Cystitis. Illustration of a female urinary bladder, dissected to show inflammation that occurs in cystitis. At centre is the bladder which stores urine. At top are two ureter tubes which lead from the kidneys and pass urine to the bladder. The urethra (at lower centre) is the channel which expels urine to the exterior. In cystitis the inner lining of the bladder becomes inflamed, as seen here, causing obstruction to the urethra. This prevents the voiding of urine. Cystitis is usually caused by bacterial infection, and is more common in women. Symptoms include pain and difficulty in passing urine. Treatment with antibiotic drugs usually cures the infection.