Role of video endoscopy in managing small bowel disease
Authors: P Swain
Journal: Gut (2004)

he small intestine has been relatively inaccessible to flexible endoscopy until recently. 1Its 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 successful.The advent of wireless video capsule endoscopy 3 has released the endoscopist from the requirement to exert force on a long floppy cable-type endoscope to examine relatively short segments of small intestine.This device exploits peristalsis to propel the video endoscope through the small intestine and can usually but not always acquire images from the whole of the small intestine from the pylorus to the caecum. TECHNICAL ADVANCES cThere has been a substantial increase in small intestinal endoscopy in the last 10 years which has followed two technical advances (table 1).The first was the development of specific endoscopes for push enteroscopy (fig 1). 1 4-6 Careful attention to the design allowed better transmission of force to the tip and shaft stiffness for use at flexible endoscopy.These instruments were longer than colonoscopes, measuring 200-240 cm, and slimmer, usually measuring 11 mm in diameter but with a 2.8 mm accessory channel.They were initially designed for use with an overtube to aid deep intubation which usually needed x ray control for safe insertion.The overtube appeared to cause some of the complications associated with push enteroscopy-for example, sometimes causing oesophageal trauma. 7The addition of video imaging 4-6 to these instruments allowed very high quality images to be obtained from the oesophagus to the jejunum (fig 2).Despite some evidence that 240 cm enteroscopes do not reach further or find more pathology than those of 200 cm, 8 some of the newer instruments are longer than the earlier enteroscopes (240-280 cm).Variable stiffness enteroscopes have recently become available. 9Most 9-16 but not all endoscopists 8 found that these instruments could be used almost as well without an overtube and thus dispensed with the need to perform this procedure under x ray control.There was evidence from two studies that the use of an overtube was associated with a significant increase in depth of insertion into the small intestine by 10-15 cm 17 18 but in neither of these studies was more pathology found.The whole of the duodenum and some of the jejunum can be examined by video colonoscopes, 19 20 especially with paediatric colonoscopes, which are more widely available than push enteroscopes.They are of the same diameter but substantially shorter (135 v 200-240 cm).