Urinary catheter is a thin, clean, flexible hollow tube that is either inserted through a patient's urinary tract into their bladder or attached to a male patient's penis. A balloon located at the end of the catheter is usually inflated with sterile water to prevent the catheter from slipping out. In this manner, the patient's urine is collected and contained for various medical purposes. They are flexible and most commonly are placed into the bladder through the urethra. The urethra is the tube that connects the bladder to the outside of the body, through which normal urination occurs.