title: [The azygos system].
abstract: The great variety of anatomical dispositions of the azygos system explains its facility of adaptation. The second lumbar vein is able to play a buffer role between the caval systems or, conversely, is able to direct venous flow to a preferential system. In case of portal hypertension, an inferior omphalo-azygos flow by the right ascending lumbar vein was noticed. Finally, the left venous system may either be the major element of the azygos system (mainly by a big ascending lumbar vein) or be divided in 2 distinct streams to the azygos venous trunc. The final disposition of the azygos system seems to correlate well with a progressive evolution towards an unique trunc, linking directly the two caval systems (this being confirmed by foetal data). Practically, the study of the arterial and venous relations of the azygos crossing have interesting applications in surgery.
mesh_terms: D001401:Azygos Vein / Q000033:anatomy & histology*; D005260:Female; D005333:Fetus / Q000033:anatomy & histology; D006801:Humans; D006975:Hypertension, Portal / Q000503:physiopathology; D011247:Pregnancy
vernacular_title: Considerations sur le système azygos.