Chronic Urinary Tract Infection (UTI)
Infections do not generally take hold in your urinary tract because bacteria are constantly flushed away by the flow of urine. Your immune system can usually cope with the few bacteria that do creep in.
Bacteria are more likely to become established and multiply in your urinary tract under certain conditions. These are when you have a reduced flow of urine (as in dehydration or kidney failure), incomplete emptying of your bladder or reduced immunity. Examples of when there is reduced immunity are pregnancy, diabetes, steroid therapy and HIV infection. This can lead to chronic urinary tract infection.
Incomplete bladder emptying can be caused by pressure from the outside, deforming the bladder wall. This can happen when a pregnant uterus presses on the bladder or when abnormalities or weaknesses of the bladder wall (or, higher up, of the urethra or kidney) prevent complete emptying.
These abnormalities are often the result of childbirth or they may be congenital (present from birth). Damage after an accident, multiple sclerosis or surgery can also interfere with proper bladder emptying by interrupting the nerve supply, which would normally coordinate the time at which and the way in which your bladder contracts.
Other abnormalities that prevent complete flushing of the system are bladder stones and wart-like growths on the bladder wall (papillomas), which harbor bacteria in their crevices. Papillomas can also bleed slightly and must be monitored because they can develop into cancer.
Factors That Increase the Risk of UTIs in Women
A womans urinary tract is flushed regularly by the flow of urine. Any bacteria that may get in are usually dealt with by the immune system. You are more susceptible to a UTI in any of the situations listed below.
Incomplete 'Flushing' of the Urinary Tract
Poor urine flow, as in dehydration or kidney failure
Anatomical abnormalities: congenital (present from birth, such as horseshoe-shaped kidney) acquired (e.g. after surgery)
Poor bladder emptying, as in old age or multiple sclerosis
Compromised Resistance to Bacteria
Reduced immunity, as in HIV infection
Other illnesses, e.g. diabetes
The Ability of Bacteria To 'Hide' In the Bladder
Bladder papillomas (wart-like growths)
Foreign bodies, such as urinary catheters