Fetal Laryngeal Atresia

Laryngeal Atresia (Hydrops)

Laryngeal Atresia-(Dilated bronchi)

Dilated fluid-filled bronchus

Findings:

Both lungs are echogenic and expanded. Two tubular fluid filled structures are identified (arrows) which represent the dilated fluid-filled main-stem bronchi. To assist in differentiation of the bronchi from vascular structures, color Doppler flow imaging was performed which shows no evidence of flow in the bronchial or tracheal segments. There was no evidence of fetal hydrops and no other malformations were identified.

Discussion:

Normally the lung echogenicity in the second trimester is equal to the echogenicity of the liver. However, lung echogenicity that is greater than liver echogenicity has been reported in 30% of cases. Although once thought to be a sign of fetal lung maturity, this has proved relatively insensitive and non-specific for this diagnosis. What makes this case different from the normally echogenic fetal lung is the mass effect and dilated tracheo-bronchial tree.

Laryngeal-tracheo-bronchial atresia results either from an obstructing lesion ie cartilaginous bar or vascular insult with atresia of the airways which occurs during intrauterine development. In the case of bronchial atresia the insult usually occurs after the 15th week when bronchial branching is complete, but may occur between the 5th and 15th weeks. Proximal obstructing lesions, as in this case, result in fetal lungs that are distended with secretions and demonstrate accelerated lung growth and maturation. The trachea and bronchi are filled with fluid and are distended. The mass effect from the distended lung can cause compression of the venous return, heart and esophagus resulting in polyhydramnios and fetal hydrops.

US and MRI of a 25 wk fetus with layyngeal atresia. The markedly expanded lungs (arrows) are readily identified with both techniques. Hydrops was present. Asc=ascites

US and MRI scans of the upper thorax and neck from the same patient demonstrate a dilated obstructed trachea (arrow) seen to the level of the larynx. Of interest in this case is that markedly dilated fluid-filled bronchi were not present as in the other case.

Laryngeal / tracheal atresia may be isolated or part of a number of syndromes. Fraser syndrome is the most common of these. It is an abnormality which includes tracheal or laryngeal atresia, renal agenesis, micropthalmia, cryptopthalmos and polydactyly or syndactyly. This syndrome is autosomal recessive. A recent case report of tracheal atresia diagnosed at 19 weeks was reported by Kassanos et al. It is of interest that oligohydramnios was present in this case. Most cases of tracheal or laryngeal atresia present with polyhydramnios which may or may not be accompanied with hydrops fetalis. The presence of normal kidneys in this case would reconfirm the importance of the production of lung fluid and its contribution to total amniotic fluid volume early in pregnancy. The authors cite the common association of increased amniotic fluid in the presence of cystic adenomatoid malformation of the lung from too much lung fluid being produced. This, they state, may be used a distinguishing feature between these two entities.

Associated Abnormalities with Laryngeal Atresia reported in the Literature*

Name of Syndrome Mode of Inheritance
Fraser syndrome Autosomal Recessive
Opitz–Frias syndrome (G syndrome or BBBG syndrome) Autosomal Dominant
MCA syndrome (multiple congenital anomalies syndrome) Unknown
Di George syndrome 22 q 11.2 deletion
Velo-cardio-facial syndrome 22 q 11.2 deletion
Marshall–Smith syndrome Unknown
Laurence–Moon–Bardet–Biedl syndrome Autosomal Recessive
Short-rib polydactyly type II (Majewski) syndrome Autosomal Recessive
Oral-facial-digital type II (Mohr) syndrome Autosomal Recessive
Pallister–Hall syndrome Autosomal Dominant
Hydrolethalus syndrome Autosomal Recessive
Schinzel–Giedion syndrome Autosomal Recessive
Oculo-auriculo-vertebral spectrum (Goldenhar Syndrome) Unknown
VACTERL association Unknown
Crouzon’s syndrome Unknown
Pfeiffer syndrome Unknown
LEL syndrome (laryngeal atresia, encephalocele, limb deformities) Unknown

* From: Onderoglu L, Karamursell S, Bulun A et al Prenatal Diagnosis of Laryngeal Atresia Prenatal Diagnosis 23:277-80, 2003

 

Interestingly, information gained from this disease is being used to treat another; congenital diaphragmatic hernia. Experimental work has revealed that if the trachea is occluded in utero, dramatic expansion of the lungs will occur which will have two benefits: reduction of the hernia downward due to the mass effect of the expanding lungs and increased lung growth, thus preventing pulmonary hypoplasia. Several centers have performed this surgery in patients sucessfully.

Differential Diagnosis:

This abnormality should be distinguished from the normally echogenic lung and from cystic adenomatoid malformation of the lung. The normal fetal lung which may have increased echogenicity should not have mass effect and will not have a dilated tracheo-bronchial tree. Cystic adenomatoid malformation (CCAM) of the lung can result in an echogenic lung that demonstrates mass effect. It usually is unilateral, although bilateral cases have been described. CCAM may have cysts and does not have dilatation of the tracheo-bronchial tree. Pulmonary sequestrations may also be echogenic and also have been reported to be bilateral, however they usually do not involve and expand the entire lung. Intrathoracic teratomas may also demonstrate an echogenic mass effect but should be distinguishable from this abnormality.

References:

Watson WJ, Thorp Jr JM, Miller RC, Chescheir NC et al. Prenatal diagnosis of laryngeal atresia. Am J Obstet Gynecol 163:1456-7, 1990

McAlister WH, Wright Jr JR and Crane JP Main-stem bronchial atresia: Intrauterine sonographic diagnosis Amer J Roentgenol 148:364-366, 1987

Choong KKL, Trudinger B, Chow C and Osborn RA Ultrasound Obstet Gynecol 2:357-359, 1992

Kassanos D, Christodoulou CN, Agapitos E et al. Prenatal ultrasonographic detection of the tracheal atresia sequence Ultrasound Obstet. Gynecol 10:133-136, 1997

Onderoglu L, Karamursell S, Bulun A et al Prenatal Diagnosis of Laryngeal Atresia Prenatal Diagnosis 23:277-80. 2003

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