A recent review article (E Sararino et al. Am J Gastroenterol 2020; 115: 1786-06. Use of the Functional Lumen Imaging Probe in Clinical Esophagology) is a terrific article for understanding Functional Lumen Imaging Probe (FLIP) techonology and uses. Thanks to Ben Gold for this reference.

Link to patient explanation of EndoFLIP at Univ Michigan

The FLIP “measures luminal cross sectional area (CSA) and pressure in the esophagus using impedance planimetry and serves as an adjunct to existing esophageal investigative tests. A distensible balloon encasing a catheter with multiple pairs of impedance electrodes is used, and the balloon is distended with fluid of known conductivity and volume.”

FLIP can be done at time of endoscopy.

• Distensibility index (DI). This is the ratio of EGJ cross sectional area to intraballoon pressure is generally considered the most useful FLIP metric. Normal DI values in adults range from 3.1 to 9.0 m3/mm Hg. Lower values indicated reduced EGJ opening.
• FLIP can complement the diagnosis of achalasia when manometry and barium studies are inconclusive or negative in patients with typical symptoms.
• FLIP can be used to assess fibrostenotic remodeling of the esophagus in eosinophilic esophagitis.
• Lumen diameter measured using FLIP in complex strictures can potentially guide management.

This review has several helpful figures to illustrate the type of visual data available. It also provides a standard protocol for using FLIP. The current limitations for FLIP include the lack of real-time software analysis of the data which hinders reporting, and limited data supporting use.

Related blog post: #NAASPGHAN17 Eosinophilic Esophagitis Session