Background and study aims: Knowledge about the extent of damage with endoscopic cryotherapy is of critical importance before its potential as an ablative therapy is explored. The aims of this study were to evaluate the extent of transmural esophageal necrosis at 48 hours after cryospraying for varying durations, using a novel device based on the Joule-Thomson effect and with carbon dioxide as the refrigerant gas, and to examine the role of submucosal injection of saline in preventing deeper injury. Methods: Cryospray was applied to several different segments of the esophagus for various lengths of time (15, 30,45, 60, and 120 seconds) in a pig model. In another set of experiments performed subsequently, 2 ml of saline was injected into the submucosa and cryospray was applied for 60 seconds. Results: Esophageal cryotherapy resulted in a dose-dependent injury to the esophagus: esophageal necrosis was minimal or limited to the mucosa after 15 seconds of cryospraying, extended to involve the submucosa after 30 seconds of cryospraying, and involved the muscularis propria also after 45 seconds, with frank transmural necrosis found after 120 seconds of cryotherapy. Prior submucosal saline injection protected against muscular necrosis from prolonged cryotherapy. Conclusions: We have shown a dose-dependent effect of cryotherapy on esophageal mucosal ablation. When more extensive lesions are encountered, it may be advisable to consider using submucosal saline injections as an additional safeguard against deeper injury.
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