Colonoscopy: Extremely Beneficial—Extremely Avoided

Dr. Zanni is a psychologist and health-systemsspecialist based inAlexandria, Virginia.

Colorectal cancer (CRC) is thesecond leading cause of cancerdeaths in the United States,resulting in an estimated 57,000 deathsannually.^1,2 Although CRC is among themost preventable cancers, <43% ofAmericans aged 50 years and olderadhere to the recommended screeningguidelines.³ The 5-year survival rate is90% with early detection of this slow-growingcancer; however, 61% of CRCcases are identified after it has metastasized.⁴

Screening Guidelines

Colonoscopy is the preferred CRC-screeningprocedure. Research demonstratesits improved accuracy in detectingadenomas (precancerous polyps),compared with other procedures. Forexample, fecal occult blood testing aloneis insufficient; patients with adenomasoften test negative.⁵

The American College of Gastroenterology(ACG) issued CRC-screeningguidelines (Table) in 2000 that varyaccording to the following risk categories⁵:

• Average risk&#8212;patients aged 50 andolder, lacking other risk factors
• Moderate risk&#8212;patients with a singlefirst-degree relative who wasdiagnosed with CRC at age 60 orolder, or patients with first-degreerelatives with adenomas diagnosedbefore age 60
• High risk&#8212;patients with multiplefirst-degree relatives with CRC or asingle first-degree relative with CRCwho was diagnosed before age 60; orpatients with families with the raresyndromes of familial adenomatouspolyposis and hereditary nonpolyposisCRC or with a history of polyps,Crohn's disease, or ulcerative colitis⁶

The ACG recommends physiciansmodify guidelines consistent with thestrength of known risk factors and medicalhistories.

Table

Understanding Nonadherence

Surveys reveal that patients find thepreparatory regimen the most objectionableaspect of colonoscopy.⁷ Somepatients fail to complete the preparationprocess because of adverse effectsexperienced with the prescribed purgatives.⁶ Colonoscopy's invasiveness isanother factor fueling nonadherence; 1survey found most patients wouldreadily accept noninvasive procedures(eg, computed tomography scans) butare less agreeable to invasive procedures.⁸ Finally, some patients refusescreening because of negative reportsreceived from their families and friends.

Bowel Preparation

Bowel preparation formulations areeither glycol-electrolyte lavage solutionformulations (eg, Golytely, Colyte, TriLyte,HalfLytely with bisacodyl tablets, Movi-Prep) or sodium phosphate preparations,available in tablet and liquid formulations(eg, Fleet Phospho-soda, Fleet Accuprep,Visicol tablets, Osmoprep tablets).Dosages vary among products; patientsmust follow directions precisely.

Common side effects for both formulationcategories include nausea, vomiting,abdominal cramping, and bloating. Somestudies report fewer side effects withsodium phosphate tablets.⁶ Rare sideeffects include bleeding in the mucousmembrane that connects the esophagusto the stomach, esophageal perforation,toxic colitis, medication malabsorption,pulmonary aspiration, hypothermia, cardiacarrhythmias, pancreatitis, inappropriateantidiuretic hormone secretion,and renal failure. Some extremely rareadverse reactions resulted in patientfatalities.⁶

Proper hydration is required before,during, and after colonoscopy to avoidelectrolyte imbalances. Although dehydrationis a significant component underlyingsome of the most serious adverseeffects, clinicians often forget to counselpatients about volume repletion. It mayseem counterintuitive that dehydrationcan occur when consuming 4 L of fluid;however, large amounts of fluids arerequired to evacuate the colon. Thesefluids, along with fluids in undigestedfood, are eliminated.

Prevention

The ACG notes that decreasing dietaryanimal fat, increasing vegetables anddietary fiber, and increasing calcium andfolic acid may help prevent colon cancer,but further study continues.² A recentreview of >7000 studies concludes thatheavy consumption of red meat, especiallyprocessed meat (eg, sausage, ham,salami) increases CRC risk, as do poordiets, physical inactivity, and obesity. Thesame review recommends consuming<18 oz of red meat per week.¹⁰

Conclusion

Researchers are refining diagnosticalternatives, and the virtual colonoscopyholds promise for the future. Until then,health professionals must promote theimportance of colonoscopy. Somepatients find the topic difficult andembarrassing to discuss and feel morecomfortable with written information.The National Institute of Diabetes andDigestive and Kidney Diseases publishesan excellent, easy-to-understandbrochure on colonoscopy that can befound at digestive.niddk.nih.gov/ddiseases/pubs/colonoscopy. Many patientstake complimentary copies placedon the counter; therefore, this method isrecommended.

References

• Jemal A, Siegel R, Ward E, et al. Cancer statistics, 2007. CA Cancer J Clin. 2007;57:43-66.
• American College of Gastroenterology. Colon cancer screening and prevention. www.acg.gi.org/patients/women/colon.asp. Accessed November 27, 2007.
• Seeff LC, Nadel MR, Klabunde CN, et al. Patterns and predictors of colorectal cancer test use in the adult U.S. population. Cancer. 2004;100:2093-2103.
• Ries LAG, Harkins D, Krapcho M, et al (eds). SEER Cancer Statistics Review, 1975-2003, National Cancer Institute. Bethesda, MD, seer.cancer.gov/csr/1975_2003, based on November 2005 SEER data submission, posted to the SEER web site, 2006. Accessed November 27, 2007.
• Rex DK, Johnson DA, Lieberman DA, Burt RW, Sonnenberg A. Colorectal cancer prevention 2000: screening recommendations of the American College of Gastroenterology. American College of Gastroenterology. Am J Gastroenterol. 2000;95:868-877.
• Lichtenstein GR, Cohen LB, Uribarri J. Review article: Bowel preparation for colonoscopy--the importance of adequate hydration. Aliment Pharmacol Ther. 2007;26:633-641.
• Harewood GC, Wiersema MJ, Melton LJ 3rd. A prospective, controlled assessment of factors influencing acceptance of screening colonoscopy. Am J Gastroenterol. 2002;97:3186-3194.
• Marshall DA, Johnson FR, Phillips KA, et al. Measuring patient preferences for colorectal cancer screening using a choice-format survey. Value Health. 2007;10:415-430.
• U.S. Food and Drug Administration. FDA alert - oral sodium phosphate (OSP) products for bowel cleansing. www.fda/gov/cder/drug/infopage/OSP_solution/default.htm. Accessed November 30, 2007.
• World Cancer Research Fund, American Cancer Institute. Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective. www.aicr.org/site/PageServer?pagename=res_report_second. Accessed November 29, 2007.