Cystitis, also known as a lower urinary tract infection (UTI), usually only affects your bladder. Your urinary tract consists of your kidneys, two ureters (the tubes that connect each kidney to your bladder), your bladder and your urethra. Sometimes the infection can go higher to your ureters or kidneys – this is known as an upper urinary tract infection and is a more serious illness.

Cystitis is usually caused by a bacterial infection from a variety of sources. It can also be triggered by irritation or bruising of your urinary tract caused by sexual intercourse. It's most common in women. Around one in three women will have at least one bout of cystitis before they are 24 years old. Doctors believe it is less common in men because they have longer urethras and bacteria have further to travel to reach the bladder.