The left renal vein usually lies anteriorly to abdominal aorta. So whenever you want to dissect an aortic aneurysm close to the renal arteries as like in a juxtarenal case you definitely have to identify this vessel and deal with it; either lift up with a retractror or securely divide it. If your inadvertently cause an injury then you will find yourself in a big trouble.
So, where is the vessel located? It is almost always on a standard position. If you approach the anterior AA first you come across the inferior mesenteric vein. This can be ligated with no cost. Then trying to dissect the AA higher, stay on the anterior surface of the aorta and you will find the left renal vein. Is there an option not to be there? Noways, as long as the vein is not retroaortic (you should have known this from the preoperative CT scan).
Can it be there and not recognize it? It is very unusual, unless the AAA is really a large one. Yesterday, we operated on a 14 cm AAA and the left renal vein was nowhere. Of course this was a misunderstanding. What was the reason? Due to the large size of the aneurysm the vein was totally compressed and it had been practically stuck on the anterior aortic wall. If we were in a hurry and did not pay close attention, we would probably have caused a severe injury on this. Luckily, the vein was identified. As we had to divide it to in order to make a safe proximal anastomosis, we dissected the vein after we had clamped the aorta (at a supraceliac level) and the pressure of the aortic sac had been disappeared.
So, always mind the left renal vein…