You've spent the better part of the day tethered to the bathroom, and every meal features Pepto-Bismol" as the main course. Could it be the flu? Or might you have food poisoning?

A better question to ask yourself when you're suffering from diarrhea, says John Brodhead, Jr., M.D., is just how serious are your symptoms.

Although inconvenient, non-inflammatory diarrhea is relatively benign in adults, says Brodhead, an associate professor of clinical medicine at USC. Most of the causes-viruses and bacterial toxins, produced in the intestine or ingested preformed in food-are self-limited and resolve without therapy within a few days.

In addition to copious fluid loss, non-inflammatory diarrhea is often accompanied by cramping and gas bloating in the upper abdomen. A number of viruses can cause the symptoms. Most follow a fecal-oral transmission route, so the best way to avoid them is to practice good handwashing, especially if you have a baby and are frequently handling soiled diapers.

Improperly cooked or stored foods-especially meats, dairy and some bakery products-also can spawn a host of bacteria that cause mild diarrhea and vomiting.

The best treatment for a mild bout of diarrhea, regardless of its origins, is to drink plenty of fluids-preferably juice or a sports drink that will replace lost electrolytes-and ride it out. Products that ease the symptoms may prolong the illness.

"You're just delaying the excretion of the toxin or the virus," explains Brodhead. "Diarrhea is your body's defense mechanism."

Brodhead cautions, however, that more aggressive medical treatment is called for in cases of inflammatory diarrhea which, like dysentery, is marked by fever, bloody stools and abdominal pain. It can be caused by many bacteria, bacterial toxins and amoebic infection and is a sign of more serious illness.

"It means the bugs are invading the colon wall," he says. "Those need to be treated."