Dangerous twisted communications between external and internal iliac veins which might rupture during catheterization.

In this report, four unusual communications between external and internal iliac veins of the left side have been presented. The lowest communication was the narrowest measuring about 2 mm in diameter, the second measured 6 mm, the third had a diameter of 7 mm and the last communication measured 5 mm in breadth. The upper three communications were twisted in a helical manner. The internal iliac vein had its normal tributaries except that the iliolumbar vein drained into the external iliac vein at the level of the third communication. The external iliac vein was slightly dilated just below the level of lowest communication.