A urinary catheter is a small, flexible tube that can be inserted through the urethra and into the bladder, allowing urine to drain. The urethra is the tube that carries urine from the bladder out of the body.

An indwelling Foley catheter remains in place continuously. To keep the catheter from slipping out, there is a balloon on one end that is inflated with sterile water after that end is inside the bladder.