Left common iliac vein compression identified by vascular ultrasonography in asymptomatic women: does standing position influence diagnosis?

BACKGROUND: Vascular ultrasonography is the imaging exam of choice for initial screening for left common iliac vein compression, which is an asymptomatic finding that can be detected in up to 25% of some patient samples. OBJECTIVE: To determine, using vascular ultrasonography, whether findings of left common iliac vein compression in asymptomatic women are different when assessed in the prone and standing positions. METHODS: This is a cross-sectional observational study of 50 adult female volunteers with no symptoms of pelvic venous compression. The parameters assessed with vascular ultrasonography in the prone and standing positions were diameters and maximum velocities of the left common iliac vein at the point at which it crosses behind the right common iliac artery and before this point, in addition to left common iliac vein velocity indices at the crossing. RESULTS: Eight cases of significant compression of the left common iliac vein were identified when assessed in prone position (16%) and just two cases (4%) were identified in the standing position. Left common iliac vein diameters were statistically larger (p = 0.002) at the point where it crosses behind the right common iliac artery in the standing position and velocities and velocity indices were statistically higher (p < 0.001) in the prone position. No significant compression of the left common iliac vein was identified in the standing position when velocity indices were normal in the prone position. CONCLUSIONS: There was no difference in detection of significant compression of the left common iliac vein when assessed in the standing position in comparison with assessment in the prone position. However, the study showed that anatomic compression of the left common iliac vein may be reduced in the standing position.