self-retaining catheter, an indwelling urinary catheter that has a double lumen. One channel allows urine to drain from the bladder into a collecting bag; the other has a balloon at the bladder end and a diaphragm at the other end. Several centimeters of air or sterile water is injected through the diaphragm to fill the balloon in the bladder and hold the catheter in place. To remove the catheter, the water or air is withdrawn through the diaphragm. See also Foley catheter.
