Diagnosing irritable bowel

JAMA. 2009 PMID: 18854541

This comprehensive systematic review by the Rational Clinical Examination is very helpful after a few adjustments. First, the review allows source studies to place patients with symptoms of irritable bowel who are found to have diverticulosis or polyps into the category of underlying organic illness. Patients with diverticulosis who have symptoms of irritable bowel probably have irritable bowel syndrome.(PMID: 3717113) Likewise, polyps seem very unlikely to cause symptoms of irritable bowel and these patients also probably irritable bowel syndrome and coincidental polyps. Now that the USPSTF recommends screening for polyps starting at age 50, the presence of polyps among patients with irritable bowel syndrome is less important.(PMID: 18838716)

The review cites the study of Bellentani(PMID: 2289644) to conclude that 60% of patients in primary care with symptoms of irritable bowel have irritable bowel syndrome. However, if you group the patients with polyps or diverticulosis with the patients with irritable bowel, the prevalence becomes 87%.

Diagnosing irritable bowel syndrome

	Likelihood ratio +	Likelihood ratio -
History alone (Manning criteria)	2.9	0.29
History and physical examination (Rome criteria)	4.8	0.34
History, physical examination, and laboratory tests (Kruis score)	8.6	0.26

Thus, the Kruis score seems good enough to diagnose irritable bowel among patients in primary care (remember that patients over age 50 probably need endoscopy to screen for polyps). The composition of the Kruis score is:

Kruis score. Abnormal is < 44

Finding	Score
Abdominal pain or flatulence or bowel irregularity	34
Duration of symptoms >2 y	16
Abdominal pain is "burning, cutting, very strong, terrible, feeling of pressure, dull, boring, not so bad"	23
Alternating constipation and diarrhea	14
History of blood in stool	-98
Physical examination or history pathognomonic for an alternative diagnosis	-47
ESR > 10 mm/hr	-13
WBC > 10k	-50
Hemoglobin < 12 g/dL for females or < 14 g/dL for males	-98

This has been added to http://en.citizendium.org/wiki/Irritable_bowel_syndrome

Ford, A., Talley, N., Veldhuyzen van Zanten, S., Vakil, N., Simel, D., & Moayyedi, P. (2008). Will the History and Physical Examination Help Establish That Irritable Bowel Syndrome Is Causing This Patient's Lower Gastrointestinal Tract Symptoms? JAMA: The Journal of the American Medical Association, 300 (15), 1793-1805 DOI: 10.1001/jama.300.15.1793