Let me warn you. This is not the article to read while you are eating breakfast. For this week the topic is diarrhea, the runs, the trots, turista, Montezuma’s revenge. Hardly the subject of polite conversation, but let’s face it, it happens all the time in Beijing.

Imagine for a moment a bucket containing everything that you ate and drank yesterday. You will realize that our diet is a very liquid one. All this material goes in at the top end, the stomach and intestines process all this stuff, take out the nutrients, absorb 90 percent of the water and put out a solid product at the other end. Normally this process is slow, giving the gut plenty of time to deal with all the water that has to be absorbed.

It is difficult to think of diarrhea in a positive way but it is in fact one of the body’s protective mechanisms. If we consume anything that feels dangerous to our bodies, the digestive tract takes action to remove it from the body as soon as possible. The gut shifts into overdrive and all the contents are rushed through as quickly as possible which does not give the colon, the last part of the digestive system, time to absorb the fluids and out it comes in a liquid state. Because it is all coming through very quickly, the colon demands to be emptied frequently and the result is frequent visits to the toilet. The gut works hard to move things through as quickly as possible and this sometimes causes stomach cramps, accompanied by quite a symphony of gurgling sounds.

In most cases the digestive tract goes back to its normal state fairly quickly, but one complicating factor is that diarrhea is often accompanied by vomiting. What a trap! Diarrhea medications taken by mouth are vomited out as fast as they are swallowed. Rectal suppositories for the treatment of vomiting are not going to be very effective and putting them in the rectum is rather like trying to run up the down escalator. Both of these conditions cause a terrific loss of fluid and this can lead to dehydration. This is a particular worry in children whose reserves of water are much smaller than adults’.

Most attacks of diarrhea are not too worrying and resolve quickly. The minor attacks that last for one or two days need simple treatment and are a nuisance rather than a serious medical condition. These are often called "Stomach Flu," a totally inaccurate name as it has nothing at all to do with the influenza virus, although it is similar in that it is a disease that lasts a short time that doctors can’t do much to cure.

Prevention is obviously a priority. Drinking untreated tap water is risky and I recommend you stick to bottled water. Check the seal to make sure it is intact: there is a lively trade in filling empty bottles with tap water. All vegetables and fruit should be meticulously washed, as feces is the most commonly-used fertilizer. Microwave cooking is remarkably good at killing bacteria. It is a good idea to at least flash vegetables through before or after washing them. Meat that is going to be barbecued should always be microwaved before being put on the grill. It would be nice if you could identify the risk of eating at local restaurants by their appearance, but this does not seem to work. I have had no problems after eating at rather suspect-looking local restaurants and have been violently ill after eating at one of the finest hotels in the city.

There is a very good argument that you should not treat diarrhea too vigorously for the first few hours, as the body needs to rid itself of whatever is bothering it. Fluid replacement however should start immediately. Special Oral Rehydration Salts (ORS) are widely available. I would advise you to keep some at home at all times. Gatorade is a good alternative for a short time but has too much sugar for long-term use. If you need some fluid in the middle of the night you can make your own. Take a liter or quart of water and add half a teaspoonful of baking soda, half a teaspoonful of salt (Lite Salt is even better) and three tablespoons of sugar. Shake it all up and start sipping on it immediately. You can tell if you are well-hydrated by observing your urine. There should be plenty of it and it should be the color of a fine white wine.

Three medications, all of which are available without prescription may be helpful:
Loperamine (also sold as Immodium, Diar-aid and Pepto Diarrhea Control) acts by slowing down the action in the guts. Adults should take two 2 mg tablets as a first dose then one after each bowel movement but not more than eight tablets a day. Children between six and twelve can take one 2 mg tablets twice a day.

Kaopectate is not really a drug as it is not absorbed into the system. It acts by absorbing the toxins in the gut and helping to solidify things. It looks like cement, tastes like cement and sets like cement. I have not been able to see this in any local drug stores and would advise you to put it on your shopping list when you take a trip home. The dose is 15 to 30 mls every four hours, but personally I just drink it out of the bottle every time I pass the bathroom. Stop taking it as soon as things start to improve as you may progress to constipation. Pepto Bismol is a similar product. I don’t think it is quite as effective and turns things a strange color, but it is widely available in Beijing.

Dr. Moreton is an Obstetrician and Gynecologist at Beijing United Family Hospital. Got a medical question? Email it in to ed@beijingscene.com