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The Pulmonary and Bronchial Vessels, Pulmonary Vascular Abnormalities including Embolism, Pulmonary and Bronchial Angiography, and A/V Malformations.
Published in Fred W Wright, Radiology of the Chest and Related Conditions, 2022
The presence of systemic arteries to the lung with the scimitar syndrome, is explained by embryology. The circulation to the primitive lung bud arises from the splanchnic plexus and in early foetal life there are numerous anastomoses between the postbranchial pulmonary plexus and the primitive ventral and dorsal aortae. When the pulmonary artery develops from the sixth branchial arch and spreads into the developing lung with the bronchial bud, anastomoses occur and the primitive vessels mainly atrophy, the bronchial vessels only remaining. These abdominal vessels commonly pass into the chest via the inferior pulmonary ligaments (ps. 2.32 - 35).
Scimitar Sign
Published in Michael E. Mulligan, Classic Radiologic Signs, 2020
John Roehm and colleagues2 (University of Minnesota) describing the scimitar syndrome said, ‘The full-blown syndrome, which invariably involves the right lung and its vascular supply, consists of: (a) hypoplasia of the right lung with subsequent dextroposition of the heart into the right thoracic cavity; (b) hypoplasia of the right pulmonary artery; (c) anomalous arterial supply from the abdominal aorta to the right lower lobe; (d) most important of all, anomalous venous drainage of the right lung by a large vein emptying into the inferior vena cava [Figure 1]. Due to its gentle curvature, the vein appears quite similar to a curved sword or scimitar.’
Respiratory Medicine
Published in Stephan Strobel, Lewis Spitz, Stephen D. Marks, Great Ormond Street Handbook of Paediatrics, 2019
Colin Wallis, Helen Spencer, Sam Sonnappa
Scimitar syndrome applies to a dysmorphic condition of the right lung classically represented by hypoplasia of the right lung with a corresponding mediastinal shift where the entire right lung drains into the right atrium or inferior vena cava and systemic collaterals are present. There are many variations on both arterial supply and venous drainage but the syndrome pertains particularly to abnormalities of the whole lung. Although the term ‘scimitar syndrome’ is in common use, we would suggest that all complex abnormalities of lung structure and blood supply are described anatomically, clearly defining the structure of the airways and pulmonary lobes, detailing the arterial supply to each area, and documenting the venous drainage of the lungs.
Monochorionic Twin Discordance for Horseshoe Lung and Tricuspid Atresia
Published in Fetal and Pediatric Pathology, 2022
Marina Sousa Gomes, José Monterroso, Otília Brandão, Carla Ramalho
In 1962, Spencer first described a horseshoe lung, a malformation in which the base of the right and left lungs were joined by an isthmus posterior to the heart [2]. The initial patient had hypoplasia of the right lung, dextroversion of the heart, anomalous pulmonary venous return, and abnormal arterial supply to the right. Since this first case, tens of cases have been reported in the literature. The common feature in all cases is the presence of unilateral pulmonary hypoplasia, mostly of the right lung [5]. These anomalies can coexist with absence or variable degrees of hypoplasia of a pulmonary artery and anomalous venous return to the inferior vena cava or right atrium (scimitar syndrome) [1, 2], abnormal systemic arterial supply from the descending thoracic or abdominal aorta to the right lung, accessory diaphragm, or pulmonary sequestration with diaphragmatic defects [3]. Pulmonary venous stenosis was frequently observed [3]. Overlapping of these features suggests a common embryogenesis error that probably occurs in a very early stage of development [2]. Different theories can be found in the literature. The parenchymatous connection between the two lungs could be a result of a fusion process due to an abnormal persistence of the normal communications between the embryonic pericardial and the two pleural cavities that facilitated the growth of the inferior lobe of the right lung into the left pleural cavity [2]. Other authors suggest that horseshoe lungs could be a result of the non-separation of the splanchnic mesoderm [5]. Some authors suggest that horseshoe lung is the first event. The hypoplastic right lung promotes the displacement of the cardiac apex to the right and the occurrence of partial anomalous pulmonary venous return, possibly due to the anomalous tropism of the right pulmonary veins. Alternately, Massumi et al. [6] suggested that the anomalous pulmonary venous drainage into the inferior vena cava was the initial event. Dextroposition of the heart, hypoplasia of the right lung, and undeveloped right pulmonary artery were the physiologic consequences of obstruction to venous return from the right lung. That the majority of horseshoe lungs are associated with scimitar syndrome favors this hypothesis [1, 2, 4]. However, as in this case, few previously published cases of horseshoe lung were associated with pulmonary hypoplasia without additional features of scimitar syndrome [4]. The present case, despite sharing some anomalies of the scimitar syndrome, did not have drainage into the inferior vena cava, not supporting Massumi et al.’s theory.