Duodenal Obstruction

Duodenal Obstruction

Complete duodenal obstruction is much more frequent than congenital gastric obstruction.

Persistent vomiting is the cardinal sign, but abdominal distension may not be a conspicuous feature. The vomiting is bile-stained when the obstruction is below the ampulla of Vater (70% of cases), and clear but persistent in supra-ampullary lesions.

The classic plain radiographic finding is the so-called double bubble image (Rathaus et al. 1992) (Fig. 1.3). The higher, more leftward and larger bubble is the stomach, and the other bubble is the dilated proximal duodenum, above the area of obstruction. Two distinct air-fluid levels are usually demonstrated on erect or horizontal beam radiographs. There is no air more distally in the gastrointestinal tract. Newborns showing evidence of complete duodenal obstruction on their abdominal radiograph rarely require further radiologic investigation. An upper gastrointestinal series provides no additional information, and there is a potential hazard of vomiting with barium aspiration. Sometimes vomiting can result in a lack of air in the obstructed segment;

Pictures Duodenal Obstruction
Fig. 1.3. Complete duodenal obstruction caused by a congenital duodenal web. The stomach (st) and duodenum (d) are dilated and with absence of air more distally in the gastrointestinal tract, producing the classical "double bubble" image

in these cases a small amount of air can be injected via a nasogastric tube when the abnormal pathology will present (Fig. 1.4). A contrast enema is not necessary when the diagnosis is obvious, although it can be performed to exclude additional more distal areas of atresia (McAlister et al. 1996). In the case of isolated duodenal obstruction, the colon should be normal.

The main causes for a "double bubble" are duodenal atresia, annular pancreas, and midgut volvulus. Less frequently it may be secondary to duodenal web, Ladd's band, or preduodenal portal vein (Crowe and Sumner 1978).

Duodenal atresia is the most important cause of complete duodenal obstruction (Fig. 1.4). It occurs in approximately 1 in 10,000 births, and 60% of the infants are premature. The etiology of this condition is thought to be failure of recanalization of the duodenum, approximately between the 9th and 11th week of gestation. Unlike jejunal and ileal atresia, this condition does not appear to be related to intrauterine vascular accidents (Boyden et al. 1967). Major associated anomalies are present in about 50% of the patients. Approximately 30% have Down's syndrome. Other anomalies include malrotation of the small bowel, esophageal atresia, congenital heart disease, imperforate anus, small bowel atresia, biliary atresia, annular pancreas, and renal anomalies (Auringer and Sumner 1994; Bailey et al. 1993).

Annular pancreas is an anomalous band of pancreatic tissue, which arises from the head of the pancreas and encircles the second portion of the duodenum to a variable extent, giving rise to a variable degree of duodenal obstruction. This anatomy results if two ventral pancreatic buds arise from the ventral mesentery and rotate in opposite directions to fuse with the dorsal pancreatic bud (Larsen 1993). If a complete ring is formed, there may be complete obstruction of the duodenum at the time of birth; if the ring is incomplete, obstruction may occur later in life or may never produce symptoms. When a complete ring is formed, radiological findings are indistinguishable from duodenal atresia with the typical double bubble sign, and the diagnosis is made at surgery (Norton et al. 1992) (Fig. 1.5).

Midgut volvulus is the most dramatic consequence of intestinal malrotation. When present at birth, the classic finding on a plain film is partial obstruction of the duodenum, but evidence of complete obstruction may also be present. In such cases, it is impossible to distinguish midgut volvulus from

Inflted Tummy And Pain

Fig. 1.4a,b. Duodenal atresia. a Plain radiograph obtained 6 h after birth shows absence of air in the gastrointestinal tract of this neonate with severe lung disease. b Radiograph made after inflation of the stomach through a nasogastric tube demonstrates complete duodenal obstruction ("double bubble" sign)

Fig. 1.4a,b. Duodenal atresia. a Plain radiograph obtained 6 h after birth shows absence of air in the gastrointestinal tract of this neonate with severe lung disease. b Radiograph made after inflation of the stomach through a nasogastric tube demonstrates complete duodenal obstruction ("double bubble" sign)

Pictures Duodenal Obstruction

Fig. 1.5a-c. Annular pancreas. Supine (a) and lateral (b) views of the abdomen show complete obstruction at duodenal level identical to that seen in duodenal atresia. The stomach (st) and duodenal bulb (d) are distended and there is no distal air. c Surgical image shows the pancreatic tissue (arrow) encircling the duodenum (d)

Fig. 1.5a-c. Annular pancreas. Supine (a) and lateral (b) views of the abdomen show complete obstruction at duodenal level identical to that seen in duodenal atresia. The stomach (st) and duodenal bulb (d) are distended and there is no distal air. c Surgical image shows the pancreatic tissue (arrow) encircling the duodenum (d)

Annular Pancreas

b a duodenal atresia or annular pancreas (Fig. 1.6). Past the immediate postnatal period, any duodenal obstruction should be assumed to be midgut volvulus until proven otherwise (Buonomo 1997). It is the only condition mentioned above that may kill the patient.

Antenatal diagnosis of duodenal obstruction is based on sonographic demonstration of polyhydramnios in conjunction with a fluid-filled "double bubble" in the fetal abdomen corresponding to the double bubble sign seen on postpartum radiographs (Nelson et al. 1982). Since there is a high incidence of associated anomalies, identification of a double bubble sign should prompt consideration of fettle karyotyping and a careful search for other fetal anomalies (Hertzberg and Bowie 1990).

Partial duodenal obstruction may be produced by duodenal stenosis, duodenal web, Ladd's bands, midgut volvulus, annular pancreas, preduodenal portal vein, and duplication cyst. Plain radiographs show gaseous distension of the stomach and duodenum with a normal or diminished quantity of air in the small bowel. Content studies may be necessary to differentiate between midgut volvulus and partial duodenal obstruction caused by a web or stenosis (Auringer and Sumner 1994). Sonography is helpful to rule out extraluminal causes such as a duplication cyst.

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