Doctor's Review: Medicine on the Move

January 22, 2022


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Treating irritable bowel syndrome with constipation

10 things you should know

1. IBS-C and CIC: two sides of the same coin?

Irritable bowel syndrome with constipation (IBS-C) and chronic idiopathic constipation (CIC) are difficult to distinguish in at least 25% of patients, and a similar percentage may alternate between the two conditions. So you’re not the only one who sees a marked overlap between IBS-C and CIC.

2. Abdominal pain is the hallmark of IBS-C

IBS-C is defined as abdominal discomfort associated with altered bowel habits over at least 3 months, whereas CIC is diagnosed as unsatisfactory defecation with infrequent stools, difficult stool passage, or both, for at least 3 months. A pragmatic way to distinguish constipation and IBS-C is to do a colonic lavage with polyethylene glycol. If symptoms persist, they're probably due to IBS-C, meaning treatments focused solely on increasing bowel movements aren't likely to help.

3. IBS-C is not a diagnosis of exclusion

In the absence of alarm features (e.g. rectal bleeding), IBS-C and CIC are unlikely to be due to sinister disease, and exhaustive testing is unnecessary.

4. Your confidence in the IBS-C diagnosis is key

It's reasonable to order a few diagnostic tests to rule out organic disease. The biggest benefit works through you: if you’re confident in the diagnosis of IBS-C, you’ll be able to convince your patients there’s no serious illness, and start treating the real problem.

5. Red flags do warrant further investigation

The classic alarm features are onset after age 50, rectal bleeding, weight loss, iron-deficiency anemia, symptoms at night, and family history of colorectal cancer, inflammatory bowel disease or celiac disease. Patients over 50 who’ve never had a colonoscopy should be screened for colorectal cancer because of their age. In women, early ovarian cancer symptoms, especially bloating due to ascites, may resemble IBS-C, so a pelvic exam and ultrasound may be warranted.

6. Optimal management requires teamwork

Since IBS-C is a chronic condition, actively involve patients in management to ensure treatment adherence. Also, try to lower expectations and set realistic treatment goals to reduce symptoms, feel better and improve coping.

7. The wrong fibre might worsen IBS-C symptoms

Adequate fibre intake increases bowel frequency and decreases straining, but can also increase gas and bloating. Over 25 g/day of fibre is likely to do more harm than good in IBS-C. However, soluble fibre, such as psyllium, oats and legumes, relieves constipation with less bloating than insoluble fibre, such as wheat bran.

8. FODMAPs may be to blame

Small carbohydrates known as FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols), found in wheat and many other foods, may cause bloating in IBS-C by: (1) osmotic effects in the bowel, and (2) fermentation by colon bacteria, producing gas. If bloating and/or gas are the chief problem, it’s worth trying the low-FODMAP diet. But it can be unhealthy if followed incorrectly, so consultation with a registered dietitian is recommended.

9. Patients may be reluctant to take medications, even if they work

Many patients may resist medications, but if nothing else has worked, appropriate drug therapy may be their only hope. Even when they find an effective medication, some people try stopping it, and the symptoms return. Emphasize that drugs for IBS-C only work while you take them.

10. Linaclotide is an effective option for IBS-C and CIC

Among drugs for IBS-C and CIC, linaclotide (Constella) has the most convincing evidence for efficacy. The main side effect of linaclotide is diarrhea. Patients who get diarrhea should call their physician to decide together whether it's severe enough to warrant stopping the drug. Often, patients are just startled by the abrupt increase in bowel movements. If they’re comfortable with it, there’s no reason to stop. Linaclotide has simplified the approach to constipation and IBS-C: if diet hasn’t worked, the next step is as simple as prescribing this drug.

This article was accurate when it was published. Please confirm rates and details directly with the companies in question.