Pyelonephritis (kidney infection) Dr Rob Hicks Pyelonephritis means inflammation of the kidney. It is usually caused by bacterial infection and the consequences are generally painful and unpleasant.

In this article

What causes it? What are the symptoms?

Who's affected? What's the treatment?

The bacteria that cause pyelonephritis get into the body through the urethra (the tube that urine passes through from the bladder). From here, they can move into the bladder and up to the kidneys.

In women, the bacteria may get in during sex or if the anal area is wiped from back to front rather than front to back as recommended. It may also happen in both men and women when catheterisation is needed for medical reasons.

Anything that obstructs the normal flow of urine will allow bacteria to multiply in the stagnant urine. For example, enlargement of the prostate gland in men may be responsible for the blockage, or kidney stones.

These conditions not only obstruct the urine, but may harbour bacteria on their surfaces. If the bacteria are already inside the body, then they may find their way to the kidneys as they are carried in the bloodstream.

Symptoms include:

• Loin pain, often severe
• Fever and shivers
• Blood-stained urine
• Foul-smelling and cloudy urine
• Painful and frequent urination
• Nausea and vomiting

Pyelonephritis usually affects young or middle-aged adults, although it can also occur in children. Women are more likely to suffer than men.

Glucose in the urine encourages bacteria to grow, so those with diabetes are more likely to be affected by pyelonephritis.

The body can function well with only one kidney, but pyelonephritis still needs to be taken seriously.

When pyelonephritis is suspected, a urine specimen is tested to establish whether bacteria are present. If this is confirmed, treatment with antibiotics is necessary. If someone is very unwell, they may need to be admitted to hospital to be given intravenous therapy.

Since pyelonephritis is less common in men and children, further hospital tests are usually carried out to determine why it has occurred in those cases. These tests may include scans and x-rays and an assessment of kidney function. Such tests aren't usually performed on women, unless the attacks are recurrent or an underlying cause is suspected.

As with all infections affecting the urine or kidneys, once the treatment has been completed it's important a further urine sample is tested to confirm the bacteria has been eradicated.

This article was last medically reviewed by Dr Rob Hicks in July 2006.