Following ASGE 2012 guidelines (ASGE Standards of practice committee 2012), colonoscopy is generally indicated in the following circumstances:

Informed consent must be obtained from the patient before performing the procedure. It must be a clear discussion about risks, benefits, and alternative to the procedure. Common risks of colonoscopy such as perforation, bleeding, infections, sedation-related adverse events, missed lesions, and intravenous site adverse events must be discussed. If an operative procedure is planned, the patient must be informed about the specific risks related to the scheduled procedure.

The management of patients under therapy with anticoagulant and/or antiplatelet agents before and after an endoscopic operative procedure must be carefully evaluated. In order to decide whether to continue or discontinue these therapies it’s critical to stratify the risk continue or discontinue these therapies is fundamental the stratification of the risk of bleeding of the endoscopic procedure scheduled and the risk of a thromboembolic event related to interruption of these drugs in accord with the patient’s consultant (e.g., cardiologist/neurologists) or treating physician.

The anticoagulants include: warfarin, heparin, low molecular weight heparins (LMWH), and, more recently, the new direct-acting oral anticoagulants (DOAC).

The antiplatelet agents (APA) are aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), thienopyridines (e.g., clopidogrel, prasugrel, and ticlopidine), and inhibitors of the receptor GPIIb/IIIa.

Recommendations of ASGE/ESGE (Boustière et al. 2011; ASGE Standards of Practice Committee 2009) are summarized in Table 15.1.

Bowel preparation is crucial for the outcome of colonoscopy and for a high-quality examination, improving adenoma detection rate and reducing costs, lowering the rate of rescheduled examinations due to inadequate preparation (Harewood et al. 2003; Froehlich et al. 2005; Rex et al. 2002b).

Some endoscopists prescribe a low-fiber diet during the 3 or 5 days preceding colonoscopy, but the benefits of this diet have not been well assessed. Based on literature data, a low-fiber diet the day before the examination seems to be enough. In order to reduce the presence of bubbles and foam, which are frequently encountered during colonoscopy (32 %–57 % of patients), the addition of simethicone to the bowel preparation is useful, which reduces the surface tension of air bubbles and improves endoscopic view (Hassan et al. 2013; Tongprasert et al. 2009; Shaver et al. 1988).

Actually the three widely accepted bowel preparations for colonoscopy are:

Sulfate-based solutions: magnesium is a well-known traditional laxative which increases water in the gastrointestinal tract and stimulates peristalsis. A combination of magnesium sulfate and sodium picosulfate (Picoprep or Citrafleet) was compared with PEG and sodium phosphate-based solutions in a meta-analysis showing that PEG provided a satisfactory colon cleansing in a similar proportion of patients, with less adverse events such as nausea, vomiting, or abdominal pain, but sodium phosphate produced better cleansing than magnesium sulfate and sodium picosulfate (Tan and Tjandra 2006). An adequate oral intake of water during preparation is essential. Given the potential for dehydration and dangerous hypermagnesemia, this combination is relatively contraindicated in the presence of congestive cardiac failure and impaired renal function.

Other nonabsorbable sugars like mannitol, sorbitol, and lactulose are ineffective and must be avoided because they may be metabolized by colonic bacteria carrying the risk of colonic explosion during procedures requiring electrosurgery.

Sedation and analgesia are usually recommended in order to improve examination quality, reduce procedure time, and minimize discomfort during colonoscopy. The reasons to use sedation and analgesia during colonoscopy are the possible pain caused by the procedure and patient’s anxiety. The level of sedation can be generally considered on a spectrum from no sedation to general anesthesia. The choice of the level of sedation depends on patient comorbidities, complexity of the procedure, discomfort expected or experienced, and availability or unavailability of the anesthesiologist. All patients that undergo colonoscopy must be under continuous monitoring before, during, and after sedation with pulse oximetry and for high-risk patients with hemodynamic measurements and continuous electrocardiogram.

The level of sedation most frequently used is conscious sedation that could be reached using benzodiazepines and centrally acting narcotic opioids, such as meperidine or fentanyl. This sedation aims at maintaining the patient’s collaboration for all the time requested to complete the procedure with drug-induced depression of consciousness, during which the patient responds purposefully to verbal commands, either alone or accompanied by light tactile stimulation. Usually the patient breathes spontaneously, without assisted ventilation. Oversedation, hypoventilation, aspiration, and airway obstruction are the most commonly reported sedation-related complications (Freeman 1994; Benjamin 1996). Elderly patients and subjects with compromised renal and hepatic functions may be at a greater risk of adverse events. One advantage of the use of conscious sedation with benzodiazepine and opioids is the possibility, in case of oversedation or in the presence of adverse event, to use narcotics and benzodiazepines antagonists such as naloxone and flumazenil. Conscious sedation does not require the presence of an anesthesiologist, but the endoscopist must be well trained in the management of complications of sedative drugs. After colonoscopy patients must be monitored in a recovery room for 30–60 min and can return to normal activities on the next day.

Some endoscopists perform unsedated colonoscopy in order to reduce the risk of sedation-related complications and costs, but the pain associated with colonoscopy can affect the quality of the examination and the patient’s compliance. It has been demonstrated that for unsedated colonoscopy, the experience of the endoscopist is fundamental. Recently, to reduce pain of scope insertion caused by stretching of intestinal wall, carbon dioxide (CO₂) insufflation, water immersion (WI), and water exchange (WE) techniques have been proposed.

Many studies on colonoscopy insertion demonstrated that WI and WE techniques reduce insertion pain when compared to air or CO₂ insufflation. The least painful technique was WE with increased completion of unsedated colonoscopy (Hsieh et al. 2014; Amato et al. 2013; Bretthauer 2010; Garborg et al. 2015).

For painful or prolonged procedures or for patients intolerant to colonoscopy under conscious sedation, deep sedation based on the use of propofol, a hypnotic drug, is commonly used. Deep sedation is defined as a drug-induced depression of consciousness, during which the patient cannot be easily aroused but responds purposefully to repeated or painful stimulations. Patient’s spontaneous ventilation is usually maintained, but sometimes ventilation assistance may be required. Deep sedation with propofol during colonoscopy is associated with improved patient’s and physician’s satisfaction, because of its rapid onset and action (induces sedation within 30–60 s), its amnesic properties, and its short context-sensitive half-life of 2–8 min. For these reasons, it is considered an attractive drug for colonoscopy. Propofol can be administrated as monotherapy or in a combination with opioids and benzodiazepine. When used in combination, total dose of propofol can be reduced. Propofol may cause respiratory depression, apnea, or hypotension. Moreover, in 14 % of patients tremors, twitches, hypertonus, and hiccups can occur. Pulmonary edema, hypertension, cardiac arrhythmias, bronchospasm, or laryngospasm happens more rarely. For this reason, monitoring and managing the airway and breathing is more critical and requires the presence of anesthesiologists with additional costs.

Quality indicators for colonoscopy (Rex et al. 2015) are summarized in Table 15.2.

For a high-quality colonoscopy, it is essential to refer to the correct principles of technique. This is essential not only to improve the technical quality of the examination but also to eliminate or minimize visceral pain during the exam. Basic rules of colonoscopy involve proper anterograde push of colonoscope, precise movements of the tip, constant identification of the bowel lumen, appropriate twist on the instrument’s longitudinal axis, and controlled suction.

The discomfort caused by colonoscopy is mostly dependent by the stretching of the mesenteric supports of the colon and, to a lesser extent, by the distension due to the air blown in the colon. Elder patients are more tolerant of the curves and twists caused by the colonoscope because the elasticity of the mesentery rises with age, while women, due to the lower abdominal area in which the colon and the angle are located that the sigmoid presents between the uterus and left inguinal area, are generally subject to more frequent traction and straightening of the mesentery, resulting in increased tenderness.

Despite the considerable individual variability, definitely the presence of loops causes pain. That is why this examination, according to a correct technique based on frequent retraction movements, aims to keep the endoscope as straight as possible, reducing the probability of marked tenderness.

Colonoscopy may be conducted by only one endoscopist that holds the instrument with his right hand, while his left hand handles the controllers on the chassis, or the doctor who commands with both hands grips the endoscope and the assistant (usually the nurse) that pushes and rotates the instrument. Most experts believe that the first option is preferable because it allows you to have a greater sensitivity about the thrust force applied, and it allows you to correct any loops as well as greater readiness to overcome difficult stretches as stenosis, particularly curves angled or rigid segments with greater caution. Only in certain moments, which require mandatory concurrent use of both knobs, the instrument is held by the assistant.

Most endoscopists use the left lateral decubitus position as a start position for the colonoscopy, although some prefer the supine position and very few the right side. A careful inspection of the perianal region and a digital exploration of the rectum should precede the introduction of the colonoscope. This procedure allows a lubrication of the anal canal, the evaluation of the sphincter tone, and the exclusion of pathological conditions such as the presence of fistulous orifices, leakage of secretions or blood, presence of palpable stenosis, etc. The colonoscope is then inserted through the anus gently holding it at about 10 cm from the tip.

Once distended the distal rectum by inflation and aspirated residues, a retroflection maneuver should be performed carefully to inspect the rear portion of the mucosa immediately above the dentate line as small lesions at this level cannot be detected in front view only. The left lateral decubitus position is more favorable to give a great exposure of the distal rectum. The rear view is performed by angling to the maximum the tip of the colonoscope while it is introduced and displacing it gently sliding along one of the side walls so turning the optics toward the internal anal orifice. This maneuver can easily lead to traumatic injuries of the mucosa and should be done with caution. If the operator encounters difficulties during the retroversion of the instrument, it is good practice to desist in order to avoid complications and observe carefully the distal rectum by front view only.

Once the rectum is explored, the progression through the sigmoid colon, the descending colon, and the splenic flexure is probably the most delicate moment of the procedure and is usually being associated with the formation of loops and onset of pain. The endoscope is advanced using a minimum thrust associated with slight movements of clockwise and counterclockwise torque impressed to the instrument by endoscopist’s right hand. This avoids having to use too often the right/left knob and makes the insertion more fluid. The direction of the intestinal lumen can be identified thanks to some details such as folds convergence, presence of a less illuminated or “shadow” area on the visual field, the observation of transverse haustral folds and small translucent interhaustral lines, or the identification of a single longitudinal fold introflexed in the lumen formed by one of the three taeniae coli. For each curve, it is necessary to exactly locate the direction of the lumen and preferentially rotate the instrument positioning the tip in the upper part of the visual field (12 h). The tip must be angulated and slightly anticipating the thrust movement. If the lens is found in direct contact with the mucosa, it is essential to retract the instrument until the lumen is seen again, identifying the right lumen direction.

Some sigmoid corners are angled to the point that their overcoming must be performed “blindly.” In these cases, the endoscopist must be extremely confident on the lumen direction and should push the endoscope using gradually the maximum angulation of the tip. During this maneuver, small translations from the axis of the curve must be corrected by locating mentally the lumen direction and consequently turning the instrument. After having passed a good part of the curve, a full rotation of the right/left knob can be associated to increase the angle of the tip and to facilitate the transition.

To aspirate residual fluids, it is convenient to place them at 6 o’clock position and aspirate while blowing air, thus preventing complete collapse of the bowel wall and unwilling suctions of the mucosa.