Squirting always produces this debate, not only in UKP, but whenever it is discussed, even it seems amongst medics.
My view is that there is certainly no place other than the bladder that can store the copious amounts of liquid squirted at great force across the room by many "squirters". Look at the videos of a well known porn squirter like Cytherea and there is no doubt that she is pissing. Is it possible that at the point of female orgasm that the involuntary muscle contractions that constrict the vagina and push down the cervix also put pressure on the bladder and relax the sphincter muscle? Girls that take a long time to climax do often complain of sore stomach muscles with all the muscle contractions going on below decks.
I seem to remember looking up scientific articles last time that this was discussed at length on UKP, and there was an article concerning an analysis that showed no difference between female ejaculate and urine.
I don't disputed the ability of some women to produce a lot of vaginal secretions when they cum. Some WGs that I have been with have produced quite a lot of fluid at the point of climax. Recently one girl "gushed" fluid as she climaxed through RO and fingering, but in reality it was only really a spoonful of fluid that came out as I removed my finger. Another covered my balls in a milky, sticky, odourless fluid as I fucked her in mish. At first we were both worried that the condon had split, but the condom was intact and the fluid didn't smell like spunk and had quite clearly come from her.
So for what it's worth here's my opinion. Some women may involuntary produce a squirt of pee at the point of climax, but most WGs and pornstars who claim to be squirters just produce a short sharp burst of pee on demand (notice how many of the pornstars rub over their vulva at the same time to disguise the fact that it is coming from their urethra). Some women do suddenly produce what seems to be a lot of vaginal secretions when they cum, but in reality it is quite a small amount and it isn't projected out of the body in a squirt.