Does the menstrual cycle affect anorectal physiology?

It has been shown that during the luteal phase of the menstrual cycle women excrete hard stools and have delayed transit, while at the time of menses, stools are looser and more frequent. The relationship between the menstrual cycle and anorectal physiology, and whether the timing of manometry testing should be standardized within the menstrual cycle has not been previously investigated. In this study, the anorectal responses to balloon distension during days 1-4 (menses), 8-10 (follicular phase), 18-20 (luteal phase) and 24-28 (premenstrual) of the menstrual cycle in 20 healthy female volunteers (ages 18-39 years) was measured. Stools were significantly looser during menses [2.32 (2.1-2.5); mean (95% CI)] compared with the luteal phase [1.98 (1.8-2.2):F(3,30) = 3.1;P