Urinary Tract Infections

Most of the bacteria that cause urinary tract infections are derived from the patient's normal flora. Often urinary tract infections are caused by coliform bacteria such as Escherichia coli, found in the commensal flora of the bowel. Because of the anatomical differences between men and women, more women suffer urinary tract infections than do men.

Retention of urine predisposes to infection. Calculi (stones) within the urinary tract disrupt urinary flow, and hence predispose to infection. More infant boys than infant girls suffer anatomical abnormalities of the urinary tract - such as urethral valves - that lead to retention of urine. Hence, more small boys than small girls suffer urinary tract infections. It is rare, however, for an otherwise fit young man to suffer urinary tract infection. In women, urinary tract infections are frequently recurrent. As men get older, prostatic enlargement restricts urine flow from the bladder and this leads to an increase in the likelihood of developing a urinary tract infection.

Celibates are less likely to succumb to urinary tract infections than are people who are sexually active. In pregnancy, the developing foetus causes mechanical obstruction of the urinary flow. This leads to an increased risk of urinary tract infections.

The introduction of a urinary catheter greatly increases the risk of the patient developing an infection. Neurological problems that affect bladder emptying, including spina bifida and multiple sclerosis, are associated with an increased risk of urinary tract infections.