Reference ranges for uterine vein dimensions in non-pregnant women with normal pelvic organs.

OBJECTIVE: To establish reference ranges for uterine vein (UtV) diameters in non-pregnant women with normal pelvic organs. METHODS: This was a prospective study of all women attending the general gynecological clinic of a university teaching hospital in the UK, between August 2015 and December 2016. All women aged ≥ 18 years underwent a transvaginal ultrasound examination in accordance with the study protocol. In women with normal pelvic organs, the largest trunk of the uterine venous plexus was identified in the transverse plane on each side. The maximum anteroposterior vessel diameter was measured by placing the calipers on the inner walls of the vein, and the mean of three measurements was used as the representative value. Inter- and intraobserver variability was assessed in a subgroup of 30 women. Maximum UtV diameter was compared between right and left UtVs and between pre- and postmenopausal women. Factors associated with UtV diameter were assessed and reference ranges were constructed. RESULTS: Of 1500 women examined, 486 (32%) had normal pelvic organs on ultrasound scan and were included in the final analysis. In all women, the uterine venous trunk was clearly visualized and there was no significant difference between the maximum median left and right UtV diameters (P = 0.37). UtV diameters were generally lower in postmenopausal, compared with premenopausal, women, with the difference being statistically significant for the right UtV and the average of left and right UtVs. There was a gradual increase in UtV diameter with advancing age, with a peak observed in women aged 41-50 years and decreasing values in older age groups. Univariable analysis showed that parity, menopausal status and age were associated significantly with UtV diameters (P < 0.01). On multivariable analysis, only higher parity was significantly associated with increasing venous size in both pre- and postmenopausal women. Reference ranges were constructed separately for nulliparous and parous premenopausal women aged between 18 and 45 years. CONCLUSION: UtVs can be identified and measured consistently in all women with normal pelvic organs using transvaginal ultrasound. Parity was the main factor influencing the maximum mean UtV diameter, which had to be taken into account when constructing reference ranges. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.