Pain in Primary Care

Constipation and Cramping: A Slam-Dunk Diagnosis?

Charles P. Vega, MD


August 03, 2022

Dr Vega's Take

Brenda's symptoms are concerning in that she has had them for a year without a diagnosis. On the basis of her history and physical examination, the most likely cause of her symptoms is irritable bowel syndrome with constipation (IBS-C). She meets the ROME-IV criteria for IBS because her abdominal pain has persisted for at least 3 months, plus the fact that her pain is related to defecation, and it has been accompanied by a change in stool frequency. These three clinical features are all that is necessary to make the diagnosis of IBS-C.

Current guidelines suggest that patients with IBS complete serologic testing for celiac disease, as IBS and celiac disease share clinical features. However, these same recommendations note that celiac disease is less likely in cases of IBS-C compared with IBS with diarrhea. It is always important to consider the possibility of inflammatory bowel disease (IBD) in patients like Brenda. Still, the lack of systemic or severe symptoms make IBD unlikely in her case. Her 5-lb weight loss over 6 months when she restricted her consumption of food does not inspire me to order fecal calprotectin or fecal lactoferrin as part of an IBD workup on this patient.

Without a further workup pending, it is time to consider pharmacotherapy for Brenda. By her report, a trial of docusate did not relieve her symptoms. Docusate sodium has a poor history of efficacy for IBS-C and constipation. A 2021 review of available over-the-counter laxatives did not recommend docusate because of its variable history of efficacy in the management of constipation. However, polyethylene glycol (PEG) and senna received strong recommendations for constipation; psyllium and bisacodyl were also found likely be effective.

Brenda has also tried over- the-counter bismuth. Because it can cause constipation, bismuth subsalicylate is clearly the wrong choice for this patient.

Fortunately, effective treatments for patients with IBS-C are available. A trial of the fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) diet is reasonable at this time. The patient can use this diet and the reintroduction of FODMAP foods to identify particularly offensive foods and eliminate them from her diet over the long term.

PEG can alleviate constipation but is not recommended for routine use in patients with IBS-C. There is little doubt that PEG can improve stool frequency and consistency in cases of chronic idiopathic constipation, but its efficacy for relief of abdominal pain or overall symptoms of IBS-C is less convincing.

Probiotics are a popular option for the treatment of gastrointestinal disorders, but their record of efficacy is decidedly mixed. Clinical trials of probiotics have been limited by variable study design and outcomes. Although some data support their use in IBS, it is challenging to identify the particular probiotic strains that are most likely to be beneficial, or which particular type of IBS is most likely to benefit from probiotics.

Instead, we should consider a recommendation for soluble fiber. Soluble fiber is found in psyllium, oat bran, barley, and beans. Randomized controlled trials have demonstrated that soluble fiber can improve symptoms of IBS, at the cost of a modestly higher risk for adverse events compared with placebo.

Another treatment worth considering is peppermint oil. In a meta-analysis of 12 randomized trials, peppermint oil was more than two times more effective than placebo in improving IBS symptoms. The number needed to treat (NNT) with peppermint oil vs placebo to achieve improvement in global symptoms was 3. Peppermint oil seems particularly effective in alleviating abdominal pain, with an NNT of 4 for this outcome.

Medications such as lubiprostone and linaclotide are also effective and safe for IBS-C. Rates of treatment response in a randomized controlled trial of patients with IBS were 18% for lubiprostone vs 10% for placebo, with a similar rate of adverse events in the lubiprostone and placebo groups. In a meta-analysis of three trials, linaclotide was associated with reduced symptoms of IBS as well as higher quality of life compared with placebo.

There are multiple options to help Brenda's symptoms. Dietary modifications plus soluble fiber and peppermint oil seem like a good place to start. Lubiprostone and linaclotide are effective and well-tolerated should she need additional treatment.

Finally, it is important to address Brenda's mental health with a stronger understanding of her anxiety and low mood, which are common in people with IBS and can make effective treatment much more difficult. A depression screening tool with appropriate follow-up care is indicated.

What do you think? I'm eager to see your responses during the next few weeks and will respond to the comments.

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