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).
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.
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.
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.
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
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