LAUSR

To the Editor, Bronchial atresia is a rare condition, typically affecting the subsegmental bronchi, and often noted on prenatal ultrasounds as a hyperexpanded fluid filled lung segment. The more proximal the atresia, the more severe and life‐threatening the presentation. Only ten cases of mainstem bronchial atresia (MBA) have been reported to date, with universally poor outcomes. Unlike peripheral bronchial atresia, MBA presents a unique challenge with expansion of the involved lung, mediastinal compression and contralateral shift, hydrops and fetal or infant death. This represents a form of unilateral Congenital High Airway Obstructive Syndrome (CHAOS), with the more common laryngeal or tracheal atresia type CHAOS causing bilateral lung hyperexpansion and diaphragmatic eversion. A 26‐year‐old female was referred for evaluation at 22 weeks gestational age (GA) for possible fetal CHAOS. Fetal magnetic resonance imaging (MRI) at 25 weeks GA revealed overexpansion of the right lung suggesting obstruction of the right mainstem bronchus (MSB), as well as ascites with polyhydramnios (Figure 1A). Fetal echocardiogram was normal. Fetal MRI at 33 weeks GA found decompression of the lung and resolution of hydrops (Figure 1B). Due to fetal distress at 36 + 1 weeks GA, a cesarean section was performed. The male infant was 1940 g and required intubation on placental support. He demonstrated asymmetric chest wall movement with absent right sided breath sounds. Chest X‐ray showed complete opacification of the right lung (Figure 2A). Echocardiogram revealed suprasystemic right ventricular pressure (RVP) with normal biventricular function. Bronchoscopy confirmed complete stenosis of the right MSB just distal to the carina with otherwise normal anatomy (Figure 3A,B). Following regression of the ductus arteriosus, the infant had a long‐ segment left pulmonary artery (LPA) stenosis. Angiographically, the distal left lung vasculature appeared normal but the right side appeared dilated and tortuous. After angioplasty, the proximal LPA peak gradient improved from 37 to 23mmHg, inotropic support weaned, and inhaled pulmonary vasodilatory agents transitioned to enteral sildenafil. Subsequent MRI of the chest (Figure 1C) revealed a completely nonaerated right lung, but with a normal bronchial branching pattern distal to the atretic segment, and a substantial amount of right lung with normal appearing vasculature. Phase contrast illustrated a flow differential of 10% and 90% effective flow to the right and left lung, respectively. Following this, the infant was extubated to noninvasive ventilatory support at 22 days of life (Figure 2B). Serial echocardiography