(Video 6.7). Which type of loop forms is likely due to variances in sigmoid anatomy? The method best suited for reduction of these sigmoid loops varies depending on the type of loop. In each of the loops, it is generally advisable to attempt to advance the scope beyond the splenic flexure, or other acute turn, if possible before attempting reduction. This allows the flexible portion of the scope tip to hook around this flexure and act as an anchor. This allows for greater direct force on the loop itself during reduction and torques maneuvers. Once anchored, the dials are held with the left thumb to prevent the scope tip from straightening out and slipping back into the descending colon. The two most common types of loops (alpha‐ and N‐loop) respond to slow scope withdrawal augmented by clockwise scope torque (Figures 6.23 and 6.24). During this maneuver, the tip of the scope may advance or simply remain motionless as the scope shaft is withdrawn. Clockwise torque and withdrawal of the shaft are continued until the scope tip begins to respond by starting to move backward in a one‐to‐one manner. This is evidence that the loop has been reduced. Torque is key to the maneuver as this will untwist the spiral nature of the sigmoid and create a straighter lumen if done correctly. The most common cause for failure of this technique is either failure to withdraw enough scope to re‐establish one‐to‐one motion or inadequate clockwise torque of the scope shaft during withdrawal. It is not uncommon to require 360° of torque or more during sigmoid reduction to adequately remove the spiral nature of this segment of the colon. Another cause of failure is the presence of a reverse alpha‐loop. Suspicion of this should arise if the usual clockwise maneuver repeatedly fails.
Figure 6.23 Alpha‐loop. One of the most common types of sigmoid loop formation is the alpha‐loop. This can be reduced with clockwise torque of the scope shaft as it is slowly pulled back. Once the loop is reduced, the scope shaft is again straight and can be readily advanced again.
(Copyrighted and used with permission of Mayo Foundation for Medical Education and Research.)
Figure 6.24 N‐loop. The N‐loop is also a common type of loop formation in the sigmoid and can also be reduced with clockwise torque and slow withdrawal like the alpha‐loop.
(Copyrighted and used with permission of Mayo Foundation for Medical Education and Research.)
Figure 6.25 Reverse alpha‐loop. A reverse alpha‐loop follows a similar configuration as an alpha‐loop; however, the loop passes posteriorly to the scope shaft. Attempts at clockwise torque of the scope shaft will typically result in tightening of this loop and a sensation of increasing resistance to torque attempts by the endoscopists. Instead, counterclockwise torque and withdrawal is needed to reduce this type of loop.
(Copyrighted and used with permission of Mayo Foundation for Medical Education and Research.)
In cases such as this, attempts at counterclockwise torque during scope withdrawal may result in successful loop reduction. Other clues that the direction of required torque should be reversed are if one experiences increasing resistance to scope shaft rotation during torque attempts, or if the tip of the scope moves backward with the torque maneuver. In general, the correct direction of torque should result in a sensation of decreasing resistance to shaft rotation and modest scope tip advancement. Once a loop is reduced and the scope is straight, the torque that was used in the reduction can be undone. If the scope is straight, this should not result in any reproduction of the spiral but rather simply rotate the entire shaft of the scope back to a comfortable position. Some scopes are equipped with a variable stiffness feature that is controlled by a dial at the base of the handle. If this feature is available, increasing the stiffness of the scope, now that the loops are removed, can help prevent the reformation of these loops as the scope is advanced. This increased stiffness should be removed during subsequent attempts at loop reduction and reengaged when pushing forward. External pressure can also help prevent the reformation of loops and will be discussed below.
Figure 6.26 Transverse colon loop. Like the sigmoid, the transverse colon is also typically very mobile and can result in an assortment of loops. Reduction techniques vary but often require a combination of torque with slow shaft withdrawal. The direction of torque required will depend on the nature of the loop.
(Copyrighted and used with permission of Mayo Foundation for Medical Education and Research.)
Angulated turns
