Pyloric Distensibility & G-POEM Selection
How pyloric FLIP separates the gastroparesis patients who will benefit from G-POEM from those who will not
Learning outcomes
- 1
Measure pyloric DI and CSA at 40 mL and 50 mL using a standardised antral-to-duodenal pullback technique
Apply - 2
Use a pyloric DI < 9–10 mm²/mmHg at 50 mL as the validated threshold to predict G-POEM response
Evaluate - 3
Differentiate the four phenotypes of refractory gastroparesis (low-DI, neuropathic, myopathic, mixed) and tailor therapy accordingly
Analyze - 4
Integrate pyloric FLIP with gastric emptying scintigraphy and symptom scales (GCSI, PAGI-SYM) for patient selection
Apply
Pre-reading anchors
Vosoughi K, Ichkhanian Y, Benias P, et al. (2022). Gastric per-oral endoscopic myotomy (G-POEM) for the treatment of refractory gastroparesis: results from an international prospective trial. Gut 71(1):25-33 PMID 33741638
Jacques J, Pagnon L, Hure F, et al. (2019). Peroral endoscopic pyloromyotomy is efficacious and safe for refractory gastroparesis: prospective trial with assessment of pyloric function. Endoscopy 51(1):40-49 PMID 30184609
Why pyloric FLIP matters
Refractory gastroparesis is a heterogeneous disease — roughly half of patients have a tight, low-compliance pylorus that responds beautifully to G-POEM (gastric peroral endoscopic myotomy), and roughly half do not. Pyloric FLIP cleanly identifies the responders. The Malik-Bhatia and Jacques studies established that a pyloric DI < 9–10 mm²/mmHg at 50 mL identifies patients who will improve symptomatically after G-POEM (GCSI drop ≥ 1.5, gastric emptying normalisation in 60–70%). Patients with normal pyloric distensibility (DI > 12) are unlikely to benefit and should be considered for alternative therapies — gastric electrical stimulation, dietary modulation, or pyloric Botox as a temporising measure.
The pylorus is not simply a sphincter in the oesophageal sense — it is a pressure-modulated outflow gate with both myogenic and vagally-mediated tone. In diabetic and idiopathic gastroparesis, vagal nerve fibre loss and ICC depletion can leave a pylorus that is mechanically tight but neurologically inert. This is exactly the phenotype where myotomy works: cutting the muscle bypasses the failed neural control.
DI < 10 at 50 mL → G-POEM candidate. DI > 12 → look elsewhere. The 10–12 range is grey and warrants joint MDT discussion plus repeat measurement.
Technique — measuring pyloric DI
Pyloric FLIP is performed at routine upper endoscopy under propofol sedation, with the patient supine. After upper-GI inspection, the FLIP catheter (EF-322N) is advanced through the working channel of the gastroscope and parked across the pylorus under direct vision. The 8 cm balloon should straddle the pylorus with the impedance segments visible in both the antrum and duodenal bulb.
Fill the balloon stepwise: 30 mL → 40 mL → 50 mL. Hold each volume for 30 seconds and record the lowest steady-state CSA at the narrowest segment (typically the pyloric ring) and the corresponding intra-bag pressure. Repeat three times for the 50 mL fill and average the DI values. Avoid measurements during obvious pyloric spasm — pull the balloon back a centimetre and re-measure once steady state returns.
A complete pyloric FLIP study takes 5–7 minutes added to the routine gastroscopy.
Four phenotypes of refractory gastroparesis
Combining pyloric FLIP with gastric emptying scintigraphy and high-resolution gastric mapping reveals four phenotypes:
PHENOTYPE A — Low-DI obstructive (DI < 10, prolonged emptying, normal antral contractility). The G-POEM responders. Approximately 35% of refractory cases.
PHENOTYPE B — Neuropathic (DI 10–14, prolonged emptying, weak/uncoordinated antral activity, often diabetic). G-POEM may help but response is variable; consider gastric electrical stimulation.
PHENOTYPE C — Myopathic (DI > 14, normal pyloric function, generalised gastric hypocontractility). G-POEM does not help. Nutritional support, prokinetics, gastric stimulator, or jejunal feeding.
PHENOTYPE D — Mixed (variable DI, multiple co-existing problems). Multidisciplinary management — surgery, dietitian, pain specialist, psychiatry.
Pyloric Botox — useful diagnostic before G-POEM?
Pyloric Botox injection has long been used as a screen for G-POEM candidacy — but the evidence is mixed. Two prospective trials (Pasricha 2013, Friedenberg 2016) found no symptomatic benefit over placebo. Pyloric FLIP outperforms Botox as a selection tool because it identifies the mechanically tight pylorus directly, without depending on a temporary pharmacological effect. The contemporary approach is: measure pyloric DI first; if low, proceed directly to G-POEM. Reserve Botox for the unusual case where FLIP is unavailable or the patient cannot proceed to definitive therapy.
Clinical pearls
- Always do FLIP under sedation with the patient supine — pyloric tone changes with body position.
- Pair pyloric DI with a baseline 4-hour gastric emptying scintigraphy — both abnormal = strongest predictor of G-POEM benefit.
- Pre-G-POEM patients also benefit from a baseline GCSI score — at 3 and 6 months postoperatively, the GCSI delta tells you whether the procedure worked.
Pitfalls
- A spasming pylorus can transiently drop the DI — record at least three steady-state 50 mL fills and average.
- Do not measure pyloric DI in a patient with recent ulcer disease or pyloric stenosis from chronic NSAID use — the anatomy is distorted and FLIP cannot separate mechanical scarring from sphincter dysfunction.
- Beware the post-bariatric surgery patient — the pylorus may have been bypassed (RYGB) or distorted (sleeve), making DI uninterpretable.
Self-assessment MCQs
Q1
A 38-year-old with diabetic gastroparesis refractory to prokinetics has pyloric FLIP showing DI 6.5 mm²/mmHg at 50 mL and prolonged 4-hour gastric retention on scintigraphy. What is the most appropriate next step?
Q2
Which patient is LEAST likely to benefit from G-POEM?
Evidence corner
Malik Z, Sankineni A, Parkman HP. (2015). Assessing pyloric sphincter pathophysiology using EndoFLIP in patients with gastroparesis. Neurogastroenterol Motil 27(4):524-531 PMID 25817713
Vosoughi K, Ichkhanian Y, Benias P, et al. (2022). Gastric per-oral endoscopic myotomy (G-POEM) for the treatment of refractory gastroparesis: results from an international prospective trial. Gut 71(1):25-33 PMID 33741638
Jacques J, Pagnon L, Hure F, et al. (2019). Peroral endoscopic pyloromyotomy is efficacious and safe for refractory gastroparesis: prospective trial with assessment of pyloric function. Endoscopy 51(1):40-49 PMID 30184609
Saadi M, Yu D, Malik Z, et al. (2018). Pyloric sphincter characteristics using EndoFLIP in gastroparesis. Rev Gastroenterol Mex 83(4):375-384 PMID 29615280
Gourcerol G, Tissier F, Melchior C, et al. (2015). Impaired fasting pyloric compliance in gastroparesis and the therapeutic response to pyloric dilatation. Aliment Pharmacol Ther 41(4):360-367 PMID 25523288
Reflection
Identify the next refractory-gastroparesis patient you see. Map their workup against the four-phenotype framework — does FLIP change your plan?