6. Overview of GI indications and cryo technology via flexible endoscopy

Since the mid-1960s, Cryotherapy was a technique in search of an indication for gastrointestinal diseases. In those early days, Cryotherapy although hampered by technical challenges was advocated for treating duodenal ulcers, gastric erosions, and hemorrhagic gastritis. By this time, Cryotherapy was showing great promise in other clinical areas such as dermatologic and prostatic conditions. Despite this initial enthusiasm, the results of clinical trials for these conditions were disappointing and when added to challenges of technically delivering freezing therapy to the gastrointestinal tract, Cryotherapy was soon forgotten as a modality to treat gastrointestinal disease. However the groundbreaking work by Pasricha and colleagues from Johns Hopkins in 1999 described for the first time an endoscopic device that was capable of delivering freezing therapy to the gastrointestinal mucosa. These initial experiments performed in an animal model demonstrated the feasibility of Cryotherapy with a compressed gas. This was soon followed by experiments demonstrating the feasibility of using low pressure liquid nitrogen by an endoscopic catheter. The initial clinical trials focused on diseases that would respond to ablating the superficial mucosa such bleeding arteriovenous malformations, radiation gastritis and proctitis and Barrett’s esophagus. Using Cryotherapy for palliation of advanced gastrointestinal tumors has shown success in case reports but has been less well studied. Two different techniques have evolved for delivering Cryotherapy. The initially described technique used compressed gas such as nitrous oxide and CO2. Rapid expansion of the gases results in a significant drop in local temperature enabling cryogenic damage to the mucosa. The second technique involves direct application of low pressure liquid nitrogen to the mucosa. The techniques appear to have similar efficacy. Although lacking in prospective randomized trials, endoscopic Cryotherapy is a promising modality for the treatment of gastrointestinal mucosal disease.