[The non-bronchial systemic vascular circulation of the lung]

The non bronchial systemic arterial circulation of the lung may, for more than one good reason, be considered as a third arterial circulation of the lung, after the bronchial and pulmonary circulation. A perfect knowledge of the anatomy of the circulation and the physiopathological mechanisms leading to its development is a vital prelude to angiographic study. A common point in the majority of situations leading to this non bronchial systemic arterial hypervascularization is the existence of a pleural symphysis allowing the pulmonary penetration of these thoracic parietal vessels. In addition to the contribution of the transpleural non bronchial systemic vessels the role of the arteries of the triangular ligament should be discussed. The pathological significance of this non bronchial systemic hypervascularization is threefold. This circulation can be the source of haemoptysis as shown by angiography and is important for considering therapy when haemoptysis needs treatment by percutaneous embolisation. The duration and the risk of catheterisation may be considerably reduced thanks to the precision of the endoscopic examination at the site of bleeding. There are other types of endothoracic haemorrhage which can be qualified as "haemoptysis like" whose treatment, preventative or curative may also be assured by embolisation of this circulation. Besides a certain number of extracardiac shunts both endo and transthoracic, without any haemorrhagic consequence at the time at which they are discovered show evidence of abnormal communication between the three circulations of the lung; certain of these may need therapy by vaso-occlusion.