Introduction

Achalasia is a rare, chronic motility disorder of the esophagus with a worldwide prevalence of 1.8 to 12.6 per 100,000 people. In the US, a study published in 2022 reported incidence and prevalence rates of 10.5 and 18.0 per 100,000 people, respectively. Individuals of all races and sex are equally affected, but incidence increases with advancing age.¹ This review examines the efficacy and safety of endoscopic treatment options for achalasia.

Etiology

The pathogenesis of achalasia is poorly understood, complex, and likely multifactorial. Affected patients have impaired function of inhibitory neurons in the distal esophageal myenteric plexus leading to a decrease in inhibitory vasoactive intestinal peptide (VIP) and nitric oxide (NO) and unopposed excitatory acetylcholine within the lower esophageal sphincter (LES) and distal esophagus. This results in impaired relaxation of the LES and diminished, or absent, esophageal peristalsis.^1,,

Achalasia is most commonly idiopathic with the leading hypothesis suggesting an autoimmune process in genetically predisposed patients or those with a preceding viral illness.^, Secondary etiologies include malignancy, specifically small cell lung cancer via paraneoplastic secretion of antineuronal antibodies, and Chagas disease from Trypanosoma cruzi infection.⁵ Chagas disease is highly common in endemic regions such as Central and South America with secondary achalasia occurring in 7-15.5% of patients with Chagas disease in these regions.

Symptoms

Patients present with progressive solid and liquid dysphagia, often accompanied by chest pain (50% of patients), regurgitation (75%), weight loss (60%), and/or heartburn (40%) which leads many patients to first be diagnosed with gastroesophageal reflux disease (GERD).^1,3,, Symptoms are quantified using the Eckardt symptom scoring system with composite scores ranging from 0-12 based on frequency of dysphagia (0-3), regurgitation (0-3), retrosternal pain (0-3), and weight loss (0-3). In most studies, post-treatment composite scores ≤3 indicate clinical remission whereas composite scores >3 indicate treatment failure.

Diagnosis

Many patients undergo upper endoscopy which is important to rule out pseudoachalasia from mechanical obstruction or malignancy and may reveal a tight, puckered gastroesophageal junction (GEJ) with saliva and/or food retention.¹ Barium esophagram may be performed revealing esophageal dilation with a classic “bird beak” appearance.¹ However, the gold standard diagnostic modality which provides important prognostic and treatment implications is high-resolution esophageal manometry.¹

Using high-resolution esophageal manometry, patients are classified into 3 subtypes according to the Chicago Classification. All three achalasia subtypes share the disorder’s hallmark of aperistalsis with impaired GEJ relaxation but vary by their dominant pattern of esophageal body contractility.¹¹ Type I achalasia occurs in 20-40% of cases and is the most severe form characterized by low or absent esophageal pressurization.^1,11, Type II achalasia occurs in 50-70% of cases and is characterized by rapid panesophageal pressurization >30mmHg.^1,11,12 Type III achalasia occurs in 5-10% of cases and is characterized by rapid spastic contractions.^1,11,12 While all the same disorder, this classification is helpful when determining the best treatment approach.

Botulinum Toxin Injections

Technique

Botulinum toxin injections (BTI) induce local, transient, and partial paralysis of the LES to decrease sphincter tone and improve esophageal emptying. Botulinum toxin (BTX) works by inhibiting the release of acetylcholine into neuromuscular junctions, thereby preventing muscle contraction at the LES.¹³ The three A1 BTX subtypes, abobotulinum, incobotulinum, and onabotulinum, are the most studied and, therefore, most commonly administered BTX formulations.¹³

To perform BTI, a standard endoscopic injection needle is used to inject 80-100U (20-25U in each quadrant) of BTX approximately 1cm proximal to the Z-line under endoscopic visualization.^1,13, (Figure 1) In general, injections of BTX produce symptom relief for several months at a time. BTX injections can be repeated every 3-6 months as needed. The procedure is usually performed on an outpatient basis, taking minutes to complete on average.¹⁴

Efficacy

Pasricha et al. performed the first RCT in 1995 with 21 patients showing a significant decrease in symptom score (5.4 vs 0.5; p=0.001) and LES pressure (33% decrease vs 12% increase; p=0.02) between BTX and placebo groups, respectively. Subsequent studies have shown good short-term efficacy with clinical success observed in 73.7-90.5% of patients at 1 month.^15,,,, Unfortunately, symptom recurrence remains a major problem. Campos et al. highlighted this in a meta-analysis of 9 studies with 315 patients which revealed a progressive decline in symptomatic improvement with 78.7%, 70%, 53.3%, and 40.6% of patients in remission at 1, 3, 6, and 12 months, respectively.¹⁷ Because of this, BTI is only recommended as first-line treatment in older patients who have decreased life expectancy and/or are poor candidates for more invasive endoscopic techniques and surgery.¹

Adverse Events

No serious adverse events were reported across multiple studies.^15,18,19,, Patients may experience minor adverse events such as transient post-procedural chest or epigastric pain as reported by D’Onofrio et al. and Annese et al.^16,19

There is potential for fibrosis to develop at the GEJ following BTI with potentially important implications for future therapeutic interventions. According to Patti et al., patients who did not respond to BTI have a lower risk for developing fibrosis and responded well to subsequent surgical myotomy. Conversely, patients who initially responded to BTI but underwent subsequent surgical myotomy for relapse of symptoms experienced an increased number of perforations and failure rates, presumably due to BTI-induced scarring at the GEJ.^22, Interestingly, recent studies suggest efficacy and safety are not impacted by post-BTI fibrosis following subsequent peroral endoscopic myotomy (POEM).^,,

Pneumatic Dilation

Technique

Pneumatic dilation (PD) utilizes single-use balloon dilators to mechanically disrupt LES fibers, resulting in a widened LES orifice and improved esophageal emptying.⁸ Becker et al.’s RCT with 35 patients compared high compliance balloons made of latex that expand with lower inflation pressures and low compliance balloons made of polyethylene that require higher pressures to expand and found no significant difference in outcomes. Despite similar outcomes, low compliance balloon dilators have overtaken high compliance balloon dilators on the market because they allow for a more controlled dilation process. Commercially available options in the US include the Rigiflex II single use balloon dilator (Boston Scientific, Natick, MA, United States), Achalasia Over the Wire Balloon Dilator (Hobbs Medical, Stafford Springs, CT, United States), and Achalasia Balloon (Cook Medical, Winston Salem, NC, United States) with fully inflated balloon diameters ranging 30-40mm.

To perform PD, a guidewire is positioned across the GEJ, and the uninflated balloon is passed over the wire until the midpoint of the balloon aligns with the LES.¹⁸ If fluoroscopy is used, the radiopaque ends of the balloon can be visualized to ensure adequate placement across the level of the diaphragm prior to inflation.^28, The next steps are operator-dependent, but the balloon is gradually inflated to 10-15 PSI and held in place for 15-60 seconds.^18,29,,, Khan et al. and Gideon et al. compared shorter inflation durations (6 and 15 seconds, respectively) to a 60-second inflation time and found no significant differences in efficacy or adverse events between groups.^29, In general, most patients are initially dilated using a 30mm diameter ballon, but serial dilations with 35mm or 40mm balloons may be required every few weeks until symptomatic relief is achieved.³¹

Efficacy

Leyden et al. performed a meta-analysis revealing symptom resolution in 80.7% (46/57) and 73.3% (55/75) of patients undergoing PD at 6 and 12 months, respectively. van Hoeij et al.’s larger meta-analysis of 10 studies with 643 patients undergoing PD compared clinical success over time following single dilation with different balloon diameters (30mm, 35mm, and 40mm). At 6 months, clinical success was observed in 81%, 79%, and 90% of patients following PD with 30mm, 35mm, or 40mm balloons, respectively.³⁵ At 12 months, clinical success was sustained in 77%, 70%, and 87% of patients, respectively.³⁵ This contrasts a single-institution prospective study published previously by Farhoomand et al. which showed dilation using a 30mm balloon dilator alone had a significantly lower 3-year success rate (37%; 95% CI 26-53) compared to serial dilation using 30mm followed by 35mm (76%; 95% CI 65-88) or 30mm followed by 35mm and 40mm (88%; 95% CI 80-97).

Remission is more likely to be achieved in patients who are female, >40-45-years-old, and those with post-PD LES pressures <10mmHg, though this measurement is not commonly performed.^1,36, Farhoomand et al. identified high early failure rates (88% within 3 months) in young men treated with 30mm balloons.³⁶ Therefore, younger men may benefit from initial dilation with a larger balloon (35mm or 45mm) and/or serial PD.

Adverse Events

Minor adverse events include chest pain or reflux symptoms, but the major, life-threatening, and well-documented adverse event associated with PD is esophageal perforation. Perforation occurs in approximately 1.0-1.6% of patients undergoing PD.^30,34,35 van Hoeij et al. compared the risk of perforation based on balloon diameter and found a significantly (p<0.027) higher rate of perforation following use of 35mm balloons (3.2%; 9/282) compared to 30mm balloons (1.0%; 6/588).³⁵ However, the use of 40mm balloons surprisingly did not result in any adverse events, including esophageal perforation (0%; 0/62).³⁵ The reason behind this lower rate of perforation following use of the largest balloon size is unclear. Perforations occurred significantly more after the initial PD compared to subsequent PD procedures (9.3% vs 0.97%, p=0.0017), and there was no correlation between inflation time or maximum balloon pressure and perforations.³⁵

Because of the high risk for perforation, routine testing after PD has been debated, but the most recent ACG guidelines discourage performing post-PD gastrograffin esophagrams unless there is clinical concern for perforation.¹

Esophageal Functional Luminal Imaging Probe Dilation

Technique

Esophageal functional luminal imaging probe (EsoFLIP) dilation is a novel method of mechanically disrupting LES fibers in a more controlled manner than PD. This FDA-approved device utilizes advanced technology to provide real-time measurements of intraluminal pressure and diameter at multiple points along the balloon catheter before, during, and after LES dilation.^38, The EsoFLIP ES-330 balloon catheter (Medtronic, Minneapolis, MN, United States) is commercially available in the US with a maximum inflated balloon diameter of 30mm.³⁹ Baumann et al. outline various step-by-step techniques to successfully perform EsoFLIP dilation.³⁸

Efficacy

Very few prospective and retrospective cohort studies have been performed to date with short-term clinical success achieved in 52.9-85% of patients.^,,,, However, no individual study included more than 28 patients with achalasia. Therefore, larger prospective studies, including studies aimed at assessing long-term symptom relief, and randomized controlled trials are needed.

Adverse Events

Similar to post-PD patients, reflux symptoms (10.7-25% of patients) and transient chest pain (15%) were the most common adverse events encountered after EsoFLIP dilation.^40,41 Esophageal perforation occurred in 1.2% (1/85) of patients in these small studies.^{40,41,42,43,44} 

Peroral Endoscopic Myotomy

Technique

Peroral endoscopic myotomy (POEM) utilizes third-space endoscopy to treat achalasia. The concept of POEM was first outlined by Pasricha et al. in 2007 through experimentation on pigs and later introduced as a treatment option for individuals with achalasia by Inoue et al. in 2009.^,

There are many variations to POEM, but in general, a mucosal entry site is made within the esophagus to expose the submucosal space. Once inside, a submucosal tunnel is created, extending a short distance past the GEJ. Then, circular LES muscle fibers are dissected until the endoscope can be easily passed through the GEJ to confirm successful myotomy. Finally, the mucosal entry site is closed. (Figures 2a-f)

Efficacy

Inoue et al. published the first prospective cohort study in 2010 which showed a significant reduction in symptom score (10 to 1.3; p=0.0003) and LES pressure (52.4mmHg to 19.9mmHg; p=0.0001).⁴⁷ Since then, many meta-analyses have demonstrated high clinical success in 90-97% of patients.^,,,, Vespa et al. performed one of the largest meta-analyses of 31 studies with 3,023 patients revealing a clinical success rate of 91% at a median follow-up of 29-months. Zhang et al. analyzed symptom resolution over time and reported clinical success rates of  91.3%, 90.4%, 89.8%, and 82.2% at 2, 3, 4, and 5 years, respectively. Post-POEM quality of life also significantly (p<0.05) improved according to a meta-analysis by Zhong et al.

Shou et al. identified risk factors for POEM failure in a meta-analysis of 27 studies with 9,371 patients. Worse outcomes occurred in patients with a sigmoid esophagus (a manifestation of advanced achalasia) (OR 1.90, 95% CI 1.45-2.47), type I achalasia (OR 1.30, 95% CI 1.04-1.63), type III achalasia (OR 1.26, 95% CI 0.89-1.78), prior Heller myotomy (OR 5.75, 95% CI 3.97-8.34), and prior PD (OR 1.18, 95% CI 1.07-1.29).⁵⁶ Better outcomes occurred in patients with type II achalasia (OR 0.59, 95% CI 0.47-0.75).⁵⁶ In contrast, there was no significant difference in symptom resolution between achalasia subtypes according to meta-analyses by Zhang et al. and Andolfi et al.^54, POEM was examined in the elderly patient population by Hayat et al. who found no significant difference in success among patients ≥65-years-old (95.74% vs 95.31%) or ≥75-years-old (99.01% vs 97.97%) compared to their younger counterparts.

When initial POEM fails, repeat POEM may be attempted with good outcomes. Hayat et al. analyzed 6 studies with 123 patients who underwent repeat POEM 12.2-13.5 months on average after their initial failed POEM. 82.69% of patients achieved clinical success after repeat POEM.⁵⁹

To optimize outcomes, many variations in POEM technique have been studied. Dhoop et al. compared full-thickness and circular myotomy and found no significant difference in clinical success at 1 or 3 years. However, full-thickness myotomy had an increased risk for post-POEM GERD (RR 3.03, 95% CI 1.53-6.02; p=0.002) and esophagitis (RR 1.79, 95% CI 1.09-2.76; p=0.02) compared to circular myotomy.⁶¹ Rodriguez de Santiago et al. and Mohan et al. performed meta-analyses comparing anterior and posterior wall tunneling, each finding no significant difference between myotomy approaches.^52, Procedure time was shorter with posterior (62.1 minutes) compared to anterior (82.7 minutes) wall tunneling.⁶² In practice, individual operators are free to perform POEM as they see fit.

Optimal myotomy length has been extensively studied, comparing short and long myotomy lengths. Zhang et al., Weng et al., and Ghazaleh et al. performed meta-analyses which showed shorter myotomy resulted in shorter procedure times, as expected, with the same or less risk of reflux but no significant difference in clinical success.^,, 

POEM has also been successfully used as rescue therapy following failed improvement with other treatment modalities for achalasia. Tan et al. and Zhong et al. demonstrated clinical success in 90.8% and 91.0% of these patients, respectively.^,

Adverse Events

Symptomatic reflux and reflux esophagitis are two of the most common adverse events seen following POEM with rates ranging from 22.0-26.2% and 5.9-19.0%, respectively.^{47,48,49,53,54,,} Mota et al. performed a meta-analysis of 25 studies and found no statistical difference in post-POEM GERD rates when comparing full-thickness, partial-thickness and circular myotomy, anterior and posterior myotomy, or subtypes of achalasia. This differs from Dhoop et al.’s more recent meta-analysis which showed an increased risk of post-POEM GERD and esophagitis with full-thickness myotomy.⁶¹ POEM combined with fundoplication (POEM-F) has been trialed in an attempt to reduce post-POEM reflux. The rate of post-POEM-F reflux reported by Gopakumar et al.’s meta-analysis of 7 studies with 127 patients was 13.8% which is lower than most reflux rates after POEM alone but comes with far higher costs.

Serious adverse events include subcutaneous emphysema   (21.8-31.6%    of    patients), pneumoperitoneum (16.2-30.6%), pneumothorax (8.7-11.0%), and in very rare instances, mediastinal emphysema/leak (0.3-4.9%), esophageal/gastric perforation (2.6%), bleeding (0.9-1.1%), and death (0.09%).^48,69

Conclusion

Achalasia is a complex and debilitating esophageal motility disorder, but there are many efficacious endoscopic treatment options available, enabling individualized treatment approaches. Botulinum toxin injections have shown decent short-term clinical success with few adverse events and are best suited for older patients and/or those who are not candidates for more invasive endoscopic modalities. Pneumatic dilation has shown better short-term outcomes but is limited by high rates of symptom relapse and a small risk of serious adverse events, most notably esophageal perforation. Peroral endoscopic myotomy offers the highest long-term success rates but may be accompanied by post-procedural reflux symptoms and/or reflux esophagitis. Treatment should be tailored to patient preferences and institutional expertise. 

References

Download Tables, Images & References

Introduction

Advances in gastrointestinal functional testing have highlighted the limitations of relying on high-resolution manometry (HRM) alone to characterize esophageal pathology, especially with regards to manometric disturbances in patients with dysphagia. While HRM remains the gold standard for evaluating esophageal motor disorders, it provides a pressure-based assessment that may not fully reflect tissue compliance during bolus transit. The functional lumen imaging probe (FLIP) (EndoFLIP developed by Crospon, now Medtronic, Minneapolis, MN, USA) is an impedance planimetry-based technology that provides real-time assessment of luminal geometry and distensibility during volumetric distension.

EndoFLIP serves as an adjunctive diagnostic tool during upper endoscopy to clarify esophageal physiology/pathology when standard testing such as HRM and/or Timed Barium Esophagram (TBE) is inconclusive or discordant with the patient’s symptoms. It is especially helpful in patients with dysphagia, chest pain, or refractory reflux when standard manometry appears normal or equivocal, as FLIP can reveal inadequate esophagogastric junction (EGJ) opening or reduced distensibility that may otherwise be missed.

In addition, EndoFLIP can be used before and after intervention to assess changes in esophagogastric junction opening and distensibility following pneumatic dilation, esophageal or gastric peroral endoscopic myotomy (POEM or G-POEM), laparoscopic Heller myotomy, fundoplication, transoral incisionless fundoplication (TIF), and endoscopic dilation of benign esophageal strictures.

EsoFLIP (Medtronic, Minneapolis, MN, USA) is a therapeutic version of FLIP designed for controlled endoscopic dilation. It uses a stiff, noncompliant balloon that dilates the lumen while measuring diameter in real time. Unlike standard through-the-scope balloons, EsoFLIP allows direct three-dimensional visualization of luminal opening during dilation, adjustment to a target diameter, and dilation without fluoroscopy.

This manuscript summarizes current evidence on EndoFLIP and EsoFLIP with an emphasis on practical indications, clinical interpretation, and recognized limitations. Using common clinical scenarios including Achalasia, Esophagogastric Junction Outlet Obstruction (EGJOO), Esophageal strictures, and anti-reflux or myotomy based therapies, we aim to provide clinicians with a practical guide for applying these technologies in routine clinical practice. 

INTRODUCTION

Principle of Impedance

Compliance refers to how easily a hollow organ stretches and increases in volume when pressure is applied, which reflects how well ingested contents can pass through the segment. Impedance planimetry measures this by calculating compliance (volume change relative to pressure) and distensibility (cross-sectional area relative to pressure).¹ EndoFLIP was first developed by Hans Gregersen in the 1980s to measure EGJ compliance and distensibility in conditions like GERD and achalasia.^,,, 

Eventually, in 2009, the first commercially available device of the functional lumen imaging probe (EndoFLIP developed by Crosson, now Medtronic, Minneapolis, MN, USA) was introduced. The EndoFLIP device helps to assess the biomechanical properties of a sphincter or a tubular organ in the gastrointestinal (GI) tract by providing a three-dimensional image of said structure.⁶ It uses a balloon catheter with impedance electrodes to calculate luminal diameter, cross-sectional area, and distension pressure, allowing for the evaluation of luminal distensibility and compliance. This provides a more detailed understanding of sphincter function compared to HRM and also helps to evaluate esophageal wall stiffness.⁷

EndoFLIP was initially used to evaluate the EGJ in patients with gastroesophageal reflux disease (GERD) and achalasia.⁷ Over the past decade, its use has expanded to other esophageal conditions like eosinophilic esophagitis (EOE), and other locations of the GI tract, mostly to the stomach for pylorus measurements in patients with gastroparesis undergoing evaluation and therapy.⁷ It can also be used before or after foregut procedures (POEM, G-POEM, TIF, surgical myotomy, and fundoplication) to assess treatment response and guide management.⁶

EsoFLIP (Medtronic, Minneapolis, MN, USA) is a variant of EndoFLIP which combines the advantage of both a diagnostic and a therapeutic tool.⁶ It is being used as an alternative device for dilation of functional and structural stenoses in the GI tract.⁶

Technology Overview: What These Tools Actually Measure

EndoFLIP

The EndoFLIP system compromises a 24 cm long catheter with a 3-mm outer diameter and a highly compliant balloon integrated into its tip.⁷ The catheter is available in two lengths: EF-322 (16 cm) and EF-325 (8 cm).⁷ The 16 cm catheter consists of 16 electrode pairs spaced 1 cm apart and measures both EGJ metrics and esophageal body contractile response, whereas the 8 cm catheter consists of 16 electrode pairs spaced 0.5 cm apart and primarily measures EGJ metrics.^,,,

FLIP measurements utilize impedance planimetry, a technique that is based on Ohm’s Law (voltage is proportional to the impedance which increases with the filling of the balloon) to determine luminal cross-sectional area (CSA), distensibility of the EGJ and/or esophageal body, and esophageal body contractile response to volumetric distention. The equipment consists of a FLIP catheter with impedance planimetry electrodes, and a pressure transducer located inside of polyurethane bag, as well as a digital data acquisition and display system.⁸

The Dallas Consensus (2025) is an expert statement that standardizes how FLIP panometry is to be performed and interpreted during endoscopy in patients with suspected esophageal motility disorders. This is important because it brings consistency to a test that has been used variably, making FLIP findings easier to interpret and compare across centers.¹³

EndoFLIP is performed after a standard upper endoscopy to inspect the mucosa and clear luminal contents, typically under monitored anesthesia care (MAC) or general anesthesia.⁷ The deflated balloon catheter is zeroed to atmospheric pressure and advanced transorally or transnasally into the esophagus or stomach.⁷ After positioning is confirmed, the balloon is inflated stepwise, starting at 30 mL and increasing in 10 mL increments up to 60 mL for the 16-cm balloon, or from 20 mL up to 50 mL for the 8-cm balloon.⁷ At each volume, measurements of diameter, cross-sectional area (CSA), intraballoon pressure (IBP), distensibility index (DI), maximum EGJ diameter, and esophageal body contractile pattern are recorded during stable distension for 15–30 seconds to account for respiration and esophageal contractions.⁷ The balloon is deflated before removal.⁷

Clinical Indications: When EndoFLIP Adds Value

Use of EndoFLIP in the Esophagus

As per American Gastroenterological Association (AGA) clinical practice update guidelines 2025, clinicians should perform a high-quality upper endoscopy evaluating for esophageal pathology immediately prior to considering FLIP to evaluate for any structural and mucosal abnormalities.⁸ Physicians should document any visible pathology such as strictures, Eosinophilic Esophagitis (EoE), post operative surgical anatomy, hiatal hernia, as it can impact FLIP catheter placement.^,, FLIP can be performed when alternate investigations like HRM or TBE are inconclusive in patients with symptoms of esophageal obstruction such as dysphagia, esophageal-type regurgitation and/or meal-related chest pain.⁸

Discordance between esophageal test findings is not unusual in patients with symptoms of esophageal dysmotility or dysphagia.⁸ In a study of 126 symptomatic patients who underwent HRM, TBE, and FLIP, concordance among all the 3 tests assessing lower esophageal sphincter was only 57%. When initial tests are discordant, clinicians should consider using more than one physiologic test to improve diagnostic confidence before proceeding with irreversible lower esophageal sphincter (LES) disruption.^,

By measuring distensibility, EndoFLIP helps to diagnose both obstructive and reflux-related processes at the LES and complements the assessment of gastrointestinal motility disorders, particularly achalasia.⁷ 

Recent studies involving healthy controls have defined normal EGJ distensibility as EGJ-DI > 2.8 mm²/mm Hg and a maximum EGJ diameter >18 mm. The EGJ opening is described using two parameters, EGJ-DI and maximum EGJ diameter as normal EGJ opening (NEO), reduced EGJ opening (REO), or inconclusive EGJ opening (IEO).¹³ Esophageal body contractile response patterns can be normal (multiple distinct antegrade contractions and/or repetitive antegrade contractions) or abnormal (absent, diminished, disordered, or spastic contractile response patterns).¹³ FLIP pressure measurements discriminate diminished ( <40 mm Hg) from disordered ( >40 mm Hg) contractility when distinct antegrade contractions or spastic contractile response are not seen.

Use of FLIP Findings in Making Obstructive Structural and Motor Diagnoses

FLIP panometry aids in distinguishing obstructive structural and motor disorders by combining EGJ opening metrics with esophageal body contractile patterns.⁸ 

Normal EGJ opening (EGJ-DI ≥ 2.0 mm²/mm Hg and maximum EGJ diameter ≥ 16 mm) with normal antegrade contractions suggests that a major motor disorder is unlikely.⁸

Reduced EGJ opening (EGJ-DI < 2.0 mm²/mm Hg and maximum EGJ diameter < 12 mm) supports a structural or motor obstruction in the presence of compatible symptoms and endoscopy findings.⁸

Absent or weak esophageal contractions, defined as no contractions or a pressure increase < 40 mm Hg, suggest non-spastic achalasia.⁸ Spastic contractile patterns, such as sustained LES contraction or sustained occluding contractions, are more consistent with spastic achalasia.⁸ If EGJ opening is reduced but contractility is preserved, a mechanical obstruction should be considered.⁸

Inconclusive EGJ opening refers to isolated EGJ-DI < 2.0 mm²/mm Hg or a maximum EGJ diameter < 16 mm that does not meet criteria for reduced opening.⁸ This can be seen with any contractile pattern, and both motor and mechanical obstruction remain possible, requiring further evaluation.⁸

Role of FLIP in Evaluating Esophageal Motility Disorders

Achalasia

Achalasia is characterized by LES dysfunction and abnormal esophageal peristalsis.⁷ HRM remains the gold standard test to diagnose achalasia, with EndoFLIP providing supplementary information in some patients.⁷ HRM has high sensitivity and can identify three distinct achalasia subtypes but may yield inconclusive results in patients with borderline pressure values.⁷

Patients with clinically suspected achalasia who do not meet the HRM criteria of the Chicago Classification v 4.0 (Integrated Relaxation Pressure (IRP) >15 mm Hg in supine position) can be recognized by the FLIP by decreased EGJ-DI or abnormal esophageal contractions.^, FLIP findings of REO and abnormal contractile response patterns are strongly associated with achalasia.⁸ (Figure 1)

Endoscopic findings of achalasia are quantified as the CARS (content, anatomy, resistance, and stasis) score. A CARS score ≥ 4 has a specificity of 99% and a sensitivity of 68-72% to identify achalasia. A CARS score of 0-1 combined with NEO on FLIP had a negative predictive value (NPV) of 100% for achalasia and a CARS >4 with REO on FLIP had a positive predictive value(PPV) of 97% for non-spastic achalasia. If upper endoscopy does not demonstrate findings suggestive of achalasia, abnormal EGJ opening on FLIP should prompt further testing with HRM and/or TBE to confirm the diagnosis.⁸

EGJOO

EndoFLIP plays an important role in evaluating non-achalasia EGJOO.⁷ EGJOO is a manometric diagnosis with elevated IRP and normal esophageal peristalsis and requires additional testing to confirm EGJ obstruction by either TBE or EndoFLIP to be considered clinically significant.⁶ 

In a validation study by Carlson et al., FLIP panometry identified clinically relevant EGJOO in 93% (229/245) of patients when the EGJ-DI was ≥ 3.0 mm²/mm Hg and the maximum EGJ diameter was > 12 mm. These thresholds help to differentiate clinically relevant EGJOO from borderline or incidental findings.²⁷

Role of FLIP in Eosinophilic Esophagitis (EoE)

Eosinophilic esophagitis (EoE) is characterized by chronic immune-mediated inflammation of the esophagus, leading to fibrous changes, stiffening of the esophageal wall with a decrease in esophageal compliance, luminal narrowing, and the formation of strictures.^, EoE surveillance normally involves upper endoscopy with biopsies and/or dilation as needed to assess histologic activity and guide treatment. 

EndoFLIP offers an alternative approach by providing an objective measurement to evaluate esophageal remodeling as well as detection and localization of esophageal narrowing and strictures. EndoFLIP measures esophageal distensibility by recording cross-sectional area and intraluminal pressure during controlled balloon distension.⁷ This helps to identify the distensibility plateau which corresponds to the luminal opening of the esophagus at its narrowest point.

Patients with EoE have significantly reduced esophageal compliance compared to healthy individuals, with lower distensibility plateaus associated with endoscopic findings such as rings, strictures, increased risk of food impaction and the need for periodic dilation.

The distensibility plateau is defined as a static esophageal diameter despite increasing distention volume and pressure.⁸ A distensibility plateau of >225 mm² (diameter > 17 mm) was associated with a lower risk of food impaction and the need for dilation in EoE patients.³³ The severity of reduced distensibility plateau correlates with symptom duration and diagnostic delay. In a study by Araujo et al., abnormal esophageal distensibility (≤17 mm) was present in 23% of patients with symptoms for less than 5 years, compared to 64% in those with symptoms for 25 years or more.³⁴ This progressive decline in distensibility supports the concept of EoE as a fibrostenotic disease that worsens over time, particularly in patients with persistent mucosal eosinophilia (≥15 eosinophils per high-powered field).³⁴ 

Carlson et al. evaluated 215 patients with EoE using FLIP panometry and found abnormal composite measures of esophageal body compliance, contractile response, EGJ distensibility, and maximal diameter were associated with higher eosinophil counts and worse endoscopic severity.

Role of FLIP in Foregut Interventions

Clinicians can consider performing EndoFLIP interprocedurally during myotomy [per-oral endoscopic myotomy (POEM) or laparoscopic Heller Myotomy (LHM)].⁸

The LES can be evaluated while performing POEM or LHM and can help direct the length of myotomy and adequacy of LES disruption in real time.^, Intra-operative EGJ-DI <2-3 mm²/mm Hg
may predict persisting symptoms and may prompt additional myotomy.^,, In contrast, high intraoperative EGJ-DI may be associated with increased postoperative reflux symptoms, and increase risk of erosive esophagitis after POEM or LHM.^,, 

Role of FLIP in Symptom Evaluation after Foregut Interventions

Clinicians should consider performing EndoFLIP in patients who have persistent symptoms of esophageal obstruction after treatment of achalasia spectrum disorders by POEM or LHM.⁸ An EGJ-DI <2-3 mm²/mm Hg after LES disruption is associated with suboptimal esophageal emptying, suggesting ineffective LES disruption, and may warrant consideration of additional LES-directed therapy.^,, In contrast, NEO on FLIP should prompt consideration of alternative explanation for symptoms, including abnormal esophageal body anatomy and gastroesophageal reflux disease (GERD).⁴⁶

FLIP can also be used to assess symptoms after antireflux surgery (ARS), such as fundoplication or bariatric intervention.⁹ EGJ-DI has been used to tailor fundoplication in attempts to prevent postoperative dysphagia.^, Tightness of hiatal closure impacts EGJ-DI more than the actual fundoplication. Ideal EGJ-DI ranges have been proposed for Toupet ( EGJ-DI 2.6-3.7 mm²/ mm Hg) and Nissen ( >2.2 mm²/ mm Hg) fundoplication, which helps with intraoperative decision making such as altering the type of ARS, or loosening or tightening the wrap.⁴⁸

Use of EndoFLIP in the Stomach

Pylorospasm (decreased pyloric distensibility) during gastric contraction plays a key role in the pathophysiology of gastroparesis. Pylorus targeted therapy such as G-POEM can help patients in reducing the symptoms of gastroparesis.⁶ While EndoFLIP can assess pyloric distensibility, its correlation with gastric emptying and symptoms in gastroparesis remains inconsistent, and the European Society of Gastrointestinal Endoscopy (ESGE) does not currently recommend routine use for pylorus-targeted therapy.

Malik et al. assessed pyloric distensibility in 54 patients with idiopathic and diabetic gastroparesis, the mean distensibility index was 10.7 ± 2.57 mm²/mm Hg, but a wide range of values for both distensibility (1–55 mm²/mm Hg) and diameter (5.6–22.1 mm) was observed. Snape et al. demonstrated that patients presenting with nausea and vomiting and confirmed delayed gastric emptying had decreased pyloric distensibility compared to patients with normal gastric emptying (8 mm²/mm Hg vs. 12.4 mm²/mm Hg). An upper cut-off of 9-10 mm²/mm Hg was used by most of the authors to define pylorospasm while using EndoFLIP.⁶ Lower pyloric distensibility index in gastroparesis has been linked to better outcomes after G-POEM.

EsoFLIP: The Therapeutic Dilation Catheter

Bougie and balloon dilation are widely used for benign gastrointestinal strictures but provide limited real-time feedback on luminal properties despite endoscopic or fluoroscopic guidance.⁶ EsoFLIP (Medtronic, Minneapolis, MN) is a more recently developed therapeutic device for esophageal hydraulic balloon dilation and uses the same hardware and technology platform as EndoFLIP, but comes with a stiffer balloon to generate sufficient pressure for dilation.⁶ The EsoFLIP system offers three catheter sizes: 10 mm (ES-310) and 20 mm (ES-320) balloons for esophageal strictures and a 30 mm (ES-330) balloon, mainly used for patients with achalasia and esophago-gastric junction outflow obstruction.⁷ 

Indications for EsoFLIP

EsoFLIP balloons are used in adults for LES dilation in achalasia and for treatment of esophageal strictures due to surgery, GERD, or radiation as well as the pylorus. (Figure 2)

The inflation of the balloon is manually controlled via an electrohydraulic pump, allowing adjustments based on the target diameter.⁷ Initial measurements of the diameter or CSA at partial filling volume (20 mL for ES-320 and 30 mL for ES-330) are followed by gradual, stepwise filling to approximately 30 mL/50 mL, with additional increments of 1–3 mL to reach the target diameter. The maximum filling volume of 42 mL/75 mL (ES-320/ES-330) is used to achieve a target diameter of 20-30 mm.⁷

The advantages of using EsoFLIP over traditional methods of dilation include dilation without the need for fluoroscopy, reducing radiation exposure, precise control of the balloon filling to a desired diameter, and measurement of stricture size and assessment of dilation effect in real time.⁷ However, these benefits may come at the expense of higher procedural costs.⁷

Although clinical outcome studies on EsoFLIP are limited, small series have demonstrated its technical feasibility, safety, and short-term efficacy.⁷ In a feasibility study of 10 patients with achalasia, EsoFLIP achieved dilation to 28–30 mm without serious adverse events with improvement in esophageal symptoms assessed by the Eckardt score as well as improved esophageal emptying recorded with TBE.

Limitations of EndoFLIP and EsoFLIP

EndoFLIP

These include high costs, lack of real-time data processing software, and limited data storage solutions.⁷ CSA and pressure measurements can vary during stable distension volumes due to respiratory artifacts, vascular effects, and both spontaneous and balloon-induced esophageal contractions. There is limited penetrance outside specialized centers despite commercial availability since 2009, due to lack of data supporting utility in general practice.

EsoFLIP

Although EsoFLIP offers several advantages, it has practical limitations, including lack of through-the-scope capability, the need to remove the external guidewire before dilation, reliance on an external pressure monitor, additional time for balloon filling and emptying, and higher procedural costs.⁵⁵

Conclusion

The EndoFLIP is an advanced diagnostic tool that helps with the evaluation of sphincters and GI luminal organs by providing real-time dynamic monitoring of distensibility, luminal geometry, and biomechanical properties. It was originally used to assess EGJ, but its application has expanded to other locations including the esophageal body and the pylorus. The device’s ability to measure distensibility can guide the tailoring of specific endoscopic and surgical therapies, such as dilation, fundoplication, and myotomy, to achieve desired outcomes during a single session.

The EsoFLIP is a therapeutic modification of the EndoFLIP catheter that provides real-time visualization and monitoring of dilation as it is being performed via controlled volumetric filling. EsoFLIP represents a useful addition to the treatment of esophageal disorders, although further studies are needed to better define its role and outcomes. 

References

Download Tables, Images & References