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Technical aspects of 3D contrast-enhanced magnetic resonance angiography are exposed, detailing more particularly the pulse sequence used and the mode of injection of contrast agent. Then, various vascular territories are analyzed, and illustrated using various examples of main pathologies observed in routine clinical practice: abdominal aorta, renal arteries, pelvic and mesenteric vessels, and peripheral arteries.

The development in the embryo of the lower limbs arteries is made by means of the retrogression of the ischiatic artery, which is initially preponderant, and of the persistence in the popliteal pit of an anastomosis between the original ischiatic axis and the final femoral axis. The tibial arteries originate from one or the other of these axes. The attention is turned to the areas rendered fragile by the complexity of their forming and likely to provoke some topographic anomaly or some dystrophic disease: persistence of the ischiatic artery, trapped popliteal artery, gelatinous dystrophy, Leriche-Fontaine aneurysmal dystrophy, anterior tibial hypoplasia. The repetition of such problems which are non-existent at the upper limbs and are localized to the same arterial segments, especially to the popliteal artery, puts stress upon an eventual dysplasic pathogenesis originating from the embryo.

Ischemic damage to the distal part of the digestive tract is rare after elective surgery for aorto-ilio-femoral aneurysm or Leriche's syndrome, but is frequent after resection of a ruptured aneurysm in older patients, who are operated on in a state of hypovolemic shock. During the past 20 years, we observed 25 ischemic manifestations of the distal digestive tract from a total of 916 surgical patients. Of these patients, 180 had an aneurysm which was ruptured in 73 cases, and 736 underwent surgery for an aorto-ilio-femoral stenosis or obstruction. Transient ischemia, which affects in a majority of cases the left colon, usually heals without leaving any sequellae. Irreversible damage which progresses to gangrenous necrosis of all or part of the colon holds an important share of the postoperative death rate. To avoid these accidents, it is important to reestablish in a correct manner all vascular axes, to avoid states of hypovolemic shock which, through a "small output syndrome", result in vascular thromboses, and finally to monitor aneurysmal patients in intensive care units so as to rapidly detect and treat ischemic complications to the digestive tract.

Importence in young subjects is often vascular in origin. This concept is recent. Selective arteriography shows isolated lesions of arterial occlusion. Revascularisation of the corpora cavernosa makes it possible to cure impotence of this type.

Key sites to be followed up are defined as a function of initial explorations of lesions in operated or unoperated arterial disease of the lower limb. Details of these key sites were obtained from pathologic examination of collateral vessel networks. Precise studies were conducted of the collateral circulation after infrarenal aortic obliterations, and femoral and tibial artery occlusions. Prediction of the ischemic risk and therefore of prognosis, and choice of therapy, can be obtained only by a detailed study of the reentry value through the bias of this collateral circulation.