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Duodenal Atresia

Duodenal Atresia with classic "Double Bubb Sign"

Coronal scan in a fetus with duodenal atresia and a distended stomach. A-plane of section through stomach resulting in true "double bubb" B-plane of section through stomach transecting incisura resulting in pseudo-"double bubb"

Findings:

Two fluid-filled structures are seen in the upper abdomen. They are due to the distended fluid-filled stomach and duodenal bulb. On other scans the two structures were continuous with one another. The pseudo-appearance of a "double bubb" can be created by obliquely scanning through the stomach across the incisura.

Discussion:

Duodenal atresia is the most common form of small-bowel obstruction in the fetus. The reported incidence is between 1 in 5000 and 1 in 10000 live births. It is thought to be the result of failure of the second portion of the duodenum to recanalize by 11-12 weeks. This may be due to a vascular insult or a membranous obstruction. The imaging diagnosis of duodenal atresia was first made on neonatal radiographs by demonstration of the "double bubb" sign. This appearance is due to a gas-filled distended stomach and duodenal bulb. The prenatal diagnosis of duodenal atresia is made sonographically by demonstration of the same "double bubb" sign, although these structures are filled with fluid, rather than air. Duodenal atresia is associated with polyhydramnios in 45% of cases and with symmetric growth retardation in 50% of cases. Importantly, nearly 50% of patients have associated congenital malformations. Approximately 35% of patients have congenital heart disease, therefore a careful evaluation of the fetal heart is indicated when this diagnosis is being considered. Trisomy 21 is seen in approximately 30% of infants with duodenal atresia.

The prenatal diagnosis of duodenal atresia is more than academic. One study reported no pre or post-surgical complications in the group diagnosed antenatally as compared to complications in five out of seven cases diagnosed postnatally.

Differential Diagnosis:

An oblique scan through a prominent but normal fluid filled stomach may create the appearance of the "double bubb" sign. In fact these cases are due to a scan that transects the stomach through a prominent incisura angularis (see above figure). When dilated fluid-filled structures are located within the right upper abdomen they may wrongly be interpreted as a dilated duondenal bulb. Recognition that these structures are not continuous with the stomach will aid in the correct interpretation. This ,may occur in cases of choledochal cysts or renal, hepatic, omental, duplication or ovarian cysts. Likewise, a double bubb" may be seen in cases of Ladd's bands, annular pancreas or volvulus, in which there is no duodenal atresia.

References:

Romero R, Ghidini A, Costigan K, Touloukian R, Hobbns JC. Prenatal diagnosis of duodenal atresia: does it make any difference? Obstet Gynecol 71:739, 1988

Hertzberg BS. Sonography of the fetal gastrointestinal tract: anatomic variants, diagnostic pitfalls and abnormalities. Amer J Roentgenol 162:1175-1182, 1994

Nelson LH, Clark CE, Fishburne JI et al. Value of serial sonography in the in utero detection of duodenal atresia. Obstet Gynecol 59:657, 1982

Grivan DP, Stephens FA. Congenital intrinsic duodenal obstruction: a twenty-year review of its surgical management and consequences. J Pediatric Surgery 9:833, 1974

Goldstein RB. Ultrasound evaluation of the feta abdomen. In: Ultrasonography in Obstetrics and Gynecology, 3rd Ed., Ed by Peter W. Callen, M.D., WB Saunders and Co., Philadelphia, 1994

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Peter W. Callen, M.D.
Professor of Radiology, Obstetrics, Gynecology and Reproductive Science
University of California Medical Center, San Francisco, California