The near-infrared electronic endoscope for diagnosis of esophageal varices.

We developed an electronic endoscope sensitive to light delivered by an infrared laser, which makes it possible to visualize submucosal vessels of the gastrointestinal tract. The system consists of a modified electronic endoscope and an image processing unit. A high output laser diode was chosen as the source of the infrared ray with a wavelength of 815 nm, an output of 200 milliwatts, and a band width of 30 nm. Using this instrument, esophageal varices were classified into three categories: venous dilation, dark spot, and diffuse dark area. The venous dilation and dark spot appearances correlated with early esophageal varices, which were rarely seen with visible light. On the other hand, the diffuse dark area appearance was considered to be a high risk sign of future bleeding. This system is useful not only for the early diagnosis of esophageal varices, but also for the localization of optimal puncture sites and the evaluation of the effect of sclerotherapy.