urinary tract infection: Quick Facts

Written and fact-checked by

The Information Architects of Encyclopaedia Britannica

Last updated

Oct. 5, 2026

Facts

Also Known As	UTI

Photos

The most common cause of urinary tract infection is invasion into the urethra of Escherichia coli, a type of bacterium that normally inhabits the bowel.

Diagram of the human excretory system showing the kidneys, ureters, bladder, and urethra, with their anatomical positions highlighted inside a human silhouette.

Bacteria such as Pseudomonas aeruginosa can cause infections of the urethra and bladder. These infections occur more often in women than in men and are typically associated with significant pain and distress.

Pink and purple bacterial colonies of Escherichia coli growing on the surface of a MacConkey agar plate inside a petri dish.

See All Images →

Topics

renal system disease urinary tract obstruction nephrosclerosis

full human skeleton

Diseases, Disorders, and More: A Medical Quiz

44 Questions from Britannica’s Most Popular Health and Medicine Quizzes