Definitions

Acute pyelonephritis: a clinical syndrome consisting of chills, fever, flank pain, bacteriuria and pyuria, accompanied by acute infection of the renal parenchyma and pelvis.

Bacterial persistence, recurrent infection or relapse: a recurrent urinary tract infection caused by the same bacteria as the first infection, which have persisted in the urinary tract.

Bacteriuria: the presence of bacteria in the urine (normally sterile); not contaminants from the skin, vagina, or prepuce.

Chronic pyelonephritis: a shrunken, scarred kidney, diagnosed by morphological, radiological, or functional evidence of renal disease (this may be post-infective but is frequently not associated with urinary tract infection).

Complicated pyelonephritis: pyelonephritis in a patient with structural or functional abnormalities of the urinary tract.

Complicated UTI: an infection in a patient with pyelonephritis and/or a urinary tract with a structural or functional abnormality that would reduce the efficacy of antimicrobial therapy.

Cystitis: inflammation of the bladder, or a clinical syndrome of abrupt onset of dysuria, increased frequency, urgency, and suprapubic pain.  Bacterial cystitis should be distinguished from nonbacterial cystitis (eg. radiation or interstitial cystitis).

Lower urinary tract infection: infection of the bladder and/or urethra.

Prophylactic antimicrobial therapy: the prevention of reinfections of the urinary tract by the administration of antimicrobial drugs, assuming for the purposes of this definition that the bacteria have been eliminated by the initial treatment.

Pyuria: white blood cells in the urine; generally indicates an inflammatory response of the urothelium to bacterial invasion. 

• Bacteriuria without pyuria — in most patients this suggests bacterial colonisation only, rather than infection.  However, in the early stages of infection or in some groups, such as neutropenic patients, bacteriuria without pyuria most probably indicates infection and hence must be investigated further.
• In addition, even if infection is present causing pyuria, the altered pH in catheter urine and in urine following infection with certain organisms such as Proteus spp. can lyse white blood cells so they may not be detectable.
• Pyuria without bacteriuria — indicates either a non-infectious cause, such as stones or cancer, or may indicate tuberculosis/fastidious organisms or recent antibiotic therapy.

Reinfection: a new infection with different bacteria from outside the urinary tract: may be complicated or uncomplicated. 

Significant bacteriuria: a number of bacteria in a suprapubically aspirated, catheterised, or voided specimen which exceeds the level usually resulting from bacterial contamination from the skin, urethra, prepuce or vagina. Often taken to be ³10⁵ bacteria/mL.  Can be symptomatic or asymptomatic.

Suppressive antimicrobial therapy: if treatment has failed to eradicate a focus of bacterial infection, eg. a small stone, bacterial growth can be suppressed by a low, nightly dosage of an antimicrobial agent.

Uncomplicated pyelonephritis: pyelonephritis in those with no structural or functional abnormalities of the urinary tract.

Uncomplicated urinary tract infections: an infection of the urinary tract in a patient with a structurally and functionally normal urinary tract.

Upper urinary tract infection:  infection of the kidneys and/or ureters.

Urethritis: inflammation of the urethra rather than the bladder.  The origin of the syndrome should be described, for example, non-gonococcal urethritis. Urethritis generally occurs in conjunction with cystitis in women.

Urinary tract infection: an inflammatory response of the urothelium to bacterial invasion, usually associated with bacteriuria and pyuria.