a related diagnosis is "nutcraker syndrome" where the left renal vein is described as being compressed between the aorta and the superior mesenteric artery. this is reported to cause collateral flow paths to open up to drain the left kidney i.e. reversed flow (reflux caudally) in the left renal vein. pelvic congestion syndrome, vaginal and vulval varices, lower limb varices are clinical sequelae. virtually all such patient are female and have been pregnant, often multiply.