Cystitis is an inflammation of the bladder (the bag in which urine is stored after it leaves the kidneys). When the bladder is full, urine is passed out of the body through a narrow tube called the urethra. Cystitis is a painful condition that is common in women – it’s been estimated that more than half the women will get cystitis at some time. It can also affect men and children, but this is less common. Although it is painful, if treated, it usually lasts no longer than a day or two, and does not usually cause any long-term problems. But if you get repeated bouts, you should see a doctor.