Relationship of Non-Polypoid Colorectal Neoplasms to Quality of Colonoscopy

Colonoscopy is a dominant modality for colorectal cancer prevention in average-risk patients aged 50 years and older. Non-polypoid colorectal neoplasms (NP-CRNs) are likely a significant contributing factor to interval colorectal cancers because they have a higher prevalence in Western populations than previously thought, are more difficult to detect visually with conventional colonoscopy, and are more likely to contain advanced histology than polypoid neoplasms, regardless of size. The accurate identification and complete removal of NP-CRNs is thus an integral part of high-quality colonoscopy, and a critical component of the ongoing efforts to make colorectal cancer screening programs widely available, effective, and accepted by patients. In this article, the authors examine the quality indicators for colonoscopy, present the reasons for interval cancers, and discuss the relation between NP-CRNs and quality colonoscopy.

Colonoscopy is a dominant modality for colorectal cancer (CRC) prevention in average-risk patients aged 50 years and older. The principal benefits of screening colonoscopy are that it allows complete examination of the colon, detection of colorectal neoplasms, removal of polyps, and risk stratification of patients according to colorectal neoplasia type and burden. Screening colonoscopy identifies patients with no adenomas who can then be selected for longer surveillance intervals; patients with adenomas who can undergo polypectomy, and the small subgroup of patients with clinically silent early stage CRC. Despite its positive impact on CRC incidence and mortality, colonoscopy affords imperfect protection because some patients are diagnosed with CRC after a short time interval (1 to 3 years) following colonoscopy with potentially devastating impact on patients and colonoscopists. There are several potential explanations for the failure of clearing colonoscopy to prevent interval cancers, including patient factors, such as inadequate bowel preparation and variation in tumor biology; and physician factors, such as suboptimal withdrawal, examination, polypectomy techniques, and perceptual and personality attributes. Non-polypoid colorectal neoplasms (NP-CRNs) are likely a significant contributing factor to interval CRCs because they have a higher prevalence in Western populations than previously thought, are more difficult to detect visually with conventional colonoscopy, and are more likely to contain advanced histology than polypoid neoplasms, regardless of size. The accurate identification and complete removal of NP-CRNs is thus an integral part of high-quality colonoscopy, and a critical component of the ongoing efforts to make CRC screening programs widely available, effective, and accepted by patients. In this article, the authors examine the quality indicators for colonoscopy, present the reasons for interval cancers, and discuss the relation between NP-CRNs and quality colonoscopy.

Quality indicators for colonoscopy

The quality indicators for colonoscopy can be broadly categorized into pre-procedure, intra-procedure, and post-procedure indicators ( Box 1 ). The indicators most relevant to NP-CRNs are bowel preparation quality, detection of adenomas in asymptomatic individuals, withdrawal time, and complete endoscopic resection of polyps. Suboptimal bowel preparation hinders the adequate performance of colonoscopy because it can prolong procedure time (during insertion and withdrawal), and is associated with a lower detection rate of small and large adenomas. At least one prospective study found that improved bowel preparation preferentially increased the detection of flat lesions, a result that seems intuitively logical because NP-CRNs are more difficult to detect given their small size and flat morphology. The impact of prolonged procedure time on colonoscopy quality and operator fatigue is difficult to quantify. However, studies have shown that cecal intubation rates decline and insertion times tend to lengthen with consecutive colonoscopies, and adenoma detection rates are higher for colonoscopies performed in the morning compared with ones performed later in the day. Thus, an inadequate bowel preparation, beyond the obvious deleterious effect on visualization, may have an adverse impact on the vigilance of colonoscopists because of fatigue or other factors leading to decreased adenoma detection rates for procedures performed later in the day.

Box 1

1.

Appropriate indication
2.

Informed consent is obtained, including specific discussion of risks associated with colonoscopy
3.

Use of recommended post-polypectomy and post-cancer resection surveillance intervals
4.

Use of recommended ulcerative colitis/Crohn’s disease surveillance intervals
5.

Documentation in the procedure note of the quality of the preparation
6.

Cecal intubation rates (visualization of the cecum by notation of landmarks and photo documentation of landmarks should be present in every procedure)
7.

Detection of adenomas in asymptomatic individuals (screening)
8.

Withdrawal time: mean withdrawal time should be greater than or equal to 6 minutes in colonoscopies with normal results performed in patients with intact anatomy
9.

Biopsy specimens obtained in patients with chronic diarrhea
10.

Number and distribution of biopsy samples in ulcerative colitis and Crohn’s colitis surveillance (goal: four per 10-cm section of involved colon or approximately 32 specimens per case of pancolitis)
11.

Mucosally based pedunculated polyps and sessile polyps less than 2 cm in size should be endoscopically resected or if unresectable, documentation should be obtained
12.

Incidence of perforation by procedure type (all indications vs screening) is measured
13.

Incidence of post-polypectomy bleeding is measured
14.

Nonoperative management of Post-polypectomy bleeding