Cystitis or inflammation of the bladder is an inflammatory response to the adhesion of bacteria to the surface of the bladder and the mucous membrane of the urethra. Urine is otherwise physiologically sterile, thanks to defense mechanisms against infections: pH concentration, urea and ammonia concentration, and the defense mechanism is also urination itself (approximately 1.5 liters of urine per day). But when cystitis occurs, all that changes.