An urethral Foley catheter can sometimes become retained in the bladder, because of its balloon being unable to deflate. A malfunctioning inflation valve or obstructed channel along the length of the catheter is the cause.
How can you deflate the balloon so that the Foley catheter can be removed?
Cut the Foley catheter's balloon port. This should remove the one-way valve device of the balloon port, and the balloon's contents should spontaneously drain. The Foley can then be easily removed.
If option 1 fails, gently pass a thin guidewire into the inflation channel along the length of the Foley catheter. This should push away any foreign material (exudate, crystals) that have formed along the path. This should allow the balloon to drain spontaneously.
Instill 10 mL of mineral oil into the inflation channel and wait 15 minutes. This should chemically dissolve the thin balloon. Repeat once if unsuccessful. This yields a 85-90% success rate of Foley removal.
I learned this from our urologist recently, who managed to pull out a retained catheter by using the guidewire trick.
Reference Shapiro AJ, Soderdahl DW, Stack RS, & North JH Jr (2000). Managing the nondeflating urethral catheter. The Journal of the American Board of Family Practice / American Board of Family Practice, 13 (2), 116-9 PMID: 10764193