Why the need to urinate after diving?

[Aquaphile]

I'm sorry to post what seems like a frivolous question, but I am very curious about this phenomenon. My buddy and I have discussed this and can't agree on the cause. Yesterday we dove. He barely had anything to drink before the dive. I was well-hydrated. Post dive, we both desperately had to urinate. I don't know whether it matters or not, but we dive in relatively cold water (mid 50's, usually).

Is it that water is a metabolic by-product and since we don't sweat underwater that by-product ends up in our bladders?

Thanks for any insight.

 

[John Reinertson]

Immersion in water has a number of physiologic effects on the body. One of these is called immersion diuresis.
When you are in the water, reflexes stimulate release of Atrial Natriuretic Peptide, which causes increased kidney clearance of water and increased urine output.

Getting chilled also increases bladder contractility, as any parent of a young child wrapped in four layers of clothing discovers on a sledding expedition..
The minute the child gets outdoors and feels the cold, they have to pee right now, with the degree of urgency being proportional to the thickness and number of layers of clothing.

Despite a theory that this is a variation on Murphy's law, especially when applied to dry suit diving, these are real physical phenomena.

Stay safe and wet,
John

 

[Former FLL Now MSP Diver]

John Reinertson once bubbled...
Stay safe and wet,
John

A rather appropriate sign off given the topic.

 

[Aquaphile]

for the speedy response. So I guess there's really nothing much you can do to prevent it. Wishful thinking.

 

[The Iceni]

Hi John et al,

Isn't this also partly explained by the zero gravity effect of submersion?

If I remember correctly, not only does the body release Atrial Natriuretic Peptide, there is a mass transfer of blood to the centre in an effective zero garvaity situation. ANP is actually released due to the increased venous return to the heart but the blood supply to the kidneys and other internal organs is also increased because the work of the heart against gravity has been removed and blood pressure remains controlled at normal levels.

Thus more, dilute, urine is produced automatically?

Added as an afterthought on 7.8.02. The excess production of urine leads to that precipitant of DCI - DEHYDRATION.

 

[Aquaphile]

Okay, I've had a day to think about the first response. I don't see how it is "immersion" in water that does the trick. I spent an hour in 70 deg water the other day without a wetsuit. I had no desperate need to urinate afterward, nor for that matter when I was first immersed in the cold water (re the bladder contractility).

Also, I ski. I get bundled up in lots of layers and I don't feel a desperate need to urinate when I step outside into the cold. I have been really cold while skiing, without the need to pee. So I don't understand the relationship between the cold and the bladder contractility.

I sure would love an explanation. Does anyone know about water being a metabolic by-product?

Thanks very much.

 

[Dr Deco]

Dear Aquaphile:

Fluid shifts

As a matter of fact, water is a metabolic by produce of life. When we metabolize food (carbohydrates composed of carbon, oxygen and hydrogen), it combines with oxygen in the air we breathe to form carbon dioxide and water. In this long, metabolic conversion process, chemical energy is produced that allows our muscles to move and heat for our bodies to be formed.

However, the primary reason that individuals urinate in the water is the shift of blood from the extremities to the trunk, as mention in the posts above.

This is a phenomenon that has been recognized for centuries. In fact, divers in ancient roman times were known as urinators , those who urinate.

In space and 0-gravity

This loss of fluid from your body with a fluid shift also occurs in space when astronauts move into the 0-g environment. Within a few hours, they begin to urinate and readjust their fluid loads in the body. Unfortunately, when they reenter Earth’s gravity, there is a shift of blood to the legs, a lack of blood in the trunk (and heart) and a feeling of dizziness with poor postural stability.

Similar events occur when we lie down to sleep. In this case, antidiuretic hormone keeps us from needing to frequently rise during the evening, thus allowing a better sleep pattern. In the morning, though, we find the need to make a trip to the bathroom.

Dr Deco :doctor:

 

[Aquaphile]

Dr. Deco,
thanks for clarifying things. I appreciate your answer.

-Aquaphile

 

[JDostal]

Thanks for the good answer as well. I've noticed this in myself too...everytime I dive, I make sure I go to the bathroom right before the dive. It doesn't seem to help at all...everytime I'm done with a dive, the first thing I do is peel off my wetsuit and head for the nearest bush. Glad there is a fairly logical explanation for the whole thing.

 

[Uncle Pug]

... P-valve... this wonderful device allows you to adjust your shifting fluid load on the fly!

Say goodbye to intentional dehydration.
Say goodbye to the post dive *I gotta go* dance.
Say goodbye to Depends!

Say hello to I. P. Freely
Ahhhhhhh..... what a relief it is....