The composition of the vaginal microbiota is a factor closely related to urinary tract infections, and changes over the course of a woman's life, depending on her hormonal status. The thickness of the vaginal mucosa, its glycogen (sugar) content and menstrual cycles influence the type of germs that predominate at any given time, as lactobacilli feed on cells shed from the vaginal wall and the glycogen they contain. This is why the incidence of cystitis increases with age, especially after the menopause, as the absence of oestrogen (female hormones) stimulus thins the vaginal wall and means that the cells are less glycogen-loaded. With less nourishment, the concentration of lactobacilli decreases and, consequently, the production of lactic acid. This is why the application of hormonal gels in the vagina, which improve the condition of the vaginal wall, has proven to be an effective measure against urinary tract infections in post-menopausal women. This also helps to understand why some young patients often suffer from infections in the days before menstruation or ovulation: at these times, there is a sharp drop in oestrogen levels in the blood, and thus a thinning of the vaginal wall, with a consequent decrease in vaginal lactobacilli. Thus, there is less protection against uropathogenic germs during these days.
In addition to hormonal changes and changes in the vaginal microbiota, there are other factors that can alter the vaginal pH and promote urine infections in women: sexual intercourse and excessive intravaginal hygiene, as well as vaginal douching. It is very common to find patients who suffer from UTIs almost systematically after sexual intercourse. The short length of the female urethra and the "rubbing" that occurs during intercourse have always been blamed. What many people do not know, however, is that semen is much more alkaline than the vagina, with a pH between 7.2 and 8 generally, sometimes even higher. Because of this, intravaginal ejaculation can quickly raise the pH and thus encourage the development of uropathogenic bacteria. Similarly, although it may seem paradoxical, excessive use of alkaline pH soaps (which are the majority) or douching in the genital area can also alter vaginal acidity and cause an imbalance in the vaginal microbiota. If you want to know more about the genito-urinary microbiota, I recommend you read this article: The Urogenital Microbiota
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