Magnetic resonance angiography of the left renal vein

Proposal for Classification of the Circumaortic Renal Collar's Morphology

In the present study, we propose a classification of the different forms of the circumaortic renal collar based on the findings of 319 patients and on a literature review. The patients underwent a CT angiography scan of the abdomen for various diagnostic reasons. The different forms in which the circumaortic renal collar may appear were categorized. The renal collar was observed in eight of the 319 (2.5%) patients. The classification we propose is the following: Type I, one left renal vein splitting into two branches, a preaortic and a retroaortic, draining into the inferior vena cava; Type II, two different left renal veins, the one preaortic and the other retroaortic, draining into the inferior vena cava; and Type III, either anastomoses between the preaortic and retroaortic vein, being multiple or not, or multiple preaortic or retroaortic renal veins without anastomoses. Although the circumaortic renal collar is usually asymptomatic, the knowledge of this variation is useful, mainly before abdominal aortic aneurysm surgery and renal transplantation. Failure to recognize the collar's retroaortic component may lead to hemorrhage and death during retroperitoneal surgery. We believe that our classification contributes to recognize the circumaortic renal collar's morphology both preoperatively and intraoperatively.

Two rare anomalies of the left renal vein

Two uncommon anatomical variations of the left renal vein were found on dissected specimens: a circumaortic venous ring and a retro-aortic bifid left renal vein. The first anomaly results from a persistence of the embryonic renal venous collar. The second one would be related to a particular pattern of left inferior vena cava. Both abnormalities have to be known for they may be undetected or be misleading in imaging. Other clinical implications are also considered.

Absence of the inferior vena cava causing repeated deep venous thrombosis in an adult--a case report

Agenesis of the inferior vena cava is an uncommon congenital vascular malformation. Although theoretically it may favor venous stasis, it is not normally associated with venous thrombosis. The authors found only three reports of the coexistence of both entities, and only one of these rules out the existence of associated hypercoagulability. They report the case of a patient with a history of repeated venous thrombosis. Magnetic resonance angiography and venography demonstrated complete agenesis of the inferior vena cava and persistence of a cardinal venous system with azygos and hemiazygos continuation, associated with right renal hypoplasia. Studies ruled out hypercoagulability syndrome, either primary or secondary to an occult neoplasm. The authors conclude that venous malformations, although rare, may cause thromboembolic disease, especially in young patients, and that magnetic resonance angiography is a useful diagnostic alternative to conventional phlebography.