Duodenal atresia
This is the most common foetal atresia, occurring in 1/5000 births and is associated with Down's syndrome. It is a condition in which a part of the GIT tract from the duodenum to the anus has failed to form correctly and that part of the gut is either completely blocked or is missing altogether. This can result in life-threatening obstruction and the defect can only be corrected surgically.
There are three main types:
- Type I : Obstruction due to a mucosal web with normal muscular wall.
- Type II : Two atretic duodenal ends joined by a short fibrous cord.
- Type III : Complete separation of atretic ends with no connective tissue.
Many cases are now picked up on antenatal scans as a 'double bubble' may appear on scan due to the dilated, fluid-filled stomach and proximal duodenum. Parental counselling, advice and support should be offered at this point to ensure that they are adequately prepared. The pregnancy may be complicated by polyhydramnios owing to the impaired absorption of amniotic fluid by the foetal intestines. The defect may be a single one or complicated by intestinal malrotation and congenital heart disease. Postnatally, it may be suspected by the presence of vomiting within hours of birth. This vomit is most often bilious,although it may be non-bilious because a small number of atresia occurs proximal to the ampulla of Vater. Because the gut is not patent the infant might have a 'hollow' looking abdomen (scaphoid). An X-ray may demonstrate agas-filled 'double bubble' which corresponds to the antenatal fluid-filled image and, unless there is perforation, there is no other gas present in the intestine or abdominal cavity.
Pre-operative management
Although the condition is potentially life-threatening it is not an emergency and, if otherwise well, the infant can be left for between 24 and 48 hours before undergoing surgery. The infant must remain nil by mouth and be maintained with IV hydration. An NGT should be passed and the gut aspirated. If prolonged NGT aspiration is necessary or the amounts copious, the IV regime should include replacment of the gastric aspirate with either 0.45% or 0.9% sodium chloride. Prior to surgical repair, the infant's fluid and electrolyte status must be checked.
Surgical management
This has been performed laparoscopically and the techniques are being continually refined (Valusek et al. 2007). However, a laparotomy and a duodenostomy are the most commonly performed procedures. There are a couple of techniques for this and they are used at the surgeon's preference,but essentially they involve opening the duodenum channel along its length and joining it to the next portion of patent intestine, and correcting the duodenal lumen end to end so that a fully open channel exists. Most surgeons place a small trans-anastomotic (TAT) feeding tube to protect the suture line and expedite gut priming; some evidence suggests that toleration of enteral feeds is quicker as a result (Arnbjornsson et al. 2002). The entire small bowel is carefully explored for other sites of obstruction, the hepatic and pancreatic anatomy is checked and any malrotation corrected.