Robert E. Sedlack

Mayo Clinic, Rochester, MN, USA


All trainees in gastroenterology must acquire competence in the basic endoscopic procedures of esophagogastroduodenoscopy (EGD) and colonoscopy. Though some skills learned in EGD may translate to colonoscopy, overall the skills required for colonoscopy are more technically demanding and require more time to achieve competence. This chapter focuses on the specific skills required in colonoscopy, how best to teach/learn these skills, and methods to assess competence in each of these skills.

Specific skills

The skills required in colonoscopy can be broken down into two main groups: motor and cognitive skills. Traditionally, the focus of many previous colonoscopy‐training chapters published has been almost exclusively on the motor skills. However, the cognitive skills are just as, if not more, important. In this chapter, we will try to address both skill sets.

These two skill groups can be broken down further into “early” and “intermediate” skills as shown in Table 6.1. It is well established in the surgical literature that the most effective method for teaching any technical procedure is to deconstruct the overall procedure down into individual core skills [1]. These skills can then be taught in a stepwise fashion, from the most basic toward the more complex, building on one another. Colonoscopy is no different. These beginning and intermediate skills are simply the skills required to complete routine screening colonoscopy safely and reliably. More advanced endoscopic skills such as complex polypectomy and hemostasis techniques will be covered in other chapters in this text. Depending on how a training program is structured, many trainees will have performed a fair number of EGDs prior to attempting colonoscopy and may have some basic mastery of a few of the early skills such as how to hold a scope correctly and use of the scope controls. Many of the other early skills, however, are specific to lower endoscopy, hence even with some EGD experience, these specific skills will be quite new.

These skills should not be confused with the metrics used to assess competency. Though these skills are an integral part of those metrics, the latter includes additional parameters such as cecal intubation times and success rates, withdrawal times, and polyp detection rates, as well as many others that will be discussed later.

Early skills

Early cognitive skills

Before a fellow attempts a colonoscopy for the first time, there needs to be a fundamental understanding of the colonic anatomy, basic elements of the colonoscopy exam, indications/contraindications for performing such an exam, the risks and benefits of the exam, and finally preparation and sedation. This section will focus on each of these issues.


c06i001 The colonic anatomy can be broken down into various segments, each with some defining characteristics that can help the endoscopist keep track of the scope’s location in the colon (Figure 6.1) (Video 6.1). The anal canal is lined with squamous mucosa. Inside the internal sphincter and puborectalis muscles, the anus transitions to the rectum at the dentate line. This line represents the transition between the anal squamous mucosa and the columnar epithelium found throughout the intestines and stomach (Figure 6.2). The rectum progresses posteriorly in the retroperitoneum. Within the rectum, there are three semicircular folds called the valves of Houston (Figures 6.2 and 6.3). These folds differ from the rest of the colon in that they are not circumferential but rather span roughly 50% of the circumference of the lumen. At the peritoneal reflection, the colon leaves the retroperitoneal space and moves into the peritoneum. At this reflection, the sigmoid colon begins and deflects anteriorly, inferiorly, and to the left in the peritoneal space. This portion of the colon varies in length and configuration from one individual to the next and accounts for a majority of the looping and difficulty with scope advancement encountered during colonoscopy, due to its mobile and circuitous nature. As one moves more proximally, the sigmoid continues toward the left flank and again progresses posteriorly to its junction with the descending colon. The descending colon rises up the left posterior abdomen in a fairly straight manner. This segment of the colon, along with the ascending colon, is partially fused to the posterior peritoneum along the colonic gutters and as a result is relatively nonmobile. In rare instances, however, these segments may be freely mobile, making endoscopic advancement quite difficult. At the splenic flexure, the colon acutely deflects anteriorly and to the right, marking the transition between the descending colon and the transverse colon. Like the sigmoid, the transverse colon is mobile in the peritoneal space attached only by the mesentery. It too can be quite variable in length and redundant, leading to difficult scope advancement. The lumen of the transverse colon also differs from the other segments of the colon in that the three tinea coli running the length of the colon produce a triangular appearance as opposed to the circular appearing folds elsewhere in the colon (Figure 6.4). As the transverse colon sweeps to the right side, it again moves posteriorly, and at the hepatic flexure, the colon deflects posteriorly and downward, becoming the ascending colon. This segment is normally fixed to the right posterior gutter of the peritoneal cavity. At the hepatic and splenic flexures, external organs such as the liver or spleen can often be seen through the wall of the colon as bluish‐gray discoloration (Figure 6.5). The ascending colon proceeds down along the right posterior flank to the cecum. The cecum marks the most proximal portion of the colon and is the location where the three tinea coli come together along the external surface of the colon and meet at the appendix. From the luminal view, this appears in the cecal base as three longitudinal folds coming together adjacent to the appendiceal orifice (Figure 6.6). These folds are often referred to as the “crow’s foot” or “Mercedes sign” as it resembles the clawed foot of a crow or the emblem of the well‐known automaker. The cecum transitions to the ascending colon at the level of the ileocecal valve that rests on the first major haustral fold above the appendiceal orifice. The valve can be identified by the asymmetric prominence of this first fold and with careful inspection, torque, and dial control, the valve os can be directly visualized and intubated.

Table 6.1 Listed are the core motor and cognitive skills trainees must acquire to be minimally competent in colonoscopy. These are broken down into early and intermediate skills to ensure the foundation of basic skills is established before building upon this with more complex abilities.

Motor Cognitive

  • Correct holding of the scope
  • Use of the scope controls
  • Scope insertion
  • Scope advancement

    • Basic tip control
    • Torque steering

  • Lumen identification
  • Withdrawal/mucosal inspection

  • Anatomy
  • Preparation
  • Scope selection
  • Sedation management
  • Assessment of indication and risks

  • Loop reduction

  • Pathology identification

  • Angulated turns

  • Therapeutic devices

  • TI intubation

  • Complication management
Schematic illustration of colon anatomy.

Figure 6.1 Colon anatomy. This illustration demonstrates the anatomy of the colon.

(Copyrighted and used with permission of Mayo Foundation for Medical Education and Research.)

Schematic illustration of rectal anatomy.

Figure 6.2 Rectal anatomy. Just inside the anal sphincter muscles, the dentate line marks the transition from the squamous mucosa lining the anal canal to the columnar epithelium of the rectum. The rectum is notable for its semilunar (half‐circle) folds called the Valves of Houston.

(Copyrighted and used with permission of Mayo Foundation for Medical Education and Research.)

Photo depicts endoscopic view of the rectum.

Figure 6.3 Endoscopic view of the rectum. This endoscopic view shows the semilunar folds of the rectum (Valves of Houston).

Basics of endoscopic anatomy

Endoscopists use anatomical landmarks to help them identify where their scope is at any given point of the procedure to ensure pathology is correctly located for the purposes of documenting disease extent, for future re‐examination, or for locating pathology for possible surgical intervention. Another method to identify location is by checking the scope length markings at the anal verge. These markings will inform the endoscopist how many centimeters of scope are inside the patient. However, relying on the scope length from the anal verge is unreliable, especially in the right colon where variances in the anatomic length of an individual’s colon segments can lead to marked variability. Also, using the scope markings during the insertion phase of the exam is also prone to substantial error as looping can greatly increase the length of scope inserted and greatly alters the reliability of these numbers as they correlate to the location. As a rule, these numbers are only used as a crude estimate of the location, typically only in the left half of the colon and only during the withdrawal phase of the exam. Instead, the anatomical landmarks of the colon are in general more reliable markers of the location than scope depth.

Photo depicts endoscopic view of the transverse colon.

Figure 6.4 Endoscopic view of the transverse colon. The transverse colon is easily identified by the triangular appearance of the lumen. Externally, the tinea coli are located at the apexes of the triangular folds.

Photo depicts endoscopic view of the hepatic flexure.

Figure 6.5 Endoscopic view of the hepatic flexure. At the splenic and hepatic flexure, the purplish hue of the spleen or liver can often be seen through the wall of the colon.

Photo depicts endoscopic view of the cecum.

Figure 6.6 Endoscopic view of the cecum. This view of the cecum demonstrates the small semilunar os of the appendiceal orifice (AO) as well as the indentations of the tinea coli coming together externally to make up the “Crow’s foot (CF).” The ileal–cecal valve (ICV) can be seen at the thickening of the first major fold above cecal base.

The major landmarks during withdrawal start with the appendiceal orifice, crow’s foot, and ileocecal valve of the cecum. The next major landmark is the acute angulation in the colon with the purplish hue of the liver representing the hepatic flexure. The triangular folds of the transverse colon make it readily identifiable. At the distal end of the triangular lumen is a second acute angulation with a purplish hue of the spleen, which signifies the splenic flexure, and is located at roughly 50 cm from the anal verge. Just past this acute turn, one often encounters a collection of retained liquid stool that collects at this point as the proximal segment of the descending colon is the most gravity‐dependent portion of the colon with the patient in the left lateral decubitus position. The descending colon is marked by a long straightaway from roughly 50 to 30–35 cm from the anal verge, followed by a number of acute turns and the more muscular haustra of the sigmoid colon. The rectosigmoid junction is located at roughly 15 cm from the anal verge. Distal to the junction, the rectum is identified by the increase in lumen caliber and the three prominent semilunar folds called the valves of Houston (Figure 6.3). The dentate line is seen on retroflexion in the rectum.


One of the most important steps in a successful colonoscopy is adequate cleaning of the colon. Without this, polyp detection or pathology identification may be hindered and adequate visualization to enable safe scope advancement may not be possible.

There are a number of different methods that have been used to prepare the colon. These fall under two main groups: osmotic and nonosmotic agents. Ingestion of highly osmotic agents, such as sodium phosphate, magnesium citrate, or mannitol, function by creating a large osmotic gradient between the bowel lumen and interstitial tissue, resulting in a large influx of fluid from the bowel lining into the lumen. This fluid is then passed, cleansing the colon in the process. These agents have been used successfully; however, they do have significant drawbacks that have led to limitations or even the discontinuation of their use in some instances. As a group, the osmotic agents result in large intravascular and intracellular fluid shifts. In healthy individuals, symptoms of dehydration are not uncommon, however, in patients with significant heart or renal disease, these fluid shifts can lead to significant heart failure or worsening of renal function. Additionally, magnesium citrate and sodium phosphate result in some absorption of their elements and can lead to dangerous elevations of magnesium or phosphate in patients. This is especially true in the elderly or patients with renal insufficiency. Mannitol, on the other hand, is a nondigested carbohydrate and does not get absorbed, which would limit the problem of electrolyte disturbances; however, colonic bacteria can metabolize this carbohydrate, leading to the production of methane and hydrogen gases within the colon. Not only do these gases lead to distention and greater patient discomfort but they are also extremely flammable and can lead to combustion with the use of electrocautery during polyp removal.

Lavage of the colon using nonosmotic agents has become the most common method of preparation. These agents use various preparations of polyethylene glycol (PEG) in electrolyte solutions. Like mannitol, PEG is a nondigestible and nonabsorbable molecule; however, it cannot be fermented by colonic bacteria. PEG preparations are formulated so that concentrations of electrolytes and PEG are isoosmotic to patients’ interstitial fluids. This results in no significant fluid shifts in either direction, leaving the patient’s fluid status largely unaffected by the preparation with no dangerous electrolyte imbalances. This makes PEG a safer alternative to cleanse the colon, especially in patients with cardiac or renal disease. The strengths of these PEG preparations, however, are also their weaknesses. Since there is no fluid recruitment from the patient’s interstitial fluid as seen with the osmotic agents, the entire volume of cleansing fluid must be ingested. This requires drinking large volumes of solution to achieve the preparation goals. These solutions are generally not very palatable, also limiting the tolerability of these. For many years, PEG‐based preparations consisted of 4 liters of solution taken the night before a procedure; however, preparations are now commonly split into two 1‐liter doses, one taken the night before and the second the morning of the procedure. Split‐dose preparation has been found to be superior in cleansing the colon and better tolerated and is currently the recommended method. Other variations have tried to reduce the volume of PEG solution needing to be ingested by concentrating the solution into a smaller volume followed by drinking a predetermined amount of free water or placing PEG in capsules, so the patient does not have to taste the medication. This pill preparation, however, requires ingesting >30 capsules over a short period of time and still requires ingesting large amounts of water or clear soda to provide the fluid volume needed to clean the colon and ensure an isoosmotic concentration in the intestines. Despite these drawbacks, PEG preparations still remain the safest, most effective, and most commonly used preparations.

Scope selection

One decision that needs to be made prior to initiating endoscopy is what instrument to use. There are a number of different types of endoscopes in the gastroenterologist’s armamentarium that can be selected to perform lower endoscopy. These include the standard adult colonoscope, pediatric colonoscope, flexible sigmoidoscope, or even a gastroscope that is dedicated to lower procedures (Figure 6.7). Understanding the advantages/disadvantages of each is an important cognitive skill that can improve one’s chances of successfully achieving the goals of a lower endoscopy.

In general, the standard adult scope is slightly larger in diameter than the other scopes (measuring roughly 13 mm in diameter) and is one of the most commonly used scopes for colonoscopy. Its thickness results in it being somewhat stiffer than the others. As a result of being slightly stiffer, it tends to loop less than other scopes, especially in patients with a very mobile sigmoid or redundant transverse colon. By the same token, its larger diameter and decreased flexibility can also make it more difficult to navigate through fixed, sharply angulated colons. Such fixation and angulation can be seen in patients with prior abdominal or pelvic surgeries (hysterectomy, C‐sections, etc.), prior radiation, or significant prior peritoneal infection (ruptured appendix or other infection). In these patients, a pediatric scope can sometimes succeed in navigating through a difficult fixed sigmoid where an adult scope could not. This is primarily due to the greater flexibility of this scope resulting from its smaller diameter (11.5 mm diameter). In a long redundant, highly mobile colon, however, this flexibility can result in excessive proximal looping, requiring greater experience and skill to advance the scope to the cecum.

Photo depicts endoscope options. Four different endoscopes can be used for lower endoscopy.

Figure 6.7 Endoscope options. Four different endoscopes can be used for lower endoscopy. Depicted here are: (A) adult colonoscope (13.2 mm diameter), (B) pediatric colonoscope (11.5 mm diameter), (C) sigmoidoscope (12.8 mm diameter), and (D) gastroscope (9.2 mm diameter). The diameter of the endoscope may vary slightly based on the manufacturer.

Gastroscopes are also used in special circumstances for lower endoscopy. Because of their smaller caliber (9.2–9.8 mm diameter), gastroscopes are ideal for lower endoscopy of an ileostomy or in a patient with an ileoanal pouch. The smaller diameter is also useful in patients who have left‐sided colonic strictures (within reach of the shorter gastroscope) that prevent the passage of either of the larger colonoscopes. For routine colonoscopy, however, these scopes loop quite a bit due to their flexibility and their short length prevents them from reaching the cecum in most cases.

Flexible sigmoidoscopes are useful if only the left colon is to be examined. Traditionally, this was the primary method for routine colon cancer screening when paired with testing such as a barium enema or fecal occult blood testing to screen the remaining colon for malignancies. For this purpose, however, colonoscopy has largely replaced flexible sigmoidoscopy (FS). FS is still useful in evaluating the severity of a flare of known ulcerative colitis, suspected ischemic or infectious colitis, to obtain colon biopsies in suspected microscopic colitis, or to evaluate radiographic abnormalities seen in the left colon.

Learning when to use each scope is a skill that comes with guidance and experience and can vary from one individual to another. Just as a golfer learns which club he/she can use most effectively in given circumstances, the endoscopist too must develop an understanding of which scope they can best employ from one case to the next. When a particular type of scope is preferred for a procedure, trainees should get in the habit of including that request at the time of booking, to better ensure that it will be available in the endoscopy unit when it is time to perform the case.


From the patient’s perspective, sedation and analgesia are two of the most important issues linked to procedure satisfaction. Considering that success of colonoscopy as a screening exam relies on serial evaluations at least every 10 years, a patient’s avoidance of pursuing repeat evaluations due to prior bad experiences can lead to potential premalignant lesions or other disease going undetected and advancing to more serious disease. Sedation, analgesia, and patient monitoring in endoscopy are covered in greater detail in another chapter of this text. In general, the use of a benzodiazepine (midazolam or diazepam) in combination with analgesia (meperidine or fentanyl) provides adequate conscious sedation for lower endoscopy. These agents work synergistically in providing sedation while the benzodiazepine provides an added amnestic effect. However, in some instances, deeper sedation may be needed. Propofol or even general anesthesia can be used for these patients.


All trainees need a solid understanding as to when a colonoscopy should be performed, and perhaps more importantly when it should be avoided. One of the most common indications for a colonoscopy is as a screening exam for colorectal cancer. In the general population, these exams traditionally begin at the age of 50 years and if normal, every 10 years thereafter. In 2018, the American Cancer Society has recommended moving this initial screening to 45 years old, which may prompt other societies to follow suit. If a few small polyps are found on a screening exam, this surveillance interval is shortened to 3–5 years depending on the findings. Certain other indications, such as more numerous polyps, larger polyps, advanced dysplasia, villous architecture, or hereditary polyposis syndromes, can result in initiating early screening before the age of 50 or shorten the next interval even further to 1–3 years. In the case of particularly large or advanced polyps, a follow‐up examination in 3 months may be required to ensure complete resection of the lesion. Screening guidelines are frequently updated and every endoscopist must keep current with the most recent recommendations. These guidelines can typically be found online at professional society web sites such as the American Society for Gastrointestinal Endoscopy (ASGE), American College of Gastroenterology (ACG), or American Gastroenterology Association (AGA) [2, 3].

Other indications for colonoscopic examination are primarily symptom driven. Of these, suspicion for GI bleeding (iron‐deficiency anemia, positive stool occult blood tests, or even frank hematochezia) is likely the most common cause for lower endoscopy [4]. A change in bowel habits (stool caliber, constipation, or chronic diarrhea), suspicion of inflammatory bowel disease, abdominal pain, and abnormal radiographic imaging studies are all common indications to pursue colonoscopy as well. Other less common causes include foreign body removal, volvulus reduction, or decompression of colonic pseudo‐obstruction.

As stated earlier, there are times when it is not safe to proceed with colonoscopy. These include recent colon surgery, recent myocardial infarction (MI), the presence of severe colitis, supratherapeutic anticoagulation, or the presence of hemodynamic instability [4]. It is advised to delay colonoscopic exam for 3 months following colonic surgery, such as a new stoma or other colonic anastomosis. In the case of a recent MI, there are no specific guidelines regarding this. For elective procedures, one should wait until well after the event and base timing on the patient’s clinical status. Emergent colonoscopy for gastrointestinal bleeding following an MI has been studied. Though there is roughly a ninefold increase in complications (9% vs. 1%), these complications are usually minor and generally the patients benefit more from the timely intervention of bleeding [5]. These are all relative contraindications and earlier exams can be performed if clinically required. In “severe” colitis (as can be associated with infections, Crohn’s, ulcerative colitis, or ischemic colitis), it is generally advised to reduce the colonic inflammation before proceeding with endoscopy; however, limited exams can be indicated if the cause of colitis is unclear or to monitor the response to therapy. Mild to moderate colitis typically do not pose a contraindication to colonoscopy. For patients on anticoagulation therapy (such as warfarin, clopidogrel, or aspirin), institutions vary with the level of acceptable risk, but in general, low‐risk diagnostic exams can likely be safely performed on some level of therapeutic‐range anticoagulation [6]. Therapeutic measures (such as biopsy or polypectomy) may require lower anticoagulation thresholds or even discontinuation of therapy prior to colonoscopy for safety reasons. Endoscopy should be delayed if levels of anticoagulation are supratherapeutic. Trainees should read and remain current on published guidelines on the practice of endoscopy for patients taking anticoagulation medications, which are available online at

Early motor skills

How to hold scope

The scope handle is held in the left hand with the umbilical cable that connects to the video processor resting between the thumb and index finger (Figure 6.8) and extending on the outside of the forearm. The base of the scope handle is held between the palm and the fourth and fifth digit. The left elbow is bent in a comfortable position to allow the arm to carry the weight of the scope for long periods of time. The right hand holds the shaft of the scope and is kept within 20–30 cm from the anal opening to allow maximum control of the shaft. The shoulders would be in a comfortable position and the height of the bed should be at a level that allows the endoscopist to stand with the hips and back straight to avoid overuse of the back muscles. In this position, the right elbow should also be bent at roughly 90°. Trainees need to be instructed early on how to correctly set the height of the bed, proper posture, and position of the arms. Improper posture or form can lead to muscle fatigue and chronic musculoskeletal problems over an endoscopist’s career [7].

Scope dials

On the medial side of the scope, there are two dials with sprockets (Figure 6.9). These dials control the deflection of the flexible scope tip and are used to steer the scope during advancement and to direct the video camera’s field of view during mucosal inspection on the withdrawal phase of the exam. The large inner dial deflects the scope tip up (counterclockwise dial rotation) and down (clockwise). The smaller, outer dial controls left (clockwise) and right (counterclockwise) tip deflection. Since the orientation of the camera in the scope’s tip is fixed in relation to the control mechanisms, the direction of tip deflection is always in relation to the video image on the display monitor, regardless of how the scope is torqued. Ideally, both dials are controlled with the left thumb, but as you will see later, the smaller dial is used less frequently as most steering directions can be achieved with rotation of the scope and the up/down control alone (referred to as torque steering).

Photo depicts the proper manner in which to hold a colonoscope. (a) The scope is held in the left hand with the cable exiting posteriorly between the thumb and index finger. (b) The handle is held with the fourth and fifth digits freeing the thumb and remaining fingers to operate the controls.

Figure 6.8 How to hold the scope. These images demonstrate the proper manner in which to hold a colonoscope. (a) The scope is held in the left hand with the cable exiting posteriorly between the thumb and index finger. (b) The handle is held with the fourth and fifth digits freeing the thumb and remaining fingers to operate the controls.

Photo depicts scope dials.

Figure 6.9 Scope dials. The colonoscope’s dials are shown here. The large inner dial deflects the scope tip up or down as indicated by the arrows. Similarly, the small outer dial deflects the scope tip left or right.

Next to these dials there are two levers that can be used to lock their respective dial in place in order to hold the scope tip in a deflected position and free up the endoscopist’s hands during therapeutic maneuvers. In general, however, it is important to remember that during the scope advancement or withdrawal, these dials should be “unlocked” in order to reduce the risk of colonic perforation due to a rigid scope tip.

Photo depicts scope valves.

Figure 6.10 Scope valves. The top “red” valve activates the scope’s suction when pressed. The “blue” valve controls air insufflation when lightly touched as well as water to rinse off the lens when fully pressed.

Scope valves

In the front of the scope handle, there are two valves (Figure 6.10). The upper “red” color‐coded valve provides suction through the working channel of the scope. When pressed all the way in, the suction can be used to remove air from the colon and improve mucosal visualization by suctioning up retained liquid within the colon, or when a trap is employed in the suctioning circuit, it can be used to retrieve removed polyps (Figure 6.11). This valve is typically controlled with the left index finger.

The lower “blue” valve has dual functions of air insufflation and water rinse of the camera lens. This valve can be controlled with either the index finger or middle finger. When the fingertip is lightly placed occluding the hole in the middle of the valve, air is forced down the scope, resulting in inflation of the colon lumen. One common error many trainees make is to “rest” their finger over this opening, resulting in overinflation. Care must be taken to limit the amount of air used during endoscopy as excessive distention of the colon results in greater patient discomfort as well as increasing the risk of colonic perforation (particularly in the thin‐walled cecum). The second function of the valve (water rinse of the camera lens) is achieved by pressing in the blue valve completely. This results in a fine jet of high‐pressured water to be sprayed horizontally across the tip of the scope, rinsing away adherent debris that can reduce or obscure the camera’s visualization of the colon. Some colonoscopes also include a special port for irrigation of the colon controlled by a foot pedal. This can be used to clean the colonic mucosal to improve inspection when suboptimal preparations are encountered. An alternative to this is simply injecting water through the biopsy port of the scope using a large syringe. If using the syringe method, a small amount of simethicone can be added to this water to assist when bubbly or foamy fluid is encountered in the colon.

Photo depicts trap in suction circuit.

Figure 6.11 Trap in suction circuit. When a polyp is removed with a snare, a trap is needed to collect the tissue. This trap is placed in the circuit of the scope’s suction line. This trap allows liquid and air to be suctioned normally but traps larger particles such as polyp tissue in a small chamber. This allows the removed polyp to be collected by suctioning it up through the working channel of the scope by pressing the red valve.

Scope insertion

c06i001Prior to insertion of the scope, a digital rectal exam is performed for the dual purpose of lubricating the anal canal as well as examining the canal for pathology and patency. The right hand is ideally double gloved so that following the rectal exam, the outer glove can be removed and discarded without the need for regloving. The scope handle is draped over the endoscopist’s left shoulder or laid on the bed freeing the left hand to lift the upper gluteal fold exposing the anal canal. The anal area is visually inspected for pathology and then the rectal exam performed with the right index finger. Following the exam, the outer glove is discarded. The distal 20 cm of the scope is then liberally lubricated. The scope insertion into the rectum is then performed by one of the following manners (Figure 6.12) (Video 6.2):

Schematic illustration of rectal intubation techniques.

Figure 6.12 Rectal intubation techniques. This illustration demonstrates the three common methods of inserting the scope through the anal canal: (a) tangential approach, (b) along‐side finger, and (c) straight insertion.

(Copyrighted and used with permission of Mayo Foundation for Medical Education and Research.)

  1. Tangential approach: The scope is held in the right hand at about 10 cm with the index finger down near the tip. The scope tip is then positioned at the anal canal at roughly a 45° angle. The index finger then gently pushes the tip of the scope though the anal canal and the scope is then advanced. This technique gives better control of the tip during insertion. With this technique and the next, the second (outer) glove on the right hand remains on until after scope insertion and can then be removed and discarded.
  2. Along‐side finger: The right index finger is inserted into the anal canal and the scope is inserted alongside this as the finger is withdrawn.
  3. Straight insertion: The scope is held with the right hand at about 20 cm from the tip and is positioned perpendicular to the anal canal. The scope tip is then inserted straight into the rectum. This is probably the most direct approach and most commonly used method.

Scope advancement

Once in the rectum, the objective is to advance the scope quickly and safely to the cecum. In order to accomplish this, the endoscopist needs to be able to steer the scope tip in the direction desired. This is done with a combination of the scope dials as well as torque of the scope. Being able to locate the colonic lumen when lost is also a mandatory early skill. Barring looping of the scope or tight angulations, the cecum can sometimes be reached with these simple techniques alone. Other skills such as loop reduction, navigation of angulated turns, and terminal ileum (TI) intubation will be covered later in this chapter.

Tip control

The large (up/down) dial is controlled with the thumb. The scope’s camera is fixed in relation to the scope’s axis, hence the up or down deflection described earlier is always in relation to the image on the video monitor. “Up deflection” of the camera (or “thumb down” on the dial) will always deflect the scope toward the top of the image displayed on the video screen and “down deflection” (or “thumb up”) will always aim the camera toward the bottom of the screen. For the teacher and student alike, it helps for the training center to conform to a single use of terms describing the desired action such as always using the terms “steer up” and “steer down” vs. “thumb down” and “thumb up.” Most find that describing which direction you want the camera to steer in relation to the video image as the most intuitive method as opposed to advising which way to turn the wheel with their thumb.


As trainees will quickly find, reaching the thumb to the smaller right/left dial can be difficult and awkward. Many trainees early in their training will be tempted to remove their right hand from the scope shaft and use this hand to turn the small dial. By correctly placing the scope’s umbilical cable on the outside of the left arm (rather than running between the left arm and flank of the endoscopists), the scope handle rotates slightly bringing the control knobs slightly closer to the users thumb. However, with correct technique, the need for this small dial can be minimized. The most efficient method of steering is combining torque with use of the up/down dial. In general, experienced endoscopists would agree that, rather than using excessive right/left dial control, it is better to teach the use of scope torque in either direction to reorient the right or left turns in the lumen so that they are oriented toward the top or bottom of the screen. This is accomplished with the right hand rotating the shaft of the scope. Firm torque of the scope’s shaft in the desired direction can rotate the entire shaft of the scope inside the patient and realign a horizontal turn in the lumen to one that is vertically oriented (Figure 6.13). Once in this position, the large up/down dial can be used to steer in the direction desired.

Scope advancement techniques

There are three techniques used to handle the scope. The “one‐handed” technique is the one most commonly used by experienced colonoscopists as it provides the most uninterrupted control of the scope shaft and is best suited to the predominant use of torque to maneuver the instrument (Figure 6.14). In this method, the dials are controlled with the left hand alone, relying primarily on the up/down dial. The right hand remains on the shaft of the scope providing torque, advancement, and withdrawal of the scope. A useful way to conceptualize this technique is to imagine flying a plane through a tunnel. If the pilot wishes to turn right, one cannot simply fishtail the plane to the right, instead the plane must roll right and then pull back on the stick (up). Occasionally, the right hand may still need to be brought up to control the smaller right/left dial but only with particularly tight turns, such as the splenic or hepatic flexure, where torque and up/down deflection may not be sufficient.

Photo depicts torque to change from horizontal to vertical.

Figure 6.13 Torque to change from horizontal to vertical. The two images depict the same turn but in different orientations. In the first image (a), the turn goes off to the right and would require the use of the small left/right dial to navigate. However, after torque of the scope shaft 90° clockwise, this turn is now oriented vertically (b) and can now be navigated with the large dial alone.

Photo depicts one-handed technique. With the one-handed advancement technique, all of the dial control is done by the left hand, primarily using the large dial. The right hand is responsible for providing torque and advancement, and generally does not leave the scope shaft.

Figure 6.14 One‐handed technique. With the one‐handed advancement technique, all of the dial control is done by the left hand, primarily using the large dial. The right hand is responsible for providing torque and advancement, and generally does not leave the scope shaft.

The “two‐handed” technique is favored by some experts who feel that when the thumb is used to cross over to the small dial, fine control of the large dial is not possible. Additionally, the left thumb cannot maximally deflect the small dial in either direction. Once the right hand has turned the small dial, it can be temporarily locked in this position to hold the intended deflection while the right hand returns to the scope shaft (Figure 6.15). The major drawback to this technique is the intermittent interruption of control of the scope shaft with the right hand. When the hand is off the shaft, the scope frequently can fall back unintentionally or rotate due to loops. Many endoscopists who employ the two‐handed technique can compensate for this decreased shaft control by positioning the scope shaft so that it hangs down by the side of the table, pinning the scope shaft between the endoscopist’s thigh and the side of the bed and rapidly moving the right hand back and forth between shaft and the outer small dial. Another stabilization method is to reach down with the left hand and while holding the scope, loop the left fifth digit around the scope shaft roughly 20 cm away from the anus and pinning it against the left palm while the right hand is busy maneuvering the right/left dial [8]. This is particularly useful when a free right hand is needed to advance a therapeutic tool down the scope shaft or if the right left knob is needed to fine‐tune targeting a tool as it will hold any necessary torque in the scope shaft and allow small forward and backward adjustments in scope advancements with the left hand.

Photo depicts two-handed technique. With the two-handed technique, the right hand is moved back and forth between the shaft of the scope and the small right/left dial, while the left thumb controls the large inner dial.

Figure 6.15 Two‐handed technique. With the two‐handed technique, the right hand is moved back and forth between the shaft of the scope and the small right/left dial, while the left thumb controls the large inner dial.

A third method is called the “two‐person” technique and is rarely used anymore. It involves the endoscopist using the two hands to control the dials exclusively while an assistant advances the shaft of the scope at their order. Again, this technique is typically no longer taught due to the many disadvantages of coordinating scope control, much like having one person steer a car while another operates the gas and brakes.

Lumen identification

During endoscopy, experienced endoscopists occasionally find it difficult to identify where the lumen is due to factors such as acute angulations, numerous large diverticula, or inadequate colon preparation. Novice endoscopists, however, find factors such as red‐out (tip of the scope up against the colon wall), or inability to recognize clues to indicate the direction of the lumen, to be far more common. In the case where the lumen cannot be seen, it is always advisable for the trainee to slowly pull back on the scope until they are away from the wall and can identify clues to the direction of the lumen or until the lumen itself again becomes visible. In order to avoid perforation, a trainee should never continue pushing inward on the scope if the lumen is not visible.

Once away from the wall and red‐out corrected, there are a number of clues that can help the endoscopist identify the direction of the lumen. The most common is observing the direction of the haustral folds. The concave portions of the folds point in the direction of the lumen. The second is the use of shadows. When identifying a bright fold close to the scope and a dark shadow behind this, the lumen is often behind this fold. A third method that is often helpful in guiding the endoscopist is following the longitudinal ridge created by the tinea coli. The length of any of the three tinea coli will point in the direction the lumen is turning.

Similar to following the haustral folds as described above, ripples in the colon wall created by the circular muscle layer of the colon can also be used. When the colonoscope light reflects off of these arcuate ripples, steering the scope toward the concave portion of the arc should guide the endoscopist in the direction of the lumen.

c06i001All of these techniques can be used alone or in combination to help the endoscopist find their way to the cecum (Figure 6.16) (Video 6.3).

Air and water during scope advancement

During scope advancement, there is a need to provide some inflation of the lumen to allow visibility and identification of lumen and these anatomical clues. However, too much air can actually make advancement around some segments of the colon more difficult to navigate as well as add to the patient discomfort. This is of particular concern when fellows early in training take a long time to pass the sigmoid colon and use excessive air in the process. This can lead to marked distention of the cecum and right colon. The use of water to fill the sigmoid colon (immersion or water exchange technique) is felt by many to make scope advancement through the sigmoid easier for trainees and more comfortable for the patient. While not necessary for more experienced endoscopists during every case, this technique is one more tool to assist navigation through a difficult sigmoid colon.

Photo depicts lumen identification.

Figure 6.16 Lumen identification. When the lumen cannot be readily identified, clues such as (A) the arcs of the colon folds, small arcs of reflected light off of the ripples of muscular rings (B), or the area of shadow behind a bright fold (C) can help. Following the indentation of the tinea coli (D) can also guide the endoscopist around acute angulations.


Once the cecum is reached, the most important portion of the exam begins, that is, careful inspection of the colon for pathology. In many instances, pathology such as polyps will be seen during the insertion phase and if desired can be treated at that time. Many endoscopists may also simply note the location of the lesion during insertion and take care of it during the withdrawal phase.

The first key to adequate visibility is adequate insufflation. Instilling air into the colon requires a balance between ensuring the colonic folds are adequately distended yet without creating too much tension on the colon wall and discomfort for the patient. Trainees often make the mistakes of using too little air or conversely leaving their finger on the air valve all of the time. Care must be taken and the endoscopist must always be cognizant of the degree of insufflation of the colon and patient comfort levels.

The second important factor of proper withdrawal technique is to ensure the colonic mucosa and the camera lens are clean enough to allow optimal visualization. The colon preparation often does not completely clear the colon of fecal debris. Suction can be used alone or in combination with water lavage. Some scopes are capable of having automatic water lavage controlled by a foot pedal while older scopes may still require manual injection of water. With the latter, water can be instilled to lavage the colon using a large (60 cc) syringe injected through the biopsy port just below the scope handle. As one injects, the scope is aimed with the dials and torque at the area in need of cleansing. After cleansing, suctioning is then used by positioning the scope so that the suction port is below the surface of the puddle but the camera lens is not. The location of this port varies modestly based on the model and type of scope used but as a general rule, it is best to position the target puddle at the six o’clock position. The suction button is then used and the scope repositioned as needed until the liquid is removed. This process often needs to be repeated multiple times throughout the colon to achieve adequate visualization. Trainees will frequently put the scope tip too deep into a puddle and obscure their view or repeatedly suctioning too close to the colon wall resulting in the mucosa being pulled into the suction port. If this occurs, the suction holding the mucosa in the port can be broken by either pulling the scope tip away from the mucosa or by briefly breaking the seal of the rubber biopsy port cap at the scope’s handle base, thereby relieving the vacuum in the biopsy channel of the scope.

The next important skill is the development of a slow, careful inspection pattern. Inspection is carried out by developing a circular inspection pattern as the scope is slowly pulled back. This circular pattern does not necessarily need to be done with the scope tip but more with the eyes and only augmented by minor deflections of the scope tip as needed to see the entire circumference of the lumen. Scope readjustments are an ongoing process involving not only the use of the dial controls but also torque of the scope to keep the tip in the center of the lumen. As the scope passes larger folds, it is often necessary to readvance the scope just above the fold and use greater deflection of the scope tip with the dials to view behind the fold and ensure pathology is not missed. In experienced endoscopists, it is felt that a minimum of 6–7 minutes is needed to examine the entire colon adequately [9, 10]. For trainees, this process initially takes much longer due to their developing skills of scope control, inspection behind folds, and pathology recognition. As skills advance, this inspection time will gradually decline. Trainees must clearly understand that while average withdrawal time is a surrogate marker for a careful exam, the key objective is complete mucosal inspection; areas poorly seen due to the colonoscope “jumping” past folds or due to puddles must be reexamined, even if it means reinserting the scope as needed to reinspect.

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Jul 31, 2022 | Posted by in GASTOINESTINAL SURGERY | Comments Off on Colonoscopy
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