Understanding the Correlation Between I-SEE and FLIP Metrics in Clinical Imaging

The I-SEE (Imaging-based Severity and Extent Evaluation) and FLIP (Functional Lumen Imaging Probe) metrics provide distinct, complementary data points for assessing esophageal motility disorders. While I-SEE offers a standardized framework for evaluating esophagitis through endoscopic findings, FLIP measures the biomechanical properties of the esophageal wall. Recent clinical research indicates that these metrics do not always align, highlighting the necessity of using both tools to achieve a comprehensive diagnostic profile for patients with eosinophilic esophagitis (EoE).

Defining I-SEE and FLIP in Clinical Practice

The I-SEE score is a validated endoscopic grading system designed to standardize the assessment of EoE severity. According to the American Gastroenterological Association, the I-SEE score evaluates specific features such as edema, rings, exudates, furrows, and strictures. By assigning points to these features, clinicians can quantify the degree of esophageal inflammation and remodeling.

In contrast, FLIP technology—specifically the use of high-resolution impedance planimetry—measures the distensibility and geometry of the esophageal lumen. As noted by the International Working Group for Disorders of Gastrointestinal Motility, FLIP provides a functional assessment that often identifies mechanical changes, such as decreased compliance, before they become apparent through traditional endoscopic visualization.

Why Metrics Often Diverge

A primary point of clinical discussion involves the discordance between morphological scores and functional measurements. Research published in Clinical Gastroenterology and Hepatology suggests that structural changes identified by I-SEE do not always correlate linearly with the functional resistance measured by FLIP. This discrepancy occurs because EoE affects the esophagus at both the mucosal level—visible via endoscopy—and the muscular/submucosal level, which is better captured by mechanical distension.

For instance, a patient may exhibit a low I-SEE score, suggesting mild inflammation, while FLIP testing reveals significant narrowing or reduced distensibility. This finding indicates that the patient may have deep-tissue remodeling that remains hidden from standard endoscopic observation. Relying solely on one metric can lead to an incomplete understanding of disease progression or treatment response.

Clinical Implications for Diagnosis and Treatment

The integration of both I-SEE and FLIP allows for a more personalized approach to patient care. By comparing these metrics, gastroenterologists can better determine the risk of food impaction and the necessity for therapeutic intervention, such as esophageal dilation.

• Comprehensive Assessment: Combining I-SEE and FLIP provides a dual-perspective view of both inflammation and physical narrowing.
• Risk Stratification: Patients with abnormal FLIP metrics, even if I-SEE scores are low, may require more aggressive monitoring for potential esophageal strictures.
• Treatment Monitoring: These tools track how well a patient is responding to dietary changes or biologic therapies by measuring both the reduction of inflammation and the improvement of esophageal function.

Future Directions in Esophageal Diagnostics

As diagnostic protocols evolve, the emphasis is shifting toward multimodal testing. Future clinical guidelines are expected to refine how these metrics are weighted in routine practice. Current evidence suggests that while I-SEE remains the gold standard for grading endoscopic severity, FLIP is becoming an essential functional adjunct. Clinicians are encouraged to interpret these results in the context of the patient’s overall symptom profile to avoid diagnostic gaps in complex esophageal cases.

Key Takeaways

• I-SEE measures endoscopic morphological changes, while FLIP measures functional esophageal distensibility.
• Discordance between the two metrics is common and reflects the complex nature of esophageal remodeling in EoE.
• Using both tools provides a clearer picture of disease severity than relying on endoscopy alone.
• Clinical management should prioritize functional testing (FLIP) when patients report symptoms that do not match their endoscopic (I-SEE) findings.