Duodenal atresia is a congenital intestinal obstruction that can cause bilious or nonbilious vomiting within the first 24 to 38 hours of neonatal life, typically following the first oral feeding. It is associated with in-utero polyhydramnios and is one of the most common causes of fetal bowel obstruction. Antenatal ultrasound can make the diagnosis. If duodenal atresia is not diagnosed antenatally, then the diagnosis can be made radiographically with plain abdominal x-ray as the first step in evaluation. This may be followed by a controlled contrast exam if needed. Either barium for a limited upper gastrointestinal (UGI) series or water/Pedialyte for an ultrasound evaluation can be performed to confirm the diagnosis. CT plays a limited if any role in the evaluation of duodenal atresia.
Obstruction of the duodenum causes duodenal atresia; usually distal to the ampulla of Vater in the second portion of the duodenum. Errors of duodenal re-canalization during the eighth to the tenth week of embryological development is the main cause of duodenal atresia. In duodenal atresia, there is complete obstruction of the duodenal lumen. Duodenal stenosis is the term used for narrowing resulting in an incomplete obstruction of the duodenum lumen. A duodenal web is a rarer cause of duodenal obstruction which tends to cause a windsock deformity of the duodenal lumen.
Duodenal atresia occurs in 1 in 5000 to 10,000 live births. It is often associated with other anomalies, including trisomy 21/Down syndrome and cardiac malformations. Approximately 30% of children with duodenal atresia have Down syndrome. There is a 3% prevalence of congenital duodenal atresia among patients with trisomy 21/Down syndrome. There is no difference in prevalence between the genders. There is an association with VACTERL, annular pancreas, and other bowel atresias including jejunal atresia, ileal atresia, and rectal atresia.
Duodenal atresia is believed to occur because of failure of the epithelial solid cord to recanalize or excessive endodermal proliferation.
Duodenal atresia presents early in life as vomiting; which usually occurs within the first 24 to 38 hours of life after the first feeding and progressively worsens if not treated. Sometimes the vomiting may be projectile; which like pylorospasm and gastroesophageal reflux, may simulate hypertrophic pyloric stenosis. The clinical presentation of bilious vomiting points to congenital intestinal obstruction distal to the ampulla of Vater. There are cases of atresia proximal to the ampulla of Vater that present without bilious vomiting. The ampulla of Vater is located in the second or descending portion of the duodenum. Excessive bilious vomiting can cause hypokalemic hypochloremic metabolic alkalosis with paradoxical aciduria, particularly if there is a delay in hydration. Patients have symptoms of abdominal distension and absent bowel movements.
Antenatal imaging will show a double bubble, an echoless stomach filled with amniotic fluid, as well as a second nearby but more distal fluid filled, often circular (but blind ended) structure (the second bubble) that is the obstructed portion of the duodenum. The use of prenatal ultrasound has allowed for an earlier diagnosis of duodenal atresia. An advantage of neonatal abdominal ultrasound is that it can be performed in the neonatal intensive care unit or nursery. When antenatal ultrasound is performed the duodenum is usually not filled with fluid, and the presence of a fluid-filled duodenum suggests duodenal atresia. If a double-bubble sign is seen on antenatal ultrasound, then it is important for the sonographer to demonstrate a connection between the two fluid-filled structures because foregut duplication cyst, as well as other abdominal cysts, may simulate the appearance of a double-bubble sign.
The initial postnatal radiographic evaluation for diagnosing duodenal atresia is a plain abdominal x-ray. In duodenal atresia, there is gas in the stomach and the proximal duodenum but an absence of gas distally in the small or large bowel. A plain abdominal x-ray may reveal the double-bubble sign which is seen postnatally as a large radiolucent (air-filled) stomach usually in the normal position to the left of the midline, and a smaller more distal bubble to the right of midline which represents a dilated duodenum. A double-bubble sign on an abdominal x-ray is a reliable indicator of duodenal atresia. Other causes of intestinal obstruction may simulate a double-bubble sign. Annular pancreas is the second most common cause of duodenal atresia. Jejunal or more distal obstruction may have dilation more distally or more than two bubbles may be present.
In patients with Down syndrome, the x-ray double-bubble has a higher positive predictive value because the prevalence of duodenal atresia in Down syndrome is much higher than in the general population and further evaluation with additional modalities is not always needed before proceeding to surgery. Duodenal stenosis can also cause the double-bubble sign; however, if stenosis is present, at least a small amount of gas may be present distal to the obstruction. The absence of gas in the stomach on abdominal x-ray is a sign of esophageal atresia without tracheoesophageal fistula. At times there may be distal air distal to a duodenal atresia that has entered distal bowel via an anomalous biliary tree. The radiographic appearance of the double-bubble sign should prompt immediate surgical consultation. For cases of suspected duodenal atresia not identified antenatally, barium fluoroscopy can be used to assess the gastrointestinal tract. If necessary further evaluation with ultrasound or upper gastrointestinal series (UGI) may be performed. More recently, neonatal ultrasound has been shown to be very helpful in clarifying the anatomy, especially using the fluid as a contrast agent. A possible mimic of the double-bubble sign is the pseudo-double-bubble sign created by the curved configuration of the stomach where the two bubbles represented normal fluid in the proximal the and distal stomach.
Barium contrast is administered sometimes via an orogastric or nasogastric tube under fluoroscopy to evaluate the esophagus, stomach, and duodenum. Only a controlled amount of barium is placed to confirm obstruction. It is then removed by nasogastric tube to prevent reflux and potential aspiration. The main purpose of the UGI is to differentiate between duodenal atresia and midgut volvulus; an important distinction, because midgut volvulus requires emergency surgery, whereas duodenal atresia can be managed on an urgent basis.
Pediatric CT plays a very limited if any role in diagnosis and evaluation of duodenal atresia. However, its 2D reconstruction may allow for further evaluation of bowel layout in confusing cases. Neonatal CT is more technically challenging as it may require sedation, bundling and, starting a neonatal intravenous line for contrast administration. Additionally, CT does involve ionizing radiation and may be more difficult to interpret because there is less abdominal fat separating abdominal viscera compared to older patients.
Treatment involves nasogastric suction to decompress the stomach and surgery to correct the obstructing lesion. Duodenoduodenostomy is the typical surgery performed. Doudenodoudenostomy can be performed as an open or laparoscopic procedure. Doudenodoudenostomy is a type of bypass procedure that is said to be technically demanding for a laparoscopic approach. A diamond-shaped anastomosis is constructed with a proximal transverse to the distal longitudinal duodenal anastomosis. The bypass procedure avoids damage to the pancreas, main pancreatic duct, accessory pancreatic duct, and common bile duct. Before surgery, the stomach and proximal duodenum are decompressed with an orogastric tube, and intravenous fluid resuscitation is performed. Possible complications of duodenoduodenostomy include gastroesophageal reflux, megaduodenum, and impaired duodenal motility. A complete operative evaluation includes looking for additional areas of intestinal obstruction.
It is helpful to know if the vomitus is bilious or not in developing a differential diagnosis. Primary considerations for cases of bilious vomiting in neonates are duodenal atresia, duodenal stenosis, annular pancreas, but particularly malrotation of the intestine caused by midgut volvulus whereby superior mesenteric artery flow to the distal bowel is compromised. Midgut volvulus usually presents days later in life than duodenal atresia. In babies with Down syndrome, it is important to look for other gastrointestinal abnormalities associated with Down syndromes such as anal atresia, Hirschsprung disease, diaphragmatic hernia, and omphalocele.
Prognosis after successful surgical treatment of duodenal atresia is excellent.
Complications are chiefly associated with surgery and include the following:
In utero, duodenal atresia, a proximal gastrointestinal tract obstruction, causes polyhydramnios by interfering with the gastrointestinal absorption of amniotic fluid swallowed by the fetus distal to the level of intestinal obstruction. Polyhydramnios is defined as abnormally large amounts of amniotic fluid in the gestational sac during pregnancy. Antenatal ultrasound is diagnostic for polyhydramnios when the amniotic fluid index is greater than 25 cm or when the total amniotic fluid is estimated to be greater than 1500 to 2000 ml. In duodenal atresia, amniotic fluid that is swallowed by the fetus is prevented from moving distally to be absorbed by the fetal gastrointestinal tract and transferred to the maternal circulation through the placenta. Rather it is refluxed back into the amniotic fluid. Eighty percent of cases of polyhydramnios are due to maternal or idiopathic causes. Maternal causes include congestive heart failure and gestational diabetes. Gestational diabetes can cause fetal hyperglycemia and fetal polyuria. Fetal causes include congenital anomalies that interfere with swallowing and intestinal obstruction including duodenal atresia. Other anomalies causing polyhydramnios include esophageal atresia, head and neck masses, thoracic masses, and supratentorial disorders that disrupt swallowing. Polyhydramnios increases the risk for cord prolapse, placental abruption, and preterm delivery.
Duodenal atresia is a relatively common intestinal disorder which often presents soon after delivery, hence it is best managed by a multidisciplinary team that includes a pediatric surgeon, obstetrician, neonatal nurse, dietitian, pediatrician, intensivist and a geneticist. The definitive management of this condition is surgery, but the procedure is often associated with complications that prolong hospital stay. Over the past three decades, the mortality rates of duodenal atresia have significantly dropped averaging 2-5%. Mortality rates are not directly related to the surgery but to the other associated organ anomalies like complex congenital cardiac defects. However, survival continues to improve with better NICU care, nutritional support and improved pediatric anesthesia. Today long-term survival of most infants (more than 80%) with duodenal atresia is the norm. The biggest controversy for the future is the use of endoscopy to excise the duodenal web. This technique remains experimental. The other controversy surrounds the time to feed the patient after surgery. Experts recommend a fluoroscopic evaluation to check for a leak before initiating feeding.