Urinary tract infection (UTI) is a common infection that usually occurs when bacteria enter the opening of the urethra and multiply in the urinary tract. The urinary tract includes the kidneys, ureters (tubes that carry urine from the kidneys to the bladder), bladder, and urethra (tube that carries urine from the bladder).
The special connection of the ureters at the bladder help prevent urine from backing up into the kidneys, and the flow of urine through the urethra helps to eliminate bacteria. Under normal circumstances, bacteria placed in the bladder are rapidly cleared, partly through the flushing and dilutional effects of voiding but also as a result of the antibacterial properties of urine and the bladder mucosa.
Urinary tract infections usually develop first in the lower urinary tract (urethra, bladder) and, if not treated, can progress to the upper urinary tract (ureters, kidneys). Bladder infection (cystitis) is by far the most common UTI. Infection of the urethra is called urethritis. Kidney infection (pyelonephritis) require urgent treatment and hospitalisation.
The causes of urinary tract infection and why some are affected more than others are explained below.
Gender and Sexual activity
The female urethra appears to be particularly prone to colonization with colonic gram-negative bacilli because of its proximity to the anus, and its short length (about 4 cm). Sexual intercourse can lead to movement of bacteria in the genital area and can be associated with the onset of cystitis. Voiding after intercourse reduces the risk of cystitis, probably because it promotes the clearance of bacteria introduced during intercourse.
UTIs are detected in 2 to 8% of pregnant women. The incidence of bladder infection is not higher during pregnancy but the chance of infection affecting the kidneys is increased.
Any impediment to the free flow of urine eg tumour, stricture, stone, or prostatic enlargement can result in an increased frequency of UTI. Infection superimposed on urinary tract obstruction may lead to septicaemia or even death. It is of utmost importance, therefore, when infection is present, to identify and alleviate obstruction as soon as possible.
Neurogenic Bladder Dysfunction
Interference with the nerve supply to the bladder, as in spinal cord injury, tabes dorsalis, multiple sclerosis, diabetes and other diseases may be associated with UTI. The infection may be initiated by the use of catheters for bladder drainage or secondary to incomplete bladder emptying with stasis of urine. An additional risk factor in these cases is bone demineralization due to immobilization, which can causes hypercalciuria with subsequent calculus formation and obstructive uropathy.
Vesicoureteric reflux (VUR) is defined as reflux of urine from the bladder cavity up into the ureters and sometimes into the renal pelvis, It occurs during voiding or with elevation of storage pressure in the bladder.
VUR is common among children with anatomic abnormalities of the urinary tract as well as among children with anatomically normal but infected urinary tracts. Long-term follow-up of children with UTI who have reflux has suggested that renal damage correlates with severe reflux and not necessarilywith infection.
Bacterial Virulence Factors
Bacterial virulence factors determine the likelihood of a bacteria to cause an infection when it is introduced into the bladder.
Increasing evidence suggests that host genetic factors influence susceptibility to UTI.
To find out whether you have a UTI, your doctor will test a sample of urine for white cell (leukocyte) and bacteria. You will collect “midstream” sample of urine in a sterile container. (This method of collecting urine helps prevent bacteria around the genital area from getting into the sample and confusing the test results.)
Urine is first examined under a microscope for white and red blood cells and bacteria(urine microscopy). Then the bacteria are grown in a culture and tested against different antibiotics for antibiotic sensitivity, to see which drug best treats the bacteria.
If you have frequent infections, your doctor may ask you to have a urinary tract ultrasound which examines your kidneys and bladder and provides useful information about structural abnormalities that can be causing recurrent infections.
A cystoscopy can also be useful to exclude early abnormal changes in the lining of the bladder. A cystoscope is a telescope that is inserted through the urethra which allows the doctor to see inside the bladder.