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IBS Diagnosis and Treatment

Irritable bowel syndrome (IBS) is difficult to diagnose because the disease causes no known physical abnormalities that doctors can identify through physical exams, imaging studies, or lab testing.

And because the symptoms of IBS overlap with so many other digestive disorders, people with the syndrome are sometimes misdiagnosed. IBS can easily be confused with diverticulitis, colon cancer, intestinal obstruction, ulcerative colitis, Crohn’s disease, gastrointestinal infection, celiac disease, and lactose intolerance.

Because IBS is more commonly diagnosed in those under age 50, older adults need to first determine that another disease more common in the elderly isn’t causing their symptoms. A doctor will take a medical history, perform a physical exam, and order blood tests.

Older individuals should have a colonoscopy or sigmoidoscopy to rule out the possibility of colorectal polyps or cancer and colitis. You should also have a blood test for celiac disease if your IBS symptoms involve mostly diarrhea or an alternating pattern of diarrhea and constipation. Your doctor also may perform a breath test for lactose intolerance if your symptoms seem to worsen when eating dairy products.

Once your doctor determines that your abdominal pain is not due to a physical abnormality, two of the following three criteria must be met to make a diagnosis of IBS:

• Bowel movements alleviate pain.

• Pain is accompanied by constipation or diarrhea.

• Pain is associated with a change in the form of the stool (watery, loose or pelletlike).

These symptoms must be present, all of the time or occasionally, for at least three months.

Treatment of IBS

Once diagnosed, treatment of IBS focuses on relieving the most bothersome symptoms:

• Constipation-predominant IBS. In 2012 the U.S. Food and Drug Administration approved a new type of prescription medication for treating constipation-predominant IBS. In clinical trials, subjects taking a daily dose of the drug, called linaclotide (Linzess), had more frequent spontaneous bowel movements and less abdominal pain than subjects taking a placebo.

Linaclotide causes elevated concentrations of an enzyme, guanylate cyclase-C, to form in the intestine, which is thought to speed up gastrointestinal transit as well as decrease the activity of pain-sensing nerves. Linzess is taken once a day at least 30 minutes before eating. The most common side effect reported during clinical trials was diarrhea. The drug should not be used in patients 17 years of age or younger.

Another medication available for individuals with constipation- predominant IBS is the prescription laxative lubiprostone (Amitiza). Approved in 2008, this selective C-2 chloride-channel activator initiates chloride secretion into the intestine, which helps promote bowel movements. Amitiza is taken twice a day; common side effects include nausea, diarrhea, and headaches.

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Selective serotonin reuptake inhibitors (SSRI) antidepressants like fluoxetine (Prozac) can improve abdominal pain and other symptoms of constipation-predominant IBS. SSRIs are thought to increase food transit speed through the gastrointestinal tract.

Another prescription medication that was approved for women with constipation-predominant IBS, tegaserod (Zelnorm), was taken off the market in 2007 due to serious cardiovascular side effects and is now available only in emergency situations.

• Diarrhea-predominant IBS. The over-the-counter antidiarrheal medication loperamide (Imodium) is an effective treatment, helping to reduce stool frequency and improve consistency. However, it does not have any effect on abdominal pain or bloating.

Low-dose tricyclic antidepressants (TCAs) such as desipramine (Norpramin) reduce pain and symptoms of diarrhea-predominant IBS by slowing food transit speed through the gastrointestinal tract.

The prescription medication alosetron (Lotronex) has been shown to relieve symptoms in women with diarrhea-predominant IBS but poses a risk of serious side effects, including severe constipation and reduced blood flow to the colon. It is available only through a special prescribing program to women with severe diarrhea-predominant IBS when more traditional treatments have failed.

• Constipation/diarrhea-predominant IBS. The latest research also shows that psychological therapies, including cognitive behavioral therapy, dynamic psychotherapy, and hypnotherapy, can provide some relief from IBS symptoms, whether they be constipation-predominant or diarrhea-predominant.

Mindfulness training—a form of meditation characterized by the nonjudgmental observation of thoughts, feelings, and sensations—may reduce symptom severity and improve the quality of life in people with IBS.

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