This germ is thought to enter the urinary tract through the urethra from the outside because E. coli is a normal inhabitant of the human bowel. Viruses rarely cause urine infections. The protective mechanisms of the urinary tract are not fully understood. It is thought that turbulent flow of urine and the sticky properties of some bacteria may lessen the effectiveness of the protective washout mechanism of urine leaving the system. When this happens, the bacteria ascend into the bladder, then may reach the kidneys via the ureters resulting in infection.
Urine infections are more common in uncircumcised boys than circumcised boys.
In these children this may result in urine remaining in the bladder after they have urinated, forming a reservoir for infection. However this is only one aspect of a complex problem. Any obstruction of the urinary tract also interferes with the outflow of urine and may lead to urine infection. What to look for in your child The actual symptoms an infection causes depend to a degree on age. In babies it is likely to result in fever, difficulty in feeding and being generally unwell.