Factors contributing to changes in viscosity and flow rate of a dedicated gel for gel immersion endoscopy

Background and study aims  Gel immersion endoscopy is a novel technique for securing the visual field during endoscopy. Clinical application of a dedicated gel for this technique with an appropriate viscosity to prevent mixing with blood and its efficacy was reported. The aim of this study was to evaluate changes in gel viscosity and flow rate under different conditions. Methods  The viscosity of the gel after injection and flow rate were measured under various conditions changing the injection route and method. Gel viscosity was measured at 25, 10, and 4 °C. Results  A decrease in gel viscosity was found when the gel was injected via the water jet channel compared to the accessory channel. The flow rate and decrease in viscosity of the gel injected via the water jet channel were 220 mL/min and 63.2 %, while when injected via the accessory channel with a clip device inserted were 560 mL/min and 35.8 %. When the gel was kept at a low temperature, the viscosity increased. Conclusions  Gel injection via the accessory channel should be the first choice for efficient use considering the viscosity and flow rate.