Patient Safety Tip of the Week

March 1, 2016    Colonoscopy Complications



Several years ago we were trying to help a hospital find benchmarks for colonoscopy complications. We were amazed that such benchmarks were not readily available. We discussed complications of colonoscopy in our November 15, 2011 Patient Safety Tip of the Week “Rethinking Colonoscopy” and noted that the few studies done did not separate out screening colonoscopies from diagnostic or therapeutic ones. Rates also depend on whether polypectomy was done, and also relate to the age of the population and associated comorbidities (Warren 2009).  All these factors make it extremely difficult to compare rates of colonoscopy complications across facilities. Some of the same factors likely explain why rates at free standing ambulatory sites tend to be lower than at hospital-based endoscopy units.


Researchers at the Yale-New Haven Center for Outcomes Research and Evaluation (CORE) also were recently struck by the paucity of readily available data on colonoscopy complications so they delved into the Medicare database to examine such (Ranasinghe 2016). Their primary outcome variable was any unplanned hospital visit within 7 days following the colonoscopy. Outpatient colonoscopies were followed by unplanned hospital visits within 7 days at an overall rate of 16.3/1000 colonoscopies, or a rate of about 1.6%. Hemorrhage, abdominal pain, and perforation were the most common causes of unplanned hospital visits.


They also note that very often the physicians performing the colonoscopies are unaware that any unplanned hospital visit occurred within 7 days after the procedure since they were often not informed of such by the hospital or patient.


The researchers then calculated a risk-adjusted measure of outpatient colonoscopy quality, which shows important variation in quality among outpatient facilities and might be used for both public reporting and quality improvement purposes.


The study did not break down the data by whether the colonoscopies included manipulation of any polyps, which we previously noted increases the risk of complications. We, thus, express concern that use of a measure that fails to take that into account might complicate interpretation of reports, whether used for public reporting or quality improvement purposes. We don’t want to hear the old chorus from our physicians “our patients are sicker” or “our population is different”.


Also the relationship of several of the reasons for unplanned hospital visits (eg. atrial fibrillation, chest pain, UTI, pneumonia) is unclear. Also, we wonder what the rate of unplanned hospital visit would be after almost any procedure. For example, in this population you might find such visits within 7 days of almost any procedure (eg. a dental procedure) or even within 7 days of a randomly chosen date! So it might be interesting to subtract such a “background” rate of unplanned hospital visits from the rate following colonoscopy.


In our November 15, 2011 Patient Safety Tip of the Week “Rethinking Colonoscopy” we cited statistics from the American Society of Gastrointestinal Endoscopy (ASGE) Standards of Practice Committee (Fisher 2011) that the overall pooled rate of serious complications is on the order of 2.8 per 1000 colonoscopies. They noted that over 85% of the serious complications occur in patients undergoing colonoscopy with polypectomy performed. Rates of colonic perforation are generally below 1 per 1000 procedures and are probably closer to 1 per 10,000 for purely screening colonoscopies. Hemorrhage, immediate or delayed, occurs in 1 to 6 cases per 1000 colonoscopies and is more common in diagnostic colonoscopies and those with polypectomy. Polyp size and type are risk factors and patient comorbidities increase the risk of hemorrhage. It’s not clear whether the latter increases the risk or is just a marker for increased use of anticoagulants and antithrombotic agents. Other more serious complications such as death, infection, and colonic gas explosions are relatively rare. They also mention the postpolypectomy electrocoagulation syndrome, where a transmural burn gives rise to signs of localized peritonitis but is usually treated medically rather than surgically. Among less serious complications, they noted transient GI symptoms in as many as one third of all patients.


Complications may also arise from the sedation used during colonoscopy, though these are likely to occur during or shortly after the procedure rather than after discharge. Enhancing colonoscopy with the use of capnography has been suggested as a patient safety intervention. However, a new study demonstrates that for most patients undergoing colonoscopy with moderate sedation, the addition of capnography did not improve either complications or patient satisfaction but did increase costs (Barnett 2016). The authors compared 465 patients undergoing colonoscopy in the pre-capnography era with 501 patients in the post-capnography era. There were no serious adverse events in either group and minor adverse events occurred in 8.2% and 11.2% of patients in the pre- and post-capnography groups respectively. Levels of procedural discomfort were actually higher in the post-capnography era, as rated by both patients and nurses. Use of capnography added $11.68 per case. However, it is important to note that these patients were not considered high risk patients. Those considered high risk were already pre-selected to have their colonoscopies under deep sedation under the supervision of an anesthesiologist. We would certainly advocate for supervision by an anesthesiologist for patients with COPD or known obstructive sleep apnea (OSA). We’d also like to see screening for OSA with a tool like the STOP-Bang questionnaire (see our many columns on OSA) to identify further high risk individuals who might benefit from more intense monitoring.


And, almost as if on cue, the Canadian Task Force on Preventive Health Care just released its recommendations on screening for colorectal cancer in primary care and these do not recommend colonoscopy as the primary screening method for colorectal cancer (Canadian Task Force 2016). Instead, they recommend screening adults aged 50 to 74 years for colorectal cancer with fecal occult blood testing (guaiac fecal occult blood testing/gFOBT or fecal immunochemical testing/FIT) every two years or flexible sigmoidoscopy every 10 years. That recommendation is graded as “strong” for those aged 60-74 and “weak” for those aged 50-59, both based on moderate quality evidence. The Canadian Task Force actually recommends not using colonoscopy as a primary screening test for colorectal cancer. But that is given as a “weak” recommendation, noting the lack of randomized controlled trial evidence of efficacy and harms. It does note ongoing trials that may provide better evidence-based answers.


So why does the Canadian Task Force not agree with recommendations of the US Preventative Services Task Force (Whitlock 2008)? It’s not so much that they really disagree. It is more a matter of semantics and really boils down to strict adherence to the standards of evidence. Recommendations in the US regarding colonoscopy have been made based upon the fact that a similar endoscopic screening method – flexible sigmoidoscopy – reduces colorectal cancer mortality. And colonoscopy has largely become the de facto gold standard for colorectal cancer screening in the US.


The upcoming revision to the USPSTF recommendations (USPSTF 2015) is likely to be more in line with those of the Canadian Task Force. While the USPSTF acknowledges that there is no direct evidence that colonoscopy reduces colorectal cancer mortality, it again notes that a similar endoscopic screening method – flexible sigmoidoscopy – reduces colorectal cancer mortality. But it acknowledges that there has been no randomized controlled trial of colonoscopy to show a reduction in mortality (several are apparently in progress) and that there may be differences related to the two procedures. It does note that a prospective cohort study found an association between persons who self-reported being screened with colonoscopy and a lower colorectal cancer mortality rate (Nishihara 2013). That study looked at self-reported data from participants in the Nurses' Health Study and the Health Professionals Follow-up Study. It concluded that colonoscopy and sigmoidoscopy were associated with a reduced incidence of cancer of the distal colorectum; colonoscopy was also associated with a modest reduction in the incidence of proximal colon cancer. Screening colonoscopy and sigmoidoscopy were associated with reduced colorectal-cancer mortality but only colonoscopy was associated with reduced mortality from proximal colon cancer. Importantly, the USPSTF notes there are likely differences in harms between colonoscopy and flexible sigmoidoscopy, the latter having roughly ten times fewer complications (Whitlock 2008), so the net benefit of colonoscopy remains undetermined at this time.


Both the Canadian Task Force and the USPSTF agree that the most important thing is that some form of screening be done.


In that November 15, 2011 Patient Safety Tip of the Week “Rethinking Colonoscopy” we highlighted an editorial in the Journal of the National Cancer Institute that challenged the colorectal cancer screening strategy currently dominant in the US. Harris and Kinsinger in the editorial (Harris 2011) pointed out that there are randomized controlled trials that demonstrate that screening for colorectal cancer with fecal occult blood tests (FOBT) and flexibile sigmoidoscopy reduces mortality from colorectal cancer but they pointed out that evidence of the magnitude of additional benefit from colonoscopy is much less robust. Maybe it is only now that the rest of the medical world is taking a step back and saying we need to be truly evidence-based in our thinking. Perhaps the ongoing studies will answer the question better and find the proper place for colonoscopy in our screening armamentarium.








Warren J.L., Klabunde C.N., Mariotto A.B., et al:  Adverse events after outpatient colonoscopy in the Medicare population.  Ann Intern Med 2009; 150:  849-857



Ranasinghe I, Parzynski CS, Searfoss R, et al. Differences in Colonoscopy Quality Among Facilities: Development of a Post-Colonoscopy Risk-Standardized Rate of Unplanned Hospital Visits. Gastroenterology 2016; 150(1): 103-113



Fisher DA, Maple JT, Ben-Menachem T, et al for the ASGE Standards of Practice Committee, Complications of colonoscopy. Gastrointestinal Endoscopy 2011; 74(4):  745-752



Barnett S, Hung A, Tsao R, et al. Capnographic Monitoring of Moderate Sedation During Low-Risk Screening Colonoscopy Does Not Improve Safety or Patient Satisfaction: A Prospective Cohort Study. The American Journal of Gastroenterology 2016; published online 2 February 2016



Canadian Task Force on Preventive Health Care. Recommendations on screening for colorectal cancer in primary care. CMAJ 2016; early release published February 22, 2016



Whitlock EP, Lin JS, Liles E, et al. Screening for colorectal cancer: a targeted, updated systematic review for the U.S. Preventive Services Task Force. Ann Intern Med 2008; 149: 638-658



USPSTF (U.S. Preventive Services Task Force). Topic Update in Progress. Colorectal Cancer: Screening. November 2015



Nishihara R, Wu K, Lochhead P, Morikawa T, Liao X, Qian ZR, et al. Long-term colorectal-cancer incidence and mortality after lower endoscopy. N Engl J Med. 2013; 369(12): 1095-1105



Harris R, Kinsinger LS. Less is More: Not “Going the Distance” and Why.

JNCI 2011; 103(23): 1-3





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