Infections beginning in the urinary tract

• Blockage anywhere in the urinary tract (for example, by stones or, in men, by prostate tumor or urethral stricture)

• Abnormal bladder function that prevents proper emptying, such as occurs in neurologic diseases (for example, spinal cord injury)

• Structural abnormalities such as urethral diverticulum

• Leaking of the valve-like mechanism between the ureter and the bladder, allowing urine and bacteria to flow backward from the bladder up the ureters, possibly reaching the kidneys (more common among children who have a UTI)

• Insertion of a urinary catheter or any instrument by a doctor

• Sexual intercourse

• Use of a diaphragm with spermicide

• Presence of an abnormal connection (fistula) between the vagina and the bladder or the intestine and the bladder

• Among men, prostate enlargement or infection of the prostate

Infections spread to the urinary tract from the blood (uncommon)

• Infection in the bloodstream (septicemia)

• Infection of the heart valves (infective endocarditis, an uncommon cause)