The longitudinal effect of ejaculation on seminal vesicle fluid volume and whole-prostate ADC as measured on prostate MRI

Abstract

Objective: To prospectively investigate the longitudinal effect of ejaculatory abstinence on MRI-measured seminal vesicle (SV) volume and whole-prostate ADC over consecutive days.

Methods: 15 healthy male volunteers (mean 35.9 years, range 27-53) underwent 3-T MRI at baseline and 1, 2 and 3 days post-ejaculation. Prostate and SV volumes were derived by volume segmentation and whole-gland apparent diffusion coefficient (ADC) values calculated. A mixed-effects linear regression compared ADC values and prostate/seminal vesicle volumes in each volunteer between studies in a pairwise manner.

Results: All subjects completed the four MRIs. Mean prostate volume was 22.45 cm3 (range 13.04-31.21 cm3), with no change between the four studies (p = 0.89-0.99). 13/15 subjects showed SV volume reduction from baseline to day 1, with group-mean decreasing from 6.45 to 4.80 cm3 (-25.6%, p < 0.001), and a significant reduction from baseline to day 2 (-18.1%, p = 0.002). There was a significant volume increase from both day 1 (+21.3%, p = 0.006) and day 2 (+10.2%, p = 0.022) to day 3 post-ejaculation. There was a significant reduction in ADC from 1.105 at baseline to 1.056 × 10-3 mm2/s at day 1 (mean -4.3%, p = 0.009).

Conclusion: The longitudinal effect of ejaculation on SV volume was demonstrated. Significant reductions in SV volume and whole-gland ADC were observed post-ejaculation, supporting a 3-day period of abstinence before prostate MRI.

Key points: • Seminal vesicle volume significantly reduced 24 h post-ejaculation remaining reduced at day 2 • Seminal vesicle fluid volume significantly increased from day 1 to day 3 post-ejaculation • There was a significant reduction in whole-gland prostate ADC values day 1 post-ejaculation • 3-day abstinence from ejaculation is required to ensure maximal seminal vesicle distension.

Keywords: Ejaculation; MRI; Preparation; Prostate; Seminal vesicles.

Conflict of interest statement

Guarantor

The scientific guarantor of this publication is Tristan Barrett.

Conflict of interest

The authors of this manuscript declare no relationships with any companies whose products or services may be related to the subject matter of the article.

Funding

This study has received funding by Royal College of Radiologists UK.

Statistics and biometry

No complex statistical methods were necessary for this paper.

Informed consent

Written informed consent was obtained from all subjects (patients) in this study.

Ethical approval

Institutional review board approval was obtained.

Methodology

• prospective

• cross-sectional study

• performed at one institution

Figures

Fig. 1

Calculating seminal vesicle fluid volume. Manual regions of interest (yellow) were drawn outlining the seminal vesicles on all slices for segmentation (a, c). To remove the SV wall component, the maximum signal in the central outlined area was identified and a threshold applied for inclusion of pixels > (Smax × f). The fraction (f) was set at either 0.8 (b) or 0.7 (d) for cases where motion blurring was present

Fig. 2

Examples of seminal vesicle volume change over time. Axial T2-weighted MR imaging performed at baseline (minimum 3 days post-ejaculation), and post ejaculation on days 1, 2 and 3. Top row subject 5 (aged 27) shows significant reduction in volume from a baseline of 9.7 cm3 to 3.6 cm3 on day 1 and subsequently to 4.7 cm3 and 6.9 cm3 on days 2 and 3, respectively. Middle row subject 11 (age 53) shows similar reductions from 7.0 cm3 at baseline to 3.3 cm3, 4.2 cm3 and 5.3 cm3 on days 2, 3 and 4, respectively. Note apparent increase in wall thickening on day 2, due to relative underdistension. Bottom row subject 14 (age 36) shows little difference in SV volume over the four scans: 10.6 cm3, 10.0 cm3, 10.5 cm3 and 10.9 cm3, respectively

Fig. 3

Box and whisker plots of seminal vesicle fluid volumes between each of the four scans. Top and bottom of boxes represent 25th and 75th percentiles of data, X in boxes represents mean, with line representing median value and bars representing data within 1.5 times interquartile range. Circles denote outliers. p values are shown for inter-group comparisons, *p < 0.05

Fig. 4

Box and whisker plots of whole-gland prostate ADC values between each of the four scans. Top and bottom of boxes represent 25th and 75th percentiles of data, X in boxes represents mean, with line representing median value and bars representing data within 1.5 times interquartile range. Circles denote outliers. p values are shown for inter-group comparisons, *p < 0.05