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The small intestine has been relatively inaccessible to flexible endoscopy until recently.1 Its length is a challenge to endoscopy. The small intestine accounts for 75% of the total length and 90% of the surface area of the gastrointestinal tract. In adults it measures about 570 cm at post mortem,2 which is substantially longer than conventional video gastroscopes. Colonoscopes and gastroscopes measure 100–180 cm. There are features about its position and anatomy which limit the endoscopist’s chance of passing longer endoscopes much further than a few centimetres into it, either through the mouth and duodenum or through the ileocaecal valve. The tight curve from the bulb around the head of the pancreas and its relatively fixed retroperitoneal posterior position as it crosses the spine to the ligament of Treitz where it passes downwards as a loosely supported much looped structure on a mesentery is a challenge. If a colonoscope is passed through the mouth into the jejunum and a surgeon pleats the small intestine over the endoscope by hand at laparotomy, the stiffness of the endoscope tends to stretch the mesentery, which is attached posteriorly as the endoscope follows the loops of small intestine and increases the friction exerted by the intestine on the endoscope. Colonoscopists can usually but not always enter the terminal ileum for a few centimetres. Either way, the distance and curved path that a conventional endoscope has to pass to reach the small intestine means that the force for effective forwards propulsion, which can be exerted on the tip of an endoscope, is small. Loops tend to form and enlarge in the stomach or in the colon, which can make deep small intestinal intubation difficult.
Recent technical developments in the design of longer flexible instruments specifically for push enteroscopy have made this examination much more …
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