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Accuracy of colonoscopy

Like most other diagnostic tests, colonoscopy has a false negative rate for detection of colorectal cancer and adenomas. This needs to be taken into consideration when decisions are made about the choice and timing of surveillance procedures. While the overall sensitivity for colorectal cancer is 95%,[1] the available literature suggests that cancer miss rates are higher in the proximal colon than elsewhere in the large bowel.[2] In a systematic review of polyp miss rates as determined by tandem colonoscopy, Van Rijn et al (2006)[3] identified studies in which patients had undergone two same-day colonoscopies with polypectomy. The research yielded six studies, involving a total of 465 patients. The pooled miss rate for polyps of any size was 22%. Adenoma miss rate by size was 2.1% for adenomas ≥10 mm, 13% for adenomas 5–10mm, and 26% for adenomas 1–5 mm, respectively. Analysis of the data suggests that, in expert hands, colonoscopy rarely misses polyps ≥10 mm, but the miss rate increases significantly with smaller sized polyps.

In a more recent study, Heresbach et al 2008[4] examined adenoma miss rate by performing a large multicentre study, with same-day back-to-back video colonoscopy performed by two different colonoscopists in randomised order and blinded to results of the other examination. The miss rates for all polyps, all adenomas, polyps ≥ 5 mm, adenomas ≥5 mm, and advanced adenomas were, respectively, 28 %, 20 %, 12 %, 9 % and 11 %. Greater diameter (1-mm increments) and number of polyps (≥3) were independently associated with a lower polyp miss rate, whereas sessile or flat shape was significantly associated with a higher miss rate.[4]

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Technological developments

In recent years there has been rapid progress in instrument design to enhance colonoscopic identification of lesions, reduce miss rates and reduce complications.[3][5][6] The new features include high definition colonoscopy, wide angle colonoscopy, narrow band imaging (NBI), hood-assisted colonoscopy and chromoendoscopy. High definition, wide angle and narrow band imaging technologies have been incorporated into most of the latest generation of colonoscopes. However, more studies are needed to assess the place of these various modifications, especially chromoendoscopy, in colonoscopic surveillance.

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High definition colonoscopy

As the name suggests, high definition (HD) colonoscopy system uses a high-definition 1080-line television and a high resolution charge-coupled device (CCD) with up to 1 million pixels, which provides images double the quality of normal television.[7][8] While Pellise et al[7] did not find any improvement over standard colonoscopy, Buchner et al indicated that adenoma detection rates are improved through use of high-definition colonoscopy, which can detect subtle mucosal changes.[8] In their retrospective study, the adenoma detection rate was higher among patients who underwent high definition white light compared with standard definition white light colonoscopy (28.8% versus 24.3%; P = .012). These findings remained after adjusting for potentially confounding variables.[8]

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Wide angle colonoscopy

With this method, the instrument has a field of vision of 170°, which is 30% more than the conventional model. The aim is to improve the detection of lesions hidden behind colonic folds. With one exception[9], all studies reported in the available literature from 2003 to 2010 suggest that prototype wide angle colonoscopes do not eliminate polyp miss rates, but have the potential to reduce examination time and improve visualisation in the periphery of the endoscopic field of view.[7][10][11][12]

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Narrow Band Imaging (NBI)

The NBI technology uses a band-restricted light source centred at 415 nm (blue) and 540 nm (green). The narrowed light penetrates the mucosa and submucosa and is absorbed primarily by haemoglobin. Thus, surface micro-vessels are visible as dark structures. Because the density and shape of micro-vessels change in neoplasia, NBI and equivalent technologies have the potential to aid in the diagnosis of neoplastic lesions. In addition, NBI helps distinguish between different histologic groups and assess depth of invasion.[13][14]

In a randomised controlled trial, 401 patients were assigned to undergo wide angle colonoscopy using either conventional high-resolution imaging or NBI during instrument withdrawal. When the two techniques were compared in consecutive subgroups of 100 patients, adenoma detection rates in the NBI group remained stable (approximately 25%) whereas these rates steadily increased in the control group (8%, 15%, 17%, and 26.5%, respectively). Significant differences in the first 100 cases (26.5% versus 8%; p=0.02) could not be maintained in the last 100 cases (25.5% versus 26.5%, p=0.91). The increased adenoma detection rates with NBI colonoscopy were statistically not significant.[15][16] Similar results were reported by Rex and Helbig19 and Kaltenbach et al.[17]

Significant differences were, however, identified when NBI was used to detect additional polyps in members of Lynch syndrome (HNPCC) families.[18]

Although less well-studied with regard to their potential additive benefit in polyp detection, other commercial image modification/enhancement technologies, I-Scan (Pentax instruments) and FICE (Fujinon), are available and are similarly conveniently accessible on the respective instruments.

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Chromoendoscopy (or dye spray) has been introduced to enhance the detection of polyps particularly diminutive flat lesions that may be otherwise difficult to detect.[19]

When combined with high magnification, chromoendoscopy was found to be highly efficient for separating adenomatous from non-adenomatous polyps[20] and for detecting changes in patients with inflammatory bowel disease.[21] Chromoendoscopy is becoming the standard method for detection of dysplasia in inflammatory bowel disease.[22]

However, based on results from their studies, Lapalus et al[23] and Le Rhun[24] could not recommend the systematic use of chromoendoscopy and structure enhancement, although the detection of small adenomas in the proximal colon was improved. In the randomised prospective study by Lapalus et al,[23] a combination of chromoendoscopy and structure enhancement was used to increase the adenoma detection rate in high-risk patients with a personal history of colorectal adenomas and/or a family history of colorectal cancer.[12]

Separate randomised controlled trials published within the same year also suggest that chromoendoscopy detects more polyps missed by standard colonoscopy than intensive inspection[25][26]particularly in patients with Lynch syndrome.[27][28] Although very promising, its use has not yet become widespread.

More recently, Sanduleanu et al[29] combined chromoendoscopy (C) with confocal laser endomicroscopy (CLE) that allows real-time in vivo microscopy of the mucosa and provides accurate histopathology. The study concluded that C-CLE accurately discriminates adenomatous from nonadenomatous colorectal polyps and enables evaluation of the degree of dysplasia during ongoing endoscopy.

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Hood-assisted colonoscopy

Hood assisted colonoscopy is colonoscopy with a transparent retractable extension. A transparent “hood” (or “cap”) is a simple device that can be attached to the tip of a colonoscope before performing the examination. Although adding to the cost of colonoscopy, it has been proposed as a method for shortening withdrawal time in addition to improving adenoma detection rates.[30]

Some consider that use of the hood mainly helps less experienced colonoscopists. With more experienced colonoscopists, the hood does not improve either the caecal intubation rate or the adenoma detection rate, but does shorten the caecal intubation time. It therefore should be reserved for selected cases, especially when initial caecal intubation fails.[31]

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Quality of colonoscopy

Many factors affect the quality of colonoscopy, including the provision and proper maintenance of appropriate equipment, adherence to up-to-date protocols for all phases of the procedure, and having processes in place for regular auditing of outcomes and on-going quality improvement.

All such factors are directly relevant to surveillance colonoscopy in the three settings covered by these guidelines, in which detection of metachronous polyps (for patients with prior adenomatous polypectomy or colorectal cancer resection) and visible dysplasia (for patients with inflammatory bowel disease) is pivotal to surveillance purposes. Above all, the colonoscopist must have the necessary technical skills and understanding to perform colonoscopy effectively and with safety. Colonoscopy is highly operator-dependent.[32] The colonoscopist therefore should have undergone supervised training that meets the requirements of appropriate professional bodies as well as meeting agreed standards for ongoing competence. Basic skills include torque steering, loop recognition and reduction, recognition of landmarks to confirm complete examination, and the ability to carefully withdraw the colonoscope to maximize lesion detection and to perform polypectomy.

Higher lesion detection rates are associated with adequate distension, suction and cleaning, position change, and slow and meticulous examination of the colonic mucosa, including areas behind folds.[33] Measurement and recording of colonoscope withdrawal time (the time taken between caecal intubation and colonoscope withdrawal from the anus, excluding the time taken for biopsy and polypectomy) is a key indicator of adequacy of the examination.[33]

Advances continue to be made in colonoscopic techniques (e.g. the use of carbon dioxide rather than air for insufflation, availability of foot pedal-operated water jets to clear faecal matter and through-channel narrow endoscopes for retroflexion in the caecum and rectum) that may allow easier examination and greater patient comfort and safety. Colonoscopy is considered to be a relatively safe procedure for the diagnosis of colorectal disease. However, as with any invasive procedure, there is a risk of adverse events occurring either directly or indirectly as a result of the procedure.[34]

The National Bowel Cancer Screening Program (NBCSP) Quality Working Group report recommends standards, objectives and performance indicators for use in Australia, as set out below. They are grouped together for three phases – before, during and after the procedure – as high quality colonoscopy depends on decisions and actions taken during each phase.

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Indicators of quality for the pre-procedure phase

Indications for colonoscopy should comply with national guidelines and risk factors should be assessed, with recording of actions taken to address specific risks (Table 1.1).

What will your patients expect?
• That there is a valid indication for the procedure

• That risk factors (e.g. anticoagulant therapy, presence of severe co-morbidities) will be identified well before colonoscopy and action taken to minimise risk

Table 1.1: Clinical standards, objectives and indicators for the pre-procedure phase - indications and assessment of risk

Standard Objective Performance indicators
Standard 1 : Patient indications and risks

A comprehensive assessment of indications for the procedure and risks and co-morbidities is undertaken for each patient prior to the performance of the procedure.

Objective 1.1: Assessment of patient indications

The colonoscopist ensures that there is full documentation and reporting of the indications for colonoscopy as listed for each patient category

A 100 per cent documentation and reporting of the following indications for colonoscopy for:

o Asymptomatic patients:

–family history (as per CRC Guidelines 2005)[35];

–previous colorectal cancer or adenomatous polyps (as per CRC Guidelines 2005)[35];

–colitis surveillance for patients with increased cancer risk; and

–positive faecal occult blood test.

o Symptomatic patients:

– symptoms documented on report.

o Date of previous colonoscopy (if applicable).

Objective 1.2: Assessment of patient risk and co-morbidity

The colonoscopist ensures that there is full documentation and reporting of information about patient risk and co-morbidity.

A 100 per cent documentation and reporting of the assessments for:

o Sedation risks with reference to the American Society of Anesthesiologists (ASA) classifications.

o Action related to specific risks including:

– the need to cease aspirin or other antiplatelet drugs or anti-coagulants;

–the need for antibiotic prophylaxis; and

– diabetes mellitus.

o Patients cancelled on the day due to unforeseen co-morbidities.

Informed consent should be obtained from all patients or their parent/legal guardian, using a structured approach. Preferably, it should be obtained before the period of bowel preparation. The patient needs to understand what is involved in the procedure and the possible risks, both in general and in the patient’s specific case (Table 1.2).

What will your patients expect?
• To be given a clear explanation of what is involved in the procedure and to have an opportunity to ask for more information

• That this information will be provided before embarking on bowel preparation

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Table 1.2: Clinical standards, objectives and indicators for the pre-procedure phase - patient consent

Standard Objective Performance indicators
Standard 2: Patient consent

Informed consent using a structured approach is obtained from all patients (or parent/legal guardian where applicable) for all procedures prior to the procedure(s) being undertaken.

Objective 2.1: Patient information, education and consent

The colonoscopist ensures that the patient (or parent/legal guardian where applicable) provides his/her informed consent to all aspects of the procedure(s) to be undertaken by confirming that the information detailed in the performance indicators is provided at all times.

A Every patient (or parent/legal guardian where applicable) is provided with:

-A full explanation about the requirements for adequate bowel preparation.

-A full explanation of the procedure.

-A full explanation of the risks and complications involved including co-morbidity and sedation risks, and also the risks associated with not having the procedure.

-Opportunities to ask questions and receive advice on options.

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Proper bowel preparation is required to allow full examination of the large bowel, to improve the outcome and to avoid the need for a repeat procedure (Table 1.3). The timing of bowel preparation also influences the quality of cleansing of the bowel.[36]

What will your patients expect?
• That they be given clear information about the details of the bowel preparation protocol, including the importance of maintaining hydration

• That the type of preparation be selected according to any special risk factors (e.g. older age, renal impairment) as well as their personal preference

Table 1.3: Clinical standards, objectives and indicators for the pre-procedure phase - bowel preparation

Standard Objective Performance indicators
Standard 3: Bowel preparation

Bowel preparation is undertaken to a high standard.

Objective 3.1: Bowel preparation

The colonoscopist ensures that high quality bowel preparation is performed that is appropriate for individual patient risk factors and preferences.

A 100 per cent of patients receive bowel preparation education.

B There is 100 per cent documentation of the type and quality of bowel preparation.

C Less than 10 percent of patients require a repeat colonoscopy examination due to poor bowel preparation.

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Indicators of quality for the procedure phase

Key indicators for competence include volume, i.e. the number of procedures performed annually[37][38], caecal intubation rate[39][40], instrument withdrawal time[41][42], adenoma detection rate[43][44] and complication rates.[38][45]

The European Panel on the Appropriateness of Gastrointestinal Endoscopy (EPAGE) multicentre study provided a unique opportunity to examine the quality and technical performance of a large number of colonoscopies performed at multiple centres in different countries in Europe. Consecutive patients were referred for colonoscopy from 21 centres in 11 countries and 6,004 patients were included. The study found that variations in colonoscopy practice exist. Patients from centres where over 50% of the endoscopists were of senior rank were roughly twice as likely to have an adenoma diagnosed. Longer average withdrawal duration was associated with more frequent detection of adenomas.[46]

The NBCSP Quality Working Group’s recommended standards, objectives and performance indicators relating to proficiency of the proceduralist are set out in Table 2.1.

What will your patients expect?
• That the colonoscopist is well trained in the procedure and meets agreed standards for competence

• That there will be skilful and thorough examination of all parts of the large bowel.

What will histopathologists expect?
• That polyps sent for examination will be identified by site within the large bowel

• That colonoscopists will carefully measure and record the size of these polyps, either in situ or after retrieval, to enable adenomas to be classified as advanced (≥10 mm in diameter) or non-advanced (<10 mm in diameter) on the basis of their size

What will quality reviewers expect?
• That colonoscopists will document the extent of the examination to be able to accurately calculate their ileo-caecal intubation rate

• That colonoscopists record instrument withdrawal times, a surrogate marker of careful examination behind folds • That colonoscopists periodically calculate their adenoma detection rate

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Table 2.1: Clinical standards, objectives and indicators for the procedure phase proficiency of proceduralist

Standard Objective Performance indicators
Standard 4: Proficiency of proceduralist

Proceduralists are proficient in providing high quality colonoscopies.

Objective 4.1: Measures of the proficiency of the proceduralist

The proceduralist ensures that the following data is captured and recorded:

o Number of colonoscopies he/she performs per annum.

o Caecal intubation rate determined by photo-documentation of caecal landmarks. (Definition of caecal intubation: passage of the instrument tip proximal to the ileocaecal valve so that the entire caecal caput is visible.)

o Mean colonoscope withdrawal time from the caecum.

o Adenoma detection rate.

o Rate of polyp recovery for pathological examination.

A Each proceduralist performs more than 250 procedures per five years.

B The caecal intubation rate for each proceduralist is 90 per cent or greater for general patients and 95 per cent or greater for screening patients.

C The mean colonoscope withdrawal time from the caecum for each proceduralist is 6 minutes or greater for procedures where there is no polypectomy performed.

D The adenoma detection rate for each proceduralist is more than 20 per cent in patients over 50 years of age undertaking an initial colonoscopy.

E The rate of polyp recovery for pathological examination for each proceduralist is more than 90 per cent.

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The literature identifies a range of complications and adverse events associated with colonoscopy. One Australian study investigated the rates of these complications.[45] The authors conducted an audit in three teaching hospitals in Western Australia from September 1989 to December 1999. The main complications identified were post-colonoscopy bleeding and post-colonoscopy perforation of the bowel. The rates of bleeding and perforation were found to be 0.21% and 0.1% respectively. Other complications included abdominal pain, nausea/vomiting, excess sedation, cardiovascular complications, cerebrovascular complications and pulmonary aspiration. The death rate associated with colonoscopy was 0.01%.

Following an extensive Medline database search (published from 2000 onwards), Panteris et al[47] found that the frequency of perforation is 1 in 1400 for all colonoscopies and 1 in 1000 for therapeutic colonoscopies. Advanced age, female sex, the presence of multiple co-morbidities, diverticular disease, and bowel obstruction have been shown to increase the risk of perforation.[38][47][48][49]

Rare complications include rupture of the spleen[50][51][52] and acute appendicitis.[53] These uncommon or rare procedural complications need to be balanced against the risks of not performing colonoscopy in each of the three clinical situations addressed by these guidelines (namely post-cancer resection, post-adenoma removal and in chronic inflammatory bowel disease). In each of these clinical scenarios, the patient is at above- average risk in their lifetime of developing CRC if surveillance colonoscopy is not repeated. while this risk (of developing CRC) differs amongst patients in each of the three different clinical situations (and even between patients with differing prior adenoma findings, e.g. one or two small adenomas versus multiple villous adenomas more than 1 cm in size) and may be difficult to accurately quantify for a given individual, it is in each scenario more than 1 in 17 by age 75 for males and more than 1 in 27 by age 75 for females.

Complications arising during a procedure should be well documented and reported as proposed by the NBCSP Quality Working Group (Table 2.2)

What will your patients expect?
• That the procedure will be performed safely and with minimal discomfort

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Table 2.2: Clinical standards, objectives and indicators for the procedure phase - minimisation of patient complication

Standard Objective Performance indicators
Standard 5: Minimisation of patient complications

Patient complications associated with colonoscopy are minimised.

Objective 5.1: Measures of patient complications

The proceduralist ensures that the following data are captured and recorded:

o Colonic perforations caused by colonoscopy.

o Post-polypectomy bleeding.

o Sedation complications:

– respiratory depression or airway obstruction requiring unplanned intervention;

– hypoxia defined as pulse oximetry greater than 10 percentage points lower than awake pre-procedural baseline for greater than 60 seconds consecutively during or after the procedure;

– hypotension requiring drug or fluid therapy;

– cardiac arrhythmia requiring intervention;

– pulmonary aspiration of gastric contents;

– the use of reversal agents; and

– patient complaint about sedation.

o Abnormal discomfort or pain: warranting hospital admission; delaying discharge; or patient complaint of inadequate pain relief during procedure.

o Procedure related death within 30 days.

A Colonic perforations caused by

colonoscopy in less than 1 in 1,000 colonoscopy procedures.

B Post-polypectomy bleeding in less than 1 in 100 patients who have had a polypectomy.

C Sedation complications:

o Respiratory depression or airway obstruction requiring unplanned intervention in less than 1 in 100 patients.

o Hypoxia defined as pulse oximetry greater than 10 percentage points lower than awake pre-procedural baseline for greater than 60 seconds consecutively during or after the procedure in less than 1 in 100 patients.

o Hypotension requiring drug or fluid therapy in less than 1 in 100 patients.

o Cardiac arrhythmia requiring intervention in less than 1 in 1,000 patients.

o Pulmonary aspiration of gastric contents in less than 1 in 1,000 patients.

o The use of reversal agents in less than 1 in 10 patients.

o Patient complaint about sedation in less than 1 in 100 patients.

D Abnormal discomfort or pain in less than 1 in 100 patients.

E Procedure related death within 30 days in less than 1 in 10,000 patients.

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Indicators of quality for the post-procedure phase

Several studies have found marked variation in the quality of reports describing findings at colonoscopy.[54] The NBCSP Quality Working Group recommendations for comprehensive reporting and management in the post-procedure phase are set out in Table 3.

What will your patients expect?
• Verbal and written information about the results of the procedure

• Verbal and written instructions about action to take if problems occur after discharge

• Information about follow-up review

What will referring doctors expect?
• Prompt receipt of a detailed report on the procedure

• A copy of any histopathology report

• Recommendations for further action

What will quality reviewers expect?
• That colonoscopists will conduct periodic audits of performance indicators

• That colonoscopists will welcome the opportunity to participate in quality improvement activities

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Table 3: Clinical standards, objectives and indicators for the post-procedure phase – documentation and reporting of performance information

Standard Objective Performance indicators
Standard 6: Provision of detailed performance information

Detailed information about the quality of the procedure and the colonoscopist’s performance is provided to relevant stakeholders.

Objective 6.1: Documenting and reporting of relevant performance information

The colonoscopist ensures that he/she:

o Completes a standard structured report on the procedure, with a copy or letter provided to the referring general practitioner (and/or NBCSP) that includes information on:

– the standard of bowel preparation;

– depth of insertion of colonoscope;

– presence of pathology;

– any intervention performed; and

– any unexpected outcomes.

o Provides a written report on colonoscopy findings for patients and ensures that patients are given contact details in case of an emergency.

o Completes and forwards a pathology request form to the pathologist, where applicable, with identification of the referring general practitioner and status as an NBCSP participant where applicable so that the information can be added to the National Register.

o Completes the required NBCSP reports where applicable.

o After a complete colonoscopy, documents a follow-up appointment with the referring general practitioner, specialist or colonoscopist and, where appropriate, provides information on the recommended time for the patient to undergo the next colonoscopy.

o After an incomplete colonoscopy, documents a plan for repeat colonoscopy, barium enema or CT colonography, and provides information on appropriate follow-up action.

Compiles an analysis of performance using the procedure indicators detailed under Standards 4 and 5 for the purpose of ongoing performance review and professional development.

A Detailed quality and

performance information in relation to the Objective is documented and provided for all patients at all times.

B Self-audit and analysis of proceduralist performance on a half-yearly basis.

Strategies for implementing the recommendations of the Quality Working Group and monitoring procedural quality are clearly beyond the scope of the current review.

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