Gut. 2007 March; 56(3): 451–452.
Patients with functional constipation do not have increased prevalence of colorectal cancer precursors
Annie On On Chan, Wai Mo Hui, Gigi Leung, Teresa Tong, Ivan F N Hung, Pierre Chan, Axel Hsu, David
But, Benjamin C Y Wong, Shiu Kum Lam, and Kwok Fai Lam
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It has always been a controversial subject whether patients with functional constipation have a higher risk of developing colorectal cancer. Watanabe et al1 showed an increase in
relative risk (RR) 1.31 of colorectal cancer in those with constipation.1 Roberts et al2 showed
an association with >twofold risk of colon cancer (OR 2.36) adjusted for age, race, sex and relevant confounders.2 On the other hand, both studies by Dukas et al3 and Kune et
al,4 after adjusting for age, sex and other risk factors showed no increase in risk. Colorectal cancer develops through the adenoma–carcinoma sequence.5 Thus, we aimed to
compare the prevalence of colorectal adenomas in patients with long‐standing functional
constipation to an age, sex and risk factors‐matched control group in a prospective study.
The result indirectly gives insight into the risk of development of colorectal cancer in patients with chronic constipation.
Patients with long‐standing constipation, satisfying the Rome II criteria6 were recruited
from the Constipation Clinic of Queen Mary's Hospital, Hong Kong. Exclusion criteria include constipation predominantly from irritable bowel syndrome, secondary causes for constipation, those who had a colonoscopy done in the past 10 years, or those under active
medical care for gastrointestinal complaints. Healthy controls were recruited from the general population who had no symptoms of constipation and did not satisfy the Rome II criteria. In addition, they were matched for age, sex, smoking history, diabetes and family history of colorectal cancer, with those in the constipated group. Subjects aged 50 years in
both groups were invited for assessment by colonoscopy. Colonoscopy was repeated the next day for those with poor bowel preparation. The withdrawal time of the colonoscopy procedure was >6 min to minimise the chance of lesions being missed.7 Incomplete
examination was excluded for analysis. Advanced colonic lesion was defined as the presence of cancer, or adenomas with villous component, or with high dysplasia, or 1 cm. The
calculated sample size was 200 people in each group, assuming the polyp prevalence in Hong Kong was 24%,8 with an OR of 2.362 for developing colorectal cancer or adenoma.
In all, 220 consecutive patients with constipation and 235 controls were invited for screening colonoscopy. The colonoscopy procedure failed in six patients due to presence of multiple sharp bends, whereas 20 controls defaulted or refused the screening colonoscopy. Twelve patients and one control had unsatisfactory bowel preparation requiring colonoscopy to be repeated.
The demographic data in both groups were comparable as they were purposely matched (table 11).). There was no difference in terms of endoscopic polyps, adenomas, hyperplastic polyp, advanced colonic lesion or colorectal cancer (table 11).
Table 1 Demographic data and prevalence of colonic lesions of the constipated and control groups
It has been a laymans' concept that constipated patients may have higher risk of developing colorectal cancer owing to the accumulation of “toxic substances”. However, this has never been proved. The studies reporting a possible link between constipation and the development of colorectal cancer, however, were mostly questionnaire based results and
,were retrospective.12 Our study confirms the results of the prospective study by Dukas et
al.3 Moreover, Nascimbeni et al9 have assessed the frequency of aberrant crypt foci in patients with sigmoid colorectal cancer and those with diverticular disease, and found that mean aberrant crypt foci did not often vary according to constipation, laxative use or melanosis coli in either group.
We have extrapolated our results and concluded that there is no increased risk in constipated patients of developing colorectal cancer, when compared with age, sex and other risk factors‐matched controls in the general population. The results can be extrapolated because most colorectal cancer develops through the adenoma–carcinoma
Competing interests: None.
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