Expanding the Physiological Role of the Endoluminal Functional Lumen Imaging Probe From the Esophagus to Pediatric Pylorus

The endoluminal functional lumen imaging probe (EndoFLIP) has expanded our understanding of gastrointestinal wall mechanics by providing a passive assessment of luminal distensibility, in contrast to manometry, which evaluates actively generated, swallow-induced intraluminal contractile activity.^1,2 While the technology has been most extensively investigated in the esophagus and the esophagogastric junction (EGJ), its broader physiological and clinical implications continue to emerge.^1,3-5

In the esophagus, EndoFLIP has been instrumental in redefining subsets of patients who were historically categorized as having “functional dysphagia” due to unremarkable endoscopy and normal high-resolution manometry. In a proportion of these patients, EndoFLIP reveals distension-mediated obstruction—characterized by abnormally low EGJ distensibility despite normal manometric pressures.^1,6 Recent studies have further identified a distinctive contraction phenotype within the lower esophageal body, termed the repeated simultaneous contractions or “Lubo pattern.”^1,7 This physiology is hypothesized to represent, at least in part, what earlier conventional manometry attempted to describe as distal esophageal spasm based on the Castell criteria.^1,7,8

Importantly, many patients with distension-mediated obstruction—with or without repeated simultaneous contractions—exhibit normal or only mildly ineffective esophageal motility on high-resolution manometry.⁶ Nevertheless, these individuals may benefit from targeted therapies aimed at improving esophageal body and EGJ distensibility, including botulinum toxin injection, balloon dilation, or peroral endoscopic myotomy (POEM).^1,6 This paradigm shift underscores EndoFLIP’s value as a complementary diagnostic tool capable of capturing mechanical dysfunctions which are not appreciated through manometry alone.¹

Compared with the esophagus, the clinical application of EndoFLIP in the pyloric region has lagged behind.⁹ In both adults and children, gastroparesis encompasses a broad range of etiologies, from metabolic and postsurgical causes to immune-mediated or idiopathic neuromuscular dysfunction, making the identification of discrete physiological endophenotypes—including pyloric outflow resistance—particularly important.^10-15 A subset of patients with gastroparesis demonstrates pyloric spasm or impaired pyloric distensibility, which appear to respond to pylorus-directed interventions such as gastric POEM.^16,17 Randomized controlled trials have supported the therapeutic role of pyloromyotomy in selected individuals, strengthening the rationale for incorporating pyloric FLIP assessment into the diagnostic algorithm.¹⁸

Despite these advances, normal reference values for pyloric distensibility remain less clearly defined than those established for the esophagus, where efforts such as the Dallas Consensus have provided standardized protocols, normative thresholds, and procedural guidance.¹⁹ Meta-analytic data in adults suggest that a pyloric distensibility index below 7-10 mm²/mmHg may serve as a pragmatic threshold for impaired distensibility and a reasonable therapeutic target.²⁰ Yet these values cannot be universally applied across all age groups.

The paucity of pediatric data is especially notable.²¹ A recent study published in the Journal of Neurogastroenterology and Motility highlights significant age-dependent variation in pyloric distensibility index among children, cautioning against the uncritical adoption of adult thresholds for pediatric practice.²² These findings underscore an urgent need for large-scale, age-stratified investigations to establish reliable normative values and clinically meaningful cutoffs in the pediatric population.

As EndoFLIP continues to reshape our understanding of gastrointestinal motility across the esophagus, stomach, and pylorus, its translational value will depend on careful physiological interpretation and robust normative frameworks. The recent pediatric data represent an important step forward, but also a reminder that developmental physiology must be respected when applying distensibility metrics in clinical decision-making. Continued collaborative research—particularly in children—will be essential towards realizing the full diagnostic and therapeutic potential of pyloric FLIP metrics.