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.

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.