Congenital high airway obstruction syndrome or sequence (CHAOS) refers to a rare, often lethal, congenital laryngotracheal condition and is primarily characterized by obstruction to the fetal upper airway.
CHAOS can be of three possible types 2:
- complete laryngeal atresia without an esophageal fistula
- complete laryngeal atresia with a tracheo-esophageal fistula
- near-complete high upper airway obstruction
Ultrasound may show some or all of the following features 4,5
- dilated trachea/bronchi: distal to the obstruction
- enlarged and echogenic lungs
- diaphragmatic inversion and/or flattening
- presence of fetal ascites
- the fetal heart may appear displaced to the midline and compressed
Ancillary sonographic features include
May confirm features detected on ultrasound as well as more accurately show the level of obstruction. Lung signal is increased 5.
Treatment and prognosis
The prenatal natural history and postnatal course of CHAOS often depends on whether the airway obstruction is complete. An ex utero intrapartum treatment (EXIT) procedure may offer potential for salvage 1,3. Overall prognosis is considered generally poor 6.
The differential diagnosis of echogenic fetal lung is congenital cystic adenomatoid malformation (CCAM) type III. In CHAOS, both lungs are echogenic, whereas CCAM is usually unilateral, but can be bilateral in rare cases. Dilated airway is another clue which is seen only in CHAOS 9-11.
- 1. Lim FY, Crombleholme TM, Hedrick HL et-al. Congenital high airway obstruction syndrome: natural history and management. J. Pediatr. Surg. 2003;38 (6): 940-5. J. Pediatr. Surg. (link) - Pubmed citation
- 2. Hartnick CJ, Rutter M, Lang F et-al. Congenital high airway obstruction syndrome and airway reconstruction: an evolving paradigm. Arch. Otolaryngol. Head Neck Surg. 2002;128 (5): 567-70. Arch. Otolaryngol. Head Neck Surg. (link) - Pubmed citation
- 3. Shimabukuro F, Sakumoto K, Masamoto H et-al. A case of congenital high airway obstruction syndrome managed by ex utero intrapartum treatment: case report and review of the literature. Am J Perinatol. 2007;24 (3): 197-201. doi:10.1055/s-2007-972928 - Pubmed citation
- 4. Mong A, Johnson AM, Kramer SS et-al. Congenital high airway obstruction syndrome: MR/US findings, effect on management, and outcome. Pediatr Radiol. 2008;38 (11): 1171-9. doi:10.1007/s00247-008-0962-2 - Pubmed citation
- 5. Guimaraes CV, Linam LE, Kline-fath BM et-al. Prenatal MRI findings of fetuses with congenital high airway obstruction sequence. Korean J Radiol. 10 (2): 129-34. doi:10.3348/kjr.2009.10.2.129 - Free text at pubmed - Pubmed citation
- 6. Cavoretto P, Molina F, Poggi S et-al. Prenatal diagnosis and outcome of echogenic fetal lung lesions. Ultrasound Obstet Gynecol. 2008;32 (6): 769-83. doi:10.1002/uog.6218 - Pubmed citation
- 7. Kuwashima S, Kitajima K, Kaji Y et-al. MR imaging appearance of laryngeal atresia (congenital high airway obstruction syndrome): unique course in a fetus. Pediatr Radiol. 2008;38 (3): 344-7. doi:10.1007/s00247-007-0693-9 - Pubmed citation
- 8. Biyyam DR, Chapman T, Ferguson MR et-al. Congenital lung abnormalities: embryologic features, prenatal diagnosis, and postnatal radiologic-pathologic correlation. Radiographics. 2010;30 (6): 1721-38. doi:10.1148/rg.306105508 - Pubmed citation
- 9. Chaemsaithong P, Chansoon T, Chanrachakul B, Worawichawong S, Wongwaisayawan S, Promsonthi P. Prenatal diagnosis and pathology of laryngeal atresia in congenital high airway obstruction syndrome. (2012) Case reports in radiology. 2012: 616905. doi:10.1155/2012/616905 - Pubmed
- 10. Laxmi Devi Padmanabhan, Sheela Nampoothiri. Prenatal detection of congenital high airway obstruction syndrome with encephalocele. (2016) Indian Journal of Radiology and Imaging. 26 (1): 70. doi:10.4103/0971-3026.178336 - Pubmed
- 11. Artunc Ulkumen B, Pala HG, Nese N, Tarhan S, Baytur Y. Prenatal diagnosis of congenital high airway obstruction syndrome: report of two cases and brief review of the literature. (2013) Case reports in obstetrics and gynecology. 2013: 728974. doi:10.1155/2013/728974 - Pubmed