Insertion Through the Anus Retrograde Approach

Initially with anal insertion, the operator holds the endoscope tip with the right hand and starts inserting it without the aid of an assistant, similar to conventional colonoscopy. Unlike conventional colonoscopy, it is not necessary to try to insert the endoscope straight from the rectum to the sigmoid colon. After the endoscope is inserted about 50 cm and the tip of the overtube is positioned close to the anus, the balloon at the endoscope tip is inflated, and the overtube is inserted along the endoscope. The overtube is inserted until its rear end reaches the 155-cm marking on the endoscope, and then the overtube balloon is inflated so both balloons grip the intestine. Slow withdrawal of the endoscope and the overtube with both balloons inflated allows easy reduction of loops because the distal ends are secured by the balloons. If it is difficult to straighten the sigmoid colon because of adhesions or other reasons, proceed to the next step without making further efforts to straighten the colon.

After overtube insertion, the assistant holds the portion of the overtube that is outside the body in a straightened position. The operator manipulates the endoscope as he or she inserts it to the rear end of the overtube. After the balloon at the endoscope tip is deflated, the endoscope is advanced as far as possible, and the balloon at the endoscope tip is then inflated to secure the endoscope in the intestine. Thereafter, the overtube balloon is deflated, and the overtube is advanced along the endoscope until it reaches the balloon at the endoscope tip. These procedures are repeated, thereby advancing the endoscope while the fixed support established by the overtube balloon is moved from the sigmoid-descending colon junction to the splenic flexure or the hepatic flexure (Fig. 8.3). In cases where insertion is easy, direct insertion into the splenic flexure and positioning the balloon in the splenic flexure may allow further insertion into the cecum. In most cases, the passage through the large intestine requires one to three sessions of balloon manipulation.

During the procedures, attention should be given to the following points: Because the large intestine has a greater internal diameter than the small intestine, an alarm may be activated during balloon inflation if the balloon pressure fails to reach the set pressure and the pump continues to supply air beyond the allowed inflation time. The pump should be stopped temporarily because continued air supply may damage the balloon. In this case, although the balloon pressure is below the set pressure, the balloon is inflated enough to grip the intestine. The operator may therefore proceed to the next step while the pump is stopped temporarily.

When it is difficult to advance the endoscope tip beyond the ileocecal valve, the overtube should be slightly pulled back, with the balloon inflated in the ascending colon. This manipulation allows the ileocecal region to form an obtuse angle (Fig. 8.4) and facilitates insertion into the ileum. After the endoscope is advanced as far as possible beyond the ileo-cecal valve, the balloon at the endoscope tip is inflated, the overtube balloon is deflated, and the overtube is then inserted along the endoscope. The tip of the overtube is presumably advanced beyond the ileocecal valve when the pump stops automatically within a short period of time because the ileum is much narrower than the large intestine, requiring only a small volume of air to inflate the balloon. In the next step, if the pump resumes applying air during further insertion of the endoscope into the ileum with its balloon deflated, the overtube balloon placed in the ileum is likely to have slipped from the ileum to the large intestine. If excess air supply makes the pump activate an alarm, the pump should be paused temporarily and endoscope insertion continued. In principle, the endoscope should be inserted into the distal small intestine after the overtube is pulled back enough to pleat the intestine over the overtube, as described later. When the overtube is barely advanced into the ileum, however, the overtube balloon tends to slip to the cecum. Thus, the endoscope should be inserted without excess pullback of the overtube. It is important to avoid excess twisting of the endoscope tip in the ileum and to advance the endoscope so it naturally forms concentric circles. It should be noted that insertion of a twisted endoscope downward results in sigmoidal insertion in the direction of the pelvis, which makes further insertion difficult.

It should be noted also that, unlike insertion through the mouth, insertion through the anus is opposite in direction to intestinal peristalsis. Care should therefore be taken to suppress intestinal peristalsis because the peristalsis pushes the balloon backward.

Fig. 8.4. Widening of the angu-lated ileocecal region
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