Diagnosing and treating irritable bowel syndrome

Irritable bowel syndrome (IBS) is a chronic disorder characterized by recurrent bouts of constipation, diarrhea, or both, as well as abdominal pain, bloating, and gas. IBS is a functional disorder, which means that it's not attributable, as far as we know, to any underlying disease process or structural abnormality. It's thought to involve various, often interacting, factors — infection, faulty brain-gut communication, heightened pain sensitivity, hormones, allergies, and emotional stress.

The good news is that IBS doesn't increase the risk for more serious conditions, such as ulcerative colitis or colon cancer. On the other hand, a disorder resulting in (at best) annoying and (at worst) debilitating and worrisome symptoms with no known cause can be difficult to diagnose and treat, not to mention live with. Managing IBS typically involves some trial and error, which can be challenging for patients and clinicians alike. Various tests or procedures may be ordered to rule out other conditions. Many diverse therapies, not all of them proven, are used in treating the symptoms, including antibiotics, antispasmodics, antidepressants, dietary changes, relaxation techniques, and psychotherapy, as well as drugs to relieve constipation and diarrhea.

In the past doctors often ordered extensive testing (complete blood count, thyroid function test, stool testing for parasites, and abdominal imaging) before diagnosing IBS. This is usually unnecessary for people with typical IBS symptoms who have no family history of colon cancer, inflammatory bowel disease, or celiac sprue — and no "alarm symptoms," including rectal bleeding, weight loss, or iron-deficiency anemia.

The language used to describe IBS has been simplified. Previous criteria incorporated a list of specific symptoms (stool consistency and frequency, for example) that the task force concluded had limited value in identifying IBS. The disorder is now defined simply as "abdominal pain or discomfort that occurs in association with altered bowel habits over a period of at least three months."

Here some therapies to consider:

Dietary changes. Many people with IBS show improvement in symptoms by avoiding fermentable oligo-, di-, and monosaccharides and polyols (FODMAPs). Other dietary changes that can help include limiting lactose containing products and gluten.

Bulking agents and fiber. Bulking agents that contain psyllium (ispaghula husk) improve overall symptoms.

Antidiarrheal agents. Loperamide (Imodium) can help reduce symptoms when the primary IBS symptom is frequent or loose stools.

Constipation predominant IBS drugs.  Linaclotide (LINZESS) is approved for adults age 18 and older who have constipation predominant IBS. Lubiprostone (Amitiza) can help relieve overall symptoms of women with constipation-predominant IBS.

Diarrhea predominant IBS drugs.  Eluxadoline (Viberzi) and rifaximin (Xifaxan) are approved to treat irritable bowel syndrome with diarrhea (IBS-D) in adult men and women. Alosetron (Lotronex) is approved for women with severe symptoms of diarrhea-predominant IBS; but its availability and use are limited because it can cause severe constipation and ischemic colitis.

Antispasmodics. Dicyclomine and hyoscyamine may provide short-term relief of abdominal pain.

Psychological therapies. These therapies, including cognitive therapy, dynamic psychotherapy, and hypnotherapy can be effective in relieving overall symptoms.

Probiotics. There are many strains of probiotics, but none have consistently shown to benefit people with IBS.

Antidepressants. Tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs) are effective in relieving overall symptoms and reducing abdominal pain.