(CHAO = CONGENITAL
HIGH AIRWAY OBSTRUCTION)
(Laryngeal atresia and webs, subglottic stenosis and high tracheal atresia
Congenital laryngeal or tracheal atresia is a rare malformation almost always
incompatible with life. The level of obstruction may be subglottic (laryngeal),
proximal or distal tracheal. The site of obstruction may be determined
antenatally (1) and may be important, as infants with subglottic atresias have
survived by performing an emergency tracheostomy (2). Congenital anomalies of
the trachea usually have associated esophageal anomalies (depending on the
timing of the derangement) as in the embryo the esophagus and respiratory tract
have a common origin from the anterior foregut.
The etiology is unknown, although sporadic, genetic (3) and vascular causes
(4) have all been proposed.
Link to Table of Reported Cases
Antenatal diagnosis is possible because of the secondary structural changes
that are present in the fetal lung as a result of the laryngeal atresia.
- Bilateral symmetrically
enlarged hyperechogenic lungs. Upper airway obstruction promotes pulmonary
hyperplasia (5) causing over-distention of the alveoli by lung fluid (6),
resulting in numerous tissue-filled spaces, which reflect far more echoes
than the normal lung producing the characteristic hyperechogenic
- Echogenic lungs increase chest
circumference and may compress the heart.
- The majority of tracheal
atresias are associated with an esophageal fistula with normal appearing
lungs as the pulmonary fluid can escape into the gastrointestinal tract.
- Ascites (the hyperplastic
and distended lungs invert the diaphragm, compress the heart and impair
venous return to the right atrium).
- Polyhydramnios (as a result
of either obstruction of the esophageal passage of amniotic fluid by the
enlarging lung mass or compression of the stomach and intestines by the
- +/- Fetal hydrops.
- Color doppler
- Normal fluid flow in
the upper trachea can be demonstrated during fetal breathing activity.
Opening of the glottis can be seen during fetal breathing.
- In CHAO there is absence
of fluid flow during rhythmic thoracic movements.
VATER association (9).
DiGeorge developmental field defect (10).
chondrodysplasia punctata (11).
The differential diagnosis of enlarged echogenic lungs includes type III
cystic adenomatoid malformation (12), pulmonary sequestration, diaphragmatic
hernia and mediastinal teratoma. However with the exception of a small
percentage of cases with type III cystic adenomatoid malformation the other
lesions are almost always unilateral whereas laryngeal atresia always produces
bilateral echogenic lungs.
Dolkart LA, Reimers FT, Wertheimer IS et.al.
Prenatal diagnosis of laryngeal atresia. J Ultrasound Med 1992;11:496.
Richards DS, Yancey MK, Duff P et.al. The perinatal
management of severe laryngeal stenosis. Obstet Gynecol 1992;30:537.
King SJ, Pilling DW, Walkinshaw S. Fetal echogenic
lung lesions: Prenatal ultrasound diagnosis and outcome. Pediatr Radiol 1995;25:208.M
McAlister WH, Wright JR Jr, Crane JP. Mainstem
bronchial atresia: Intrauterine sonographic diagnosis. AJR 1987;148:364.
Wigglesworth JS, Desai R, Hislop AA. Fetal lung
growth in congenital laryngeal atresia.
Pediatr Radiol 1987;7:515-525.
Hullu JA, Kornman LH, Beekhuis et.al. The
hyperechogenic lungs of laryngotracheal obstruction. Ultrasound Obstet Gynecol
Meagher SE, Fisk
NM, Harvey JG et.al. Disappearing
lung echogenicity in fetal bronchopulmonary malformations: a reassuring sign?
Prenat Diagn 1993;13:495-501.
Schauer GM, Dunn LK, Godmilow L et.al. Prenatal
diagnosis of Fraser syndrome at 18.5 weeks gestation, with autopsy findings at
19 weeks. Am J Med Genet 1990;37:583-591.
Baarsma R, Bekedam DJ, Visser GHA. Qualitative
abnormal fetal breathing movements, associated with tracheal atresia. Early Hum
10. Moerman P,
DeZegher F, Vandenberghe K et.al. Laryngeal atresia as part of the DiGeorge
developmental field defect. Genet Couns 992;3:133-137.
11. Storm W,
Fasse M. Laryngeal atresia in a child with Rhizomelic chondroplasia punctata.
Monatsschr Kinderheilkd 1991;139:629-631.
Scott JN, Trevenen CL, Wiseman DA, Elliot PD.
Tracheal atresia: Ultrasonographic and pathologic correlation. J Ultrasound Med