Duodenal Atresia and Stenosis

Etiology

Obstruction of the duodenum causes duodenal atresia, usually distal to the ampulla of Vater in the second portion of the duodenum. During the eighth to the tenth week of embryological development, errors of duodenal re-canalization are 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 more rare cause of duodenal obstruction, which tends to cause a windsock deformity of the duodenal lumen.[2]

Epidemiology

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% to 40% 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.[3]

Pathophysiology

Duodenal atresia is believed to occur because of failure of the epithelial solid cord to recanalize or excessive endodermal proliferation. However, the exact etiology remains unknown at this time.[4]

History and Physical

Duodenal atresia presents early in life as vomiting, usually occurring 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.[5][6] 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.

Evaluation

Antenatal imaging will show a double bubble, an echoless stomach filled with amniotic fluid, and a second nearby but the 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 the sonographer needs 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.[7][8]

The initial postnatal radiographic evaluation for diagnosing duodenal atresia is a plain abdominal x-ray.  There is gas in the stomach and the proximal duodenum in duodenal atresia 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 the 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.  The annular pancreas is the second most common cause of duodenal atresia.  Jejunal or more distal obstruction may dilate more distally, or more than two bubbles may be present.[8]

In patients with Down syndrome, the x-ray double-bubble has a higher positive predictive value. The prevalence of duodenal atresia in Down syndrome is much higher than in the general population. Further evaluation with additional modalities is not always needed before proceeding to surgery.  Duodenal stenosis can also cause the double-bubble sign; however, if the 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 an abdominal x-ray signifies esophageal atresia without a tracheoesophageal fistula.  At times there may be air distal to a segment of duodenal atresia that has entered the 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 is very helpful in clarifying the anatomy, especially using the fluid as a contrast agent.[9]  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 and distal stomach.

Barium contrast is sometimes administered 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 a 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. In contrast, duodenal atresia can be managed on an elective basis.[10]

Pediatric CT plays a very limited if any, role in the diagnosis and evaluation of duodenal atresia.  However, a CT 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 than in older patients.

Treatment / Management

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.[11]

Differential Diagnosis

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. It is important to look for other gastrointestinal abnormalities associated with Down syndrome, such as anal atresia, Hirschsprung disease, diaphragmatic hernia, and omphalocele.[8]

Prognosis

Prognosis after successful surgical treatment of duodenal atresia is excellent. A study following infants from 1972 to 2001 demonstrated late complications in up to 12% of patients and late mortality of 6%.[12]

Complications

Complications are chiefly associated with surgery and include the following:

• Megaduodenum 
• Blind loop syndrome
• Cholecystitis
• Esophagitis
• Peptic ulcer disease
• GERD
• Pancreatitis
• Anastomotic leak