Would a sea water enema help hydration?

Knowing that medications can be absorbed from suppositories, would a sea water enema help hydration?
05 December 2010



As a matter of survival, and in dire need of fluids without potable drinking water, would an anal infusion of sea water work?  If it would how much fits down there, a glass, a litre? I know of an occurrence where brackish water was administered that way to avoid the stomach upset and consequent problems drinking it would have resulted in.
John Burgess


We put this to Miles Parkes, Gastroenterologist, and Ari Ercole, Intensivist, both from Addenbrooke's Hospital...

Miles - Using the rectum as a means of administering fluid replacement in dehydrated individuals is an interesting idea. The colon or large bowel functions primarily to absorb fluid, normally doing so of course as material enters to the caecum from the small intestine, the material which has not been digested, fibrous products and so on, together with a substantial amount of fluid and solute enters into the colon, and the fluid is then sucked out as the material goes around the 4 feet or so of the colon to form up the stool. And so, you can see the colon is well designed for absorbing liquid but it really needs to do so in the context also of transport of solute, that's to say of sodium and chloride ions, and so on. It's the absorption of these, of the solute itself, which then creates the osmotic gradient which sucks fluid across the lining of the bowel, and into the bloodstream. So, bearing these things in mind, I do think that water enemas on their own, or water on its own, is perhaps unlikely to be absorbed in a clinically significant quantities, and of course, it's just likely to come out of the rectum again whereas, I think administering saline or something of that type would potentially lead to quite a significant absorption of fluid.

Diana - Water on its own probably wouldn't do very much, but a saline solution could give one a better chance of a drink. But what if you're stuck for saline drips and all you've got is a much saltier seawater?

Ari - Unfortunately, giving yourself a seawater enema for hydration if you've had the misfortune to be stranded at sea is a complete thermodynamic nonstarter. The problem is that the salt in seawater is much more concentrated than the concentration of all the various solutes found in body tissues. Since, to a first approximation at least, the gut can be thought of as a sort of semipermeable membrane, this will lead to water molecules tending to move from the body through the gut wall, and into the seawater to reduce the concentration difference. This process where water moves along its own concentration gradient across a semipermeable membrane is called osmosis, and it's very important in biology. In this case it will actually result in you becoming increasingly dehydrated. The situation is reversed with freshwater which would be successfully absorbed. Having said that, neither procedure would be very safe especially if the water was dirty. So, giving yourself a seawater enema if you're trapped at sea is likely to make you lose water. Of course, giving yourself a seawater enema if you're trapped at a cocktail party is likely to make you lose friends as well!


No one put this debate to rest. I volunteer for the experiment. Lol!

A simple test could be performed.

Take 10 individual and conduct a 5 day test. The first 5 drink no water and receive no Enema. Their vitals are constantly monitored, and when it is determined they are dangerously dehydrated, the time is recorded, and the test ends for them, (they can now drink water and re-hydrate) The second group would receive saltwater enimas from licensed medical staff. Their vitals also monitored. If at the end of the 5 days their vitals displayed healthy levels of hydration, the test would continue for up to 15 days, at which point there is no need to go on, but the test could go for 30 or even 60 days if desired. I think the variable time frame would lead to irrefutable data on this topic.

Something tells me that the Military did some test of this sort, if an ex SAS officer said it openly as some sort of common knowledge in the Military.

On one of Bear Grylls' survival programs he used a water bottle and a piece of tubing to give himself sea water enemas to hydrate himself and stated that it is standard knowledge taught at some military survival schools now. if Bear says it, it MUST be true!

Yes, a family survived six weeks at sea thanks to seawater enemas from their nurse mum. It was in the 1970s. The book is called "Survive the Savage Sea"- it was made into a movie. There are also other similar stories to be found. FYI to that rude person 'Dale' commenting about Phillip B. Flexon MD - he is a well-respected surgeon - look him up and feel ashamed of yourself!

They survived by drinking rain water. What they stuck in their hind end likely helped pass the time but would not have helped their hydration status

Look up osmolarity, hypertonicity, hypotonicity, osmosis. Then look up osmotic diarrhea. This is why you cannot use sea water enema. The glucose sodium co-transporter is effective in the gut, but sea water is way to hypertonic and you will cause fluid to move from the plasma through the gut lumen.

A family of 4? survived approximately 212 days at sea after their boat sank. Wife/mother was a nurse, and this was her solution. It worked. Water was absorbed, while salt and etc. were passed. After being rescued a docter inspected them. Except for salt water sores, they were in great health.

Can't remember name of the book i read this in. It was on ocean sailing, being ship wrecked, and possible survival solutions.

This incident took place somewhere southwest of Hawaii. All that i can remember.

The above discussion is completely wrong and somewhat shocking coming from MD's. The colon transfers water by active transport of NA+ ions.. In normal digestion by the time our digestive effluent reaches the colon it is hyper-tonic. The cells lining the colon first pump sodium into their capillaries and the water follows. The cells then pump the sodium out. A salt water enema with sodium chloride would allow the colon to net absorb iso-tonic water. That is what the colon does; it grabs water from a hyper-tonic solution.

Have you got a reference you can refer us to for the active transport of water from the colon please?

Phillip Flexon,”MD”, I guarantee you never went to med school and are a fraud. Basic sciences taught at even a community college will teach you something called osmolarity, hyertonicity, hypotonicity. Sea water is more concentrated with solute, therefore the more dilute water in your body will move across the gut wall to try to dilute the very salty sea water. Open a basic science book and stop spreading false info with your fake credentials.

MD Case Western Reserve University. Residency Harvard School of Medicine.
The Colon receives routinely hypertonic fluid from the small intestine. The mucosa of the colon has very active sodium pumps in their basolateral membranes.They actively pump Na ions into their capillaries and this creates the osmotic gradient that allows our colons to absorb water from a hypertonic. The overall salt absorbtion is small relative to the overall movement of free water. . It is a well known phenomenon that our colons are specialized to do. My understanding that Na must be the ion present. Other ions which can not be actively abosrbed in the basolateral membrane capillaries will cause an osmotic diarrhea. There are some good explanations of this by Richard Bowen colostate.edu.

Actually if you have a science or medical background you might enjoy a old paper free on internet about colon active Sodium pumps. See Sandle, Gut 1998 Vol 43(2) “Salt and Water Absorbtion in the Human Colon: a modern appraisal”. Point is Colon uses active Na pumps to move water out of hypertonic solutions in the colon and I am very much an MD and also Emeritus Associate Professor of Surgery. Also you can google my name and read publications of mine on line which include Nature, Genetics, Otolaryngology Head and Neck Surgery and American J of Surgery.
There is no study on sea water enemas just an anecdotal account. But the biophysical phenomenon of the Colon extracting water from hypertonic solutions by using active sodium transport
in its epithelium is well known

It was reported that seamen adrift for a month survived by rigging up a sea water enema. Dr Mark Pimentel, gastroenterologist feels that this would work because of the colon's function to absorb water.
Administering enemas in the early part of the last century were quite common and a means of administering medications. A favorite Rx for migraine was the coffee enema - because of the stomach sensitivity that was associated with vomiting.
As a scuba diver and medic I feel it is important to decide if this is a feasable method. Should be an easy experiment to conduct. I am thinking of the many lives that could be saved. If anyone has experience of information please contact me at the grossan institute. Thanks

Add a comment