Vòng sigmoid Đẩy mạnh thông qua một sigmoid dài và vào và lên đại tràng giảm dần là đôi khi dễ dàng và có thể chứng minh là lựa chọn tốt nhất (Hình 29,24) (xem thêm phần alpha vòng lặp). Tuy nhiên, đẩy thông qua bất kỳ vòng lặp là không thể chấp nhận được nếu lực lượng | Chapter 29 Insertion Technique 325 Fig. Pre-steer before pushing into an acute bend. Fig. Pulling back flattens out an acute bend and improves the view. the view is poor gently pull back the angled hooked tip which should simultaneously reduce the angle shorten the bowel distally straighten it proximally and disim-pact the tip to improve the view Fig. . Maneuvering around a bend may cause a mobile colon to swing around on its attachments seen in close-up as a rotation of the visible vessel pattern indicating which direction to follow Fig. . Sigmoid loops Pushing through a long sigmoid and into and up the descending colon is occasionally easy and may prove to be the best option Fig. see also section on alpha loop . However pushing through any loop is unacceptable if force is required or pain results. Pain indicates potential for damage to the bowel or mesentery. Similarly pushing blindly around any bend should be limited to a few centimeters and only if slide-by of the mucosal vascular pattern view continues smoothly and only toward the predetermined direction of the lumen. Fig. Rotation of vessel pattern from a to b indicates rotation of the colon so the endoscopist needs to change steering direction correspondingly. Fig. A very long sigmoid may allow the scope to push through without a hairpin bend. Stop if the mucosa blanches indicating excessive local pressure or the patient experiences pain indicating undue stress on the bowel or mesentery perforation is a possibility if excessive or unrelenting force is used. Patients with short sigmoid loops tend to experience more pain since their shorter mesenteric attachments are more aggressively stretched. Long colons with longer mesenteries simply stretch upward and adapt to let the colonoscope pass relatively easily into the descending colon without an acute hairpin bend Fig. . Inward push should be applied gradually avoiding sudden shoves and limited to a tolerable .
