"Low caliber stool" and "pencil thin stool" are not signs of colo-rectal cancer

Dig Dis Sci. 2009 Feb;54(2):208-11. doi: 10.1007/s10620-008-0356-1. Epub 2008 Aug 6.


Over the past several years, primary care providers have been referring a large number of their patients to gastroenterologists for colonoscopy because of "low caliber stool" or "pencil thin stool." Most textbooks of internal medicine and gastroenterology consider "small caliber stool" as one of the presenting signs of colorectal cancer (CRC). A review of the literature reveals that this rather lay misconception-i.e. presence of tumor results in narrowing of the colon, which in turn decreases the caliber of the stool-was conceived late in the nineteenth century. In the absence of reliable data to support this concept, the authors of gastroenterology textbooks in the mid-twentieth century practically dismissed the concept. Nevertheless, this misconception somehow permeated the standard textbooks of medicine and even the newer editions of text-books of gastroenterology. Our own everyday experience shows that low caliber stool is noticed whenever we have loose stool. Since diarrheal states are much more common than CRC, in the absence of authentic symptomatology of CRC, such as rectal bleeding, change in the bowel habit, tenesmus, left-sided abdominal cramps, anemia, etc., the referral of these patients for colonoscopy based solely on "decreased stool caliber" is unwarranted. Such unwarranted referrals expose the patients to unnecessary risks and discomforts and put a strain on an already over-stretched healthcare resources.

Publication types

  • Review

MeSH terms

  • Colorectal Neoplasms / diagnosis*
  • Feces*
  • Humans