Teaching Case

A 33-year-old primiparous woman was referred with polyhydramnios at 37 weeks + 1 day gestation. The patient felt fetal movements normally and denied contractions or leakage of amniotic fluid. The pregnancy was poorly controlled, complicated by the Rh-immunisation. The patient is a former heroin addict with chronic hepatitis C infection (genotype 1A).

Fetal ultrasound scan showed normal fetal heart action with biometry measures indicating fetal intrauterine growth restriction; estimated fetal weight (EFW) less than the 10th percentile for gestational age, paired with high level of amniotic fluid (AFI 28). Fetal abdominal scan revealed dilated stomach and duodenum, which was measuring 3 cm in diameter, representing "double-bubble" sign. The diaphragm was intact, the bladder was dilated. Fetal echocardiography showed partial AV canal.

Duodenal atresia (DA) is a complete obstruction of the duodenal lumen caused by the lack of recanalisation of occluded embryonic gut during eight to ten weeks of gestation [1]. Reported incidence is 0.9 infants per 10000 births. The disease affects boys more frequently than girls. This type of defect represents up to 60% of all cases of intestinal atresia. The defect is often accompanied with other organ involvement and can be a marker of chromosomal anomalies [2].

The sensitivity of ultrasound in the prenatal diagnosis of bowel obstruction is 50%. The probability of detection depends on the anatomic level of bowel obstruction, with proximal obstructions tending to be more frequently diagnosed [3]. The anomaly is often detected after the first trimester of pregnancy. Diagnosis is often preceded by identifying polyhydramnios, which is present in 50% of cases.

Characteristic ultrasound finding suggestive for DA is a dilation of the stomach and the first part of the duodenum, described as "double-bubble" sign. According to the literature, the presence of double bubble is highly associated with duodenal atresia [4]. Since duodenal atresia implies complete obstruction of the small intestine, no air should be seen distal to the obstruction site. The appearance of two dilated adjacent structures in duodenal atresia is explained by the presence of an alternative route in cases of bifid common bile duct [5, 6].

This type of defect can be an isolated finding in fetuses with normal karyotype, whereas 30% of children with duodenal atresia have trisomy 21. Presence of DA can also be related to VACTERL association [7].

Reported findings in our case suggested trisomy 21, which was later confirmed by a genetic assessment. Our patient gave birth to a female child. Duodenal atresia more commonly affects males. In the present case, the finding of proximal duodenum could easily be mistaken for ovarian cyst. Additional causes are duodenal stenosis, duodenal webs, annular pancreas, midgut volvulus, preduodenal position of portal vein [5,6].

Beside the duodenal atresia, additional features in this case were partial AV canal and intrauterine growth restriction which could both be a manifestation of trisomy 21. Potential cause of intrauterine growth restriction in our case could be polysubstance abuse by the mother.

Once the DA is suspected, heart defects, urinary tract, spine, and limb abnormalities should be ruled out. Furthermore, other gastrointestinal anomalies such as intestinal stenosis, atresia, malrotation or annular pancreas should be investigated [7]. As soon as the diagnosis is made, the appropriate treatment including surgical repair after the birth can be timely initiated.

Written informed patient consent for publication has been obtained.