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Patient education: Kidney infection (pyelonephritis) (Beyond the Basics)

Thomas M Hooton, MD
Section Editor
Stephen B Calderwood, MD
Deputy Editor
Allyson Bloom, MD
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A kidney infection, also known as pyelonephritis, is a urinary tract infection that affects the kidneys. Kidney infections are less common than bladder infections, and are more common in women than men.

Kidney infections can usually be treated at home with antibiotics, but are sometimes treated in the hospital if the infection is severe.

This article will review the causes, symptoms, and treatment of kidney infections. An article about bladder infections is available separately. (See "Patient education: Urinary tract infections in adolescents and adults (Beyond the Basics)".)

More detailed information about kidney infections is available by subscription. (See "Acute uncomplicated cystitis and pyelonephritis in women".)


Most kidney infections occur when bacteria, which normally live in the gut and travel to the genital area and from there into the bladder through the urethra. From the bladder, the bacteria travel up the ureter(s) into the kidney(s) (figure 1). You can have a kidney infection in one or both kidneys.

Factors that increase the risk of developing a kidney infection include:

Having sex frequently or having a new sex partner

Having diabetes

Having a bladder or kidney infection in the past 12 months

Using a spermicide for birth control or prevention of infection

Having a condition that blocks or changes the flow of urine in the kidneys (eg, kidney stones, ureteral reflux)

Having a mother, sister, or daughter with a history of urinary tract infection


Symptoms of a kidney infection include:

Fever (temperature greater than 100.4º F or 38º C)

Pain in the flank (side of lower back, where the kidney is located)

Nausea and/or vomiting

Some people also have burning or pain with urination, a need to rush to the bathroom frequently, bloody or cloudy urine, or pain above the pubic bone (near the bladder).

If you do not have a fever or flank pain, but you do have pain with urination, you may have a bladder infection rather than a kidney infection. Your healthcare provider can help to determine your diagnosis. (See "Patient education: Urinary tract infections in adolescents and adults (Beyond the Basics)".)

If you have one or more of these symptoms, you should see a healthcare provider as soon as possible. Although most kidney infections do not cause permanent damage, delaying treatment can lead to serious complications.


Kidney infections are usually diagnosed based upon your symptoms, a physical examination, and urine testing. A urine test should be done to determine which bacteria are causing the infection and whether the usual antibiotics are likely to be effective. Imaging tests are not usually needed, but might be done if the diagnosis is not clear or if your healthcare provider suspects a blockage in the urinary tract.


The optimal treatment for a kidney infection depends upon the severity of your infection and your general health. (See "Acute uncomplicated cystitis and pyelonephritis in women".)

Home treatment — If your fever and pain are mild and you are able to eat and drink, you will probably be given a one to two week course of antibiotics to take by mouth at home. The first dose of antibiotics may be given as an injection in the office, clinic, or emergency department. Let your healthcare provider know if you do not begin to feel better within one to two days after starting treatment. Your provider may need to call you to change the antibiotic if the urine test shows that you have an antibiotic-resistant bacteria causing your infection.

For fever and pain, you can take a non-prescription medication like acetaminophen (eg, Tylenol and others) or ibuprofen (Motrin, Advil).

Hospital treatment — If you have a high fever, severe pain, or cannot keep down food/fluids, you will need to be hospitalized and given intravenous (IV) antibiotics and fluids. As you begin to improve, you will be switched to oral antibiotics and allowed to go home and continue taking antibiotics there.

Most pregnant women with a kidney infection are hospitalized and treated with intravenous (IV) antibiotics and fluids. (See "Urinary tract infections and asymptomatic bacteriuria in pregnancy".)

Recovery — Most people recover from a kidney infection within a few days. Some people need to take time off from work or school, although this is not always necessary.

Prevention — Ways to prevent bladder and kidney infections are discussed separately. (See "Patient education: Urinary tract infections in adolescents and adults (Beyond the Basics)", section on 'Preventing recurrent UTIs'.)


Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Prenatal hydronephrosis (The Basics)
Patient education: Diabetes and infections (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Urinary tract infections in adolescents and adults (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Bacterial adherence and other virulence factors for urinary tract infection
Treatment of enterococcal infections
Urinary tract infections and asymptomatic bacteriuria in pregnancy
Acute uncomplicated cystitis and pyelonephritis in women

The following organizations also provide reliable health information.

National Library of Medicine

     (http://www.nlm.nih.gov/medlineplus/ency/article/000521.htm, available in Spanish)

National Institute of Diabetes and Digestive and Kidney Diseases



Literature review current through: Nov 2017. | This topic last updated: Sun Oct 08 00:00:00 GMT+00:00 2017.
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