Functional lumen imaging probe for esophageal disorders: Too soon, too complex and too expensive for prime time

This is half of a two-part debate — read the opposing argument.

Preamble to this article:  I did not volunteer to write this opinion paper, but was asked by the outgoing editor, Dr. Gary Falk. Why, I’m not sure, because I don’t have this technology in our Esophageal Center at the University of South Florida. On the other hand, I am a seasoned esophagologist and motility expert, who has helped develop new technology commonly used to evaluate esophageal diseases including the Bravo ambulatory pH probe, timed upright barium esophagram, and now the esophageal sweep to add diagnostic accuracy to the modified barium esophagram.  Admittedly, I’m a slow introducer of new technology into my lab having ready access to high-quality manometry/impedance pH testing and radiology tests which are done onsite under my direction. Finally, over 40 years, I have seen the community gastroenterologists struggle greatly as we introduced impedance pH testing, high-resolution manometry and even the relatively simple Bravo pH prolonged monitoring system, reinforcing a theme—“keep it simple”—before broad, uncontrolled introduction into general practice, where the vast majority of gastroenterologists and nurses aren’t trained in esophageal physiology and motility.

Current functional luminal imaging probe (FLIP) uniquely measures the compliance and distensibility of the esophago-gastric junction (EGJ) and esophageal body as well as motility generated by esophageal distention. This requires usually a secondary endoscopy; the equipment is expensive (>$40,000) and the impedance probes are not cheap ($500 apiece and non-reusable). Patients may like it because they are asleep, but the overall cost is much more expensive than two competing tests – timed barium esophagram (TBE) and high-resolution manometry (HRM). The former is a simple, cheap, non-invasive barium test where esophageal emptying is measured in the upright position over five to ten minutes after ingesting 250cc of barium and a 13 mm tablet. Normal values are available with excellent sensitivity and specificity for the diagnosis of achalasia and EGJ outflow obstruction.1 Furthermore, the rate of esophageal emptying and degree of retention correlates closely with symptom improvement after various treatments for achalasia and was comparable in accuracy to the EGJ distensibility index measured by FLIP, both being superior to HRM measured LES pressure and integrated relaxation pressure (IRP).

Well, where do I see the most utility for FLIP technology? Certainly, as an adjunct test in patients with difficult to diagnosis achalasia or EGJ outflow obstruction, when more available tests are conflicting.4 In our busy Esophageal Center, untreated achalasia patients are rarely a diagnostic dilemma, but FLIP might be useful in patients with persistent dysphagia and/or regurgitation and non-diagnostic HRM/TBE, especially after multiple surgeries or pneumatic dilation. On the other hand, we find EGJ outflow obstruction more problematic and here it is reassuring to have either retention on TBE or low EGJ distensibility index before performing more aggressive treatments like pneumatic dilation or surgical myotomy.3 Finally, it seems logical that this measure of EGJ compliance would be superior to intra-operative endoscopy for assessing the success of either laparoscopy Heller myotomy or POEM.4 However, this unique niche for this test, which was proposed initially, has been very slow to be incorporated into surgical practices.

“I strongly believe FLIP technology is exciting but not ready for routine use in the GI community.”

Additional proposed uses for FLIP technology includes eosinophilic esophagitis (EoE) and gastroesophageal reflux disease (GERD), especially for tailoring the tightness of fundoplications. In the former, narrow luminal diameters correlate with lower distensibility plateau values,5 which in turn correlates with lamina propria fibrosis, and occurrence of food impactions. Early use of the FLIP device could contribute to better diagnosis of fibrostenotic EoE, especially those not responding to medical/dietary therapy, and guide the use of esophageal dilation. However, the barium esophagram is a cheaper test to do the same evaluation, especially if a 13 mm tablet is given and simple bougie/balloon dilation is a very accurate assessment of lumen diameter available in all endoscopy centers, while allowing prompt and successful treatment of potential strictures.6 Here again, the use of FLIP in the operative theater to gauge the tightness of the fundoplication, especially in the laparoscopic area, seems a much needed role for this test, but more studies are needed.

However, it is disturbing that the sale of this technology in the community is not being based on these relatively uncommon esophageal problems, but rather as a primary test for evaluating patients with dysphagia, chest pain and possibly regurgitation. The idea being proposed without supportive data, is to perform FLIP at the initial endoscopy if there is no obvious evidence of esophagitis (erosive or EoE) and the esophageal lumen can be easily dilated to greater than 18 mm. Normal FLIP testing of EGJ compliance associated with normal topography pattern of ≥3 consecutive repetitive antegrade contractions would exclude structural and motility issues and preclude the need for HRM and/or barium esophagram. Not sure what diagnosis would then be made (maybe functional disease?) and much too early for this new technology to be replacing the gold standards of HRM and barium esophagram.

What does this all mean?  I strongly believe FLIP technology is exciting but not ready for routine use in the GI community. Rather, the use of this needs to be concentrated in medical and surgical esophageal centers of excellence where further clinical studies can be done including developing a larger cohort of healthy controls of all ages and studies to assess cost efficacy and comparisons.  New is always attractive, but old (TBE) and not so old (HRM) are reliable, easy to use, less expensive and well standardized. Because we can do it, doesn’t mean it should be for all.  The time “may” come for FLIP, but currently it is too soon, too complex and too expensive for general application.

Dr. Clarke makes the case that they are ready.


Key takeaways

  1. FLIP technology currently has limited utility in the diagnosis of achalasia / EGJ outflow obstruction and adequacy of surgical myotomy.
  2. Role in eosinophilic esophagitis, GERD and undiagnosed dysphagia is unknown and needs further studies.
  3. High resolution manometry and timed barium esophagram still remain the gold standards tests for assessing complex achalasia and dysphagia cases.
  4. FLIP requires much more studies in surgical and medical esophageal centers of excellence before proliferation into the general GI community.

Disclosures: Dr. Richter is a member of the American Foregut Society.



1 Blonski W., Kumar A., Feldman J., Richter J.E. Timed barium swallow: Diagnostic role and predictive value in untreated achalasia, esophagogastric junction outflow obstruction and non-achalasia dysphagia. Am J Gasteroenterol. 2018;113:196-203.

2.Robof W.O., Hirsch D.P., Kessing B.F., et al. Five-year outcome after laparoscopic anterior partial versus Nissen fundoplication: Four randomized trials. Ann Surg. 2012;255:637-642.

3. Richter J.E., Clayton S.B. Diagnosis and management of esophagogastric junction outflow obstruction. Am J Gasterenterol. 2019;114:544-547.

4. Teitebaum E.N., Soper N.J., Pandolfino J.E. et al. Esophagogastric junction distensibility measurements during Heller myotomy and POEM for achalasia predict preoperative symptomatic outcome. Surg Endosc. 2015;29:522-528.

5. Chen J.W., Pandolfino J.E., Lin Z., et al. Severity of endoscopically identified esophageal rings correlates with reduced esophageal distensibility in eosinophilic esophagitis. Endoscopy. 2016;48:794-801.

6. Richter J.E. Eosinophilic esophagitis dilation in the community – try it – you will like it – but start low and go slow. Am J Gastroenterol. 2016;111:214-216




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