Assessment on the potential role of applying cryoprobe for tissue ablation

Background/Aims: Cryotherapy is the therapeutic application for tissue ablation. Clinical applications of cryotherpy such as in pulmonology have increased. Until now, its development in gastroenterology has been insignificant. But, as clinical application such as mucosal ablation on Barrett's esophagus became possible, various applications have been developed. Therefore, it is important to make standards of tissue injury's extent in cryotherapy prior to clinical trial. We evaluated the tissue injury according to the application of cryoprobe with a pig model. Methods: Cryoprobe was applied to several different segments of the esophagus and stomach for various lengths of time using various number of probe's contact in a pig model. After 48 hours, esophagus and stomach were harvested and histological tissue injury was assessed. The extent of tissue injury was decided by the injury of the deepest layer. Results: Endoscopic application of cryoprobe on esophagus and stomach resulted in a dose-dependent injury: esophageal necrosis was limited to the submucosa after 10 seconds of cryotherapy, and extended to involve the transmural necrosis after over 15 seconds. Necrosis on stomach was extended to involve the transmural necrosis after over 20 seconds. Conclusions: Positive relationship was seen between the duration and frequency of cryoprobe application and the extent of tissue injury.