EGJ Disorders — Achalasia & Reflux
EGJ-DI thresholds, FLIP topography subtypes, and how FLIP rescues the inconclusive HRM
Learning outcomes
- 1
Apply the EGJ-DI threshold of ≤ 2.0 mm²/mmHg at 60 mL fill to diagnose obstructive EGJ physiology
Apply - 2
Classify FLIP topography patterns (RACs, absent contractility, RRCs, sustained occluding, disordered) and link to Chicago v4.0 phenotypes
Analyze - 3
Decide when to refer for POEM, pneumatic dilation, Heller, or fundoplication revision based on combined FLIP + HRM data
Evaluate - 4
Recognise post-fundoplication FLIP patterns: tight wrap (DI < 2.0), too-loose wrap (DI > 4), and slipped/recurrent hernia
Analyze
Pre-reading anchors
Carlson DA, Prescott JE, Baumann AJ, et al. (2022). Esophageal motility classification can be established at the time of endoscopy: a study evaluating real-time functional luminal imaging probe panometry. Gastroenterology 162(1):142-156 PMID 34520731
The 2.0 rule
An EGJ-DI ≤ 2.0 mm²/mmHg at a 60 mL fill is the canonical threshold for obstructive EGJ physiology. Combined with absent repetitive antegrade contractions (RACs) on FLIP topography, it confirms achalasia even when HRM is non-diagnostic. A DI between 2.0 and 3.0 with disordered contractility is the classic "inconclusive" zone — these patients need provocative HRM testing (rapid drink, solid swallows) or repeat workup. A DI > 3.0 with normal RACs effectively excludes obstructive physiology.
The threshold was derived from a Northwestern cohort of more than 700 patients with combined HRM and FLIP and validated against the long-term clinical course. Sensitivity for achalasia is approximately 95% at DI ≤ 2.0; specificity rises to 99% when combined with absent or disordered topography. The DI is not just a number — it is the integral of physical resistance to passive distension and correlates directly with the patient's lived experience of dysphagia.
Carlson 2022 (Gastroenterology): in 539 patients undergoing simultaneous HRM and FLIP, EGJ-DI ≤ 2.0 + absent RACs had > 95% concordance with Chicago achalasia.
FLIP topography — five patterns to know
The FLIP topography panel displays the 16 impedance segments as a colour-coded space-time heatmap during sustained 60 mL filling. Five canonical patterns appear:
1. NORMAL — repetitive antegrade contractions (RACs) at ~6 per minute, organised, propagating from proximal to distal. Seen in healthy controls and most patients with non-obstructive symptoms.
2. ABSENT CONTRACTILITY — a flat, featureless heatmap. Characteristic of Type I and Type II achalasia. The lower oesophageal lumen does not contract because the inhibitory neurons are largely gone.
3. RRC (repetitive retrograde contractions) — propagation from distal to proximal, often vigorous. Strongly associated with Type III achalasia and oesophageal spasm.
4. SUSTAINED OCCLUDING CONTRACTION — a single, prolonged contraction band that holds for tens of seconds. Less specific, may be seen in EGJ-OO and some atypical motility.
5. DISORDERED — short, weak, non-propagating activity. Common in Chicago "ineffective oesophageal motility" and absent contractility on HRM.
Subtyping achalasia with FLIP
Chicago v4.0 classifies achalasia into three subtypes based on HRM; FLIP topography complements that. Type I (no oesophageal pressurisation, flat HRM) maps to ABSENT topography on FLIP. Type II (pan-oesophageal pressurisation) also maps to ABSENT topography in most cases. Type III (premature, spastic contractions on HRM) maps to RRC or disordered topography on FLIP — and these patients tend to respond better to a longer, tailored myotomy via POEM than to pneumatic dilation. FLIP topography is therefore not just confirmatory; it informs treatment choice.
Post-fundoplication and post-POEM evaluation
FLIP is invaluable in the patient who returns with dysphagia or recurrent reflux months after surgery. Tight wrap: EGJ-DI < 2.0 with persistent dysphagia — consider revision or pneumatic dilation. Too-loose wrap: EGJ-DI > 4.0 with recurrent reflux on pH studies — consider redo fundoplication or magnetic sphincter augmentation. Slipped wrap or recurrent hiatus hernia produces a heterogeneous DI pattern and is best characterised with combined imaging.
Post-POEM, a target DI of 6–9 is associated with the best balance between durable dysphagia relief and acceptable reflux rates. DI > 9 carries a 50% risk of clinically significant reflux at 2 years — these patients should be monitored with ambulatory pH and considered for early acid-suppression strategy.
Clinical pearls
- A symptomatic patient with normal HRM and EGJ-DI ≤ 2.0 + absent RACs is treated as achalasia — do not let HRM veto the FLIP.
- Post-fundoplication dysphagia with EGJ-DI < 2.0 suggests a tight wrap — useful for surgical decision-making.
- RRC topography on FLIP in a clinically suspected achalasia points to Type III — favour POEM over pneumatic dilation.
- In jackhammer / hypercontractile oesophagus, FLIP often shows a normal DI but disordered or sustained topography — useful adjunct to HRM diagnosis.
Pitfalls
- Do not interpret a DI in isolation in the patient with a hiatus hernia >5 cm — the FLIP balloon position matters and can artefactually elevate the DI.
- A single FLIP fill is insufficient — always step from 30 → 40 → 50 → 60 mL to capture the distensibility curve, not a single point.
- Avoid FLIP within 4 hours of pneumatic dilation — acute oedema artefactually lowers the DI and may misclassify response.
Self-assessment MCQs
Q1
A 42-year-old woman with progressive dysphagia has HRM showing IRP 13 mmHg (borderline). FLIP shows EGJ-DI 1.6 at 60 mL with absent RACs. The MOST appropriate interpretation is:
Q2
In suspected type III achalasia (HRM shows premature contractions), which FLIP topography pattern would you most expect?
Q3
Two years after Nissen fundoplication, a patient returns with bothersome solid-food dysphagia. FLIP shows EGJ-DI 1.4 at 60 mL. What does this suggest?
Evidence corner
Carlson DA, Prescott JE, Baumann AJ, et al. (2022). Esophageal motility classification can be established at the time of endoscopy: a study evaluating real-time functional luminal imaging probe panometry. Gastroenterology 162(1):142-156 PMID 34520731
Carlson DA, Baumann AJ, Donnan EN, et al. (2021). Evaluating esophageal motility beyond primary peristalsis: assessing esophagogastric junction opening mechanics and secondary peristalsis in patients with normal manometry. Neurogastroenterol Motil 33(10):e14116 PMID 33705602
Pandolfino JE, de Ruigh A, Nicodème F, et al. (2013). Distensibility of the esophagogastric junction assessed with the functional lumen imaging probe (FLIP) in achalasia patients. Neurogastroenterol Motil 25(6):496-501 PMID 23413801
Triggs JR, Carlson DA, Beveridge C, et al. (2019). Functional luminal imaging probe panometry identifies achalasia-type esophagogastric junction outflow obstruction. Clin Gastroenterol Hepatol 17(11):2218-2226 PMID 30708111
Su B, Dunst C, Gould J, et al. (2020). Experience-based expert consensus on the intra-operative usage of the EndoFLIP impedance planimetry system. Surg Endosc 35(6):2731-2742 PMID 32556760
Reflection
Pull up your last three "inconclusive" HRM reports. Walk through what an EGJ-DI value would have added to each decision.