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.
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.
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.
Withdrawal/inspection
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.
The final maneuver of a colonoscopy is retroflexion within the rectum. This is performed to better inspect the distal rectum for very low‐lying polyps, internal hemorrhoids, or other perianal pathology. This is best accomplished by returning the patient to their left side if they have been repositioned during the exam. The scope is then inserted to the first (or most distal) semilunar valve in the rectum at roughly 10–12 cm from the anal verge. The large dial is then deflected maximally upward while at the same time the shaft of the scope is torqued in either direction roughly 180° and the scope inserted another few centimeters. When these three steps are done simultaneously, it should result in a view of the distal rectum with the scope shaft entering the rectal vault (Figure