Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.
A 42-year-old woman is evaluated for an 8-month history of crampy abdominal pain and three loose bowel movements per day. The pain is relieved by a bowel movement. There are no nocturnal bowel movements, and there is no blood or dark tarry material in the stool. She has not had fever, night sweats, or weight loss. She has a history of Hashimoto disease and is treated with levothyroxine.
On physical examination, temperature is 36.8 °C (98.2 °F), blood pressure is 128/84 mm Hg, pulse rate is 64/min, and respiration rate is 16/min; BMI is 23. No rash is noted. There is mild diffuse abdominal tenderness without peritoneal signs and no abdominal masses. Rectal examination is normal. Complete blood count and thyroid-stimulating hormone level are normal.
Which of the following is the most appropriate next step in management?
A: Breath test for bacterial overgrowth
B: Colonoscopy with random biopsies
C: Stool culture
D: Tissue transglutaminase antibody testing
MKSAP Answer and Critique
The correct answer is D: Tissue transglutaminase antibody testing.
This patient should undergo tissue transglutaminase antibody testing. The American College of Gastroenterology recommends routine serologic testing for celiac disease in patients who present with symptoms of diarrhea-predominant or mixed irritable bowel syndrome (IBS). Additionally, there is a well-established association between comorbid autoimmune disorders and celiac disease, especially type 1 diabetes mellitus and autoimmune thyroid disease.
Although some evidence suggests a role of small-bowel bacterial overgrowth in the pathogenesis of IBS, evidence is insufficient to warrant testing for this condition with a breath test.
Approximately 2% of patients with features of diarrhea-predominant IBS are found to have microscopic colitis. A history of nocturnal or large-volume diarrhea or a stool osmotic gap less than 50 mOsm/kg (50 mmol/kg) would make a compelling case for microscopic colitis. In the absence of these features, a colonoscopy and random biopsies might be indicated, but the yield is low.
In patients who meet clinical criteria for IBS without alarm features, routine testing with stool culture is unlikely to result in an alternative diagnosis. Similarly, other laboratory tests such as the erythrocyte sedimentation rate and thyroid-stimulating hormone have a low yield. Patients who should be considered for colonoscopy and additional evaluation with blood and urine studies include those older than 50 years or those with a short history of symptoms, documented weight loss, nocturnal symptoms, family history of colon cancer or rectal bleeding, and recent antibiotic use.
Key Point
- The American College of Gastroenterology recommends routine serologic testing for celiac disease in patients with symptoms of diarrhea-predominant or mixed irritable bowel syndrome.
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