Frequent urination during episodes of diarrhoea?

[Absinthia]

Does anyone else find that during an episode of diarrhoea that you also experience an almost constant need to urinate? It happens to me every time, if I have a few bouts of diarrhoea, I also suddenly find myself needing to urinate, sometimes like every five minutes. And yes, once the diarrhoea starts I start drinking an electrolyte drink to try to prevent dehydration, but it seems like it just goes right through me, before my body can even absorb it so I still end up getting dehydrated. And the urination will continue for several hours even after the diarrhoea has stopped. Why is this?

[Superzob]

Yes. The IBS website lists this as a common side effect. I’ve had a lot of this recently, with alternating IBS, and it’s a real nuisance (can sometimes be on the toilet for almost 1 hour, squeezing out the last drop of urine, which seems to be endless). The cause may be either rectal pressure on the bladder or a nervous response to the IBS; also, since the anal sphincter remains open during the evacuation process, the lower urinary sphincter also remains open, and I suspect this might also be a trigger. The next day or two, I tend to be a bit dehydrated and not urinate much; this seems to rectify itself. I have discussed this with doctors and they have not been unduly concerned, but the solution seems to be to control the IBS and, to date, I’ve not had much success with that.