Most people with kidney infections look and feel very ill. The symptoms usually come on suddenly over a few hours or one day.
The main symptoms are:
Your kidneys help to make urine and pass it out of your body. So a kidney infection may mean you often need to urinate. You may also get pain when you urinate or generally have pain in your pelvis.
Your urine may also look cloudy or be a different colour. It may smell bad or just smell stronger than usual.
Older people with kidney infections sometimes have different symptoms. These could be:
A high temperature without any other symptoms
Pain in their side or back, along with a fever
Confusion and sluggishness
Loss of appetite.
Up to a third of older people with a kidney infection don't get a high temperature. About 2 in 10 have symptoms that mainly affect their bowels or their lungs.
Some people with a kidney infection get very few symptoms or even none at all. This is known as a silent kidney infection.
Infections in other parts of your body that deal with urine, such as your bladder or urethra, can also cause pain when you urinate or make you need to urinate more often. These parts of your body are called your lower urinary tract. It's possible to get a kidney infection and just have the symptoms of an infection in your lower urinary tract.
Some researchers think that up to 3 in 10 people who seem to have an infection in the lower part of their urinary tract actually have a silent kidney infection.
You are more likely to have a silent kidney infection if you:
Are taking drugs that weaken your immune system
Have had a kidney transplant
Had urinary tract infections before you were 12
Have had three or more urinary tract infections in the last year.
The symptoms of a kidney infection can be similar to those of other illnesses. For example, pelvic inflammatory disease, an inflamed gall bladder, appendicitis, and kidney stones can all cause similar symptoms. To check if you really have a kidney infection, your doctor may ask you for a urine sample. Your urine can then be tested for signs of infection.
You will be asked to wash your genital area and collect a sample of urine halfway through urinating. This way of collecting urine helps stop bacteria on the skin around your genital area from getting into the sample and confusing the test results.