Ultrasonographic Prenatal Diagnosis of Upper Respiratory Tract Atresia M. J. Weston, FRCR, H. J. Porter, MRCPath, P. J. Berry, MRCPath, H. 5. Andrews, FRCR
Congenital laryngeal atresia is a rare malformation generally incompatible with life. 1 To our knowledge, Z:.J antenatal diagnosis has only rarely been described in the literature, and in these cases the diagnosis was not made until after 22 weeks of gestation. This report is of two cases of upper respiratory tract atresia detected at routine sonographic examination at 18 weeks' gestational age.
CASE REPORTS Patient JH is a 32 year old gravida 4, para 1 white women. Her three previous pregnancies resulted in a mistarriage at 13 weeks' gestation, a normal full -term delivery, and a therapeutic abortion at 19 weeks' gestation for a fetus with cerebral ventriculomegaly and bilateral renal agenesis. In the present pregnancy, routine sonography at the referring hospital at 18 weeks' gestational age revealed fetal ascites and an apparently abnormal heart. The patient was transferred to our tertiary referral center where further sonographic examination confirmed fetal hydrops and ascites (Fig. 1). However, bilateral, large, symmetrical, echogenic intrathoracic masses were found that were compressing the heart (Fig. 2) and causing eversion of the diaphragm (Fig. 3). No normal lung was seen. The heart was structurally normal. After counseling, therapeutic abortion was performed. Autopsy demonstrated laryngeal atresia, which had caused massive pneumomegaly and ascites. Apart from a thoracic hemiReceived February 10, 1992, from the Departments of Radiology (M.J.W., H.S.A) and Paediatric Pathology(H.J. P~ P.J.B.), St. Michaels Hospital, Bristol. England, Revised manuscript accepted for publication June 23, 1992, Address correspondence and reprint requests to M. J, Weston, FRCR. Department of Clinical Radiology, Bristol Royal Infirmary, Marlborough Street, Bristol BS2 8HW, England.
vertebra and associated absence of one rib no other structural abnormalitie$ were found. Chromosome studies showed a normal male karyotype. The abnormal fetus from her earlier pregnancy and the fetus with laryngeal atresia were believed to have had unrelated abnormalities, and the risk of recurrence of either was thought to be low. Patient CS is a 26 year old white primigravida. Early dating sonographic scan at 14 weeks' gestation was normal. A routine sonographic scan at 18 weeks' gestation showed bilateral, large, symmetrical, echogenic masses compressing the heart with no normal lung (Fig. 4). Ascites and oligohydramnios also were present. The sonographic features were considered almost identical with those of the previous case, and a diagnosis of laryngeal atresia was made. Therapeutic abortion was performed. Autopsy showed a normal larynx and upper 2.5 em of trachea. Thereafter, the trachea was replaced by a fibrous strand. No tracheoesophageal fistula
Figure 1 Parasagittal scan of the fetus showing the liver (asterisk) surrounded by ascites and the abnormal echogenic lung (arrows). Oligohydramnios is present.
© 1992 by the American Institute of Ultra,;ound in Medicine • J Ultrasound Med 11:673- 675, 1992 • 0278-4297/ 92/ $3.50
J Ultrasound Med 11:673- 675, 1992
UPPER RESPIRATORY TRACT ATRESIA
Figure 2 Axial scan of the fetal thorax in patient JH showing the compressed heart (arrow) and the bilateral echogenic lungs.
.Figure 4 Axial scan of the fetal thorax in patient CS, also showing a compressed heart and enlarged echogenic lungs (arrows).
noted. The fetus had a normal male karyotype. A final diagnosis of tracheal atresia was made.
Figure 3 Pathologic specimen of the fetus showing the large lungs and the everted diaphragm.
was present. Both lungs were grossly enlarged, causing dis placement and compression of other structures. The lungs together weighed more than five times that expected for gestational age (28.6 g versus 5.3 g). Apart from a single umbilical artery, no other structural abnormalities were 9
These two cases, one of laryngeal atresia and the other of tracheal atresia, exhibited almost identical ultrasonic features. The previous reports of antenatal ultrasonic diagnosis of laryngeal atresia 2.3 also document the striking feature of enlarged echogenic fetal lungs together with ascites and hydrops. However, in these two cases the diagnosis was made at 22 and 23 weeks' gestation, the ultrasonographic examinations at 18 and 15 weeks, respectively, having been normal. A report of the an· tenatal diagnosis of right main bronchus atresia has been published previously:' In this case, too, normal sonographic examinations had been obtained at 15 and 20 weeks' gestation, but then at 24 weeks a unilateral echogenic thoracic mass producing mediastinal shift was observed." Our cases illustrate that the readily recognizable changes in the lungs may be manifest earlier in gestation than 20 weeks. The enlarged lungs found in those cases of laryngeal atresia diagnosed antenatally are thought to be attributable to excessive retention of fluid within the lung.' The clearance of lung secretions is normally via the upper airways. The lungs appear echogenic on sono· grams owing to the multiple small fluid-filled spaces within them, analogously to infantile polycystic kidneys. The concomitant ascites and hydrops most likely arise from the compression of the heart and great vessels by the lungs.
J Ultrasound Med 11:673- 675, 1992
Nearly all cases of laryngeal atresia have been diagnosed at autopsy, only four patients having been re1 ported to have survived the neonatal period. Cases of laryngeal atresia found at birth either have been associated with multiple unrelated abnormalities or with other abnormalities of the esophagus and trachea or have been isolated abnormalities. 6 Tracheal agenesis also is a very rare congenital disorder7 that is usually fatal in the first day of life. Warfel and Schulz8 noted that laryngeal atresia occurred in association with tracheal agenesis in 40% of the cases they reviewed. None of these authors remarked on the presence of massive lung enlargement, as in our cases, although in most of their cases an esophagobronchial fistula was present, which would have allowed drainage of the lung secretions. Shen-Schwartz and coworkers9 included in their series of fetal anomalies one case of tracheal agenesis, in which congenital cystic adenomatoid malformation (CCAM) and hydrops were diagnosed sonographically. We speculate that the CCAM was a misdiagnosis of the enlarged echogenic lungs encountered in tracheal and laryngeal atresia. Although CCAM could be included in the differential diagnosis of the sonographic appearances of upper respiratory tract atresia, it almost invariably is unilateral. The fetal insult that causes tracheal agenesis is thought to occur at 4 to 6 weeks' gestational age. Other organs are undergoing critical development at this time, so that the presence of multiple unrelated abnormalities would not be unexpected, although these were not present in our cases. Alternatively, it is possible that an insult, probably vascular, may occur later in gesta+ tion to cause obliteration of the main stem or lobar bronchi.
WESTON ET AL
CONCLUSION Laryngeal and tracheal atresia (in the absence of tracheal fistula), although rare conditions, are readily diagnosable antenatally by identical characteristic changes in the lungs. These may be observed at an earlier gestational age than reported previously.
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