THURSDAY, July 5 (HealthDay News) -- As many as one in five Americans has to deal each day with symptoms of irritable bowel syndrome, a digestive disorder for which treatment options remain limited.

"Treatment is challenging because we have only one approved drug from the FDA [U.S. Food and Drug Administration] right now," explained Dr. Satish Rao, director of the Digestive Health Center at Georgia Health Sciences University and Health System.

But there's good news, too, he said, because non-drug ways do exist to help control symptoms and several new drugs are in the pipeline. And though IBS, as it's called, can significantly affect people's quality of life, Rao said it doesn't damage the bowels and "nobody dies from IBS."

The most common symptoms of IBS are abdominal pain or discomfort and altered bowel function, according to Rao.

Dr. William Sandborn, chief of gastroenterology at the University of California San Diego Health System, explained that IBS "is more of a problem in the muscles and the nerves of the bowel."

"If you have problems with the bowel contracting too much, you'll have cramping and diarrhea," he said. "If the bowel doesn't contract enough, the contents of the bowel won't move forward sufficiently, and you'll have constipation."

If you have diarrhea associated with abdominal symptoms, doctors will refer to your disorder as diarrhea-predominant IBS. If constipation is more of an issue, you have constipation-predominant IBS. Those who experience both diarrhea and constipation have what's called mixed IBS.

Exactly what causes IBS remains a mystery -- or what Rao called "the million dollar question."

"We have unearthed some factors," Rao said. "It looks like people with certain genes are predisposed to IBS, and environmental factors play a role. Changes in the gut flora [the types of bacteria in the intestine] may predispose you to IBS." He also said that some people develop IBS after having a viral or bacterial infection. That's called post-infectious IBS.

Some people also have dietary intolerances to substances such as fructose, he said, and those symptoms can mimic IBS.

One factor that definitely does not cause IBS, Rao said, is stress -- though he said it could trigger symptoms in people who already have the digestive disorder.

A specific diagnostic test doesn't exist for IBS so to diagnose it, doctors must rule out other potentially more serious causes of digestive symptoms, such as colon cancer or Crohn's disease. Methods used to do this, Sandborn and Rao said, include blood tests, CT scans, a hydrogen breath test, endoscopy and colonoscopy.

Treatment generally aims to ease symptoms. People whose major problem is diarrhea may be given fiber supplements and possibly anti-diarrheal medications, according to Sandborn. For those whose main symptom is constipation, a doctor might suggest stool softeners.

Sandborn cautioned that people with IBS should "try to avoid stimulant laxatives as these can damage the bowel if used chronically." But he said that natural, beneficial bacteria known as probiotics -- whether from yogurt or a supplement -- may help ease some IBS symptoms.

Dietary changes also may help, but there's "not a perfect diet for this that helps everyone," Sandborn said. He suggested working with a nutritionist to try to eliminate foods that might trigger symptoms while still maintaining a balanced diet.

On the medication front, the antibiotic rifaximin, which is prescribed for traveler's diarrhea, may prove helpful for some people with IBS, though Sandborn said it's currently not approved for this use. Another medication that's being investigated for use in IBS with constipation and is currently under review by the FDA is linaclotide.

The only FDA-approved drug for IBS is alosetron (Lotronex), which was approved for IBS with diarrhea. But because of serious potential side effects, its use is restricted and only certain doctors are allowed to write prescriptions for it. Another IBS drug, tegaserod (Zelnorm), was pulled from the U.S. market several years ago and is now available through the FDA only in emergencies that are life-threatening or require hospitalization. Sandborn said it had been linked to a rare but increased risk for heart attack.

Irritable bowel "is an illness that doesn't look like a major disease, but it significantly affects quality of life," Rao said. "We have to tailor treatment to the needs of the patient, and that often includes a whole host of wonderful people like doctors, nutritionists, pain specialists and more, depending on the situation and the patient's needs."

More information

The U.S. National Institute of Diabetes and Digestive and Kidney Diseases has more on irritable bowel syndrome.

A companion article details one woman's methods for coping with IBS.