Functional lumen imaging probe for esophageal disorders: Ready for prime time

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

Esophageal symptoms are common and affect at least a quarter of the population. There are a multitude of diagnostic tests available, but no true gold standard and each test is complementary.  Endoscopy allows direct visualization of the mucosa, biopsy acquisition and potential dilation but does not directly assess motility, biomechanical properties or bolus transit. Fluoroscopy provides an assessment of esophageal diameter, structure and emptying but requires radiation, has limited sensitivity for detection of dysmotility and may not be an accurate gauge of esophageal diameter in the context of under-distention. Manometry evaluates pressure patterns and motility, but is uncomfortable for many patients and provides no information regarding esophageal diameter or wall stiffness. Impedance assesses bolus transit and emptying, but is of limited diagnostic utility in isolation. Each of these provides a different measurement of some aspect of esophageal pathophysiology yet, often the diagnosis is not clear despite these interventions — or the diagnosis is achieved only after a plethora of studies resulting in significant cost, time and patient discomfort.

“In my practice, FLIP has become an essential tool.”

The functional lumen imaging probe (FLIP) utilizes impedance planimetry to measure luminal diameter, and when combined with intra-balloon pressure measurements, can detect wall distensibility. This allows direct measurement of luminal caliber and wall stiffness, both of which have value in diagnosis of esophageal disease and may be a better predictor of therapy for certain conditions such as achalasia than current measurements. In addition, the latest version of FLIP adds topography, essentially a space-time continuum plot of esophageal diameter providing a direct measurement of secondary peristalsis. Thus, FLIP provides a single test that can measure diameter of the entire esophagus, esophageal wall stiffness and motility. This can be combined with an index endoscopy, potentially reducing time to diagnosis, allowing earlier and more tailored therapy — it can be done when the patient is sedated, potentially eliminating the discomfort of manometry.

In my practice, FLIP has become an essential tool. I was fortunate to be at an institution that obtained this technology relatively early and was able to incorporate FLIP in my clinical practice in early 2014.  Initially, I was using it only for patients with achalasia with continued symptoms despite therapy and for patients with esophagogastric junction (EGJ) outflow obstruction on manometry. In both cases, FLIP allowed me to directly measure the EGJ diameter and distensibility and then provide tailored therapy accordingly. As my experience with FLIP increased, and the technology improved, use of FLIP in my clinical practice expanded to include evaluation of non-obstructive dysphagia, assessment of motility in patients unable to tolerate manometry, assessment of wall stiffness in the context of eosinophilic esophagitis, and non-esophageal indications such as gastroparesis. Similarly, when I initially incorporated FLIP in my practice almost all of the patients were from my own clinic; however, as knowledge regarding FLIP has disseminated in the community now over half of my FLIP cases are referrals from outside my own direct practice. As of now, I have personally performed 470 FLIP procedures and feel strongly that I could not provide the same level of care to my patients without this technology.

FLIP has not only changed my practice but has also changed the landscape of esophagology. There are now over 100 published papers involving FLIP and two years ago Clinical Gastroenterology & Hepatology published an Expert Review from the Clinical Practice Updates Committee of the AGA Institute, which concluded that FLIP has a complementary role in the diagnosis of esophageal disorders.1 Northwestern has now published normative data2 and there are multiple case series from across the world utilizing FLIP in patients with achalasia, EGJ outflow obstruction, eosinophilic esophagitis, non-obstructive dysphagia and non-esophageal indications such as gastroparesis — as well as to tailor intervention in myotomy and fundoplication.3 Like any technology in evolution, the data are not perfect and this needs to be acknowledged. We need more robust normative data from larger patient populations. Multicenter outcome studies need to be performed in specific disease states to truly characterize the spectrum of disease and ensure that findings are transposable. Studies from non-academic centers are needed to ensure that this technology is portable and not limited to tertiary facilities. Software and potentially hardware changes are needed to ensure that the interpretation is as reproducible and easy as possible.

Harvard psychologist Howard Gardner proposed criteria in 2004 for successful implementation of change: reason, research, resonance, representational redescription, resources/rewards and real-world events.4 While these criteria were developed for business purposes, they can also be applied to FLIP. With regards to the first criteria (reason), FLIP provides a means of assessing esophageal pathophysiology that is different from the other modalities currently available and fills a void in our current diagnostic arsenal. The research is emerging, but with over 100 papers in press and an AGA technical review, the second criterion seems to be satisfied — and more papers are coming out on almost a weekly basis.  Resonance refers to the gestalt sense that something makes sense and just feels right. The fact that FLIP can combine an assessment of diameter, wall stiffness and motility in one study and can potentially enable one to avoid the discomfort of manometry makes it intuitively attractive. Representational rediscription refers to the concept being marketed in multiple manners — papers on FLIP are barraging the literature but it has also attracted enough interest to be featured in this debate. With regards to resources and rewards, FLIP has a CPT code, is reimbursed in the areas where I have practiced and is popular with patients and referring providers. Finally, even for those skeptics of FLIP, real-world events may force inception. Discussion of FLIP is now an integral part of any esophageal conference and it will become harder to be an esophageal center of excellence without including it as an option. Even critics of FLIP are being forced to respond and consider where it falls in their management pathway.

Is FLIP ready right now to replace fluoroscopy, manometry and impedance? No. However, is FLIP a complementary tool that can provide useful information and improve patient care? Yes.  More research is needed to determine where FLIP best fits in the algorithm; however, it is possible — and I would argue likely — that within the next five years FLIP will become the first test performed for a patient with suspected non-obstructive dysphagia (in conjunction with endoscopy). The idea that wall stiffness, diameter and motility can be safely assessed in one study without the discomfort of manometry is too compelling to ignore.

Dr. Richter says it is too soon for prime time.

Key takeaways

  • FLIP allows simultaneous measurement of diameter, distensibility and motility in one study during endoscopy without the discomfort of manometry.
  • FLIP has been shown to predict clinical outcomes in achalasia and eosinophilic esophagitis, among other disorders.
  • While more research is needed to establish where FLIP fits in the algorithm for evaluation of esophageal disorders, it fills a clinical niche and is attractive to patients.

Disclosures: Dr. Clarke has consulted for Medtronic, Isothrive and Sanofi. Dr. Clarke is a member of the AGA Graduate Training Exam Subcommittee and the ACG Educational Affairs Committee.


1 Hirano I, Pandolfino JE, Boeckxstaens GE. Functional lumen imaging probe for the management of esophageal disorders: expert review from the Clinical Practice Updates Committee of the AGA Institute. Clin Gastroenterol Hepatol. 2017;15(3):325-334.

2. Carlson DA, Kou W, Lin Z, Hinchcliff M, Thakrar A, Falmagne S, Prescott J, Dorian E, Kahrilas PJ, Pandolfino JE. Normal values of esophageal distensibility and distention-induced contractility measured by functional luminal imaging probe panometry. Clin Gastroenterol Hepatol. 2019;17(4):674-681.

3. Ahuja NK, Clarke JO. The role of impedance planimetry in the evaluation of esophageal disorders. Curr Gastroenterol Rep. 2017;19(2):7.

4. Teitebaum E.N., Soper N.J., Pandolfino J.E. et al. Changing minds: the art and science of changing our own and other people’s minds. Boston: Harvard Business School Press, 2004.




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