[The left superior intercostal vein (author's transl)].

Study on the LSIV has several points of value: It enters into the normal mediastinal outline, forming the aortic "nipple". It may be the site of dilatation, either congenitally or secondary to haemodynamics changes. This venous dilatation should not be confused with a mediastinal tumour. It forms, in the majority of cases, an anastomosis between the superior vena cava and the azgos vein and therefore plays a part in the collateral circulation of caval obstruction syndromes. Its transverse course explains its involvement in the anterior and posterior mediastinal syndromes. Opacification of the LSIV should be part of the study of mediastinal tumours. By virtue of its relations with the left upper lobe, its study should be part of the pre-therapeutic assessment of such lesions.