What causes a strong urge to pee after being in the water?

What causes a strong urge to pee after being in the water for a while?

It’s happened to me. So I wanted to know exactly what causes the sudden urge to pee.

Note: the sudden urge to pee at OTHER times, like when arriving home, or shen you first wake up in the morning, or when you hear running water, is due to a different cause, namely bladder hypersensitivity. That is covered in a different blog post and bladder retraining is required in that case. It’s easy, no worries, but IS a different cause than this one. Just FYI.

Turns out, that the sudden urge to pee after being in water for about 20 minutes has to do with your body adapting to a new, aquatic, environment.

1st: Effects of Hydrostatic Pressure

Hydrostatic Pressure is the pressure exerted by any fluid at a certain point, due to the forces of gravity. The deeper you go in a fluid, the more hydrostatic pressure there is.

Water acts like a ginormous compression body-stocking

Since your feet are (usually) deeper than your head, so they have the most compression forces from the water, and this SQUEEZES fluids back towards our torso.  This is GREAT for swelling, and one of the many reasons that aquatic exercise is so good for us in the prenatal and postpartum phases (and really, anytime in our lives).  

All this fluid from our legs is pushed back into our torso.

Your KIDNEYS sense this rapid increase in perceived blood volume, and say “gee, Dr. Kelly just drank a ton of water. That’s cool. I better ramp up my filtration rate (the speed at which I make urine).”  

And the kidney’s speed up their work to get rid of the extra water, they fill your bladder up, and quickly.  This part takes about 20 minutes, at least, but is why you might always notice a slow building urge around this time.  

This relatively rapid filling of our bladder is what causes the sudden urge to pee after being in water!

COOL, huh?  Know what else is cool?  

That increase in central fluid volume from being in the water makes your heart fill a bit faster, pump a bit more effectively AND lowers your blood pressure for about 2-3 hours after even just sitting in chest deep water for 20 minutes!  

If we could bottle this positive effect to treat high blood pressure, we’d make millions. Luckily, we can try to find access to water, & get this positive effect for ourselves.  

🚩 WARNING, though.  This ‘cool’ process will lead to dehydration if we’re not careful, as our kidneys are processing liquids faster, so drink water during and after! If you need a reminder of how much water you should drink each day, revisit this post by a really great Pelvic PT 🙂

Remember that if you take half of your body weight in pounds, that it will give you the number of fluid ounces that is your baseline intake for each day. This should be increased if exercising, breastfeeding or living in a dry climate, and must be increased if you are doing water exercise.

So that’s why you get the urge to pee in the water.

In this particular case, the urge to pee isn’t abnormal at all, it’s just your body taking care of you, and working to manage your blood volume and blood pressure. So get out of the pool, pee, and get back in and back to exercise or fun.

But, if you commonly get sudden, strong, urges to pee when you’re not swimming…

Like when you first get home (“Key In Door Syndrome”, Pelvic PTs refer to it as), or when you hear water, or when you first awaken…this is ABNORMAL. That type of urgency is due to bladder hyperactivity or hyperirritability, and needs to be addressed by a Pelvic PT, or other pelvic health professional.

Thanks for Reading!

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