Case #04 Discussion:

This baby is the 32 week, 1275g infant daughter of a 39 year old female who is Hepatitis B core+ and Hepatitis C+. The pregnancy was complicated by trisomy 21, twin gestation, alcohol, tobacco, and cocaine use, and poor prenatal care. The infant was born via C-section with some respiratory insufficiency. On physical exam, she was hypotonic with slanting palpebral fissures, epicanthal folds, and minimal tongue thrusts. Her abdominal, pulmonary, and cardiac exams were unremarkable. Her anus was patent and she had clinodactyly of the 5th fingers bilaterally. Prenatal ultrasound showed gastric distension.

At birth, plain film (Image #1) showed gasseous distension of the stomach with a lack of air in the distal small bowel and colon. This finding is characteristic of the"double-bubble" found in duodenal obstructions. Swallowed air collects in the stomach and proximal duodenum and causes distension. The differential diagnosis for this is as follows:

1. There could be a lack of air in the distal bowel simply because enough time has not elapsed to allow air to pass completely through the digestive system. However, there should not be gastric or duodenal distension. Repeat plain films should show progression of air through the GI tract.
2. DuodenalAtresia: Complete obstruction of the duodenum results in a blind pouch either with fibrous bands connecting to the distal GI tract or no communication whatsoever. Duodenal atresia is strongly associated with Down's syndrome (trisomy 21) and results from a failure of the duodenal lumen to properly form between the 8th and 10th weeks of gestation. The site of the obstruction is often near the Ampulla of Vater with the atretic point beyond the ampulla in 80% of cases. As a result, these patients often present with bilious vomiting and abdominal distension. The combination of Down's syndrome and vomiting necessitates a work up for atresia or some other form of duodenal obstruction. Associated conditions include esophageal or tracheoesophageal fistulas, and bony abnormalities of the thorax and pelvis. Atresia can be recognized on prenatal ultrasound screening.
3. Duodenal web/stenosis: Symptomatically similar to duodenal atresia, resulting from partial obstruction. The lumen remains intact but is decreased in size.
4. Malrotation of the midgut: Failure of the 270 degree counterclockwise rotation of the small bowel about the superior mesenteric artery. As a result, there is proximity between the cecum and the duodenum resulting in shortened mesenteric attachments. This predisposes the bowel to volvulus around the SMA. Malrotation also predisposes to obstruction secondary to Ladd's bands crossing the duodenum.
5. A less common cause of the "double-bubble" is the congenital malformation resulting in the portal vein forming anteriorly to the duodenum. Such a condition causes duodenal obstruction.
6. Annular pancreas: This congenital abnormality results due to the persistence of the ventral pancreatic anlage.

While it can be seen that the "double-bubble" is not necessarily specific for one condition per se, its presence does require prompt evaluation and therapeutic intervention.

Therapy

In the case of duodenal atresia, stenosis, or web, surgery is indicated. A nasogastric tube is first placed to decompress the abdomen. The surgical procedure of choice is a duodenoduodenostomy with a diamond shaped anastamosis. A duodenojejunostomy may also be peformed. In the case of a malrotation, a Ladd's procedure is indicated. A catheter is passed through the duodenum to identify other points of obstruction. While distal obstruction occurs in only 3% of these patients, it is important to identify them with the catheter as they will not present radiologically on the initial films. Failure to do so will result in plain films showing gastric and duodenal distension more distally than before and would necessitate a second surgery and subject the patient to further morbidity and surgical risks. The surgery for annular pancreas is the same as for atresia. Finally, membranes may be surgically excised.

Post Surgical Course

A post surgical plain film (Image #2) shows residual air within the peritoneum. There was no significant bowel gas distal to the surgical anastamosis. On post-op day 5, there is free air in the abdomen in an unusual distribution. There appears to be mass effect pushing abdominal contents towards the left. An upper GI series showed no duodenal stricture or obstruction, but did demonstrate a leak at the duodenal anastamosis (Image #4). Incidentally, the contrast did not freely disperse in the abdomen indicating right sided loculation. The patient had a pig-tail catheter placed for drainage of the collection.