Prevalence: The incidence of duodenal atresia is approximately 1:10,000 births.
Etiology: Most of the cases are sporadic. Nevertheless, some different etiologies have been described. Exposure to thalidomide between the 30th and 40th day of gestation has resulted in duodenal atresia (2). Duodenal atresia may also result from a vascular accident causing infarction of a segment of fetal bowel and then atrophy and absorption. In our case, we think that the extension of the obstruction was severe and involved the duodenum and the beginning of the jejunum. Duodenal atresia has been reported after intra-uterine midgut strangulation in a fetus with an omphalocele.
Pathogenesis: During the 5th week of embryonic life the epithelium of the primitive duodenum proliferates and obliterates the lumen. During the 11th week, vascularization leads to restoration of luminal patency. Defective vascularization results in segment obstruction or stenosis of the duodenum (2). Spontaneous activity of the small intestine is rarely observed before 10 weeks and the existence of peristalsic movements is demonstrated after four months of age. There are four types of intestinal atresia:
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Type 1: there are one or more transverse diaphragms.
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Type 2: the blind-ending loops are connected by a fibrous string.
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Type3: there is a complete separation of the blind-ending loops.
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Type 4: there is an "apple-peel" atresia of the small bowel.
The most frequent from of duodenal atresia results form the presence of a diaphragm (type 1), as in our case. The most common site of atresia (85%) is the second part of the duodenum, distal to the ampula of Vater.
Sonographic findings: Prenatal diagnosis is usually performed in the second half of pregnancy. There are only a few cases in which the diagnosis was made at the end of the first trimester or during the beginning of the second trimester. The ultrasound diagnosis relies on the detection of the classic "double-bubble" sign which represents the dilated stomach and the duodenum. This sign is due to the simultaneous distention of the stomach and the first portion of the duodenum (3-4). A stricture between the two "cysts" can be seen with accentuation of the peristalsis and polyhydramnios. In our case, we did not see polyhydramnios before the spontaneous rupture of membranes occured.
3D imaging may help to differentiate the gastric and the duodenal cavities. It was also possible to demonstrate the communication between the pylorus and the duodenum. Abdominal 3D imaging may help to establish the relative positions of the abdominal organs and the visceral displacement (5).
Implications for targeted examinations: Early diagnosis of duodenal atresia is possible during the end of the first trimester. However, not until 11 weeks when the lumen of the duodenum becomes obstructed by proliferating epithelium. Zimmer et all (1996) described one case discovered at 15 weeks with a characteristic "double-bubble" sign. Tsukerman et al (1993) described the "double-bubble" sign at 12 weeks in a fetus which also had an esophageal atresia (4). Petrikowsky (1994) made the diagnosis at 14 weeks. Tsukerman et al (1993) described at 12 weeks a duodenal atresia associated with esophageal atresia. Romero et al (1994) described one case at 19 weeks.
Differential diagnosis: The differential diagnosis includes:
- Choledochal cyst
- Prominent incisura angularis of the stomach (the coronal plane may demonstrate a pitfall diagnosis)
- Congenital segmental dilatation of the duodenum: (Only three cases of duodenal segmental dilatation have been described, two after the antenatal period and one during the antenatal period) (3).
- Extrinsic obstruction
- Duodenal diverticula
- Duodenal duplication
Associated Anomalies: Duodenal atresia can be associated with different anomalies in more than 1/3 of cases as:
- Vertebral anomalies: 1/3 of cases
- Cardiac anomalies: 1/3 of cases
- Gastro-intestinal anomalies: 1/4 of cases
- Association with esophageal atresia: 5% (frequently with trisomy 21 and 18)
- Malrotation of the bowel (commonly mesenteric)
- Ano-rectal malformation
- Renal anomalies: 8%
- Aneuploidies: 1/3 of cases (trisomy 21). The association of duodenal atresia with chromosomal abnormalities supports the view that the lesion is due to an early embryonic insult.
Prognosis: The prognosis of duodenal atresia depends on:
- Gestational age at delivery
- Diagnosis delay
- Associated anomalies
Management: The importance of antenatal recognition of duodenal atresia for the outcome of affected infants is well known. When duodenal atresia is diagnosed a detailed fetal scan is indicated and fetal karyotyping is necessary. The standard obstetrical management is usually the same than in fetuses without anomalies. However, delivery in a tertiary center is indicated to perform a rapid surgical repair.
References:
1- Caspi B., Deutsch H., Grunshpan M., Flidel O., Hagay Z., Appelman Z.- prenatal manifestation of superior mesenteric artery syndrom. Prenat Diagn 2003 ; 23 : 932-4.
2- Sanchez M.A.- Duodenal atresia. Sanchez www.thefetus.net/ 2006-05-22-10.
3- Cuming T., Asif M., Babu R., kalidasan V.- Congenital dilatation of the duodenum-differential diagnosis for an antenatally-diagnosed intra-abdominal cyst. Eur J Pediatr Surg 2001 ; 11 : 133-5.
4- Zimmer E.Z., Bronshtein M.- Early diagnosis of duodenal atresia and possible sonographic pitfalls. Prenatal diagn 1996 ; 16 : 564-6.
5- Tsukerman G.L., Krapiva G.A., Kirillova A.I.- First-trimester diagnosis of duodenal stenosis associated with oesophageal atresia. Prenatal diagn 1993 ; 13 : 371-6.
6- Lopez Ramon y Cajal C., Ocampo Martinez R.- Prenatal diagnosis of duodenal atresia with three-dimensional sonography. Ultrasound Obstet Gynecol 2003 ; 22-956-7.
7- Sajja S.B.S., Middlesworth W., Massoma Niazi, Moshe Schein, Gerst P.H.- Duodenal atresia associated with proximal jejunal perforations : a case report and review of the literrature. J Pediatr Surg 2003 ; 38 : 1396-8.