CONGENITAL DUODENAL ATRESIA.
Etiology: Most cases of duodenal atresia are sporadic. Investigations of familial cases of duodenal atresia suggest an autosomal recessive inheritance in these individuals.
The duodenum develops from the caudal part of the foregut and the cranial part of the midgut. At 4 weeks' gestation, it consists of an epithelial tube surrounded by mesenchyme. During the fifth to sixth weeks of gestation, the epithelium proliferates while the surrounding mesenchymal walls are still narrow; the epithelial cells fill the lumen, completely obliterating it. Subsequent epithelial apoptosis at 8-10 weeks' gestation leads to vacuolation and recanalization of the duodenum. Failure of vacuolation may lead to intrinsic duodenal obstruction
Clinical: Most of the times intrinsic duodenal obstruction is associated with another significant congenital anomaly Approximately 30% of cases are associated with Down syndrome, and 23-34% of cases are associated with isolated cardiac defects. Other gastrointestinal anomalies include malrotation, anterior portal vein, second distal web, anorectal anomalies, intestinal atresias, cloacal anomalies, and renal tract anomalies. Duodenal atresia is associated with prematurity and low birth weight.
Duodenal atresia is detected antenatally. Sonographic features of high intestinal obstruction (ie, duodenal obstruction with a dilated stomach [double bubble sign]) become apparent in the third trimester. Polyhydramnios develops in 32-59% of cases, and in the presence of polyhydramnios, normal findings on ultrasonography of the fetus do not exclude duodenal atresia. A similar appearance can be observed in fetuses with a choledochal cyst, external duodenal compression, and a normal stomach with a sharp incisura.
Following delivery, a thorough physical examination should be performed, including careful examination of the anus.
Normal newborn infants have gastric aspirates that measure less than 5 mL. Congenital intestinal obstruction is associated with gastric aspirates that measure greater than 30 mL. An infant with a gastric aspirate that measures greater than 30 mL in the delivery room or newborn nursery should be evaluated for duodenal atresia and other causes of upper intestinal obstruction.
TYPES: Duodenal atresia or stenosis usually occurs in the first or second part of the duodenum, most often near the papilla of Vater. The common bile duct may open into an intraluminal mucosal web.
The 3 anatomic types of duodenal atresia as described by Gray and Skandalakis are as follows:
- Type 1: The most common type is formed by a membrane composed of mucosa and submucosa. This membrane traverses the internal diameter of the duodenum. The duodenum and stomach proximal to the obstruction are dilated and hypertrophied. The duodenum distal to the obstruction is narrowed. A variation of this occurs when the membrane is elongated in the shape of a windsock, and the site of origin of the membrane is proximal to the level of obstruction.
- Type 2: The atretic ends of the duodenum are connected by a fibrous cord.
- Type 3: Complete separation of the atretic segments occurs. Most of the biliary duct anomalies associated with duodenal atresia are observed in type 3 defects.
Plain abdominal radiography
- This study usually demonstrates a dilated stomach, a dilated first part of duodenum (double bubble), and absence of air beyond the second air bubble.
- Abdominal/renal ultrasonography: This study is useful in detecting renal anomalies and an annular pancreas.
Treatment - Surgery is the treatment of choice.