Left-sided “Scimitar-like” Vein: Partial Anomalous Left Pulmonary Venous Drainage to Main Portal Vein

A4-year-old boy presented to the pediatric cardiology clinic with cyanosis and poor exercise tolerance. Chest radiography revealed dilated central pulmonary arteries with peripheral pruning. Note was also made of bilateral bronchi of the right bronchial morphology. Superior mediastinal widening was noted likely due to the thymic shadow [Figure 1]. Transthoracic echocardiography revealed an atrioventricular septal defect with single ventricular morphology. The left-sided pulmonary veins were not seen draining into the left atrium, and a suspicion of left-sided partial anomalous pulmonary venous connection (PAPVC) was raised. Subsequently, the patient underwent cardiac computed tomography (CT) angiography for further anatomical evaluation of the intra-cardiac morphology, including the pulmonary venous system, and to look for other associated cardiovascular anomalies.Figure 1: Chest radiograph demonstrates dilated central pulmonary arteries with peripheral pruning. Note is also made of bilateral bronchi of right bronchial morphology. Superior mediastinal widening is noted likely due to the thymic shadowCardiac CT angiography revealed levocardia with asplenia with a large transverse liver. Both atrial appendages showed right atrial appendage morphology, and bilateral bronchi were of right bronchial morphology [Figure 2]. Atrioventricular septal defect with single ventricle of right ventricular morphology, double outlet right ventricle, and confluent dilated pulmonary arteries were observed. The right superior caval vein and the inferior caval vein, along with the right and middle hepatic veins, were seen draining into the right-sided atrium, whereas the left hepatic vein was seen draining independently into the left-sided atrium.Figure 2: Axial image (a) at the abdomen level shows asplenia with a large transverse liver and stomach (s) on the left side. Oblique axial image (b) reveals both right atrial appendage (RAA) and left atrial appendage of RAA morphology. Coronal minimum intensity projection image (c) shows the right (r) and left (l) bronchi of right bronchial morphology. Oblique axial image (d) shows confluent dilated right pulmonary artery and left pulmonary artery. LPA: left pulmonary artery, RPA: right pulmonary artery, RAA: Right atrial appendage, LAA: Left atrial appendageThe right-sided pulmonary veins were draining orthotopically into the left-sided atrium. However, the left superior and inferior pulmonary veins joined together to form a vertical descending vein which traversed along the midline in the posterior mediastinum and coursed caudally across the esophageal hiatus to drain into the main portal vein [Figure 3 and Supplementary Video 1]. The main portal vein showed fusiform aneurysmal dilatation (measured 18 mm in caliber). No stenosis or obstruction was seen. No hypoplasia of either pulmonary artery or lung was noted. No inter-or intra-lobular septal thickening was noted.Figure 3: Cinematic rendered images (a) anterior view; (b) right lateral view; (c) posterior view; and (d) posterior view with pulmonary arteries subtracted show the left superior pulmonary vein (white arrowhead) and left inferior pulmonary vein (yellow arrowhead) joining together to form vertical descending vein (asterisks) which courses along the midline in the posterior mediastinum and traverses caudally across the esophageal hiatus to drain into the main portal vein. The right-sided pulmonary veins (thick white arrow in D) are seen draining orthotopically into the left-sided atrium. LPA: left pulmonary artery, RPA: right pulmonary artery, MPV: Main portal vein, LA: Left-sided atrium {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 1","caption":"","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_gsvlfrpr"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} During the initial intrauterine period, around day 25–27 of gestation, primordial pulmonary venous plexus connects with the cardinal and umbilico-vitelline venous system. Eventually with development of out-pouching from posterior wall of left atrium which incorporates the pulmonary venosus system, there is involution of connections with cardinal and umbilico-vitelline veins resulting in normal drainage of pulmonary veins into the left atrium. Failure of incorporation of pulmonary veins into left atrium results in persistence of embryological connections with cardinal and umbilicovitelline venous system resulting in partial or total anomalous pulmonary venous drainage.[1] The infra-cardiac type of PAPVC is characterized by subtotal anomalous drainage of pulmonary veins into the inferior vena cava, hepatic veins, or portal venous system. Infra-cardiac PAPVC is usually seen in conjunction with congenital pulmonary venolobar syndrome (also called Scimitar syndrome), wherein anomalous infra-cardiac drainage of right-sided pulmonary veins is accompanied by dextrocardia, pulmonary hypoplasia, pulmonary sequestration, and systemic arterialization of the lung.[2] Puthiyedath et al. also reported a case wherein anomalous drainage of right pulmonary veins to the portal vein was observed in the setting of Scimitar syndrome.[3] Few cases of left-sided congenital pulmonary venolobar syndrome have been reported wherein PAPVC of left-sided pulmonary veins was seen in the inferior vena cava, hepatic veins, and azygous vein.[4-6] An isolated left-sided PAPVC draining into the inferior vena cava has previously been reported in a 22-year-old female by Juraszek et al. with a normal left pulmonary artery and left lung.[7] Infracardiac type of PAPVC is most frequently associated with stenosis/obstruction owing to extrinsic compression at level of diaphragmatic hiatus and physiological flow obstruction at the level of hepatic sinusoids. In cases with obstruction, severe pulmonary venous hypertension develops, and the prognosis is poor with high mortality, if left untreated.[8] In the present case, the left-sided PAPVC into portal vein is seen resulting in fusiform aneurysmal dilatation of portal vein, likely secondary to elevated portal system pressures. Absence of any stenosis or obstruction in vertical descending vein along its entire course and at drainage site mitigated development of pulmonary venous hypertension till his current age of presentation. Infra-cardiac PAPVC of left-sided pulmonary veins into the portal venous system in conjunction with normal left pulmonary artery and left lung (in the setting of complex congenital heart disease) has been hitherto unreported. The present case highlights this unique variant of infra-cardiac PAPVC in the absence of Scimitar syndrome and the role of CT angiography in the accurate presurgical evaluation of such cases. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.