CHAOS - Refers to a rare & fatal congenital anomaly seen due to obstruction of upper airway in fetal life either due to oropharyngeal or neck masses , & or most common being laryngeal / tracheal atresia. The risk of associated chromosomal anomaly is very rare , and overall the prognosis is considered to be poor. However some cases can be treated with neonatal intervention such as , ex - utero – intrapartum treatment By- Dr.Subhash Tailor
Antenatal ultraound diagnostic criterias are -
1. Dilated fluid filled trachea / bronchi distal to obstruction
2. Bulky echogenic lungs
3. Diaphragmatic flattening and or inversion
4. Midline positioned & compressed fetal heart
5. Fetal ascites and Anasarca
6. Fetal neck mass , if any
A case of CHAOS diagnosed antenatally with ultrasound at about 17 weeks of gestation is being presented here featuring classical findings .
Case details - A 28 yrs old 2nd gravida was asked for anomaly scan . Her previous pregnancy was stated to be normal .
AT USG - fetal chest showed bulky echogenic lungs with dilated and fluid filled trachea and proximal bronchi. The domes were also inverted . Fetal heart was seen narrowed , midline positioned and appeared compressed between bulky echogenic lungs . Fetal hydropic changes were also seen as skin / soft tissue edema and ascites [ likely due to fetal heart failure ]. See figures 1 to 4
The liquer amnio was average in this case . These antenatal ultrasound findings were diagnostic of CHAOS . The parents decided to terminate the pregnancy .
Figure 1- Fetal coronal thoracic & axial head scans shows bulky echogenic both lungs , dilated fluid filled trachea & bronchi with inverted diaphragms ,& scalp edema .
Figure 2- Coronal US scan of fetal chest including part ofupper abdomen - shows enlarged echogenic lung masses & mild ascites
Figure 3- Fetal thorax coronal color Doppler scan shows fluid filled dilated trachea –bronchi [color void]
Figure 4 – TS fetal thorax shows midline narrow compressed heart[arrows]