Medical Definition of Infection, urinary tract (UTI)

Reviewed on 3/29/2021

Infection, urinary tract (UTI): An infection in the urinary system that begins when microorganisms cling to the opening of the urethra (the canal from the bladder) and begin to multiply. Most UTIs are due to one type of bacteria, E. (Escherichia) coli, a normal denizen of the colon. An infection in the urethra leads to inflammation called urethritis. From there bacteria may move up, causing a bladder infection (cystitis) and if the infection is not treated promptly, bacteria may go up the ureters to infect the kidneys (pyelonephritis). Factors leading to UTI include any abnormality of the urinary tract (such as a urinary tract malformation or a kidney stone) that obstructs the flow of urine, an enlarged prostate gland that slows the flow of urine, catheters (tubes) in the bladder, diabetes (due to changes of the immune system), and any disorder that suppresses the immune system. Women have more UTI than men, probably because a woman's urethra is shorter (allowing bacteria quick access to the bladder) and nearer sources of bacteria from the anus and vagina. For many women, sexual intercourse seems to trigger an infection, as may the use of a diaphragm. Not everyone with a UTI has symptoms but symptoms commonly include a frequent urge to urinate and a painful, burning when urinating (dysuria). The urine may look milky or cloudy, even reddish if blood is present. Kidney infection can cause pain in the back or side below the ribs. In children, symptoms may be easily missed or misunderstood. A child with a UTI may be irritable, not eat normally, have an unexplained fever, have incontinence or loose bowels, or just not thrive.



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