浸水法を用いた大腸内視鏡検査の開発と応用

The sigmoid colon tends to form loops and bends easily and is therefore considered a difficult site for colonoscope insertion. Inexperienced trainees may accidentally dilate the sigmoid colon following excessive air insufflation, and colonoscope insertion is challenging in such cases even with the use of the axis-retaining shortening method. The water infusion method developed in Japan involves injection of a small amount of water, which facilitates shortening and straightening. The collapse-submergence method, which includes a combination of degassing at the sigmoid colon and the water infusion method, is an improved technique that eliminates the water-air interface to provide a better field of view. The water immersion method can be easily learned even by trainees and is shown to improve the cecal intubation rate and suppress loop formation, which minimizes patient discomfort. This method is also utilized to perform detorsion of sigmoid volvulus and evaluation of irritable bowel syndrome and intestinal morphological abnormalities. Water-aided colonoscopy is popular in the U.S. and Europe, and studies have reported improved adenoma detection rates using “water exchange.” This innovative method is not only useful for endoscope insertion but also aids with underwater endoscopic mucosal resection. Water infusion-related techniques put to advantage the characteristics of water and overcome the limitations encountered with air insufflation methods and are expected to become increasingly popular in the future.