Variations of the iliac and pelvic venous systems with special attention to the drainage patterns of the ascending lumbar and iliolumbar veins.

The anatomy of the inferior vena cava (IVC) and common, external and internal iliac veins (CIV, EIV, IIV respectively) was examined in 59 embalmed adult human cadavers of Caucasian origin. In the present study, we focus our attention on the drainage patterns of the ascending lumbar and iliolumbar veins (ALV, ILV) when there are variations in the major pelvic veins by highlighting and describing the variations themselves. The above patterns, when no variations exist, have already been reported. Among the 59 cadavers, nine (9/59, 15.3%) presented anomalies of the major pelvic veins, as follows: anomalous drainage of both EIV and IIV in 8.5% of the specimens (5/59, Type I); variations of the IVC in 3.4% (2/59, Type II); duplication of the IIV (1/59=1.7%, Type III); anastomotic branch between the right IIV and the left CIV (1/59=1.7%, Type IV). ALV drained either into the CIV (8/18 sides, 44.4%) or in EIV (5/18 sides, 27.8%), while absence of ILV was the most frequent pattern (8/18 sides, 44.4%). A common trunk, joining the two veins, was observed in 5/18 sides (27.8%). Those drainage patterns were in accordance with the ones discovered in our previous study. In Type I the two veins always drained into the EIV. Knowledge of the surgical anatomy of all studied veins may prevent injury to these veins during operations in the retroperitoneal space and pelvis or malposition of venous catheters placed from the groin.