Cross-sectional area of the femoral vein varies with leg position and distance from the inguinal ligament

PURPOSE: The risk of complications associated with femoral venous catheterization could be potentially reduced if the procedure was performed at the location where the cross-sectional area (CSA) of the vessel is the largest. The diameter of the femoral vein depends on leg position as well as the distance from the inguinal ligament. We determined the CSA of the right femoral vein in three different leg positions at two distances from the inguinal ligament. SUBJECTS AND METHODS: Informed consent was given by 205 healthy volunteers aged 19–39 years, mean: 23±3 years (108 women, 97 men). Ultrasonographic examinations were performed using a linear 14-MHz transducer with CSA measurements in three leg positions: abduction, abduction+external rotation, abduction+external rotation+90° knee flexion/frog-leg position; at levels 20 mm caudally to the inguinal ligament, and 20 mm caudally to the inguinal crease. RESULTS: We found significant differences in mean values of CSA in three leg positions regardless of the measurement level. The largest mean CSA (114 mm(2)±35 mm(2)) was found at the proximal level in the frog-leg position. There was a significant association of the CSA with sex and height. The CSA in males was greater than in females in all leg positions at the level of 20 mm caudally to the inguinal crease, while 20 mm caudally to the inguinal ligament the CSA was larger in females. The CSA of 25% of the femoral vein was smaller than 45.0 mm(2) at the proximal level, and 31.5 mm(2) at the distal level, which refers to diameters of 5.3 mm, and 4.5 mm, respectively. CONCLUSIONS: The cross-sectional area of the femoral vein is the largest in the frog-leg position, and depends on gender.