It coursed laterally posterior to the left suprarenal vein (shown in the inset of figure 2) and then crossed the anterior surface of the left kidney accompanying the lumbar vein to reach the posterior abdominal wall.
According to Jack Baniel et al in their study on lumbar vessels, a lumbar vein entering the left renal vein was documented in 43% of cases.
Cases of lumbar vein forming a tributary of the renal vein have been reported by Satheesha, Jyotsna et al and Bandopadhyay et al.
But the lumbar azygos vein was absent (though present on the right side) and a dilated communicating vein (of almost equal thickness as the left renal vein) was seen to pass deep to the left psoas major muscle into the left para-vertebral gutter and communicate with the left ascending lumbar vein (figure 1 & 2).
The LRV is usually formed from the transverse anastomotic vessel between the left and right sub-cardinal veins and the supra-cardinal veins along with the azygos venous line (which develops subsequently) gives rise to the azygos venous system including the ascending lumbar vein. Variations in the development of the veins give rise to conditions like double IVC, circum-aortic renal vein, post-caval ureter etc.
As mentioned in Gray's anatomy (9) the ascending lumbar vein is usually joined by a small vessel from the back of inferior vena cava or left renal vein on the left and this vein represents the azygos line and hence is termed as the lumbar azygos vein.
The thrombosed infrarenal IVC filter may have acted as a valve, slowing anterograde flow, increasing pressure in the lumbar vein, and causing it to rupture.
(b) Initial noncontrast CT coronal reformatted images demonstrated a large high density left retroperitoneal hematoma (dashed arrow) contiguous with high-attenuated tubular structure arising from the left side of IVC (arrow), likely a lumbar vein. There is an expansile appearance of infrarenal IVC.
(b) Contrast CT coronal reformatted image during delayed (120 sec) venous phase demonstrated hyperattenuated contrast material below the IVC filter contiguous with dilated left lumbar vein (arrow) extending to left retroperitoneal hematoma (dotted arrow).