Tracheoesophageal Fistula

Esophageal Atresia with absent stomach (arrow)
Esophageal Atresia & Polyhydramnios

Findings:

In this case the normal fluid-filled stomach was not identified in its normal location in the left upper quadrant (arrow). In addition, there was evidence of polyhydramnios. These findings were the result of esohageal atresia.

Discussion:

Tracheoesophageal fistula results from a failure of division of the foregut into the trachea and esophagus which normally occurs between the 4th and 6th week of gestation. While five types of tracheoesophageal fistula exist, the most common of these is the combination of an esophageal atresia with a fistula connecting the lower esophagus with the trachea. Although esophageal atresia may occur in isolation, this is unusual. Over 90% of cases of esophageal atresia occur in association with a tracheoesophageal fistula.

The incidence of esophageal atresia is between 1 in 1500 and 1 in 2000 live births. The risk of recurrence in a fetus with a parent or sibling with a tracheoesophageal fistula is approximately 1%. As in most congenital malformations, associated malformations are common in fetuses with tracheoesophageal fistula. Associated anomalies, seen in nearly 60% of patients include: cardiac, gastrointestinal, genitourinary and musculoskeletal malformations. Congenital heart disease, usually atrial and ventricular septal defects, are seen between 15% and 39% of patients. Chromosomal abnormalities can also be seen with these cases. In the 1970's the VATER association was described; a non-random association of abnormalities resulting in vertebral abnormalties, anal atresia, tracheoesophageal fistula, esophageal atresia and radial and renal abnormalities. As such, when a fetus with an esophageal atresia is identified careful scrutiny for associated abnormalities in the VATER association should be done.

Unfortunately, neither the normal or even abnormal esophagus is often identified sonographically. As such, the diagnosis is considered when there is indirect evidence of esophageal obstruction, manifest as an absent fluid-filled stomach in association with polyhydramnios. The rationale behind this approach is that in most studies the fetal stomach is seen in greater than 98% of cases. One of the more common reasons for absence of the fetal stomach at the time of sonography is oligohydramnios, in which there is little to no fluid for the fetus to swallow. Fortuntely this rarely occurs with the fetus with esophageal atresia. While in theory fluid can enter the stomach through the coexistant tracheoesophageal fistula, this rarely happens due to the higher intra-abdominal than intra-thoracic pressure during inspiration. A further confounding problem is that the stomach may secrete mucus which may simulate the normal passage of amniotic fluid into the stomach. A recent study evaluating the utility of these signs found a 56% positive predictive value and a 42% sensitivity for the detection of esophageal atresia when a small or absent stomach were seen in association with polyhydramnios. Most cases of gastrointestinal obstruction, including esophageal atresia, do not exhibit polyhydramnios until the late 2nd or early 3rd trimester. It therefore is unusual to make the diagnosis prior to this time. The prognosis in these fetuses depends on the associated abnormalities, the birth weight and whether the neonate will develop pneumonia secondary to aspiration.

References:

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

Pretorius DH, Drose JA, Dennis MA, Manchester DK, Manco-Johnson ML. Tracheoesophageal fistula in utero:twenty-two cases. J Ultrasound Med 6:509-513, 1987

Farrant P. The antenatal diagnosis of oesophageal atresia by ultrasound. Br J Radiol 53:1202, 1980

Scott JS, Wilson JK. Hydramnios as an early sign of oesophageal atresia. lancet 21:569, 1957

Pretorius DH, Meier PR, Johnson ML. Diagnosis of esophageal atresia in utero. J Ultrasound Med 2:475, 1983

Barkin SZ, Pretorius DH, Beckett MK et al. Severe polyhydramnios: incidence of anomalies. Amer J Roentgenol 148:155, 1987

Fraser FC, Czeizel A, Hanson C. Increased frequency of neural tube defects in sibs of children with other malformations. Lancet 17:144,1982

McKenna K, Goldstein RB, Stringer MD, Harrison MH. Esophageal atresia Radiology 3:729-733,

Rahmani MR, Zalev AH. Antenatal detection of esophageal atresia with distal tracheoesohageal fistula. J Clin Ultrasound 14:143-145, 1986

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