Overview of colonoscopy in adults

INTRODUCTION — 

Colonoscopy is used both diagnostically and therapeutically and permits examination of the rectum, colon, and a portion of the terminal ileum. Guidance statements from professional societies have advocated the following quality indicators before, during, and after colonoscopy [1] (see 'Quality indicators' below):

●Preprocedure – Attention must be paid to the general issues of patient preparation, targeted history and physical examination, evaluation of bleeding risk, assessment for appropriate sedation, and team pause before commencing sedation. It is also important to understand appropriate indications and recommended surveillance intervals based on the patient's risk factors (eg, family history of colorectal cancer, prior adenomatous polyps, hereditary colon cancer syndrome, or inflammatory bowel disease). Finally, obtaining informed consent with a detailed explanation of the risks associated with colonoscopy is essential.

●Intraprocedure – Performing a high-quality examination requires careful visualization of the entire colonic mucosa. Metrics such as cecal intubation rates, withdrawal times, and adenoma detection rates serve as surrogate markers of careful visualization.  

●Postprocedure – Complete and accurate documentation (both written and photographic) of preparation quality and findings, as well as recommendations for follow-up, must be provided. Tissue samples taken during colonoscopy must also be documented. Pathology results should be reviewed, and results and recommendations communicated to the patient and referring providers. Finally, a system for tracking adverse events should be established.

This topic will review factors associated with performing a colonoscopy including indications, patient preparation, technical aspects, and adverse events. Issues related to colon cancer screening, bowel preparation, procedural sedation, and the management of antiplatelet or anticoagulant medications in patients undergoing endoscopy are discussed separately. (See "Screening for colorectal cancer: Strategies in patients at average risk" and "Screening for colorectal cancer in patients with a family history of colorectal cancer or advanced polyp" and "Overview of colon polyps" and "Bowel preparation before colonoscopy in adults" and "Gastrointestinal endoscopy in adults: Procedural sedation administered by endoscopists" and "Management of antiplatelet agents in patients undergoing endoscopic procedures" and "Management of anticoagulants in patients undergoing endoscopic procedures".)

PATIENT SELECTION — 

Patient selection for colonoscopy focuses on the indication for the procedure and patient comorbidities to enable proper risk stratification.

Endoscopy may be appropriate if any of the following criteria are fulfilled [2]:

●The results are likely to change the patient's management

●Empiric treatment of a benign disease has failed

●A therapeutic intervention is anticipated

●It is being used as an alternative to radiologic evaluation

On the other hand, endoscopy is not indicated when the results are not expected to impact management or for the follow-up of benign diseases that have healed, unless surveillance of a premalignant condition is appropriate.

Indications — Colonoscopy is performed for both diagnostic and therapeutic indications (table 1). Diagnostic indications include screening or surveillance for colon cancer, evaluating signs and symptoms suggestive of possible colonic or distal small bowel disease, assessing response to treatment for colonic disease (eg, inflammatory bowel disease), and evaluating abnormalities found on imaging studies. Therapeutic indications include stricture dilation, stent placement, colonic decompression, and foreign body removal. In addition, lesions found during diagnostic procedures may require therapeutic intervention (eg, polypectomy or treatment of a bleeding lesion). (See 'Diagnostic and therapeutic maneuvers' below.)

●Screening or surveillance for colon cancer – Colonoscopy is considered the gold standard for colon cancer screening and surveillance. The age at which screening starts will depend upon the patient's medical and family history. If polyps are found during colonoscopy, they should be removed endoscopically if at all possible. (See "Screening for colorectal cancer: Strategies in patients at average risk" and "Screening for colorectal cancer in patients with a family history of colorectal cancer or advanced polyp" and "Surveillance and management of dysplasia in patients with inflammatory bowel disease" and 'Polypectomy' below.)

The interval for repeat screening or surveillance will again depend upon the patient's medical and family history, as well as the findings on prior colonoscopies. (See "Overview of colon polyps" and "Post-treatment surveillance for colorectal cancer".)

●Lower gastrointestinal bleeding – Patients with active or recent hematochezia, positive fecal occult blood, or melena after an upper gastrointestinal source has been excluded should undergo colonoscopy for diagnosis and, if a source of bleeding is identified, potentially endoscopic therapy. In addition, unexplained iron deficiency anemia should be evaluated via colonoscopy, as colon cancer is an important cause of iron deficiency anemia in adults. (See "Approach to acute lower gastrointestinal bleeding in adults" and "Determining the cause of iron deficiency in adolescents and adults", section on 'Evaluation for the cause'.)

●Lower gastrointestinal symptoms – Colonoscopy should be performed in patients with chronic, clinically significant diarrhea without an explanation. Random colon biopsies should be obtained throughout the colon to rule out microscopic colitis. Colonoscopy is generally not indicated as part of the evaluation for chronic constipation unless warning signs are present (eg, anemia, weight loss) or the patient has not undergone recommended screening or surveillance. Whether to perform a colonoscopy in a patient with chronic abdominal pain will depend upon patient risk factors (eg, age >45 years), the character and location of the pain, and associated signs and symptoms. (See "Evaluation of the adult with abdominal pain".)

●Abnormal imaging – Colonoscopy is indicated to evaluate abnormalities detected on imaging studies, including but not limited to barium enema, abdominal computed tomography (CT), positron emission tomography CT, or magnetic resonance imaging. Radiographic findings requiring colonoscopic evaluation include thickening of the wall of the colon or terminal ileum (image 1), mass lesions (figure 1), filling defects (image 2 and image 3), and strictures (image 4). In addition, colonoscopy may be indicated in patients with metastatic adenocarcinoma of unknown primary or who are found to have polyps on CT colonography (virtual colonoscopy), depending upon the size of the polyp (image 5). (See "Computed tomographic (CT) colonography in adults", section on 'Indications' and "Overview of the classification and management of cancers of unknown primary site", section on 'Adenocarcinoma'.)

●Evaluation for synchronous or metachronous cancer – Patients with colon cancer are at risk for synchronous cancer. As a result, patients with colon cancer require a complete examination of the colon. Ideally, this is done prior to surgery, though in some patients complete preoperative colonoscopy will not be possible (eg, due to inability to pass the colonoscope beyond an obstructing tumor). Such patients require colonoscopy soon after resection of the primary tumor. (See "Post-treatment surveillance for colorectal cancer", section on 'Perioperative colonoscopy'.)

Following treatment of the primary tumor, patients require routine surveillance to look for new polyps or metachronous cancer. Several expert groups have made recommendations regarding the timing and frequency of posttreatment endoscopic surveillance. (See "Post-treatment surveillance for colorectal cancer", section on 'Postoperative endoscopic surveillance' and "Post-treatment surveillance for colorectal cancer", section on 'Guidelines from major groups'.)

●Intraoperative lesion localization – Colonoscopy may be performed intraoperatively to identify a lesion identified on imaging or prior colonoscopy that is not apparent at surgery, such as a bleeding site or small mass. More commonly, colonoscopy is used to mark lesions identified during the procedure (picture 1A-C). In such cases, lesions are typically tattooed a few centimeters distal to the lesion. Exactly where the tattoo was performed in relationship to the lesion must be clearly documented and communicated to the surgeon. (See "Tattooing and other methods for localizing gastrointestinal lesions".)

●Inflammatory bowel disease – Colonoscopy is often performed in patients with inflammatory bowel disease to assess the extent and/or severity of disease and to assess treatment responses. In addition, patients with colitis require routine surveillance for colonic dysplasia. (See "Endoscopic diagnosis of inflammatory bowel disease in adults" and "Surveillance and management of dysplasia in patients with inflammatory bowel disease".)

●Evaluation of the terminal ileum – Colonoscopy can be used to evaluate the terminal ileum in patients with suspected disease involving the distal small bowel, such as Crohn disease.

●Therapeutic indications – Therapeutic indications for colonoscopy include hemostasis, foreign body removal, decompression of sigmoid volvulus, balloon dilation of strictures, and palliative treatment of bleeding or stenosed neoplasms. (See "Rectal foreign bodies" and "Sigmoid volvulus" and "Acute colonic pseudo-obstruction (Ogilvie's syndrome)" and "Management of anastomotic complications of colorectal surgery" and "Enteral stents for the management of malignant colorectal obstruction".)

Contraindications — Colonoscopy is contraindicated in the following situations:

●When the risks of the colonoscopy outweigh the expected benefits

●Consent cannot be obtained for a non-urgent procedure

●A perforation is known or suspected

●Documented acute diverticulitis

It is important to carefully weigh the expected benefits of colonoscopy against the risks, particularly in older adults and patients with comorbid illnesses. These patients are at increased risk for serious adverse events from colonoscopy. (See 'Adverse events' below.)

If a patient cannot be adequately sedated despite a reasonable attempt at moderate procedural sedation, colonoscopy should be delayed until adequate sedation can be provided (eg, monitored anesthesia care or general anesthesia). Finally, a suspected poor preparation is a relative contraindication to colonoscopy. (See 'Patient preparation' below and "Gastrointestinal endoscopy in adults: Procedural sedation administered by endoscopists".)

Important considerations — Before the procedure, patients should be evaluated for factors that may affect the ability to perform a colonoscopy safely and successfully, including:

●Anatomic issues, such as recent colonic surgery, history of abdominal and/or pelvic surgeries, abdominal hernias, and presence of a colostomy

●Comorbidities that may increase the risks associated with sedation (see "Gastrointestinal endoscopy in adults: Procedural sedation administered by endoscopists", section on 'Presedation evaluation')

●Presence of an implanted cardiac defibrillator and some pacemakers that may require special management during application of electrocautery

●Chronic use of benzodiazepines, opioids, or cannabis may increase a patient's tolerance to the effects of sedation or may affect the quality of the bowel preparation [3]

●A history of difficult intubation by anesthesia

PATIENT PREPARATION

Diet — Patients need to consume a low-residue diet or clear liquids for at least one day prior to elective colonoscopy [4]. A low-residue diet is low in fiber, and patients should be instructed to avoid foods that are high in fiber such as fruits, vegetables, and whole grains (table 2). Clear liquids include water, clear broth, coffee or tea (without milk), ices, gelatin, and fruit juices such as apple, grapefruit, and lemonade. Liquids that are red can be mistaken for blood in the colon or can obscure mucosal details and should be avoided. One trial found that there was no significant difference in preparation quality between patients treated with 4L of polyethylene glycol who were assigned to receive either a low-residue diet or clear liquids the day prior to the examination [5]. Similarly, a randomized trial with 230 patients who were receiving a sodium sulfate-based preparation assigned patients to either a low-residue diet for breakfast and lunch the day prior to the colonoscopy or to clear liquids [6]. Again, there was no difference between the groups with regard to preparation quality. However, patients in the low-residue arm reported greater satisfaction with the preparation and were less likely to cancel their procedure (9 versus 20 percent). Whether similar results would be seen outside of a randomized trial is not yet known. Our approach is to recommend a low-residue diet for three days prior to colonoscopy, with only clear liquids allowed the day prior to the examination.

Patients should follow preoperative fasting guidelines as they would for any type of anesthetic (table 3). (See "Preoperative fasting in adults".)

Specifically, the American Society of Anesthesiologists (ASA) guidelines state that patients should fast for a minimum of two hours after ingestion of clear liquids and six hours after ingestion of light meals before sedation is administered [7].

Medications — Most medications may be continued up to the time of colonoscopy and are taken with a small sip of water the day of the colonoscopy. Some medications may need to be adjusted prior to colonoscopy, such as medications for diabetes, due to decreased oral intake prior to the procedure. Glucagon-like peptide (GLP)-1 receptor agonists and sodium glucose cotransporter (SGLT)-2 inhibitors deserve special consideration pre-procedure given impact on gastric emptying and potential for euglycemic diabetic ketoacidosis, respectively. (See "Anesthesia for patients with diabetes mellitus and/or hyperglycemia", section on 'Preanesthesia evaluation' and "Anesthesia for gastrointestinal endoscopy in adults".)

Oral iron should also be stopped at least five days before the colonoscopy since it makes the residual feces black, viscous, and difficult to purge.

Decisions regarding the management of antiplatelet agents or anticoagulants must weigh the risks of bleeding from the procedure with the probability of a thromboembolic event occurring while the antithrombotic medication is interrupted (table 4 and table 5) [8]. Furthermore, the urgency of the procedure and the availability of alternative tests must be evaluated. Management decisions about antithrombotic agents should be made following discussion with the patient and the clinician prescribing the medication. Aspirin and nonsteroidal antiinflammatory drugs in standard doses may be continued safely in patients having colonoscopy. (See "Management of anticoagulants in patients undergoing endoscopic procedures" and "Management of antiplatelet agents in patients undergoing endoscopic procedures" and "Gastrointestinal endoscopy in patients with disorders of hemostasis".)

Because the risk of infection related to routine diagnostic or therapeutic colonoscopy is low, antibiotic prophylaxis is not recommended for colonoscopy. (See "Antibiotic prophylaxis for gastrointestinal endoscopic procedures".)

Preprocedure testing — It is generally recommended that patients not undergo routine preprocedure laboratory testing, chest radiography, or electrocardiography [9]. Instead, preprocedure testing should be used selectively based on the patient's medical history, physical examination findings, and procedural risk factors.

We agree with guidelines from the American Society for Gastrointestinal Endoscopy that recommend preprocedure testing in the following settings [9]:

●Pregnancy testing for patients of childbearing potential who provide an uncertain pregnancy history or who have a history suggestive of a current pregnancy (particularly if fluoroscopy is to be used).

●Coagulation studies for patients with active bleeding, a known or suspected bleeding disorder (including a history of abnormal bleeding), an increased risk of bleeding due to medication use (eg, ongoing anticoagulant use, prolonged antibiotic use), prolonged biliary obstruction, malnutrition, or other conditions associated with acquired coagulopathies.

●Chest radiograph for patients with new respiratory symptoms or decompensated heart failure.

●Hemoglobin/hematocrit for patients with preexisting significant anemia or active bleeding, or if there is a high risk of significant blood loss during the procedure.

●Blood typing for patients with active bleeding or anemia who are likely to need a blood transfusion.

●Serum chemistry testing for patients with significant endocrine, kidney, or liver dysfunction if medications are to be used that may further impair function.

Management of anticoagulants and antiplatelet agents is discussed separately. (See "Management of anticoagulants in patients undergoing endoscopic procedures" and "Management of antiplatelet agents in patients undergoing endoscopic procedures".)

Bowel preparation — An adequate bowel preparation is critical for colonoscopy because it permits visualization of the colonic mucosa and increases the safety of therapeutic maneuvers [10,11]. Poor preparation leads to increased procedure time, risk of adverse events, and probability of missing lesions [12]. Multiple bowel preparations exist, with the ideal preparation being effective, safe, and palatable. It is important to consider the patient's comorbid illnesses when choosing an appropriate preparation. (See "Bowel preparation before colonoscopy in adults".)

To standardize assessment of the bowel preparation, systems for reporting bowel preparation quality have been developed, including the Boston bowel preparation scale [13]. The score ranges from 0 to 3 (picture 2) for individual colonic segments: the right side of the colon (including the cecum and ascending colon), the transverse section of the colon (including the hepatic and splenic flexures), and the left side of the colon (including the descending colon, sigmoid colon, and rectum). These segment scores are summed for a total Boston bowel preparation scale score, which ranges from 0 (poor) to 9 (excellent):

●Score 0: Unprepared colon with mucosa not seen because of solid stool that cannot be cleared

●Score 1: Portion of the mucosa of the colon segment seen, but other areas of the colon segment not seen well because of staining, residual stool, and/or opaque liquid

●Score 2: Minor amount of residual staining, small fragments of stool and/or opaque liquid, but most mucosa of the colon segment seen well

●Score 3: Entire mucosa of colon segment seen well with no residual staining, small fragments of stool, and/or opaque liquid

SEDATION ASSESSMENT — 

Options for sedation for colonoscopy include no sedation, moderate procedural sedation, or deep sedation. Deciding upon the appropriate approach requires an assessment of the patient's sedation needs and risks prior to the colonoscopy [14,15]. This includes taking a history of factors that might make sedation more difficult such as prior difficulties with sedation, chronic opioid or benzodiazepine use, cognitive impairment, and agitation or severe anxiety. Special attention should be paid to whether the patient has an increased risk for difficult airway management (eg, obesity, non-visibility of the uvula, prior history of difficult intubation) or increased cardiopulmonary adverse events of endoscopy (eg, comorbidities, obesity, older age). (See "Gastrointestinal endoscopy in adults: Procedural sedation administered by endoscopists".)

Although deep sedation with propofol is associated with greater patient satisfaction, faster post-procedure recovery time, and in some studies shorter procedure time, it does not lead to improvements in other clinically important outcomes such as cecal intubation rates or adenoma detection rates [16,17]. Use of anesthesia during colonoscopy may be associated with increased adverse events, including perforation following polypectomy, bleeding, abdominal pain, and adverse events associated with anesthesia [18] as well as aspiration pneumonia [19]. (See "Gastrointestinal endoscopy in adults: Procedural sedation administered by endoscopists".)

INFORMED CONSENT — 

Informed consent encompasses all the interactions between the clinician and the patient. Informed consent includes full disclosure with a clear and complete explanation of the procedure. (See "Informed procedural consent".)

Five essential elements to discuss in preparation for any procedure include [20]:

●Nature of the procedure

●Benefits

●Risks

●Alternatives

●Limitations of the procedure

The use of clear and simple language is critical during the process of obtaining consent. For example, colonoscopy may be explained as "a procedure in which a doctor passes a flexible tube with a light and a camera through your anus into your colon." Discussion of the possible risks of colonoscopy, including adverse events, must occur and be tailored to the specific patient and procedure. Incidences of possible adverse events should be mentioned. (See 'Adverse events' below.)

Written documentation of the consent process is mandatory. When needed, translators and materials written in the patient's native language are also important.

EQUIPMENT — 

Routine colonoscopy is performed using a high-definition white-light colonoscope. Both adult and pediatric colonoscopes are used for colonoscopy in adults (with pediatric colonoscopes often being used for females or patients with a history of abdominal surgery). The choice of colonoscope does not affect cecal intubation rates or times [21]. Adult colonoscopes have a diameter of approximately 13 mm, whereas pediatric colonoscopes have a diameter of approximately 11 mm. Use of a pediatric colonoscope may enable easier passage through narrowed or fixed areas of the colon. However, the smaller diameter makes the pediatric colonoscope more flexible, which predisposes to loop formation. The choice of an adult versus pediatric colonoscope is typically a matter of endoscopist preference. Occasionally the endoscopist may need to change from one type of colonoscope to the other to facilitate completion of the colonoscopy (see 'Looping' below). An ultra-slim colonoscope with a diameter of approximately 9.5 mm may be particularly helpful in patients with tight turns.

Variable stiffness colonoscopes allow the endoscopist to stiffen the shaft of the colonoscope and appear to increase cecal intubation rates [22]. Often the colonoscope is stiffened after passage through the sigmoid colon to reduce loop formation. The colonoscope is typically loosened during withdrawal, retroflexion, or passage around tight turns.

Various accessories are available that can be passed through the accessory channel of a colonoscope. These include biopsy forceps, brushes, snares, baskets, nets, injection needles, hemostatic clips, and argon plasma coagulation probes.

COLONOSCOPE ADVANCEMENT AND MUCOSAL INSPECTION — 

Colonoscopy routinely begins with the patient in the left lateral decubitus position, with the exception of patients with a colostomy, who typically remain supine. The first step is inspection of the perianal region and digital rectal examination. Topical anesthetic lubricating gel should be used for patients with perianal discomfort, whereas standard lubricant can be used for patients without discomfort. The tip of the colonoscope is then inserted into the rectum with gas (usually carbon dioxide) insufflation, suctioning of residual fluid, and pulling back of the colonoscope to enable visualization. The rectosigmoid junction is at approximately 15 to 20 cm, at which point the colon enters the peritoneum. Particular care must be taken when advancing the colonoscope in patients with colonic strictures or severe diverticulosis, as gas insufflation can increase the risk of perforation in such patients. (See 'Perforation' below.)

Important techniques used during colonoscopy include using the up-down and left-right knobs and aspirating. Using the knobs is particularly helpful in negotiating turns. Although gentle insufflation helps visualization as the colonoscope is advanced, filling the colon with gas lengthens and distends the colon, which may cause discomfort and increase the difficulty of the procedure. Aspirating will deflate and shorten the colon, bringing the next fold closer to the tip of the colonoscope, reducing abdominal discomfort and often aiding with scope advancement. The use of carbon dioxide may reduce distension and patient discomfort as well [23]. Although limited data suggest that carbon dioxide insufflation in patients with underlying pulmonary disease is not associated with an increased risk of respiratory depression or carbon dioxide retention, additional studies are needed [23-25].

Distending the lumen of the colon with water may facilitate advancement of the colonoscope with decreased pain [26-28]. This technique may be especially helpful when navigating a left colon filled with numerous diverticula that make it difficult to identify the colonic lumen. Studies support decreased sedation requirements and improved patient tolerance with the use of water rather than gas insufflation; however, some studies suggested decreased adenoma detection rates (ADRs) [27,29-31]. In a meta-analysis with 16 randomized trials that compared insufflation with water and insufflation with air, insufflation with water was associated with less pain (-1.57 point difference in pain score on a 0 to 10 scale, 95% CI -2.00 to -1.14), a higher likelihood of being able to complete the examination without sedation or analgesia (risk ratio [RR] 1.20, 95% CI 1.14 to 1.27), and higher ADRs (RR 1.16, 95% CI 1.04 to 1.30) [28]. There was no difference in cecal intubation rate.

Intubating the terminal ileum can be performed with two different approaches. The colonoscope may be advanced through the opening of the valve by direct visualization during forward movement. Alternatively, the colonoscope may be positioned in the cecum near the appendiceal orifice and slowly withdrawn, with the tip of the colonoscope angled toward the direction of the valve opening in an attempt to "hook" the valve.

Looping — A major barrier to successful advancement of the colonoscope to the cecum is looping. Looping occurs due to the attachment of the sigmoid and transverse colon to a mobile mesentery (figure 2). Advancing the colonoscope becomes more difficult, and in some cases, attempts to advance the colonoscope result in reverse movement of the colonoscope tip, termed paradoxical movement. In addition to impeding advancement of the colonoscope, looping can cause pain and perforation. Pain occurs due to the presence of sensory receptors in the mesentery responding to torsion, distension, compression, and stretching. Repeated loop reduction during the colonoscopy is critical and requires pulling back the colonoscope while applying torque, often clockwise. Stopping any maneuver if it causes significant pain, pressure, or difficulty is important to decrease the risk of adverse events. Loops formed in the instrument shaft outside the patient should be removed by rotating the colonoscope, keeping the lumen in view.

Applying abdominal pressure and changing the patient's position are important adjunctive techniques to enable passage of the colonoscope to the cecum. Abdominal pressure was the most important non-instrumental factor for cecal intubation in patients referred for incomplete colonoscopy [32]. Loops should be removed before the assistant applies pressure to help prevent loop further formation.

Asking the patient to demonstrate the location of abdominal discomfort may also help identify the appropriate area to apply pressure. In addition, abdominal pressure should be applied to abdominal hernias. In such patients, loops that form within the hernia may lead to entrapment of the colonoscope [33].

The use of a lower abdominal compression device may reduce the need for manual pressure and patient repositioning in patients with a BMI 30 to 40 kg/m² [34]. Furthermore, the use of this type of device may reduce the frequency of staff-related musculoskeletal pain experienced [35]. While not widely available, an alternative method for determining where to apply pressure is magnetic endoscopic imaging. Magnetic endoscopic imaging provides real-time three-dimensional views of the colonoscope shaft configuration and its location within the abdomen. This information can aid with loop reduction and can be used to identify where to provide external pressure [36,37].

Changing the patient's position also may aid advancement of the colonoscope. In addition to the standard left lateral position, patients may be positioned in a supine, right lateral, or prone position. One study demonstrated that position changes were effective two-thirds of the time in allowing forward advancement of the colonoscope or improved luminal visualization [38].

Inspection

Essential elements — Careful inspection of the colonic mucosa is primarily performed during withdrawal of the colonoscope. In addition to polyps (and tumors if present), the presence of erythema, erosions, ulcers, diverticula, melanosis coli, hemorrhoids, and condyloma should be noted. A withdrawal time of at least six minutes improves adenoma detection rates, but inspection technique appears to be as important as time spent inspecting [39,40]. The following techniques are important for ensuring optimal visualization:

●Cleaning the colon of residual fluid during insertion and withdrawal. Residual stool may be aspirated into a plastic trap for microbiology analysis if needed.

●Clearing bubbles with simethicone in the water flushes used during insertion or withdrawal.

●Adequate insufflation during withdrawal.

●Visualizing the entire circumference of the colon by moving the tip of colonoscope in a systematic "circular" pattern.

●Second examination of the proximal colon from hepatic flexure to cecum on withdrawal or retroflexion in the right colon [41-43].

●Inspecting behind and in between folds.

●Repeated inspection of areas by back and forth movement of the colonoscope, especially around turns.

●Reducing colonic contractions by cleaning during colonoscope advancement to minimize suctioning upon withdrawal. Antispasmodics may also be used, although studies have failed to demonstrate improved ADRs with their use [44].

●Changing the patient's position during withdrawal has been shown to improve adenoma detection rates, with the following positions used based upon the location of the tip of the colonoscope: cecum to hepatic flexure, left lateral position; transverse colon, supine position; splenic flexure and descending colon, right lateral position [45].

●Careful inspection of vascularity and areas with mucus since flat lesions may manifest only as subtle changes to the vascular pattern or may be obscured by adherent mucus.

●Having experienced nurses, fellow trainees, and assistants examine the colonic mucosa simultaneously with the endoscopist has led to improved ADRs [46,47].

The endoscopist cannot always accurately identify the location of the colonoscope tip in the colon. Identifying position by the distances marked on the shaft of the colonoscope is not reliable due to looping, although approximately 60 to 80 cm of the instrument will typically be inserted upon reaching the cecum once loops have been removed. Only the terminal ileum (picture 3), cecum (picture 4), and rectum (picture 5) can be recognized 100 percent of the time by experienced endoscopists. The appendiceal orifice (picture 6) and ileocecal valve (picture 7) with two lipomatous lips identify the cecum. Care must be taken not to confuse the cecum with a tight turn or the appendiceal orifice with a diverticulum. The hepatic and splenic flexures may be identified by the bluish hue of adjacent organs (the liver and spleen, respectively) visualized through the colonic mucosa (picture 8). The transverse colon typically has a triangular fold configuration (picture 9).

Enhanced visualization tools — Multiple options are available to enhance visualization to improve polyp detection during colonoscopy, though many require specialized equipment and training. These imaging enhancements include narrow band imaging, magnification endoscopy, and chromoendoscopy. These techniques are not routinely used but may be employed in certain circumstances (eg, detecting dysplasia in patients with inflammatory bowel disease). In a systematic review and network meta-analysis that compared the efficacy of different endoscopic techniques in increasing ADRs, low-cost measures optimizing existing resources (water-aided colonoscopy, second observer, dynamic position change) were associated with a moderate increase in ADR compared with high-definition colonoscopy alone (odds ratio [OR] 1.29, 95% CI 1.17-1.43) [48]. Low-cost measures appeared to be as effective as enhanced imaging techniques (chromoendoscopy, narrow-band imaging, flexible spectral imaging color enhancement, blue laser imaging) (OR 1.21, 95% CI 1.09–1.35). However, the use of enhanced scopes (full-spectrum endoscopy, extra-wide-angle-view colonoscopy, dual focus) was not associated with significant increases in ADR during high-definition colonoscopy.

Add-on devices to the colonoscope (cap, Endocuff, EndoRing, G-EYE and AmplifEYE) enhance colonic mucosal visualization and have been shown to modestly increase ADR (OR 1.18, 95% CI 1.07-1.29). A meta-analysis of randomized controlled trials, high-quality case-control, cohort, and observational studies (>10 subjects) mostly using Endocuff showed an increase in the sessile serrated polyp detection rate with a pooled rate of 12.3 percent as compared with 6.4 percent with standard colonoscopy (OR 1.81, 95% CI 1.6-2.0) [49].

Artificial intelligence (AI)–assisted polyp detection — Computer-aided diagnosis can improve ADRs [50-56]. However, the efficacy of this technology has not been demonstrated in the detection of advanced adenomas. In a systematic review and meta-analysis of five randomized trials that included 4354 patients, colonoscopies performed with a computer-aided detection (CADe) system had higher pooled ADRs as compared with conventional colonoscopy [56]. CADe resulted in higher adenoma per colonoscopy regardless of size and polyp location. While CADe also resulted in a higher sessile serrated lesion per colonoscopy (relative risk [RR] 1.52; 95% CI 1.14-2.02), rates of advanced ADR were not significantly different (RR 1.35; 95% CI 0.74-2.47). However, no difference in ADR, detection of sessile serrated polyps or advanced adenomas between AI-assisted and standard colonoscopy was detected in a retrospective study at a large academic medical center [57]. Similarly, no significant difference in ADR between AI-assisted and standard colonoscopy (71.4 versus 65.0 percent, p = 0.09) was reported in a randomized trial from the United Kingdom where Endocuff Vision was used in approximately 70 percent of patients in each arm [58]. Three CADe systems have been approved for use in the United States by the Food and Drug Administration including GI Genius, EndoScreener, and SKOUT [59-61].

A systematic review and network meta-analysis of randomized controlled trials that assessed the impact of AI compared with other endoscopic interventions aimed at increasing ADR such as distal attachment devices, dye-based/virtual chromoendoscopy, water-based techniques, and balloon-assisted devices included 94 randomized controlled trials with 61,172 patients and 20 discrete study interventions [62]. ADRs for AI were significantly higher as compared with autofluorescence imaging, dye-based chromoendoscopy, Endocap, Endocuff, Endocuff vision, EndoRing, flexible spectral imaging color enhancement, full-spectrum endoscopy, high definition, linked color imaging, narrow band imaging, water exchange, and water immersion. Further studies are needed to determine if the use of computer-aided polyp diagnosis methods can consistently provide reliable and reproducible accuracy in the detection and characterization of colorectal polyps, improve detection of advanced polyps and sessile serrated polyps, improve polyp detection in endoscopists with a high ADR, and improve long-term patient outcomes.

DIAGNOSTIC AND THERAPEUTIC MANEUVERS — 

A variety of diagnostic and therapeutic maneuvers can be performed during colonoscopy. The most common maneuver is tissue sampling. Other interventions include:

●Endoscopic hemostasis (picture 10) (see "Argon plasma coagulation in the gastrointestinal tract" and "Endoscopic clip therapy in the gastrointestinal tract: Bleeding lesions and beyond" and "Approach to acute lower gastrointestinal bleeding in adults", section on 'Colonoscopy')

●Dilation of colonic or anastomotic strictures (see "Management of anastomotic complications of colorectal surgery", section on 'Strictures')

●Stent placement for malignant disease (movie 1) (see "Enteral stents for the management of malignant colorectal obstruction")

●Endoscopic mucosal resection and endoscopic submucosal dissection of gastrointestinal tumors (see "Overview of endoscopic resection of gastrointestinal lesions")

●Foreign body removal (image 6 and picture 11A-B) (see "Rectal foreign bodies", section on 'Endoscopy')

●Placement of a colonic decompression tube (see "Acute colonic pseudo-obstruction (Ogilvie's syndrome)", section on 'Colonoscopic decompression')

●Percutaneous endoscopic cecostomy tube placement (see "Acute colonic pseudo-obstruction (Ogilvie's syndrome)", section on 'Colonoscopic decompression')

Tissue sampling — Visible lesions identified during colonoscopy should be sampled or removed for pathology. Because the colonic mucosa lacks pain receptors, patients generally do not feel pain with these maneuvers. Tissue sampling includes biopsies, brushings, and polypectomy [63]. Specimens obtained can be sent for histology, cytology, microbiology, or virology, depending upon the clinical situation. When submitting samples, the endoscopist should provide the pathologist, cytologist, or microbiologist with the patient's clinical history, endoscopic findings, and questions to be answered. Access to the endoscopy report and photographs of the sampled area may also be helpful.

Polypectomy — Most polyps less than 2 cm in size can be removed endoscopically, as well as many larger polyps, although larger polyps may require referral to an endoscopist with expertise in the removal of large polyps [64]. Small polyps (≤3 mm) may be completely removed using cold biopsy forceps and appeared noninferior to cold snare polypectomy, while cold snare is preferred for larger polyps up to 9 mm [65,66]. Even larger polyps may require snare resection with electrocautery. Advanced endoscopic mucosal resection and endoscopic submucosal dissection techniques are used for large polyps (typically greater than 2 cm) (picture 12). Nearly all pedunculated polyps without invasive cancer can be removed endoscopically. If polyps are too numerous for removal, representative samples should be obtained. (See "Endoscopic removal of large colon polyps" and "Clinical manifestations and diagnosis of familial adenomatous polyposis", section on 'Clinical manifestations'.)

Endoscopists should not attempt removal of polyps beyond their skill or comfort level. In such cases, the lesion may be sampled with biopsies although this may also interfere with future attempts at endoscopic resection, the area (but not the lesion) tattooed, and the patient referred to an endoscopist with expertise in the removal of large or difficult polyps. In some cases, endoscopic removal is not possible, and surgical resection is required.

AI-assisted prediction of polyp histology — Computer-aided diagnosis (CADx) has been studied for predicting histology of small polyps in real time; however, the benefits of this investigational technology have been uncertain [67,68]. Many small polyps, especially in the distal colon, are non-neoplastic and may potentially remain in situ through use of a noninvasive method to establish a likely histologic diagnosis. Leaving such lesions in place should not affect cancer risk while potentially lowering procedure risk and cost. In a meta-analysis of 10 studies assessing CADx in 3620 patients with over 4000 small rectosigmoid polyps, CADx had a sensitivity and specificity of 87.3 and 88.9 percent, respectively, for predicting neoplastic change using histology as the reference standard [67]. In four studies comparing the accuracy of CADx with endoscopic visualization alone in 2503 small colon polyps, there were no significant differences in rates of detecting non-neoplastic polyps that could be safely left in situ (55.4 versus 58.4 percent) or in rates of missing neoplastic polyps that would be erroneously left in situ (8.2 versus 7.5 percent). As an example of one of the studies from the meta-analysis, use of CADx was compared with endoscopic visualization in 1252 patients undergoing colonoscopy [68]. There was no significant difference between methods in regard to sensitivity for predicting neoplasia in small polyps using histology as the reference (90.7 versus 90.8 percent) [68]. Among 743 small (≤5 mm) rectosigmoid polyps, CADx was associated with higher rates of identifying non-neoplastic polyps that could be left in situ (49.5 versus 47.9 percent; difference, 1.5 percentage points). However, the clinical significance of this small difference is uncertain. Future studies may help inform the application of CADx in clinical practice.

PHOTODOCUMENTATION AND REPORTING — 

All colonoscopic procedures should include a complete report detailing the extent of the colon examined, quality of the preparation, and all normal and abnormal findings encountered. Photodocumentation greatly enhances the record and should be included when possible. The following are components of a complete report [69]:

●Patient name along with the names of the personnel performing the procedure (endoscopist, nurses, assistants).

●Date and time of procedure.

●Patient's age and sex.

●Documentation of informed consent.

●Type of facility where the colonoscopy was performed.

●American Society of Anesthesiologists classification (table 6).

●Indication(s) for the procedure.

●Sedation details, including the type, dose, level of sedation, and the provider responsible for sedation.

●Extent of the examination, including reasons for an incomplete procedure, if applicable, with photodocumentation of landmarks in the cecum (appendiceal orifice, ileocecal valve, and terminal ileum, if intubated).

●Bowel preparation type, dose, and quality.

●Difficulty of the procedure, patient tolerance, and any special maneuvers required to complete the examination.

●Type of instrument used, with model and instrument number either in the procedure or nursing report.

●Colonoscopic findings with descriptions of the location, size, and morphology of lesions and whether pathology samples were obtained. For polyps, removal method, completeness of removal, whether the tissue was retrieved, and tattoo placement (if done) should be documented.

●Unplanned events or adverse events, including any interventions performed as a result. This should include immediate events and, ideally, events occurring within 30 days following the colonoscopy.

●Endoscopist's assessment based on colonoscopy findings and available clinical data.

●Documentation of communication of pathology results with the patient and referring provider(s).

●Recommendations including further tests, referrals, medication changes, and appointments.

ADVERSE EVENTS — 

The risk of serious complications following colonoscopy is low. In a review of 12 studies with 57,742 screening colonoscopies, serious harm occurred in 2.8 per 1000 examinations [70]. Over 85 percent of the adverse events occurred in the setting of polypectomy. In a second study that used a database with 2.3 million colonoscopies performed between 1997 and 2004, the overall rate of adverse events resulting in hospitalization was 1.98 per 1000 examinations [71]. A third study pooled data from 21 studies with nearly 2 million colonoscopies from 2001 to 2012 and reported perforation in 0.5 per 1000 colonoscopies, post-colonoscopy bleeding in 2.6 per 1000 colonoscopies and death in 2.9 per 100,000 colonoscopies [72].

The mortality rate related to colonoscopy is 0.007 percent [73].

However, the risk of colonoscopy is not constant across groups. Older adults are at increased risk for serious adverse events compared with younger patients. In a study of 53,220 colonoscopies, patients aged 80 to 84 years had a higher rate of serious adverse events compared with patients aged 66 to 69 years (8.8 per 1000 procedures versus 5.0 per 1000 procedures) [74]. The risk of serious adverse events was also increased among patients with comorbid conditions such as a history of stroke, chronic obstructive pulmonary disease, atrial fibrillation, and heart failure.

Adverse events related to sedation — Cardiopulmonary adverse events are the most frequent complication related to procedural sedation. Reducing the risk of sedation-associated adverse events requires appropriate anesthesia risk assessment of patients; management of high-risk patients by qualified medical personnel; appropriate monitoring before, during, and after the procedure; and delay of non-urgent procedures in unstable patients. adverse events related to procedural sedation are discussed in detail elsewhere. (See "Adverse events related to procedural sedation for gastrointestinal endoscopy in adults".)

Adverse events related to preparation — All bowel preparations can cause adverse effects, which include fluid and electrolyte disturbances, nausea, vomiting, abdominal bloating, abdominal discomfort, aspiration, and esophageal tears from vomiting. Adverse events related to the various colonoscopy preparations are discussed in detail elsewhere. (See "Bowel preparation before colonoscopy in adults".)

Bleeding — Bleeding is usually associated with polypectomy and rarely accompanies diagnostic colonoscopy [75]. The reported rates of postpolypectomy bleeding vary (typically 1 to 2 percent), with higher rates seen with the removal of larger polyps (ie, >2 cm) especially on the right side of the colon [75-82]. The risk of postpolypectomy bleeding may be increased in patients with thrombocytopenia or coagulopathies. It has been suggested that overall, endoscopists should have postpolypectomy bleeding rates of less than one percent [39]. In addition to the increased risk seen with polypectomy, the risk of bleeding is increased with other therapeutic maneuvers such as stricture dilation and endoscopic mucosal resection. (See "Gastrointestinal endoscopy in patients with disorders of hemostasis".)

Postpolypectomy bleeding may be immediate or delayed. Immediate bleeding is associated with polypectomy techniques that may occur with or without the use of cautery current polypectomy. It often is recognized during the colonoscopy, in which case it typically can be treated immediately and controlled using endoscopic hemostatic methods. If not recognized at the time of colonoscopy, it can usually be managed by a repeat colonoscopy to identify and treat the bleeding site. (See "Management and prevention of bleeding after colonoscopy with polypectomy", section on 'Immediate bleeding' and "Endoscopic clip therapy in the gastrointestinal tract: Bleeding lesions and beyond", section on 'Postpolypectomy bleeding'.)

Delayed bleeding is typically seen five to seven days after the procedure, but it has been reported up to four weeks later. It is thought to occur due to sloughing of an eschar that was covering a blood vessel or due to extension of the cautery-induced zone of thermal necrosis to non-injured tissue, which could result in bleeding if it involves a blood vessel. Patients may present with hematochezia or with melena, depending upon the location of the bleeding (bleeding from the right colon may present as melena). Delayed bleeding can often be managed with colonoscopy to identify and treat the bleeding site. (See "Management and prevention of bleeding after colonoscopy with polypectomy", section on 'Delayed bleeding'.)

Perforation — Perforations typically occur by one of three mechanisms: (1) mechanical trauma from pressure exerted by the colonoscope on the wall of the colon (often in the rectosigmoid region) or at the site of a stricture; (2) barotrauma, where pressure in the colon exceeds the bursting pressure of a colonic region (typically the cecum); or (3) from electrocautery injury during polypectomy. Perforation rates during colonoscopy vary with the procedure being performed [70,71,83]:

●Screening colonoscopy: 0.01 to 0.1 percent

●Anastomotic stricture dilation: 0 to 6 percent

●Crohn disease stricture dilation: 0 to 18 percent

●Stent placement: 4 percent

●Colonic decompression tube placement: 2 percent

●Colonic endoscopic mucosal resection 0 to 5 percent

Due to the mechanism of injury (mechanical trauma or barotrauma), perforations from a screening or diagnostic colonoscopy are typically large. On the other hand, perforations from a therapeutic colonoscopy may be small and located at the site of the therapeutic intervention, though such patients may also suffer perforations due to mechanical trauma or barotrauma.

Mortality rates from iatrogenic colonic perforation range from 0 to 0.65 percent [84]. Risk factors for perforation include advanced age, multiple comorbidities, diverticulosis, obstruction, resection of polyps over 1 cm in size that are located in the right colon, and other therapeutic maneuvers [70,71,82,85,86]. Anesthesia for sedation may increase the risk of perforation compared with moderate procedural sedation (eg, with a narcotic and benzodiazepine) [18,87]. However, other studies have not noted this association [86,88,89]. Additional risk factors for perforation include reduced mobility of the colon, existing weakness in the colon wall, previous incomplete attempt at endoscopic removal of a colonic lesion, performance of colonoscopy by a non-gastroenterologist, and endoscopist inexperience [71,86,90-93]:

●Reduced colon mobility can result from adhesions, diverticula, radiation therapy, malignancy, or infection.

●Mucosal abnormalities may occur as a result of inflammatory bowel disease, malignancy, infection, radiation therapy, necrosis, or a partial tear. These abnormalities may cause weakness in the colon wall and predispose to perforation [92].

●Endoscopists with low procedure volume have increased rates of perforation [90,91].

In general, perforation rates greater than 1 in 1000 screening colonoscopies or 1 in 500 for all colonoscopies should initiate evaluation of the endoscopist's technique [39]. (See 'Quality indicators' below.)

Techniques to decrease the risk of perforation include creating a fluid cushion by injection of submucosal fluid underneath large or flat polyps before resection, avoiding dilation in patients with significant inflammation in the area to be dilated, minimizing air insufflation during placement of a colonic stent, and avoiding colonic stent placement in patients who are or will be receiving bevacizumab [69,94]. (See "Enteral stents for the management of malignant colorectal obstruction", section on 'Stenting in the setting of adjunctive therapy'.)

Symptoms will vary depending upon the location and size of perforation, the degree of fecal seepage into the peritoneum, and the patient's comorbidities. Colonic perforation may be retro- or intraperitoneal. The ascending colon, hepatic and splenic flexures, and descending colon are retroperitoneal, whereas the distal rectum is below the peritoneum (figure 3). The most common symptom of a colonic perforation is abdominal pain. Other symptoms include fever, nausea, vomiting, dyspnea, chest pain, scapular pain, and neck pain. However, patients with retroperitoneal perforations may have minimal or atypical symptoms. The physical examination may be notable for diffuse or localized abdominal tenderness with peritoneal signs.

If perforation is suspected, immediate abdominal radiographs (plain and upright or lateral decubitus) and an upright chest radiograph should be obtained to look for free air under the diaphragm, retroperitoneal air, pneumomediastinum, pneumothorax, or subcutaneous emphysema. If plain films are normal but there is a high suspicion of perforation, an abdominopelvic computed tomography scan with water-soluble contrast should be obtained since it has higher sensitivity for detecting extraluminal air than plain films (particularly for retroperitoneal perforations) [95]. (See "Overview of gastrointestinal tract perforation".)

Management includes giving the patient nothing by mouth and starting intravenous fluids and intravenous broad-spectrum antibiotics. Surgical consultation should be obtained immediately. Large perforations typically require surgery. A minority of patients can be managed nonsurgically. Such patients have a clean colon with no signs of peritonitis and improve symptomatically over 24 hours. Usually these patients have a retroperitoneal perforation and/or sustained the perforation during a therapeutic colonoscopy. Reported success rates for nonsurgical management are variable (between 33 to 64 percent in some series) [96-98]. Successful endoscopic clip closure of perforations has been reported and may be attempted if the perforation is visualized at the time of the colonoscopy and is accessible [99,100]. However, colonoscopy is contraindicated in patients with a suspected perforation and is not used to treat perforations recognized after completion of the colonoscopy. (See "Endoscopic clip therapy in the gastrointestinal tract: Bleeding lesions and beyond", section on 'Perforations and fistulas' and "Endoscopic removal of large colon polyps", section on 'Adverse events' and "Enteral stents for the management of malignant colorectal obstruction", section on 'Stenting in the setting of adjunctive therapy'.)

Surgical treatment is indicated in patients with diffuse peritonitis, patients who deteriorate while undergoing nonsurgical treatment, and patients with a concomitant colonic lesion that requires surgery (eg, colorectal cancer) [85]. Pneumoperitoneum alone is not an indication for surgery [94].

Postpolypectomy syndrome — Postpolypectomy syndrome results from electrocoagulation injury to the bowel wall, creating a transmural burn and focal peritonitis without frank perforation. Clinical manifestations include pain, fever, focal abdominal tenderness, and leukocytosis one to five days following polypectomy. Management includes intravenous hydration, antibiotics, and bowel rest. Outpatient management has been reported in reliable patients with mild symptoms. (See "Postpolypectomy coagulation syndrome".)

Infection — The rate of infection related to gastrointestinal endoscopy is very low. Cases of hepatitis B, hepatitis C, and bacterial transmission related to defective equipment and/or breaches in protocols for proper endoscope reprocessing have been reported. (See "Antibiotic prophylaxis for gastrointestinal endoscopic procedures" and "Preventing infection transmitted by gastrointestinal endoscopy" and "Epidemiology and transmission of hepatitis C virus infection", section on 'Other percutaneous exposures'.)

Gas explosion — Gas explosion is exceedingly rare and results from the ignition of hydrogen or methane gas in the colonic lumen from use of electrosurgical energy. The gas results from an incomplete or poor preparation or from the use of incompletely absorbable carbohydrate preparations such as lactulose, mannitol, or sorbitol. The use of argon plasma coagulation (APC) for bleeding control from radiation-induced proctitis has been associated with gas explosions when enemas were used before a sigmoidoscopy or the colonoscopy preparation was poor quality [101]. A death has been reported as a result of gas explosion during colonoscopy [102].

Gas explosion has also been reported in a patient who had previously undergone colectomy for Gardner syndrome [103]. The patient was found to have rectal polyps on proctoileoscopy. The polyps were treated with APC, resulting in the explosion, with multiple rectal and ileal perforations. The patient had not received a preparation prior to the procedure.

QUALITY INDICATORS — 

The goal of applying quality indicators is to perform high-quality colonoscopy and decrease the number of missed lesions. The accuracy of colonoscopy for detecting precancerous lesions and for detecting colon cancer is discussed separately. (See "Tests for screening for colorectal cancer" and "Clinical presentation, diagnosis, and staging of colorectal cancer".)

The American Society for Gastrointestinal Endoscopy (ASGE)/American College of Gastroenterology (ACG) Quality Task Force has endorsed multiple quality indicators [1]:

●Preprocedure:

•Indications – Endoscopists should document an appropriate indication for the colonoscopy (table 1). (See 'Indications' above.)

•Bowel preparation – The quality of the preparation should be adequate to allow screening and surveillance time intervals to be followed. (See 'Photodocumentation and reporting' above and "Bowel preparation before colonoscopy in adults".)

●Intraprocedure:

•Cecal intubation rate – Endoscopists should achieve acceptable cecal intubation rates (ie, visualization of the cecum by notation and photo documentation of landmarks). The target cecal intubation rate is ≥95 percent when the procedure indication is screening in a healthy adult.

•Adenoma detection rate (ADR) – The ADR is the percentage of patients who are ≥45 years of age and undergoing colonoscopy for screening, surveillance, or diagnostic indications and who have one or more adenomas detected and confirmed by pathology. The target ADR in this patient population is 35 percent [1]. Patients excluded from ADR calculations include those with positive noninvasive screening tests (eg, stool-based testing or CT colonography), known neoplasia, genetic cancer syndromes (eg, polyposis), or inflammatory bowel disease (IBD). (See "Tests for screening for colorectal cancer".)

In addition, ADRs are based on complete examinations with adequate bowel preparation.

Studies have suggested that this target ADR is achievable for most endoscopists [104-107]. In a report from a US-based registry (GI Quality Improvement Consortium) including over two million colonoscopies, the average ADR for screening colonoscopies per endoscopist was 37 percent (44 percent in male patients and 31 percent in female patients) [107].

•Other polyp-related indicators – The sessile serrated lesion detection rate is the percentage of patients who are ≥45 years of age and undergoing colonoscopy for screening, surveillance, or diagnostic indications and who have one or more sessile serrated lesions detected and confirmed by pathology. The target sessile serrated lesion detection rate is 6 percent [1]. Patients excluded from this calculation include those with positive noninvasive screening tests, known neoplasia, genetic cancer syndromes, or IBD [1]. In the same patient population, the target number of adenomas detected per colonoscopy is 0.6.

•Withdrawal time – The target mean withdrawal time is ≥8 minutes for a normal colonoscopy in patients with normal anatomy.

●Postprocedure:

•Adverse events – A quality improvement program should track, document, and review the frequency of serious adverse events (eg, perforation, post-polypectomy bleeding, mortality) associated with colonoscopy.

•Follow-up – Endoscopists should communicate and document recommendations for follow-up screening and surveillance intervals. (See "Overview of colon polyps".)

Surveillance colonoscopy and management of dysplasia in patients with inflammatory bowel disease are discussed separately. (See "Surveillance and management of dysplasia in patients with inflammatory bowel disease".)

SOCIETY GUIDELINE LINKS — 

Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Colon polyps".)

INFORMATION FOR PATIENTS — 

UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Colonoscopy (The Basics)")

●Beyond the Basics topics (see "Patient education: Colonoscopy (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Indications – Colonoscopy includes visualization of the rectum, colon, and the distal portion of terminal ileum, with real-time assessment and interpretation of the findings encountered. (See 'Introduction' above.)

Colonoscopy is indicated for the diagnostic evaluation of signs and symptoms of a wide variety of gastrointestinal disorders, for colon cancer screening, and for therapeutic interventions (table 1 and table 7 and table 8). (See 'Indications' above.)

●Patient preparation – Preparation for colonoscopy typically involves the ingestion of a low-residue diet or clear liquids for at least one day prior to the examination, combined with an oral bowel preparation. Most medications may be continued up to the time of colonoscopy, but management of antiplatelet agents and anticoagulants must take into account the procedure-related risk of bleeding and the risk of thrombosis. (See 'Patient preparation' above and "Management of antiplatelet agents in patients undergoing endoscopic procedures" and "Management of anticoagulants in patients undergoing endoscopic procedures".)

●Equipment – Routine colonoscopy is performed using a high-definition white-light colonoscope. Multiple accessories are available to aid with diagnostic and therapeutic maneuvers. In addition, options are available to enhance visualization during colonoscopy (eg, chromoendoscopy), although many require specialized equipment and training. (See 'Equipment' above.)

●Tissue sampling and interventions – A variety of diagnostic and therapeutic maneuvers can be performed during colonoscopy. The most common maneuver is tissue sampling, including routine polypectomy. (See 'Diagnostic and therapeutic maneuvers' above.)

Other common interventions include:

•Endoscopic hemostasis

•Dilation of colonic strictures

•Stent placement for malignant disease

•Endoscopic mucosal resection and endoscopic submucosal dissection of large colonic polyps

●Adverse events – Serious adverse events of colonoscopy are rare (approximately 3 per 1000 screening colonoscopies) and include sedation-related events, bleeding, and perforation. (See 'Adverse events' above and "Adverse events related to procedural sedation for gastrointestinal endoscopy in adults" and "Bowel preparation before colonoscopy in adults".)

Bleeding is usually associated with polypectomy and rarely accompanies diagnostic colonoscopy. Postpolypectomy bleeding occurs in approximately 1 to 2 percent of polypectomies, with higher rates seen with the removal of larger polyps. Patients may present with hematochezia or melena days to weeks after the colonoscopy. The majority of patients can be managed with a repeat colonoscopy to both identify and treat the source of bleeding. (See 'Bleeding' above and "Management and prevention of bleeding after colonoscopy with polypectomy".)

Perforation rates vary with the procedure being performed, with rates of 0.01 to 0.1 percent for screening colonoscopy. The most common symptom of a colonic perforation is abdominal pain. Other symptoms include fever, nausea, vomiting, dyspnea, chest pain, scapular pain, and neck pain. However, patients with retroperitoneal perforations may have minimal or atypical symptoms. The physical examination may be notable for diffuse or localized abdominal tenderness with peritoneal signs. (See 'Perforation' above.)

If perforation is suspected, immediate abdominal radiographs (plain and upright or lateral decubitus) and an upright chest radiograph should be obtained. If plain films are normal but there is a high suspicion of perforation, an abdominopelvic computed tomography scan with water-soluble contrast should be obtained. All patients with perforations should receive intravenous fluids and broad-spectrum antibiotics. Many patients with perforations will require surgery, though nonsurgical management may be possible in those with small perforations without evidence of peritonitis.