What causes UTIs?
A UTI is usually caused by bacteria entering the urinary tract. This bacteria often comes from poo and is moved into the urinary tract through sex or wiping. Other factors can irritate the urinary tract and make it more susceptible to infection.
Women are more likely to get a UTI because their urethra (the tube that connects the bladder to the outside of the body) is shorter. Therefore, it is easier for bacteria to reach the bladder or kidney.
It is estimated that UTIs only affect 3% of men each year worldwide. When a man gets a UTI, it is usually because of bacteria already present in his body.
What increases your risk of getting a UTI?
Your risk of bacteria in your urinary tract causing a UTI increases with the following:
A large body of evidence links sex with UTIs in women. Sex can transfer bacteria from the genitals and anus into the urinary tract. Research has also shown that using diaphragms, spermicides and condoms can increase your risk because these can all introduce bacteria.
Studies suggest that older people are more likely to get a UTI. Bladder and pelvic floor issues, lower oestrogen levels in women and weakened immune systems are more common the older you get. These factors make it harder for your body to fight bacteria in your urinary tract.
A review of UTIs in pregnancy indicates that the chance of getting bacteria in the urineI in pregnancy is similar to women who are not pregnant. However, if you have had a UTI before, there is a much higher chance (estimated at 25%) of developing another one. However, changes in your body due to pregnancy such as pressure on your bladder from the foetus mean your body is more likely to develop a UTI.
Constipation, incontinence or holding on
If you are constipated, there can be pressure on your bladder causing bacteria to be trapped inside it, which can cause a UTI. Studies show there is a higher chance of bacteria being around the urinary tract if you are incontinent and that holding on to your urine allows bacteria to remain in your bladder rather than being flushed out.
If you are dehydrated, you do not frequently urinate, which means that the bacteria which would usually be flushed away, will stay in your urinary tract. Drinking enough fluids allows your body to flush everything out of the bladder regularly, so bacteria cannot grow.
Conditions which impact the bladder
Conditions that put pressure on the bladder (such as enlarged prostate) or those that impact how the bladder functions (for example, bladder stones or having a urinary catheter) can increase your risk of a UTI. If the bladder is under pressure or cannot empty itself properly, bacteria can be trapped in it. A urinary catheter can allow bacteria to enter your bladder through the catheter.
Kidney stones can block the urinary tract, allowing urine (and any bacteria) to build up and cause a UTI.
People with Type 2 diabetes are more likely (46.9 per 1,000 people) to have a UTI than those without (29.9 per 1,000). Excess sugar in your blood is removed through your urine, and this excess sugar can make bacteria grow, causing a UTI. People with diabetes also often have a weakened immune system, making it harder for their bodies to fight the infection.
Having had a previous UTI
A review from 2010 found that specific genes may make someone more likely to get a UTI and to have recurring UTIs.
Weakened immune system
If your immune system is weakened due to auto-immune disease, cancer treatment or other factors, it makes it harder for your body to fight bacteria when it is in your system.
Why does sex cause a UTI?
During sex, bacteria from the genitals and anus can be introduced to the urethra. You can reduce the chance of this happening by:
- going for a pee as soon as possible after sex
- washing the skin around your vagina with warm as soon as you can after sex
- using different contraception instead of a condom
- avoiding using lubricant
What is a recurrent UTI?
A recurrent UTI is when you have 3 or more UTIs within one year or 2 or more within 6 months. Studies suggest that recurrent UTIs are caused by reinfection by the same bacteria. Having sex is the most significant risk factor for a recurrent UTI, but all the factors listed above that increase your risk of getting a UTI can be reasons for recurrent UTIs.