Urinary Tract Infections

Urinary tract infections are most often caused by a single bacterial pathogen, frequently originating in the patient's commensal enteric or skin flora. They range from the relatively trivial symptoms of cystitis through to potentially life-threatening infections affecting the kidney. The majority of urinary tract infections are caused by bacteria ascending through the urethra to the bladder. From here bacteria may reach the kidney to cause pyelonephritis, although in a minority of cases bacteria may reach the kidney via the bloodstream.

The urinary tract is one of the commonest sites of bacterial infections, and considerable time and effort go into their diagnosis. Apart from the distal urethra, the urinary tract in health should be sterile. Urine samples are, however, easily contaminated, and urine makes a good growth medium for bacteria. This makes the laboratory diagnosis of urinary tract infections difficult.