The role of chronic constipation, diarrhea, and laxative use in the etiology of large-bowel cancer. Data from the Melbourne Colorectal Cancer Study

Chronic Constipation as a Risk Factor for Colorectal Cancer: Results From a Nationwide, Case-Control Study

BACKGROUND & AIMS

Prolonged colon transit times may increase the contact time between potential carcinogens in the stool and the colonic mucosa. Nonetheless, previous studies have yielded conflicting results connecting chronic constipation with the risk of colorectal cancer (CRC). We examined the association between chronic constipation and later CRC.

METHODS

In this nationwide case-control study, we identified 41,299 CRC cases by colorectal biopsy in Sweden between July 2007 and December 2016 and matched them to 203,181 age- and sex-matched controls from the general population. We compared odds of earlier chronic constipation (defined as ≥2 laxative prescriptions in the Prescribed Drug Register with ≥6 months between the first and last prescription) between CRC cases and controls using logistic regression. In separate analyses, we compared odds of earlier constipation between CRC cases and sibling comparators, but also examined earlier risk of having an inpatient/outpatient specialty diagnosis of chronic constipation before CRC.

RESULTS

Overall, 3943 patients with CRC met our criteria for chronic constipation before CRC. The crude proportion of chronic constipation in CRC patients was 9.5% compared with 8.8% in controls. After multivariable adjustment, there was a modest association between chronic constipation and later CRC (odds ratio [OR], 1.10; 95% CI, 1.06-1.14) that vanished using sibling comparators to control for residual confounding (OR, 1.04; 95% CI, 0.97-1.13). In a sensitivity analysis of 126,650 CRC patients diagnosed from 1989 to 2016, we found no association with earlier chronic constipation diagnosed in inpatient/outpatient specialty clinics (OR, 0.88; 95% CI, 0.75-1.04).

CONCLUSIONS

In a nationwide case-control study, chronic constipation was not associated with later CRC.

Colorectal neoplasms in melanosis coli: a survey in Japan and a worldwide meta-analysis

PURPOSE

The association between melanosis coli (MC) and colorectal neoplasms remains unclear. Thus, we primarily aimed to clarify the epidemiology of MC in the Japanese population, identify the relationship between the use of anthranoids and MC, and determine the prevalence of detected intestinal lesions in patients with MC. We subsequently conducted a meta-analysis of published data, including our results, to summarize the influence of MC on the prevalence of colonic neoplasms.

METHODS

We conducted a retrospective survey in Japan to investigate the effects of MC on intestinal disorders. The prevalence of colorectal neoplasms and ileal ulcers was evaluated by colonoscopy, and the clinical characteristics of the participants were investigated using an electronic database. Odds ratios for colorectal neoplasms were calculated. We also performed a meta-analysis using Review Manager to reveal the comprehensive relationship between MC and colorectal neoplasms.

RESULTS

We enrolled 690 Japanese participants in the primary study. The prevalence of regular anthranoid use was significantly higher in the MC group than in the control group (50.9% vs. 6.5%, p < 0.01). Hyperplastic/inflammatory polyps and adenomas were more frequently detected in the MC group than in the control group. In a meta-analysis of five studies, a significantly higher prevalence of hyperplastic/inflammatory polyps and adenomas was reported in the MC group than in the control group, while the incidence of adenocarcinoma was not significantly different between the two groups.

CONCLUSION

Although hyperplastic polyps and adenomas were more frequently detected in MC patients, MC was not associated with an elevated risk of colorectal cancer.

Safety of hydroxyanthracene derivatives for use in food

The Panel on Food Additives and Nutrient Sources added to Food (ANS) was asked to deliver a scientific opinion on the safety of hydroxyanthracene derivatives and to provide advice on a daily intake that does not give rise to concerns about harmful effects to health. Hydroxyanthracene derivatives are a class of chemical substances naturally occurring in different botanical species and used in food to improve bowel function. The ANS Panel reviewed the available scientific data on a possible relationship between hydroxyanthracene derivatives exposure and genotoxic and carcinogenic effects. On the basis of the data currently available, the Panel noted that emodin, aloe-emodin and the structurally related substance danthron have shown evidence of in vitro genotoxicity. Aloe extracts have also been shown to be genotoxic in vitro possibly due to the presence of hydroxyanthracene derivatives in the extract. Furthermore, aloe-emodin was shown to be genotoxic in vivo and the whole-leaf aloe extract and the structural analogue danthron were shown to be carcinogenic. Epidemiological data suggested an increased risk for colorectal cancer associated with the general use of laxatives, several of which contain hydroxyanthracene derivatives. Considering the possible presence of aloe-emodin and emodin in extracts, the Panel concluded that hydroxyanthracene derivatives should be considered as genotoxic and carcinogenic unless there are specific data to the contrary, such as for rhein, and that there is a safety concern for extracts containing hydroxyanthracene derivatives although uncertainty persists. The Panel was unable to provide advice on a daily intake of hydroxyanthracene derivatives that does not give rise to concerns about harmful effects to health.

Melanosis coli in patients with colon cancer

INTRODUCTION

Melanosis coli is a benign lesion affecting the mucosa of the large intestine. There is a relationship between the presence of melanosis and anthraquinone laxative use. Melanosis coli is also observed in patients with colon cancer, but there is doubt whether these two conditions are related.

AIM

To analyze the correlation between melanosis and colon cancer.

MATERIAL AND METHODS

We analyzed retrospectively 436 patients undergoing colon cancer surgery. There were 246 women and 190 men. Patients were divided into three age groups: under 50 years, between 51 and 65 years, and over 66 years. We analyzed sections of the cancer and intestinal mucosa from the tumor's proximal (2-5 cm) and distal (8-10 cm) zone.

RESULTS

Melanosis coli was present in 52 patients, which represents 11.9% of patients with colon cancer. More often it was present in women. The most common location of melanosis and colon cancer was the terminal part of the large intestine. In patients below 50 years of age in both sexes melanosis coli did not occur. In men, melanosis was more common in the age group over 66 years. Intensity of pigmentation was higher in the tumor's distal zone.

CONCLUSIONS

The incidence of melanosis coli increases with age, similar to that of colon cancer. Melanosis was not present inside tumors, in almost half of the cases it was not present in the proximal zone, and the degree of pigmentation increased in distal zone. The cause-effect relationship between melanosis coli and colon cancer remains uncertain.

Editorial: Constipation and colorectal cancer risk: a continuing conundrum

There are conflicting data regarding the association between bowel movement frequency, constipation, and colorectal cancer (CRC). In this issue, Citronberg et al. present data from a large prospective study that was designed to examine this issue. In addition to examining bowel habits, these authors included information about the participants' laxative use, distinguishing between fiber and non-fiber-based laxatives. The investigators also collected data with respect to CRC risk factors including demographics, family history, lower endoscopy exposure, smoking, medication use, and detailed dietary information. The results demonstrated no relationship between bowel movement frequency or constipation and CRC. The authors also observed an increased CRC risk in patients who were in either the low or high non-fiber laxative use groups as compared with individuals who never used these agents (low risk: hazard ratio (HR)=1.49; and high risk: HR=1.43; Ptrend=0.05). Conversely, there was a statistically significant lower risk for those patients who reported a high use of fiber laxatives (HR=0.44, 95% confidence interval: 0.21-0.95) as compared with the nonuse group. These data have implications for physicians who treat patients with constipation.

Risk of developing colorectal cancer and benign colorectal neoplasm in patients with chronic constipation

BACKGROUND

Chronic constipation (CC) is a highly prevalent health problem, potentially associated with increased risk of colorectal cancer (CRCancer).

AIM

To investigate the association between CC, its severity, and CRCancer by estimating the relative risk of developing CRCancer and benign colorectal neoplasm (BCN) among severity-stratified patients with and without CC.

METHODS

Chronic constipation patients from a large retrospective US claims database were matched 1:3 with CC-free controls by demographic characteristics. CRCancer and BCN prevalence were measured over 1 year. In pre-index CRCancer- and BCN-free patients, incidence rate ratios (IRRs) of new CRCancer and BCN were calculated. Multivariate regression models adjusted for comorbidities and family history. CC patients' disease severity was rated based on CC-related resource use. IRRs for new CRCancer and BCN were estimated for CC severity groups and controls.

RESULTS

Chronic constipation (N = 28,854) and CC-free (N = 86,562) patients had mean age 61.9 years; 66.7% were female. One-year CRCancer prevalence was 2.7% and 1.7%, and BCN prevalence was 24.8% and 11.9% for CC and CC-free patients, respectively. Adjusted IRRs between CC and CC-free patients were 1.59 [95% confidence interval (CI): 1.43-1.78] and 2.60 [95% CI: 1.51-2.70] for CRCancer and BCN, respectively. Patients with severe and very severe CC had significantly greater incidence of CRCancer and BCN. At ≥ 2 and ≥ 5 years of observation, CRCancer and BCN incidence remained consistently and significantly higher for CC patients.

CONCLUSIONS

Patients with chronic constipation are associated with significantly higher prevalence and incidence of colorectal cancer and benign colorectal neoplasm than matched chronic constipation-free patients. These risks increase with the severity of chronic constipation.

Association between constipation and colorectal cancer: systematic review and meta-analysis of observational studies

OBJECTIVES

Constipation is common in the community, and may affect survival adversely. An association between constipation and development of colorectal cancer (CRC) could be one possible explanation. We performed a systematic review and meta-analysis examining this issue.

METHODS

We searched MEDLINE, EMBASE, and EMBASE Classic (through July 2012). Eligible studies were cross-sectional surveys, cohort studies, or case-control studies reporting the association between constipation and CRC. For cross-sectional surveys and cohort studies, we recorded number of subjects with CRC according to the constipation status, and for case-control studies, number of subjects with constipation according to CRC status were recorded. Study quality was assessed according to published criteria. Data were pooled using a random effects model, and the association between CRC and constipation was summarized using an odds ratio (OR) with a 95% confidence interval (CI).

RESULTS

The search strategy identified 2,282 citations, of which 28 were eligible. In eight cross-sectional surveys, presence of constipation as the primary indication for colonoscopy was associated with a lower prevalence of CRC (OR=0.56; 95% CI 0.36-0.89). There was a trend toward a reduction in odds of CRC in constipation in three cohort studies (OR=0.80; 95% CI 0.61-1.04). The prevalence of constipation in CRC was significantly higher than in controls without CRC in 17 case-control studies (OR=1.68; 95% CI 1.29-2.18), but with significant heterogeneity, and possible publication bias.

CONCLUSIONS

Prospective cross-sectional surveys and cohort studies demonstrate no increase in prevalence of CRC in patients or individuals with constipation. The significant association observed in case-control studies may relate to recall bias.

Diagnostic yield of colonoscopy for constipation as the sole indication

AIM

There is controversy over whether constipation as the only symptom should be an indication for routine diagnostic colonoscopy. The study was carried out to assess the prevalence of abnormal pathology on colonoscopy and to assess the risk factors for colonic neoplasia in patients with constipation but without 'high risk symptoms'.

METHOD

A cross-sectional, single-centre study was conducted on individuals who underwent colonoscopy for constipation as the sole indication between 2005 and 2008. Standardized endoscopic and pathology reports were reviewed. Univariable and multivariable analyses were performed.

RESULTS

A total of 786 patients (595 women, 75.7%; mean age, 57.4±13.5 years) underwent diagnostic colonoscopy for constipation. Forty-three (5.5%) had polyps, of whom 19 (2.4%) had hyperplastic polyps and 19 (2.4%) adenomas. No cancers were found. In patients with adenoma, the detection rate was 2.9% for patients below age 40 years and 1.7% for patients below age 50 years. Older age was associated with a polyp in both univariate and multivariate analysis. Gender, ethnicity and smoking were not associated with polyp or adenoma.

CONCLUSION

Colonoscopy for patients with constipation as the sole indication had a lower yield of neoplastic lesions than that for patients undergoing routine screening colonoscopy. Colonoscopy in constipation may only be warranted in patients who are over 50 years of age.

Most bowel cancer symptoms do not indicate colorectal cancer and polyps: a systematic review

BACKGROUND

Bowel symptoms are often considered an indication to perform colonoscopy to identify or rule out colorectal cancer or precancerous polyps. Investigation of bowel symptoms for this purpose is recommended by numerous clinical guidelines. However, the evidence for this practice is unclear. The objective of this study is to systematically review the evidence about the association between bowel symptoms and colorectal cancer or polyps.

METHODS

We searched the literature extensively up to December 2008, using MEDLINE and EMBASE and following references. For inclusion in the review, papers from cross sectional, case control and cohort studies had to provide a 2×2 table of symptoms by diagnosis (colorectal cancer or polyps) or sufficient data from which that table could be constructed. The search procedure, quality appraisal, and data extraction was done twice, with disagreements resolved with another reviewer. Summary ROC analysis was used to assess the diagnostic performance of symptoms to detect colorectal cancer and polyps.

RESULTS

Colorectal cancer was associated with rectal bleeding (AUC 0.66; LR+ 1.9; LR- 0.7) and weight loss (AUC 0.67, LR+ 2.5, LR- 0.9). Neither of these symptoms was associated with the presence of polyps. There was no significant association of colorectal cancer or polyps with change in bowel habit, constipation, diarrhoea or abdominal pain. Neither the clinical setting (primary or specialist care) nor study type was associated with accuracy.Most studies had methodological flaws. There was no consistency in the way symptoms were elicited or interpreted in the studies.

CONCLUSIONS

Current evidence suggests that the common practice of performing colonoscopies to identify cancers in people with bowel symptoms is warranted only for rectal bleeding and the general symptom of weight loss. Bodies preparing guidelines for clinicians and consumers to improve early detection of colorectal cancer need to take into account the limited value of symptoms.

Laxative abuse: epidemiology, diagnosis and management

Laxatives have been used for health purposes for over 2000 years, and for much of that time abuse or misuse of laxatives has occurred. Individuals who abuse laxatives can generally be categorized as falling into one of four groups. By far the largest group is made up of individuals suffering from an eating disorder such as anorexia or bulimia nervosa. The prevalence of laxative abuse has been reported to range from approximately 10% to 60% of individuals in this group. The second group consists of individuals who are generally middle aged or older who begin using laxatives when constipated but continue to overuse them. This pattern may be promulgated on certain beliefs that daily bowel movements are necessary for good health. The third group includes individuals engaged in certain types of athletic training, including sports with set weight limits. The fourth group contains surreptitious laxative abusers who use the drugs to cause factitious diarrhoea and may have a factitious disorder. Normal bowel function consists of the absorption of nutrients, electrolytes and water from the gut. Most nutrients are absorbed in the small intestine, while the large bowel absorbs primarily water. There are several types of laxatives available, including stimulant agents, saline and osmotic products, bulking agents and surfactants. The most frequently abused group of laxatives are of the stimulant class. This may be related to the quick action of stimulants, particularly in individuals with eating disorders as they may erroneously believe that they can avoid the absorption of calories via the resulting diarrhoea. Medical problems associated with laxative abuse include electrolyte and acid/base changes that can involve the renal and cardiovascular systems and may become life threatening. The renin-aldosterone system becomes activated due to the loss of fluid, which leads to oedema and acute weight gain when the laxative is discontinued. This can result in reinforcing further laxative abuse when a patient feels bloated and has gained weight. Treatment begins with a high level of suspicion, particularly when a patient presents with alternating diarrhoea and constipation as well as other gastrointestinal complaints. Checking serum electrolytes and the acid/base status can identify individuals who may need medical stabilization and confirm the severity of the abuse. The first step in treating laxative misuse once it is identified is to determine what may be promoting the behaviour, such as an eating disorder or use based on misinformation regarding what constitutes a healthy bowel habit. The first intervention would be to stop the stimulant laxatives and replace them with fibre/osmotic supplements utilized to establish normal bowel movements. Education and further treatment may be required to maintain a healthy bowel programme. In the case of an eating disorder, referral for psychiatric treatment is essential to lessen the reliance on laxatives as a method to alter weight and shape.

Impact of functional gastrointestinal disorders on survival in the community

OBJECTIVES

Functional gastrointestinal disorders (FGIDs) comprise a constellation of symptoms that have no identifiable structural or biochemical abnormality. In view of the lack of data from large-scale population-based studies evaluating the effects of these disorders on survival, we aimed to examine whether FGIDs are associated with impaired survival.

METHODS

Between 1988 and 1993, valid self-report questionnaires that recorded gastrointestinal symptoms required for the diagnosis of irritable bowel syndrome (IBS), chronic constipation, chronic diarrhea, dyspepsia, and abdominal pain were mailed to randomly selected cohorts of Olmsted County, Minnesota residents. Minnesota administrative death records were used to identify which of the survey respondents had died over the follow-up period (through April 2008). The association between survival and each FGID was assessed using proportional hazards regression models with univariate and adjusted hazard ratios (HRs, 95% confidence intervals (CIs)), adjusting for age at time of survey, gender, smoking, alcohol, marital status, and Charlson Comorbidity Index (CCI).

RESULTS

Of the 5,262 randomly selected eligible subjects who received a questionnaire, a total of 4,176 responded to the surveys (overall response rate 79%). From these respondents, 243 subjects were excluded because of lack of research authorization (or were registered solely at a different medical institution in Olmsted County, MN), resulting in 3,933 eligible subjects for analysis (eligible response rate 75%); 10% reported symptoms of IBS; 16% chronic constipation; 18% chronic diarrhea; 2% dyspepsia; and 15% abdominal pain. At baseline, the mean (s.d.) age was 54 (18) years, and 52% were female. No association with overall survival was detected for IBS (HR=1.06 (95% CI: 0.86-1.32)), chronic diarrhea (HR=1.03 (95% CI: 0.90-1.19)), abdominal pain (HR=1.09 (95% CI: 0.92-1.30)), or dyspepsia (HR=1.08 (95% CI: 0.58-2.02)). Reporting symptoms of chronic constipation was associated with poorer survival (HR=1.23 (95% CI: 1.07-1.42)). This association remained significant after adjusting for the CCI (HR=1.19 (95% CI: 1.03-1.37)).

CONCLUSIONS

In this large population-based cohort study with over 30,000 person-years of follow-up, no significant association was observed between survival and IBS, chronic diarrhea, dyspepsia, or abdominal pain. Furthermore, no association was found between increasing burden of FGIDs and survival. However, in contrast to these other FGIDs, subjects with symptoms of chronic constipation were found to be at increased risk of poorer survival. Further investigation is required to determine the cause of this observed association.

Constipation is not associated with an increased rate of findings on colonoscopy: results from a national endoscopy consortium

BACKGROUND AND STUDY AIMS

There are no definite guidelines regarding colonoscopic evaluation for the indication of constipation, a common gastrointestinal complaint. The aim of our study was to determine the risk of finding significant lesions in patients undergoing colonoscopy for the indication of constipation alone compared with constipation with another indication or average-risk screening.

PATIENTS AND METHODS

A retrospective review of the Clinical Outcomes Research Initiative database was carried out for colonoscopies undertaken between 1 January 2000 and 30 June 2003. A total of 41,775 index colonoscopies performed for the indications of average-risk screening, constipation only or constipation with another indication were identified. Logistic regression analyses were performed for constipation alone versus constipation with another indication, and for constipation alone versus average-risk screening.

RESULTS

Constipation alone did not show any increased risk of significant findings on colonoscopy. Constipation and the presence of another indication, however, had a statistically significant increased risk of a significant finding on colonoscopy. The indication of constipation alone had a lower risk of significant findings on colonoscopy compared with average-risk screening. Variations in the definition of constipation used was a limitation of the study.

CONCLUSIONS

Colonoscopy for constipation alone has a lower yield for significant findings compared with average-risk screening and constipation with another indication; hence, colonoscopy should not be done for constipation alone.

Upregulation of colonic ion channels in APC ( Min/+ ) mice

The adenomatous polyposis coli (APC) tumor suppressor gene is mutated in almost all human colonic cancers. Disturbances in Na(+) absorption have been observed in colonic cancer, and ion channels such as ether a go-go (Eag) or Ca(2+)-sensitive BK channels have been recognized for their oncogenic potential. APC ( Min/+ ) mice have reduced APC expression and develop multiple intestinal neoplasias (Min). Ion channels in the colonic epithelium were examined using electrophysiology and molecular techniques. APC ( Min/+ ) mice developed intestinal neoplasia and experienced a significant weight loss. Due to intestinal bleedings, the hematocrit was largely reduced and plasma aldosterone levels were enhanced. Rectal potential measurements in vivo indicated an increase in amiloride-sensitive Na(+) absorption in APC ( Min/+ ) mice. Quantitative Ussing chamber studies demonstrated enhanced Na(+) absorption via epithelial Na(+) channels (ENaC) and suggested enhanced activity of oncogenic BK and Eag-1 channels. Patch clamp and fluorescence measurements on isolated crypts suggested enhanced K(+) channel activity in the surface epithelium. ENaC-mRNA and membrane protein expression was enhanced in colonic surface epithelial cells. The data suggest that reduced expression of the APC gene with upregulation of the downstream proteins Akt and mTOR and subsequent hyperaldosteronism is paralleled by upregulation of oncogenic potassium channels and enhanced colonic Na(+) absorption.

Colorectal cancer protective effects and the dietary micronutrients folate, methionine, vitamins B6, B12, C, E, selenium, and lycopene

The data reported here were obtained from the case-control arm of a large, comprehensive, population-based investigation of colorectal cancer incidence, etiology, and survival, the Melbourne Colorectal Cancer Study, conducted in Melbourne, Australia. This part of the case-control study was designed to identify dietary factors associated with colorectal cancer risk in 715 incident cases compared with 727 age/sex frequency-matched randomly chosen community controls, in which a quantitative assessment of all foods eaten was made. New data are presented on the potential of two groups of micronutrients as protective agents, namely, those involved in DNA methylation, synthesis, and repair (folate, methionine, and vitamins B6 and B12) and those with antioxidant properties (selenium, vitamins E and C, and lycopene). The adjusted odds ratios showed that for folate there was significant protection for rectal cancer in second and third quintiles of consumption but not for colon cancer, and this was similar for methionine consumption. Vitamin B6 consumption was significantly protective for both colon and rectal cancer at the higher quintiles, and this was similar for vitamin B12. Dietary selenium was significantly protective at middle quintiles of consumption at both cancer sites. Dietary vitamins E and C were statistically significantly protective for both colon and rectal cancer at all levels of consumption, and for both vitamins there was a dose-response effect of increasing protection, particularly so for colon cancer. Lycopene was not associated with colorectal cancer risk. A combined model included vitamins E, C, and B12 and selenium as micronutrients protective for colorectal cancer and folate, which, however, showed an increased risk at the highest level of consumption. These data support the proposition that a diet containing the dietary micronutrients involved in DNA methylation (folate, methionine, and vitamins B6 and B12) and some of those with antioxidant properties (selenium and vitamins E and C) may have a role to play in lowering colorectal cancer risk and also that such protection can be achieved by dietary means alone.

Bowel Movement, State of Stool, and Subsequent Risk for Colorectal Cancer: The Japan Public Health Center–Based Prospective Study

PURPOSE

Evidence about whether irregular bowel movements or unusual stool conditions are associated with colorectal cancer is still inconsistent.

METHODS

We identified 479 newly diagnosed cases of colorectal cancer (303 men and 176 women) during a 7.9-year follow-up of a cohort consisting of 57,940 subjects (27,529 men and 30,411 women) aged 40 to 69 years at baseline. Bowel movements and stool conditions were asked through a self-administered questionnaire.

RESULTS

Neither high nor low frequency of bowel movements was associated with colorectal cancer incidence compared with one bowel movement per day. Multivariate hazard ratios (HRs) and 95% confidence intervals (CIs) for two bowel movements or more per day were 1.03 (95% CI, 0.76-1.41) in men and 1.16 (95% CI, 0.68-2.00) in women. HRs for two to three bowel movements per week were 0.97 (95% CI, 0.61-1.55) in men and 0.75 (95% CI, 0.49-1.13) in women. There was no clear association between an unusual stool state, such as diarrhea or hard stools, and colorectal cancer.

CONCLUSION

Our results suggest that neither bowel movement frequency nor any specific state of stool causes colorectal cancer.

Myths and misconceptions about chronic constipation

There are many strongly held beliefs about constipation that are not evidence based. The purpose of this review is to address these beliefs concerning various aspects of constipation. There is no evidence to support the theory that diseases may arise via "autointoxication," whereby poisonous substances from stools within the colon are absorbed. Dolichocolon, defined as an elongated colon, should not be seen as a cause of constipation. The role of sex hormones altering gut function during the menstrual cycle appears to be minimal. During pregnancy they may play a role in slowing gut transit. Hypothyroidism can cause constipation, but among patients presenting with constipation, hypothyroidism is rare. A diet poor in fiber should not be assumed to be the cause of chronic constipation. Some patients may be helped by a fiber-rich diet but many patients with more severe constipation get worse symptoms when increasing dietary fiber intake. There is no evidence that constipation can successfully be treated by increasing fluid intake unless there is evidence of dehydration. In the elderly constipation may correlate with decreased physical activity, but many cofactors are likely to play a role. Intervention programs to increase physical activity as part of a broad rehabilitation program may help. It is unlikely that stimulant laxatives at recommended doses are harmful to the colon. A proportion of patients with chronic constipation is dependent of laxatives to achieve satisfactory bowel function, but this is not the result of prior laxative intake. Tolerance to stimulant laxatives is uncommon. There is no indication for the occurrence of "rebound constipation" after stopping laxative intake. While laxatives may be misused, there is no potential for addiction.

Constipation, laxative use and risk of colorectal cancer: The Miyagi Cohort Study

The objective of this study was to investigate the association between constipation or laxative use and the risk of colorectal cancer in Japanese men and women. In 1990, we delivered a self-administered questionnaire to 41670 subjects who were 40-64 years old. During the seven years of follow-up, 251 incident cases of colorectal cancer were documented. Constipation was defined as a bowel movement frequency of less than daily. The multivariate relative risk (RR) of colorectal cancer for constipated subjects compared with those with daily bowel movements was 1.35 (95% Confidence Interval: 0.99-1.84). The RR for laxative users over non-users was 1.31 (0.88-1.95), and for frequent users (twice a week or more) it was 2.75 (1.48-5.09). When colorectal cancers were divided into colon cancers or rectal cancers, a significant association was found with colon cancer alone. Our results support the hypothesis that constipation or laxative use increases the risk of colon cancer.

Constipation, laxative use, and colon cancer in a North Carolina population

OBJECTIVE

The aim of this study was to determine whether bowel movement frequency and laxative use and type were associated with risk of colon cancer in white and black men and women.

METHODS

We conducted a population-based, case-control study with equal representation by blacks. Eligible subjects between ages 40 and 80 yr residing in urban and rural communities in North Carolina were asked about bowel habits and laxatives during face-to-face interviews. There were 643 cases (349 white, 294 black) and 1048 controls (611 white, 437 black).

RESULTS

Constipation, defined as fewer than three reported bowel movements per wk, was associated with a greater than two-fold risk of colon cancer (OR 2.36; 95% CI = 1.41-3.93) adjusted for age, race, sex, and relevant confounders. The association was greater for women (OR 2.69; 95% CI = 1.46-4.94) than for men (OR 1.73; 95% CI = 0.61-4.88) and stronger in blacks than whites. Black women had the highest risk (OR 3.42; 95% CI = 1.60-7.34), which remained significant (OR 3.21; 95% CI = 1.46-7.04) even after excluding subjects with late stage (distant) disease. The OR for constipation was slightly higher for distal than for proximal colon cancers. There was no association with laxative use (OR 0.88; 95% CI = 0.69-1.11). Fiber commercial laxatives appeared to exert a protective effect in a small subgroup.

CONCLUSIONS

This study provides support for a positive association between constipation and increased risk for colon cancer. Women, especially black women with constipation, seem to be at the highest risk.

A retrospective study of histopathological findings in 894 cases of megacolon: what is the relationship between megacolon and colonic cancer?

Patients with megaesophagus (ME) have increased prevalence of cancer of the esophagus. In contrast, a higher incidence of colorectal cancer is not observed in patients with megacolon (MC). MC is very common in some regions of Brazil, where it is mainly associated with Chagas disease. We reviewed the pathology records of surgical specimens of all patients submitted for surgical resection of MC in the Hospital das Clínicas of the Faculty of Medicine of Ribeirão Preto (HC-FMRP), from the University of São Paulo. We found that 894 patients were operated from 1952 until 2001 for MC resection. Mucosal ulcers, hyperplasia and chronic inflammation were frequently found, while polyps were uncommon. No patients with MC presented any type of colonic neoplasm. This observation reinforces the hypothesis that MC has a negative association with cancer of the colon. This seems to contradict the traditional concept of carcinogenesis in the colon, since patients with MC presents important chronic constipation that is thought to cause an increase in risk for colon cancer. MC is also associated with other risk factors for cancer of colon, such as hyperplasia, mucosal ulcers and chronic inflammation. In ME these factors lead to a remarkable increase in cancer risk. The study of mucosal cell proliferation in MC may provide new insights and useful information about the role of constipation in colonic carcinogenesis.

Physical exercise, use of Plantago ovata and aspirin, and reduced risk of colon cancer

To evaluate certain risk and protective factors for colon cancer in our population, we conducted a paired case-control study where cases were all people diagnosed with colon cancer who were registered at the Cancer Data Exchange Systems of the Community of Madrid between January 1995 and December 1996, and controls were randomly taken from electoral lists. The study population consisted of 424 persons. Using SPSS for Windows, variables were adjusted by multiple logistic regression. The results indicate that lack of physical exercise is associated with an increased risk of colon cancer, with an odds ratio (OR) of 2.8 (95% confidence interval (CI) 1.28-6.21) as compared with moderate activity 1-2 days a week. The risk decreases linearly with increasing physical exercise, and this association remains after stratifying the analysis for the existence of constipation. The consumption of is associated with a reduced risk of colon cancer in constipated patients, with an OR of 0.094 (0.014-0.639), as is aspirin use, with an OR of 0.980 (0.898-0.999). These results were obtained after adjusting all the ORs for diet, smoking, alcohol consumption, family history and socio-demographic factors such as marital status and educational level.

Review article: the therapy of constipation

Constipation is a common symptom that may be idiopathic or due to various identifiable disease processes. Laxatives are agents that add bulk to intestinal contents, that retain water within the bowel lumen by virtue of osmotic effects, or that stimulate intestinal secretion or motility, thereby increasing the frequency and ease of defecation. Drugs which improve constipation by stimulating gastrointestinal motility by direct actions on the enteric nervous system are under development. Other modalities used to treat constipation include biofeedback and surgery. Laxatives and lavage solutions are also used for colon preparation and evacuation of the bowels after toxic ingestions.

Review article: anthranoid laxatives and their potential carcinogenic effects

Anthranoid laxatives are widely used laxatives of natural origin. Because of their chemical structure they are carried unabsorbed to the large bowel, where metabolism to the active aglycones takes place. These aglycones exert their laxative effect by damaging epithelial cells, which leads directly and indirectly to changes in absorption, secretion and motility. Damaged epithelial cells can be found as apoptotic bodies in the pigmented colonic mucosa, characteristic for pseudomelanosis coli. Pseudomelanosis coli is a condition caused by chronic (ab)use of anthranoid laxatives and has recently been associated with an increased risk of colorectal carcinoma. In vitro and animal studies have shown a potential role of anthranoid laxatives in both the initiation and promotion of tumorigenesis. Studies in humans have also suggested tumour promoting activities for these laxatives. Although the short-term use of these substances is generally safe, long-term use cannot be recommended.

Clinical pharmacology and use of laxatives and lavage solutions

Laxatives and lavage solutions are used in the treatment of constipation and toxic ingestion and also for preparation of the colon before endoscopic or surgical procedures. Several different categories of agents are available for use. These include bulking agents, osmotic agents, secretagogues and agents with direct effects on epithelial nerve or smooth muscle cells, and lubricating agents. Each category has different pharmacologic effects, side effects, and clinical indications. This review summarizes current information about these agents.

Basis and consequences of primary and secondary prevention of gastrointestinal tumors

Carcinomas of the gastrointestinal tract (GI) are among the most common malignancies with regard to their incidence and mortality. Nutritional factors play an important role in the tumor development. The strength of their influence varies with the localization in the GI tract. Epidemiological studies focusing on GI cancer incidence or mortality as an endpoint necessitate large numbers of subjects to achieve significant results. Generally, a low energy and fat intake and a high intake of antioxidative vitamins (vitamin C, E, beta-carotene) and secondary plant metabolites (especially polyphenols) appear to be protective in GI carcinogenesis. Moderate drinking of alcohol and increased consumption of whole grain products, as opposed to highly refined carbohydrates, may help to reduce the risk of colon cancer. The recommended type of diet is low in fat, especially in saturated fatty acids, includes monounsaturated fatty acids, and includes moderate amounts of polyunsaturated fatty acids (no more than 10% of calories). Moderate consumption of salt and of highly salted, smoked, and barbecued foods should be encouraged. Obesity should be avoided by trying to match energy intake with expenditure while increasing physical activity levels. The mechanisms by which nutritional factors act especially on molecular events still remain to be examined. The use of molecular biomarkers will help us better understand cancer development as well as the role and significance of nutritional factors in this process.

Anthranoid laxative abuse--a risk for colorectal cancer?

Anthranoid-containing laxatives--aloe, cascara, frangula, and rheum--may play a role in colorectal cancer. This risk is particularly important in view of the wide abuse of self administered laxatives for chronic constipation. There are data on the genotoxic potential of anthranoids and there is evidence of a tumourigenic potential in rodents. A case report and clinical-epidemiological studies have evaluated the cancer risk in patients who have abused anthranoid laxatives over a long period. Pseudomelanosis coli is a reliable parameter of chronic laxative abuse (> 9-12 months) and is specific for anthranoid drugs. In a retrospective study of 3049 patients who underwent diagnostic colorectal endoscopy the incidence of pseudomelanosis coli was 3.13% in patients without pathological changes. In those with colorectal adenomas, the incidence increased to 8.64% (p < 0.01), and in those with colorectal carcinomas it was 3.29%. This lower rate was probably caused by incomplete documentation of pseudomelanosis coli in those with carcinoma. In a prospective study of 1095 patients, the incidence of pseudomelanosis coli was 6.9% for patients with no abnormality seen on endoscopy, 9.8% (p = 0.068) for patients with adenomas, and 18.6% for patients with colorectal carcinomas. From these data a relative risk of 3.04 (1.18, 4.90; 95% confidence interval) can be calculated for colorectal cancer as a result of anthranoid laxative abuse.

Alcohol consumption and the etiology of colorectal cancer: a review of the scientific evidence from 1957 to 1991

The relationship between alcohol consumption and colorectal cancer in humans has been examined in 52 major studies in the past 35 years. An association was found in five of the seven correlational studies. An elevated risk was found in about half of the 31 case-control studies and, of these, in 9 of the 10 studies using community controls but in only 5 of the 17 studies using hospital controls (p = 0.008), suggesting that the absence of association when hospital controls are used is due to a high prevalence of alcohol consumption/alcohol-related illness in the hospital controls. Of the 14 cohort studies, an association with alcohol was found in 10, while in 3 of the 4 cohort studies in which an association was not found the alcohol data obtained were somewhat restricted. A positive dose-response effect was found in two of three cohort studies and in all four case-control studies with community controls in which this effect was examined. In both case-control and cohort studies, the association was found for females and males and for colon and rectal cancer. When the type of alcohol consumed was examined separately, beer was the principal type of at-risk alcoholic beverage, with much less risk for spirits and least risk for wine. Statistically significant elevations of risk were more often found in males than in females and slightly more frequently for rectal than for colon cancer and were related almost entirely to beer, rather than to wine or spirit, consumption. The alcohol risk was independent of the dietary risk in those studies that controlled for this factor. There was some confirmatory evidence for alcohol augmentation in rodent models of chemically induced carcinogenesis in six of nine studies. The hypotheses of alcohol as a direct and specific colorectal carcinogen include increased mucosal cell proliferation, the activation of intestinal procarcinogens, and the role of unabsorbed carcinogens, particularly in beer. Also, five of six other human studies showed an association between alcohol/beer consumption and adenomatous polyps, consistent with the hypothesis that alcohol stimulates the colorectal mucosa. General or indirect carcinogenic effects of alcohol include immunodepression, activation of liver procarcinogens, and changes in bile composition, as well as nitrosamine content of alcoholic beverages and increased tissue nitrosamine levels. With alcohol/beer consumption, the overall conclusion on present evidence is that alcohol, particularly beer consumption, is an etiologic factor for colon and rectal cancer for females and males.(ABSTRACT TRUNCATED AT 400 WORDS)

Recent life change and large bowel cancer. Data from the Melbourne Colorectal Cancer Study

In a large, population based, epidemiological study of colorectal cancer, The Melbourne Colorectal Cancer Study, several etiological factors were investigated. Persons' recent life changes, as well as the degree of upset they experienced as a result of these changes, were included. Interviews with 715 histologically confirmed new cases of colorectal cancer occurring over a 12-month period in Melbourne, Australia, and with 727 age and sex matched community controls were conducted. As one of the methods of assessing any effect of recall bias, 179 hospital controls were also investigated. Major illness or death of a family member, major family problems and major work problems were found to be significantly more common for cases over the 5 years preceding diagnosis compared to controls. Cases also reported being significantly more upset with their recent life changes than did controls. No significant differences in results were found between males and females, or between colon cancer and rectal cancer patients. Although the possibility of recall bias, was not completely controlled for in this study, it was probably not an important factor in explaining case-control differences. Recent life changes, and their perceptions, may have significance in the development of large bowel cancer.

Survival in patients with large-bowel cancer. A population-based investigation from the Melbourne Colorectal Cancer Study

Five-year survival data were obtained in 97 percent or 1105 of 1140 new patients with histologically confirmed colorectal adenocarcinoma during a 12-month period in 1981 and 1982, as part of a large comprehensive population-based study of colorectal cancer incidence, etiology, and survival, The Melbourne Colorectal Cancer Study. Fifteen percent of patients were Dukes' A stage, 32 percent were Dukes' B, 25 percent were Dukes' C, and 29 percent were Dukes' D. At five years after diagnosis, the observed survival rate was 36 percent and the adjusted rate was 42 percent. Dukes' staging was a highly discriminating factor in survival (P less than 0.001). Survival rates were better in women than in men and better for patients with colon cancer than for patients with rectal cancer. Survival by Dukes' staging was not affected by colon subsite or by the tumor being the first and single tumor, metachronous tumor, or synchronous tumor. The survival of younger patients was better for Dukes' stages A, B, and C, and worse for Dukes' D. Survival was worse in the presence of bowel perforation in Dukes' C and D stages. Within Dukes' D (incurable cases), survival was best in the absence of hepatic metastases, slightly worse when only hepatic metastases were present, and poorest in the presence of both hepatic and extrahepatic metastases. Statistical modeling of survival determinants other than staging indicated that cell differentiation had the largest effect (survival decreasing with poor cell differentiation), followed by site (survival worse for rectal cancer than colon cancer), then age (survival better for younger patients), while bowel perforation had the smallest effect on survival.