what causes frequent urinary tract infections
Causes. Urinary tract infections typically occur when bacteria enter the urinary tract through the urethra and begin to multiply in the bladder. Although the urinary system is designed to keep out such microscopic invaders, these defenses sometimes fail.he most common UTIs occur mainly in women and affect the bladder and urethra. 1  Infection of the bladder (cystitis). 2  Infection of the urethra (urethritis). 3  Symptoms. 4  Risk factors.