Causes  of UTIs

UTIs occur when the urinary tract becomes infected, usually by bacteria. In most cases, bacteria from the gut enter the urinary tract through the urethra.

This may occur when wiping your bottom or having sex, for example, but often it's not clear why it happens.

The following may increase your risk of getting a UTI:

• conditions that obstruct your urinary tract, such as  kidney stones
• difficulty emptying your bladder fully
• using a  contraceptive diaphragm or  condoms coated in spermicide
• diabetes
• a weak immune system  from  chemotherapy or HIV , for example 
• a  urinary catheter  (a tube in your bladder used to drain urine)
• an enlarged prostate gland in men

Women may be more likely to get UTIs because their urethra is shorter than a man's and is closer to their anus (back passage).