A 2-year-old-child presented to our hospital with complaints of persistent cough, difficulty in breathing and dysphagia, especially with liquids. On echocardiography, there were changes of pulmonary arterial hypertension (PAH) without any definite congenital cardiac abnormality. Computed tomography angiography (CTA) was performed for further evaluation of PAH and to rule out any vascular cause for dysphagia. CTA depicted the presence of a “Horse-shoe lung,” manifesting as a band of pulmonary parenchyma, representing the “lung isthmus” connecting the bases of both the lungs, posterior to the heart and anterior to the esophagus and aorta. The pulmonary arterial supply to the isthmic segment was from the right pulmonary artery, which gave off two branches to the isthmus. Both the branches were seen crossing the midline, had a prominent caliber with a tortuous “serpentine” like course. The larger inferior branch was seen crossing anterior to the esophagus, causing anterior extrinsic esophageal compression. There was ostial stenosis noted in the superior isthmic pulmonary artery branch. The dilated pulmonary arteries suggested changes of PAH. The bronchial supply to the isthmus was derived from the right main bronchus, which was also seen crossing the midline. There was reduced attenuation and increased volume of the isthmus, likely secondary to air trapping. Additionally, there was presence of right upper lobe aplasia and right-sided partial anomalous pulmonary venous connection (PAPVC), with the right sided pulmonary veins draining into the right atrium at the junction of the superior vena cava and the right atrium, which was the cause of PAH with the dilated pulmonary artery causing extrinsic esophageal compression.
As discussed in the Heart Team meeting, the child underwent successful surgery with rerouting of the right sided pulmonary veins into the left atrium, thus causing hemodynamic correction of PAH. Postoperatively, the child had a significant relief in his dysphagia symptoms, that did not warrant any additional intervention (Figure 1).
Figure 1
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Contrast-enhanced CTA thorax. Axial lung window CT image (A) shows the typical appearance of horseshoe lung with isthmus connecting both the lower lobes (white asterix) and a thin pleural line seen separating the left lung from the isthmus (white arrow). Coronal oblique mediastinal window CT image (B) and volume rendered image (C) showing the dual pulmonary arterial supply to the lung isthmus from RPA (red arrow), with prominent and tortuous course of the branch vessels and ostial stenosis of the superior branch (white arrow head). Axial maximum intensity projection (D) and sagittal minimum intensity projection (E) CT images depicting the esophageal compression (red asterix) by the anteriorly placed tortuous inferior pulmonary artery branch of the isthmus (red arrow). Coronal oblique minimum intensity projection CT image (F) showing the bronchial supply to isthmus arising from the right bronchus (black arrow). Volume rendered CT image (G) showing the right side pulmonary veins draining into the right atrium at superior vena cava-right atrial junction establishing the diagnosis of partial anomalous pulmonary venous return. Note the absent right upper lobe pulmonary artery (B) and right upper lobe bronchus (F) suggesting right upper lobe aplasia. Eo, esophagus; LPA, left pulmonary artery; MPA, main pulmonary artery; PV, right sided pulmonary venous confluence; RA, right atrium; RPA, right pulmonary artery; RV, right ventricle; SVC, superior vena cava; Tra, trachea. [Color figure can be viewed at wileyonlinelibrary.com]
Horseshoe lung is a rare congenital malformation with a poorly understood embryogenesis, characterized by an isthmus of pulmonary parenchyma between both the lower lobes.1 Isthmus extends across the midline, between the heart anteriorly and the esophagus and spine posteriorly. The fusion of the lungs occurs through a defect in parietal pleura, with or without an intervening visceral pleura.2 It is most commonly associated with hypogenetic lung syndrome with arterial and bronchial supply of the isthmic portion invariably from the hypoplastic lung, which are easily demonstrable on CTA.3 Horseshoe lung may also present as a component of congenital venolobar syndrome which is characterized by various anomalies in the thorax. Major components of this syndrome include hypogenetic lung syndrome, PAPVC (scimitar syndrome), pulmonary sequestration, absence of the pulmonary artery, systemic arterialization of the lung without sequestration, and absence or interruption of the inferior vena cava.4
Few cases of esophageal atresia with or without tracheoesophageal fistula associated with horseshoe lung have been previously reported, however to the best of our knowledge, esophageal compression due to an anteriorly placed pulmonary arterial branch of lung isthmus has not been described before.5 One needs to be aware of this potential vascular cause of dysphagia which can masquerade as partial anomalous pulmonary artery forming a pseudo-pulmonary sling on imaging.