Diagnosis of Kidney Infection (Pyelonephritis)

How do health care professionals diagnose a kidney infection?

Health care professionals use your medical history, a physical exam, and tests to diagnose a kidney infection.

A health care professional will ask if you have a history of health conditions that make you more likely to develop a kidney infection. During a physical exam, the health care professional will ask you about your symptoms.

If you are a man and the health care professional suspects you have a kidney infection, he or she may perform a digital rectal examination (DRE). During a DRE, the health care professional has you bend over a table or lie on your side while holding your knees close to your chest. After putting on a glove, the health care professional slides a lubricated finger into your anus to check for a swollen or enlarged prostate blocking the neck of your bladder.

What tests do doctors use to diagnose a kidney infection?

Doctors may use lab or imaging tests to diagnose a kidney infection.

Lab tests

Urinalysis. For a urinalysis, you will collect a urine sample in a special container at a doctor’s office or at a lab. A health care professional will look at the sample under a microscope for bacteria and white blood cells, which the body produces to fight infection. Bacteria also can be found in the urine of healthy people, so a kidney infection is diagnosed based both on your symptoms and a lab test.

Urine culture. A health care professional may culture your urine to find out what type of bacteria is causing the infection. A health care professional can see how the bacteria have multiplied, usually in 1 to 3 days, and can then determine the best treatment.

A small container used to collect a urine sample for testing at a lab.
You may provide a urine sample in a special container to be tested for a kidney infection.

Imaging tests

A health care professional may use imaging tests, such as a computed tomography (CT) scan, magnetic resonance imaging (MRI), or ultrasound, to help diagnose a kidney infection. A technician performs these tests in an outpatient center or a hospital. A technician may perform an ultrasound in a doctor’s office as well. A radiologist reads and reports on the images. You don’t need anesthesia for these tests. Read more about imaging tests for your urinary tract.

April 2017
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This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The NIDDK translates and disseminates research findings through its clearinghouses and education programs to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by the NIDDK is carefully reviewed by NIDDK scientists and other experts.

The NIDDK would like to thank:
Ann E. Stapleton, MD, FIDSA, FACP, University of Washington School of Medicine