives clues to the underlying pathology:

●Pneumoperitoneum indicates an intestinal perforation and requires emergent laparotomy.

●A "double bubble" sign (image 2) is caused by dilation of the stomach and proximal duodenum and strongly suggests duodenal atresia; distal gas is absent. This sign may be obscured by excessive fluid in the stomach. In that case, a repeat abdominal radiograph after aspiration of the stomach through a nasogastric tube and injection of 30 to 60 mL of air may confirm the diagnosis. Although duodenal atresia is the most common cause of high-grade duodenal obstruction in neonates, other problems such as malrotation (with or without volvulus) or jejunal duplication can present with similar findings on plain radiograph [44-46]. Malrotation should be particularly suspected if there is any air distal to the "double bubble" on plain films. A double bubble with distal air also may be caused by a perforated duodenal web, or by duodenal atresia in association with a bifid bile duct, but these causes are rare [7,37].

●An air-fluid level in the duodenum is nonspecific, but may be caused by duodenal atresia or duodenal stenosis, which causes only partial obstruction. Malrotation and volvulus may also cause duodenal dilation with an air fluid level.

●Dilated loops of bowel with air-fluid levels are characteristic of jejunal or ileal atresia. The bowel distension is more obvious in infants with distal small intestinal atresias.

●Intraperitoneal calcifications suggest prenatal perforation of the gut and meconium peritonitis. The most likely cause is meconium ileus due to cystic fibrosis. Similar findings may be seen on prenatal or postnatal ultrasound, if performed.

Contrast radiographs — Selection of further imaging studies depends upon the results of the plain radiograph (algorithm 1):

●Upper gastrointestinal contrast study – If the plain radiograph shows signs of intestinal obstruction but no evidence of perforation, most infants should be further evaluated with an upper gastrointestinal contrast study. The main purpose is to rule out malrotation with midgut volvulus, which is a true surgical emergency. If surgery will be delayed because of extreme prematurity, metabolic disturbance, or another anomaly, it is particularly important to perform contrast radiography to rule out malrotation.

Signs of malrotation on upper gastrointestinal contrast studies include low-lying or displaced duodenojejunal junction and coiling of the bowel with partial or complete mechanical obstruction. Infants with this combination of findings should be taken urgently to surgery. At surgery for malrotation, intrinsic bowel obstruction should always be excluded by passing saline or a catheter through the duodenum into the upper jejunum because malrotation may be associated with duodenal atresia or stenosis. (See "Intestinal malrotation in children", section on 'Clinical presentation'.)

If the plain radiograph shows a classic double bubble sign and no distal gas (image 2), the diagnosis of duodenal atresia is very likely. In this case, contrast radiography is not essential, provided that the infant is taken to surgery promptly for definitive diagnosis and repair. If contrast radiography is performed, duodenal atresia is demonstrated by a dilated stomach and duodenum and lack of distal bowel gas (image 3). If the radiograph shows complete obstruction, the contrast should be emptied from the stomach immediately after the study.

●Contrast enema – Unless the radiograph and upper gastrointestinal contrast study are diagnostic of duodenal atresia or malrotation with midgut volvulus, a contrast enema should be performed. The goal is to identify the site of atresia or to identify another cause of obstruction such as Hirschsprung disease or meconium ileus. In most cases, barium can be used to perform the contrast enema. However, if obstruction is thought to be due to meconium ileus and the infant is adequately hydrated and clinically stable, use of water-soluble contrast can be both diagnostic and therapeutic [47].

In cases of small bowel atresia, the contrast enema often reveals a microcolon, resulting from lack of use of this portion of the bowel. In small bowel atresia, it is not possible to reflux contrast medium into the dilated loops of more proximal bowel. A microcolon may also be present in meconium ileus. In meconium ileus, water-soluble contrast medium given by enema can, in some cases, be advanced retrograde through the microcolon into dilated loops of ileum containing the typical intraluminal filling defects caused by inspissated meconium, thereby ruling out an atresia. A contrast enema can also reveal evidence of colonic atresia or Hirschsprung disease. (See "Congenital aganglionic megacolon (Hirschsprung disease)".)

Laboratory studies — In a symptomatic infant, laboratory studies that should be obtained to help assess the infant's clinical condition include:

●Complete blood count and differential, total, and direct bilirubin

●Serum electrolyte concentrations, blood urea nitrogen (BUN), and creatinine – To evaluate fluid and electrolyte status

●Blood culture – If sepsis is suspected

●Pulse oximetry, and possibly arterial blood gas measurements – If the infant shows signs of respiratory distress

●Blood type and antibody screen and coagulation studies (prothrombin time and partial thromboplastin time) – In preparation for surgery

Evaluation for other congenital anomalies — Other studies may be required to evaluate the infant for associated congenital anomalies [48]. In some cases, testing should occur prior to surgery.

●Echocardiogram – For infants with duodenal atresia, and particularly for those with Down syndrome, to evaluate for associated cardiac malformations. This should be done prior to proceeding to laparotomy.

●Chest radiograph (anterior-posterior and lateral) - For infants with any small intestinal atresia, to evaluate for vertebral anomalies.

●Renal ultrasound – For infants with duodenal atresia, to detect associated renal anomalies.

●Rectal biopsy – For infants with duodenal atresia and suspicion for Hirschsprung disease, including any infant with Down syndrome. (See "Congenital aganglionic megacolon (Hirschsprung disease)".)

●Cystic fibrosis mutation testing – For infants with small bowel atresia and meconium plugs proximal to the atresia. If this screen does not detect a mutation causing cystic fibrosis, a sweat test should be obtained. (See "Cystic fibrosis: Clinical manifestations and diagnosis".)

DIAGNOSIS — The possibility of intestinal atresia is suspected based upon findings on prenatal ultrasound, or when an infant presents with symptoms of intestinal obstruction during the first few hours or days of life. These include abdominal distension, vomiting (usually bilious), and sometimes failure to pass meconium.

The diagnosis of intestinal obstruction is confirmed by plain radiography. A proximal obstruction (duodenal atresia) causes a classic double bubble sign due to dilation of the stomach and proximal duodenum, with absent distal gas. A more distal obstruction (as in jejunal or ileal atresia) usually causes dilated loops of small bowel with air-fluid levels. (See 'Abdominal radiograph' above.)

The diagnosis of intestinal atresia is usually confirmed by contrast radiographs, followed by direct examination at surgery. Contrast radiographs are important to differentiate intestinal atresia from other causes of intestinal obstruction such as meconium ileus, Hirschsprung disease, and malrotation. They also serve to identify the exact location and extent of the atresia(s), which determine surgical management and prognosis. (See 'Contrast radiographs' above.)

Differential diagnosis — In addition to intestinal atresia, the differential diagnosis of neonates who present with symptoms and signs of intestinal obstruction includes (table 1):

●Malrotation with volvulus (see "Intestinal malrotation in children")

●Hirschsprung disease (see "Congenital aganglionic megacolon (Hirschsprung disease)")

●Meconium ileus (see "Cystic fibrosis: Overview of gastrointestinal disease", section on 'Meconium ileus')

These disorders usually can be distinguished by contrast radiographs. A rectal biopsy is needed to confirm the diagnosis of Hirschsprung disease.

TREATMENT — The treatment of intestinal atresia consists of initial preoperative management followed by surgical correction.

Initial management — Patients with intestinal obstruction should have feedings withheld and a nasogastric or orogastric tube placed to suction. Intravenous hydration should be provided and abnormalities in fluid and electrolyte balance corrected.

If the infant is ill, and malrotation with midgut volvulus has been excluded by contrast radiography, immediate surgery for intestinal atresia may not be indicated. Continued decompression of the gastrointestinal tract with an orogastric or nasogastric tube and optimization of the patient's metabolic, cardiac, and/or respiratory abnormalities should be completed before surgical repair of the intestinal atresia. Timing of the repair is balanced by the risks of deferring surgery, which include vomiting and aspiration, sepsis, and complications of prolonged total parenteral nutrition.

Surgical approach — The surgical approach depends upon the site of the atresia. In every case, the possibility of a second or multiple atresias should be considered. With a proximal obstruction, distal atresias may be overlooked at operation, especially if they are not associated with a gap in the bowel or mesentery. Routine perioperative antibiotics should be given.

Duodenal atresia — Duodenal atresia may be approached through a transverse right upper quadrant incision or laparoscopically. The best and safest procedure is an end-to-side or side-to-side duodenoduodenostomy. A duodenojejunostomy is also acceptable. During surgery, a small catheter is passed into the distal bowel. Either air or saline should be injected through the entire small bowel to rule out additional stenoses or atresias.

In cases of stenosis or atresia due to a persistent membrane, a duodenoduodenostomy is often the operation of choice. Often, excision of the obstructing web may not be feasible, as there is risk of injury to the ampulla of Vater, which is typically in close proximity to the membrane.

Jejunal and ileal atresia — Jejunal and ileal atresias can be approached through a transverse incision below or just above the umbilicus. Some surgeons prefer a transumbilical approach to minimize the scar from the incision. Primary repair usually is best [49]. In most, a simple end-to-end or end-to-back anastomosis can be made [50].

In patients with jejunal atresia, the proximal segment of bowel usually becomes dilated due to peristalsis proximal to the obstruction. This dilated segment may cause technical difficulties with the anastomosis. In addition, it may lead to functional obstruction after the repair due to ineffective peristalsis, which may result because the dilation prevents apposition of the bowel mucosa as peristaltic waves pass through it and because muscle activity is poorly coordinated. Therefore, in order to minimize dysfunction at the site of the anastomosis, some surgeons taper or resect the most dilated proximal bowel.

Technique to restore intestinal continuity depends on anatomy. Primary repair is preferred if multiple atresias are present and care is taken to preserve intestinal length to avoid short bowel syndrome. In cases with short segments between atretic lesions, it may be preferable to resect the entire section of involved bowel rather than perform multiple anastomoses, provided that this will leave an adequate length of bowel. The use of transluminal stent to facilitate multiple anastomoses has been successfully described in cases where resection of intervening atretic segments will lead to short gut syndrome [51]. Adequate bowel length is considered to be ideally more than 75 cm, although 30 cm with the ileocecal valve may be adequate in some children. (See "Management of short bowel syndrome in children".)

Small bowel atresia and gastroschisis — There are several approaches to the management of small bowel atresia associated with gastroschisis. A majority of patients undergo reduction of bowel and primary closure of the abdominal wall defect, with continued orogastric or nasogastric decompression of the proximal intestine and delayed repair of intestinal atresia to permit resolution of inflammation. A primary repair can be performed at the time of reduction of the bowel and closure of the abdominal wall if intestinal inflammation appears limited. A third approach is to make a stoma at the time of abdominal wall repair and defer reanastomosis of the bowel until the infant is older [52].

Colonic atresia — Primary repair often is technically feasible in colonic atresia. If this approach is taken, we suggest obtaining a suction rectal biopsy prior to the primary repair, to rule out Hirschsprung disease. However, a better approach may be to exteriorize the proximal colon as a colostomy and defer anastomosis until the child is several months of age [53]. This approach allows time for a rectal biopsy to rule out Hirschsprung disease. It may preserve bowel length by allowing the proximal colon to shrink back to a more normal size and to recover its tone. This may avoid unnecessary resection of the proximal colon and preserve its ability to absorb salt and water. Most babies thrive with a colostomy and can be discharged earlier from the hospital than with a primary repair.

Postoperative care — Following surgery, intravenous hydration and nasogastric or orogastric drainage should be provided until bowel function returns. In most cases, total parenteral nutrition is started and continued until adequate enteral or oral feeding is established.

Most infants recover uneventfully following repair of intestinal atresia. Repair of duodenal atresia may be complicated by delayed emptying of the duodenum. Reoperation is indicated only when radiographic studies demonstrate obstruction, but should not be attempted for at least three weeks following the initial surgery.

Patients with atresia associated with meconium ileus due to cystic fibrosis require treatment for cystic fibrosis. (See "Cystic fibrosis: Overview of gastrointestinal disease" and "Cystic fibrosis: Overview of the treatment of lung disease".)

PROGNOSIS — The prognosis for intestinal atresia is very good. Most of the mortality occurs in infants with medical conditions such as prematurity or respiratory distress syndrome, associated anomalies, or complications such as short gut syndrome [34,54]. As an example, in a series of 277 newborns with intestinal atresia and stenosis treated from 1972 to 1997 in Indiana, long-term survival for duodenal atresia, jejunoileal atresia, and colonic atresia was 86, 84, and 100 percent, respectively [6]. Similar results were reported in a series of 83 patients with jejunoileal atresia and without gastroschisis born from 1976 to 1998 in the United Kingdom, with overall survival of 90 percent [34].

The major causes of morbidity and mortality are short bowel syndrome and cardiac anomalies, often associated with duodenal atresia, especially in infants with Down syndrome [7,20]. The prognosis of newborns with meconium ileus is similar to other children with cystic fibrosis. (See "Cystic fibrosis: Clinical manifestations and diagnosis".)

The prognosis of complex atresias depends upon the length and function of the remaining bowel. Bowel function determines the required duration of total parenteral nutrition with its associated risks of sepsis and liver failure. Patients at especially high risk for short bowel syndrome include those with Type IIIB and IV atresias and gastroschisis. (See "Management of short bowel syndrome in children".)

Late operative complications include recurrent obstruction from anastomotic dysfunction, stricture, and adhesions, and are more likely to occur in complex atresias. Late duodenal dysmotility with significant dilation of the duodenum has been described and may require reoperation with tapering duodenoplasty [6]. Anastomotic dysfunction often complicates the recovery of infants with type IIIB (apple peel) atresia, who usually require prolonged total parenteral nutrition and may develop cholestasis, sepsis, and multisystem organ failure [55]. Despite these complications, contemporary surgical techniques and newborn intensive care have improved survival in this disorder [55].

SUMMARY AND RECOMMENDATIONS

●Incidence – Intestinal atresia, a congenital complete obstruction of the lumen of the intestine, is one of the most frequent causes of bowel obstruction in the newborn and can occur at any point in the gastrointestinal tract. Other causes of neonatal intestinal obstruction include malrotation with volvulus, Hirschsprung disease, and meconium ileus (table 1). (See 'Incidence' above.)

●Classification and pathogenesis (see 'Classification and pathogenesis' above)

•Duodenal atresia is the most common form, occurring in approximately one-half of cases. It is thought to be caused by an interruption of recanalization during normal gastrointestinal tract development in the first trimester.

•Jejunal and ileal atresias each occur in approximately one-fifth of cases (figure 1). These forms are acquired in utero, resulting from vascular disruption leading to ischemic necrosis of the fetal intestine.

•Colonic atresia is the least common form.

●Prenatal presentation – Findings on prenatal ultrasound that suggest the possibility of intestinal atresia include polyhydramnios, dilated bowel, or increased bowel echogenicity. Duodenal atresia is suggested by the "double bubble" formed by the dilated proximal duodenum and stomach (image 1). Prenatal ultrasonography is not always accurate, and plain radiographs and contrast examinations should be obtained after birth to confirm the diagnosis. (See 'Prenatal findings' above.)

●Postnatal signs and symptoms – Infants with intestinal atresia typically present with signs and symptoms of intestinal obstruction (abdominal distension and vomiting), usually beginning in the first two days of life. The presentation may be delayed for days or weeks in infants with stenosis (partial obstruction) of the intestine rather than atresia. Associated findings vary by anatomical site and include:

•Duodenal atresia – Vomiting may or may not be bilious. Approximately 30 percent of newborns with duodenal atresia have Down syndrome. In infants without Down syndrome, other congenital malformations are common, including gastrointestinal (biliary atresia, agenesis of the gallbladder), cardiac, renal, and vertebral anomalies. (See 'Postnatal presentation and associated anomalies' above.)

•Jejunal and ileal atresia – Vomiting is typically bilious. Hyperbilirubinemia is common. Approximately 10 percent of infants with jejunal or ileal atresia have cystic fibrosis and meconium ileus. (See 'Clinical features' above.)

●Evaluation

•Conventional radiograph – The first step in the evaluation of suspected neonatal intestinal obstruction is a conventional abdominal radiograph (algorithm 1). A double bubble sign strongly suggests duodenal atresia; with rare exceptions, distal gas is absent (image 2). Jejunal or ileal atresia typically appears as dilated loops of small bowel with air-fluid levels. The bowel distension is most prominent in more distal atresias. (See 'Abdominal radiograph' above.)

•Other – Additional evaluation for most infants includes contrast radiographs to confirm and better define the anomaly (algorithm 1), plain chest films for vertebral anomalies, and laboratory studies to assess the infant's clinical condition including complete blood count and differential, serum electrolyte concentration, blood urea nitrogen (BUN), and creatinine. (See 'Laboratory studies' above.)

●Evaluation for other congenital anomalies – Additional tests to assess for associated conditions are indicated in patients with (see 'Evaluation for other congenital anomalies' above):

•Duodenal atresia – Echocardiogram and renal ultrasonography

•Down syndrome – Echocardiogram and rectal biopsy to evaluate for Hirschsprung disease

•Meconium plugs – Test for cystic fibrosis

•Colonic atresia – Rectal biopsy to evaluate for Hirschsprung disease

●Management

•Preoperative management for an infant with intestinal atresia includes withholding feedings and placing a decompressive nasogastric or orogastric tube, establishing intravenous access and providing parenteral fluids, correcting any abnormalities in fluid and electrolyte balance, and giving routine perioperative antibiotics. (See 'Initial management' above.)

•The surgical approach depends upon the site of the atresia. In every case, the possibility of a second or multiple atresias should be considered. (See 'Surgical approach' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges David E Wesson, MD, who contributed to an earlier version of this topic review.