Pyelonephritis (Kidney Infection)
Diseases and Disorders

Pyelonephritis (Kidney Infection)

Pyelonephritis is an infection of one or both kidneys, most commonly caused by bacteria that have spread upward from the lower urinary tract.

2 min read Reviewed by Medinall Editorial Team Updated 28 Sep 2026 Healthcare benefits for all
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What It Is

Pyelonephritis is an infection of one or both kidneys, most commonly caused by bacteria that have spread upward from the lower urinary tract.

How It Develops

Pyelonephritis typically begins as a bladder infection that isn't adequately cleared and gradually spreads upward through the ureters, the tubes connecting the bladder to the kidneys, eventually reaching and infecting kidney tissue itself. Certain factors, such as conditions that affect normal urine flow or drainage, can increase the likelihood of an infection spreading in this way.

General Symptoms

Common symptoms of pyelonephritis include fever, chills, and pain in the back or side, typically on the affected side. Symptoms often associated with a lower urinary tract infection, such as a frequent or urgent need to urinate and a burning sensation during urination, are also commonly present. Nausea and vomiting can occur as well, particularly as the infection becomes more significant.

General Treatment Approaches

Pyelonephritis is generally treated with antibiotics targeted at the bacteria responsible for the infection, with the specific choice and duration guided by the individual case and local bacterial resistance patterns. Adequate fluid intake and rest are also commonly recommended to support recovery. In more severe cases, particularly when nausea prevents adequate oral intake or when complications are suspected, hospitalization and intravenous treatment may be needed.

Background

Kidney infections have been recognized as a distinct clinical entity for a long time, though the specific bacterial causes weren't clearly identified until the development of microbiology in the 19th century. The introduction of antibiotics in the mid-20th century dramatically changed the treatment and outlook for pyelonephritis, transforming what had previously been a potentially very serious infection into a generally well-managed condition when identified and treated appropriately.

Medinall Editorial Team

Common questions

Frequently Asked Questions

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Pyelonephritis is an infection of one or both kidneys, most commonly caused by bacteria that have spread upward from the lower urinary tract.

This article was prepared by the Medinall Editorial Team to explain health topics in plain language.

No. Medinall articles are for education only. For personal medical advice, diagnosis, or treatment, consult a qualified healthcare professional.

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