Bladder infection - Causes of cystitis

The most common cause of cystitis is a bacterial infection. If bacteria reach the bladder, they can multiply and irritate the bladder lining, leading to the symptoms of cystitis.

Cystitis can also result from damage or irritation around the urethra. 

Bacterial infection

This develops when bacteria get into the bladder and multiply. It can happen if you don't empty your bladder properly. Try to empty your bladder fully each time you go to the toilet to help prevent bacterial infection.

You may not be able to empty your bladder fully if:

• you have a blockage somewhere in your urinary system – this could be caused by a tumour or, in men, an enlarged prostate (a gland located between the penis and the bladder)
• you are pregnant – pregnancy puts pressure on the pelvic area and the bladder

Bacterial infection can also happen when bacteria from the anus are transferred to the urethra. This is more common in women than in men, as the urethra is closer to the anus in women.

In women, transferring bacteria in this way can happen when you are:

• having sex
• wiping after going to the toilet (you're less likely to transfer bacteria in this way if you wipe from front to back)
• inserting a tampon
• using a diaphragm for contraception

In women who have had, or are going through, the menopause, the lining of the urethra and the bladder become thinner because of a lack of the hormone oestrogen. The thin lining is more likely to become infected or damaged.

Women also produce fewer vaginal secretions after the menopause, which means that bacteria are more likely to multiply.

Damage or irritation

Cystitis can also be caused by damage or irritation in the area around the urethra in both men and women. 

The urethra is the tube that carries urine from the bladder out of the body. In men, the urethral opening (where urine leaves the body) is at the tip of the penis. In women, it's just below the clitoris.

This damage or irritation could be the result of:

• sex
• chemical irritants – for example, in perfumed soap or talcum powder
• other bladder or kidney problems, such as a kidney infection or prostatitis
• diabetes 
• damage caused by a catheter (a tube inserted into the urethra to allow urine to flow into a drainage bag, which is often used after surgery)