Two courses of antibiotics should be enough to deal with any bacterial cause of cystitis, presuming your doctor tested your urine for infection to check which antibiotics were appropriate, although sometimes resistant bacteria can persist. There are other, less common causes of cystitis and your doctor should rule these out.

Rather than an acute infection requiring antibiotics, you may have a condition called interstitial cystitis.

Recent discovery

Interstitial cystitis is a chronic condition in which the bladder wall becomes inflamed, causing all the symptoms often ascribed to an infection - an urgent need to pass urine frequently, pain and so on.

These symptoms usually have to have been present for at least nine months before the diagnosis is made.

Interstitial cystitis is a newly recognised condition - for decades it was given scant credibility and dismissed in some reports as a condition of 'hysterical women', despite the fact that many thousands of women suffer from symptoms. Only in the past 15 years has it been found to be a real, physical problem.

Some women improve after a few months. For others, the symptoms can go on for years although they rarely getting worse. A few develop long-term complications as the bladder becomes ulcerated, small and stiff.

Possible causes

The cause of interstitial cystitis isn't know. It may begin with infection, but the urine is usually sterile and no micro-organisms can be detected.

However, some experts believe there's a hidden infection, much like the one recently found to cause stomach ulcers.

Some research has pointed to a defect or alteration in the surface of the bladder, which may allow harmful chemicals in urine to pass into the tissues and cause inflammation and damage to the bladder nerves.

Recently it has been shown that some women with interstitial cystitis lack a protective protein that normally blocks these toxic chemicals.

Other research has found auto-antibodies against the lining of the bladder, suggesting it might be under attack from the body's own immune system.

Treatments

As yet there is no cure for interstitial cystitis, but many treatments are being tried, including:

• Antibiotics
• Treatments to distend the bladder
• Bladder washes
• Bladder training strategies
• Surgery
• Medications such as pentosan polysulphate sodium, and anti-inflammatory drugs such as ibuprofen

This article was last medically reviewed by Dr Trisha Macnair in December 2007