The post dive queue for the toilet is generally a lengthy one, no matter how many times you urinate before the dive, less than an hour later the end of the dive see’s most people legs crossed and desperate for the toilet. This month we ask our doctors why this happens and more importantly if there is anything we can do to alleviate this (preferably something which does not result in an aromatic wetsuit!)
Whenever the body enters a body of water cooler than the air it is affected by a phenomenon known as immersion diuresis. It is caused by the constriction of the blood vessels of the extremities which means that the central organs (heart, lungs … etc) receive an increased volume of blood. This physiological effect is the body’s method of protecting the vital organs from damage from accidental and prolonged exposure to cool waters.
The kidneys, which are responsible for the production of urine, are controlled by an anti-diuretic hormone (ADH) which tells them how much to produce and when. The larger volume of blood mentioned previously causes the body to register a fluid overload causing ADH production to stop. The kidneys start to produce urine to help lower the volume of fluid which gives you a full bladder and an urge to urinate.
The best way to control this phenomenon is to reduce the intake of diuretics whilst on a dive trip. Caffeine is a well known diuretic and therefore present in tea, coffee and cola’s. Switching to a de-caffeinated brand or an alternate refreshment will therefore reduce the need to urinate. What is vitally important is that you do not attempt to dehydrate yourself before diving as a means of controlling this situation. De-hydration is a major factor in occurrences of decompression sickness (DCS), the inconvenience of a rush to the bathroom or even a good rinse of a wetsuit, is infinitely preferable to DCS.
Dr. Adel Taher & Dr. Ahmed Sakr: your diving docs
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