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    Colon Cancer Screening

    Colon Cancer Screening
    Emmanuelm at English Wikipedia [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

    Many of you, as primary care providers, might know the difficulties that come along with colon cancer screening. Oftentimes, patients are fearful, and there might be flat-out refusal to proceed with screening.

    Today, we will discuss the options available for colon cancer screening, when to screen, follow up intervals for repeat procedures, and specific conditions which require different screening schedules.

    The current recommendation, given by the USPSTF, is that screening should begin at age 50 years and continue until age 75 years; this carries a Grade A recommendation. The screening method which the patient chooses will dictate the frequency of screening. Comorbid diagnoses may also change the frequency of testing.

    colon cancer screening
    source: http://www.aafp.org/news/health-of-the-public/20140528colorectscreen.html

    Patient Objections to Colon Cancer Screening

    Many of my patients are very hesitant to have a colonoscopy performed. Many times, this is because friends complain how bad the prep is, the patient might not want to miss work, and/or because they fear the adverse complications which they’ve heard about.

    When speaking to my patients, I explain the colonoscopy is a safe and simple procedure that could potentially save their life. Delaying a colonoscopy, could lead to underlying indolent polyp growth, that could transition into cancer.

    Usually, their response is, “well if I had that going on, I would have belly pain or blood in my stool.”

    However, most often this is not the case. Patients could potentially have a slow growing and evolving polyp, and over time, that benign polyp can slowly transition into cancer, long before symptoms present.

    By starting the screening process at age 50, these noncancerous polyps can be found, and removed.

    Unfortunately, some of my patients continue to decline to have the screening colonoscopy performed. In these instances, I recommend other types of colon cancer screening tests, including the guaiac-based fecal occult blood test, FIT, FIT-DNA, CT colonography, flexible sigmoidoscopy, or flexible sigmoidoscopy with FIT testing.

    Of course, if the patient is unwilling to do a colonoscopy, they often will be reluctant to do a flexible sigmoidoscopy as well.

    The American Journal of Gastroenterology, as of June 2017, listed that capsule colonoscopy can be done every five years for screening as well.

    It is essential to let your patient know, that if they choose an option other than a colonoscopy, and there is a positive test result found, this would necessitate a colonoscopy to be completed urgently.

    colon cancer screening intervals
    source: http://annals.org/data/Journals/AIM/22170/10TT2.png

    High Risk For Colon Cancer

    More often than not, colon cancer screening should be recommended to begin at 50 years of age. However, there are some instances where testing is recommended earlier. These reasons include:

    1) The patient has any first degree relative diagnosed with colorectal cancer before age 60.

    2) The patient has two or more first-degree relatives with CRC at any age.

    3) The patient has a known diagnosis of familial adenomatous polyposis (FAP) or it is suspected.

    4) The patient has been diagnosed with Lynch syndrome or is at an increased risk based on family history.

    5) The patient has been diagnosed with inflammatory bowel disease, such as ulcerative colitis, or Crohn’s disease.

    Now, for the second most common question that patients ask me, “when will I have to do this again?”

    This depends on the findings from the screening colonoscopy. If the patient doesn’t have polyps, or has normal biopsy results, the follow-up interval for repeat colonoscopy is 10 years.

    Findings on Colonoscopy

    If the patient has a <10 mm in size hyperplastic polyp in the rectum or sigmoid colon, then the follow-up interval is 10 years.

    If there are one or two <10 mm tubular adenomas found on the colonoscopy, then the follow-up interval for repeat colonoscopy is 5 to 10 years.

    If there is a sessile serrated polyp <10 mm in size, without dysplasia, then the follow-up interval for colonoscopy is 5 years.

    If the patient is found to have 3 to 10 tubular adenomas, a tubular adenoma or serrated polyp that is greater than or equal to 10 mm in size, an adenoma with villous features or high-grade dysplasia, a sessile serrated polyp with cytological dysplasia, or a traditional serrated adenoma the recommended follow-up interval repeat colonoscopy is 3 years. (Am Fam Physician. 2015 Jan 15;91(2):93-100.).

    If more than 10 adenomas are found on initial colonoscopy, repeat procedure should be done within 3 years.

    If the patient was found to have serrated polyposis syndrome, then the follow-up interval for repeat colonoscopy is 1 year. The criteria for serrated polyposis syndrome is as follows:

    1) At least 5 serrated polyps proximal to the sigmoid colon with 2 or more that are >10 mm in size,

    2) Any serrated polyp proximal to the sigmoid colon with a family history of serrated polyposis syndrome

    3) Twenty or more serrated polyps of any size throughout the colon.

    (Huber AR, et al. (2013) Hereditary Gastrointestinal Polyposis Syndromes: A Review Including Newly Identified Syndromes).

    colon cancer polyp
    By Bernstein0275 (Own work) [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
    If, during the initial colonoscopy, the patient has a piecemeal removal of a large (>15 mm) sessile adenoma or serrated polyp, a repeat colonoscopy should be considered in less than 1 year if there was any question of a residual polyp.

    Lastly, following curative resection of colon cancer, repeat colonoscopy should be performed 1 year after the resection, then in 3 and 5 years if normal. (Am Fam Physician. 2015 Jan 15;91(2):93-100.).

    Colon Cancer Screening Complications

    A significant cause as to why my patients are typically opposed to getting a colonoscopy, is due to the proverbial “horror stories” regarding complications that they have heard about.

    Three large studies have looked at complications and the frequency that they have occurred. In one study, which reviewed 57,742 screening colonoscopies, serious harm occurred in 2.8 per 1,000 examinations. Over 85% of the complications that happened in the study were in the setting of polypectomies.

    In a second study which looked at 2.3 million colonoscopies performed between 1997 and 2004, the overall rate of complication was 1.98 per 1,000 examinations.

    A third study gathered data from 21 previous studies which resulted in nearly 2,000,000 colonoscopies from 2001 to 2012. This study found a rate of 0.5 per 1,000 colonoscopies that led to perforation and postoperative bleeding in 2.6 per 1,000 cases. The overall mortality rate related to colonoscopy complications was found to be 0.007%.

    Regarding the type of complications that can occur during a colonoscopy, cardiopulmonary complications are the most frequent, which are related to sedation and anesthesia. This is aimed to be avoided by appropriate management of high-risk patients, monitoring before, during, and after procedures, and by delaying if a patient is unstable.

    Electrolyte disturbances, nausea, vomiting, abdominal pain, aspiration, and esophageal tears have all been documented as complications related to the bowel preparation needed for appropriate colonoscopy.

    Postpolypectomy bleeding has been documented as a complication which has been reported to occur around 1-2% of the time, with higher rates seen after removal of larger sized polyps. This complication is increased in patients with known thrombocytopenia, coagulopathies, or on antiplatelet medications.

    The bleeding that occurs after the polyp is removed may be immediate or delayed. Immediate bleeding typically occurs if the polyp is removed without the use of cautery, such as if the polyp is blended. If this is the case, it is often recognized before the colonoscopy is completed, and is treated immediately using hemostatic methods endoscopically.

    Delayed bleeding typically is seen around 5-7 days after the procedure, but it has been documented as being late as 29 days postoperatively. Delayed bleeding is believed to be due to the sloughing of eschar that was covering a blood vessel, or due to the area of hemostatic tissue damage extending into non-injured tissue, which could result in bleeding if it involves vasculature.

    Perforations Following Colonoscopy

    Colonic perforations typically occur by three potential mechanisms including mechanical trauma caused by the pressure of the colonoscope on the wall of the colon, barotrauma, or electrocautery during a polypectomy.

    During screening colonoscopies, the risk of perforation has been found to be 0.01% to 0.1%. This risk can increase if there are other colonic comorbidities such as Crohn’s disease, ulcerative colitis, FAP, or stent placement.

    Mortality rates from iatrogenic colonic perforations have been shown to be between 0% to 0.65%. Risk factors for perforation include age, multiple chronic comorbidities, diverticulosis, obstruction, and resection of polyps over 1 cm in size that are in the right colon.

    Reduced colon mobility due to adhesions, radiation therapy, malignancy, infection, or IBD are also risk factors. Providers with low procedure volume additionally have increased rates of perforations.

    If a perforation is expected, the patient should have immediate abdominal radiographs (plain and upright or left lateral decubitus) and an upright chest radiograph, to look for free air underneath the diaphragm, retroperitoneal air, pneumomediastinum, pneumothorax, or subcutaneous emphysema. If radiographs are negative, but suspicion is still high, abdominal and pelvis CT with water-soluble contrast can be completed.

    Additional management includes assuring that the patient is NPO, has been started on IV fluids, IV broad-spectrum antibiotics, and surgical consultation made.

    Surgical treatment is indicated in patients with diffuse peritonitis, those who continue to decline with conservative non-surgical management, and patients with a colonic lesion that require surgery (colon cancer).

    Any time during a surgical procedure that you are introducing abnormal equipment into the body’s environment there is a risk of infection. With colonoscopies, the rate of infection is very low. Although, there have been a few cases recorded of hepatitis B, hepatitis C, and bacterial transmission related to defective/improperly sterilized equipment or breaches in the sterile field.

    An extremely infrequent complication is a gas explosion. This occurs from the ignition of hydrogen or methane gas in the colon during use of electrocautery. The associated hydrogen or methane gas results from an incomplete bowel preparation.

    Colonoscopy False Negative Rates 

    Even though a patient undergoes a screening colonoscopy, there is a potential risk that a polyp might be missed. The overall miss rate of adenomas was found to be around 22% in a systematic review of 6 studies with 465 patients.

    The rate of missed polyps was found to be related to the size of the polyp. Those sized 1-5 mm had a 26% miss rate. Polyps 5-10 mm in size a 13% miss rate, and those >10 mm a 2% miss rate.

    The Takeaway Regarding Colon Cancer Screening

    Overall, there are risks and benefits to everything we do in medicine, whether that be starting a patient on lisinopril for hypertension, ordering a CT scan of the brain, or having a screening colonoscopy completed. What both providers and patients must do is weigh the risks and benefits of what we ask our patients to do.

    I never force a medication, screening test, or diagnostic testing on my patients.

    I can lecture and rant about the importance of colonoscopies to my patients, but if they don’t want to do it, they aren’t going to.

    Remember, you can lead a horse to water, but you can’t force them to drink. It is our job to present this information to our patient’s so they can make an informed decision for their health.


    • American Cancer Society. https://www.cancer.org/cancer/colon-rectal-cancer/detectiondiagnosis-staging/acs-recommendations.html. Accessed on 12/21/17.
    • USPSTF.https://www.uspreventiveservicestaskforce.org/Page/Document/ RecommendationStatementFinal/colorectal-cancer-screening2. Accessed on 10/21/17.
    • UpToDate. Overview of Colon Polyps. Accessed 10/21/17.
    • UpToDate. Overview of Colonoscopy in Adults. Accessed 10/21/17.
    • AAFP. Colorectal Cancer Screening and Surveillance. Accessed 10/21/17.
    • AAFP: Colorectal Cancer: A Summary of the Evidence for Screening and Prevention. Accessed 10/21/17.
    • American College of Gastroenterology. https://gi.org/guideline/guidelines-forcolonoscopy-surveillance-after-screening-and-polypectomy-a-consensus-update-by-theus-multi-society-task-force-on-colorectal-cancer/. Accessed 10/21/17.
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    Clay Walker
    Clay Walker is a board-certified physician assistant practicing in family medicine and urgent care in rural southern Illinois. He is a graduate of Southern Illinois University School of Medicine Physician Assistant Program - class of 2016. Prior to going to PA school, Clay worked as a histology technician in southern Illinois.  From an early age, he has been interested in medicine. Clay was diagnosed as a type 1 diabetic in the first grade. He began learning about his condition and teaching others about T1DM; since then, he began to have a passion to learn medicine and make a difference in the lives of others. In his free time, Clay enjoys watching sports and going to sporting events, specifically the Chicago Cubs and Philadelphia Eagles.