Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 67-year-old woman is evaluated for a 1-year history of loose stools. She reports approximately four episodes per day without abdominal pain. She has not had nausea, vomiting, weight loss, bright red blood per rectum, or melena.

On physical examination, temperature is 36.7 °C (98.1 °F), blood pressure is 115/85 mm Hg, pulse rate is 76/min, and respiration rate is 18/min; BMI is 25. No rashes are noted. Abdominal examination is normal. Rectal examination demonstrates normal resting anal tone.

Laboratory studies reveal a normal complete blood count, thyroid-stimulating hormone level, tissue transglutaminase IgA level, and total IgA level. Results of a routine screening colonoscopy for colon cancer done 1 year ago were normal.

Which of the following is the most appropriate next step in management?

A. Begin dicyclomine
B. Check antigliadin antibody
C. Initiate loperamide
D. Perform flexible sigmoidoscopy with colon biopsies

MKSAP Answer and Critique

The correct answer is D: Perform flexible sigmoidoscopy with colon biopsies.

This patient should undergo flexible sigmoidoscopy with random colon biopsies. She does not fulfill the simplified American Gastroenterological Association (AGA) clinical diagnostic criteria for irritable bowel syndrome diarrhea subtype (IBS-D) or the Rome III criteria for IBS. The AGA criteria require abdominal pain or discomfort as well as diarrhea for diagnosis of IBS-D. The Rome III criteria for IBS require recurrent abdominal pain or discomfort at least 3 days per month in the last 3 months associated with two or more of the following: (1) improvement with defecation, (2) onset associated with a change in frequency of stool, and (3) onset associated with a change in form of stool. Although these criteria have not been formally validated, they are the guidelines most frequently used in clinical practice to diagnose IBS.

Because this patient has painless diarrhea and does not meet the IBS diagnostic criteria, further diagnostic testing is required. Although the differential diagnosis for chronic painless diarrhea is broad, microscopic colitis could be considered as a cause of painless, watery diarrhea in a 67-year-old woman. A recent normal colonoscopy does not exclude microscopic colitis, because this diagnosis requires random colon biopsies to look for a thickened subepithelial collagen band (collagenous colitis) or a subepithelial lymphocytic infiltrate (lymphocytic colitis).

Antispasmodic agents, including dicyclomine, hyoscyamine, and possibly peppermint oil, function as gastrointestinal smooth-muscle relaxants. Although these agents may reduce abdominal pain in the short term for patients with IBS, their efficacy is not well substantiated, and because their action is not specific to the gut, they may be associated with side effects that preclude their use. Furthermore, this patient does not have abdominal pain and does not meet clinical criteria for IBS.

In this patient with a normal tissue transglutaminase IgA level, celiac disease is unlikely, and additional testing for celiac disease is unnecessary. Furthermore, antigliadin antibody studies are less accurate than tissue transglutaminase antibody studies and have high false-positive test rates.

Initiating treatment for painless diarrhea in a 67-year-old woman without understanding the cause of diarrhea is not appropriate. Although loperamide can be part of the treatment approach for microscopic colitis, it would be most appropriate to diagnose first and initiate treatment thereafter.

Key Point

• Patients with painless diarrhea who do not meet American Gastroenterological Association or Rome III diagnostic criteria for irritable bowel syndrome should undergo further diagnostic testing.

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