The Role of Functional Lumen Imaging Probe (FLIP) Before Submucosal Tunnel Myotomy

Peroral endoscopic myotomy (POEM) is increasingly employed as therapy for sphincteric abnormalities of the gastrointestinal tract, including achalasia, gastroparesis, Zenker's diverticulum, and other esophageal dysmotility syndromes. The capabilities of functional lumen imaging probe (FLIP) testing include measurement of sphincteric distensibility, diameter, cross-sectional area (CSA), and pressure in these disorders before and after POEM. FLIP can also characterize phasic contractility in non-sphincteric regions, including the esophageal body and pre-pyloric gastric antrum. Increases in distensibility and CSA after POEM are associated with reductions in symptoms and improvements in gut transit, including esophageal barium clearance in achalasia and gastric emptying in gastroparesis. Several studies have identified FLIP metrics that are associated with successful POEM outcomes in these 2 conditions. Intraprocedural FLIP can determine the adequacy of the initial myotomy and suggest the need for additional incision before mucosotomy closure. However, the definition of pre-myotomy FLIP parameters that can be used for reliable patient selection for subsequent POEM remains incomplete. Future investigations to establish normal sphincter parameters in healthy controls, standardize FLIP methods across sites, and adopt the technology in multicenter trials are warranted.