Going for the loop: a unique overtube for the difficult colonoscopy.

In up to 10% to 20% of colonoscopies, complete intubation of the colon may be considerably difficult. A principal cause of difficulty is looping of the endoscope shaft in a floppy, often tortuous segment of the colon that typically happens in the sigmoid colon. Also, if looping is not recognized and the scope is advanced with abandon, the risk of perforation will rise. Special "variable stiffness" colonoscopies are expensive and have not been unequivocally shown to be useful in preventing looping. The simplest approach to prevent looping is perhaps the use of an over-tube to prevent the shaft from bowing out. The ShapeLock could offer an ideal over-tube that is flexible enough to safely and easily negotiate bends in the colon but when needed be rigid enough to prevent looping with just a snap of its handle. It also has potential other applications including enteroscopy, transgastric endoscopy and access to difficult regions of the upper gastrointestinal tract.