[Arterial supply in the left colonic flexure].

The authors study the behaviour of the middle colic, left colic superior, middle and inferior and the first sigmoidal arteries in the territory of the terminal portion of the transverse colon, the left colonic flexure and the descending colon. The study was carried out on 1200 angiographies of the superior and inferior mesenteric aa. and on 150 anatomical specimens, surgically extirpated in the course of left emicolectomy operations. Contrary to what is believed by most authors, the left flexure is a colonic tract very well supplied by blood while the descending colon results to be poorly supplied, being served only by one artery (the left sup. colic a.) often of limited caliber and with branches (the middle and the inf. left colic aa.) sometimes totally or partially lacking. In this last colonic tract the vascular continuity, represented by the arterial arcades, is often interrupted. The Riolan's arcade, variously shaped, is to be considered a constant vascular structure (only once it was lacking in this study). Sometimes it is doubled by a second more internal arcade which must not be confused with the intermesenteric arcade. In four of the observed cases, the Riolan's arcade resulted strengthened by a second retroperitoneal arcade, derived from a branching of the middle colic a., whose branches of division went to the two colonic flexures and descended along the postero-lateral walls of the ascending and descending colon, often parallel to the regular abdominal branches. Exceptionally the colonic flexure is supplied by the only left colic a., which behaves as a specific artery, by us called "dominant artery". The central branches of the artery go to the flexure while the lateral ones join the branches of the middle colic and the first sigmoidal aa., effecting tenuous connections, surgically unreliable. In this case the arterial continuity of the Riolan's arcade can be considered interrupted, at least for the surgical practice. The intermesenteric arcade, in its three forms (direct, mixed and indirect), was observed in 20% of the cases. The colic marginal a. is considered by the authors a tier of arches formed by the colic aa. The left colonic flexure is also supplied by particular vessels originated from the middle colic and the left colic aa. (angular branches and arcades and bridge-branches) or from the superior mesenteric a. (angular artery of Donati) and from other sources, particularly from the splenic a. These vessels then join the colic "vasa recta" through the phrenocolic ligament and the marginal omental vessels. This research shows that the vascular continuity of the left colon is not a constant element, able to reassure the surgeon, for possible interruptions that may occur in its composition.