MKSAP Quiz: Treatment of diarrhea and abdominal pain

This month's quiz asks readers to determine the most appropriate treatment for a 35-year-old man with a one-year history of diarrhea and abdominal cramping and bloating.


A 35-year-old man is evaluated for a 1-year history of near-daily postprandial diarrhea, episodic abdominal cramping relieved with a bowel movement, and abdominal bloating. He is otherwise healthy, and his only medication is loperamide. This treatment has not been consistently effective in reducing diarrhea symptoms and has had no effect on the cramping and bloating, despite increased frequency of dosing.

Vital signs are normal. Diffuse tenderness to abdominal palpation is noted. Other physical examination findings are normal.

Stool testing for infection and celiac antibody testing are negative.

Colonoscopy findings are unremarkable.

Which of the following is the most appropriate treatment?

A. Alosetron
B. Linaclotide
C. Low-FODMAP (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, And Polyols) diet
D. Lubiprostone


MKSAP Answer and Critique

The correct answer is C. Low-FODMAP (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, And Polyols) diet. This content is available to MKSAP 18 subscribers as Question 6 in the Gastroenterology and Hepatology section. More information about MKSAP is available online.

A low-FODMAP (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, And Polyols) diet is the most appropriate treatment for this patient. FODMAPs consist of short-chain carbohydrates that are poorly absorbed and rapidly fermented by gut bacteria, resulting in the production of gas and an increased osmotic fluid load within the gut lumen. The patient has diarrhea-predominant irritable bowel syndrome (IBS-D). IBS is a heterogeneous symptom complex characterized by abdominal pain and altered bowel habits. The diagnosis of IBS requires symptoms of recurrent abdominal pain or discomfort at least 1 day a week for a period of 3 months, along with two of the following three additional criteria: pain relieved by defecation, change in stool frequency, or change in bowel consistency. IBS can then be further subtyped into IBS with predominant constipation (IBS-C), predominant diarrhea, mixed bowel habits, or unclassified.

The effects of dietary FODMAPs may contribute to the symptoms of IBS-D. A randomized controlled trial involving 84 adults with IBS-D compared a low-FODMAP diet to a diet based on modified National Institute for Health and Care Excellence (mNICE) guidelines. In this study, more patients on the low-FODMAP diet reported adequate relief of their IBS-D symptoms (52% versus 41%) and response in abdominal pain (51% versus 23%) than those on the mNICE diet.

Alosetron is a peripherally acting serotonin type 3–receptor antagonist approved by the FDA for the treatment of IBS-D in women aged 18 years or older after failure of conventional therapy. Due to the risk for adverse events with the use of alosetron, including serious complications of constipation and ischemic colitis, a prescriber must first complete an FDA-mandated Risk Evaluation and Mitigation Strategy training program that is available online. Alosetron is not FDA-approved for the treatment of men with IBS-D due to the small number of men involved in the pivotal clinical trials, and it would not be appropriate as an initial treatment for IBS in this male patient.

Linaclotide is a peripherally acting guanylate cyclase-C activator approved by the FDA for the treatment of IBS-C. Lubiprostone is a peripherally acting chloride channel activator that is approved by the FDA for the treatment of IBS-C in women aged 18 years or older. In this patient whose predominant bowel symptom is diarrhea, use of either of these agents will worsen his diarrhea and is therefore not indicated.

Key Point

  • A low-FODMAP (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, And Polyols) diet can reduce abdominal pain and bloating and improve stool consistency, frequency, and urgency in patients with diarrhea-predominant irritable bowel syndrome.