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Abstract

We thank Massey for his interest in our manuscript and his critical comments on the technical aspects and performance of the Endoflip device. We agree that the lower esophageal sphincter (LES) is asymmetric and therefore may influence calculation of the diameter based on the obtained impedance data. However, it has to be emphasized that the Endoflip measures cross-sectional areas (CSAs) based on impedance planimetry, independent of asymmetry. The shape of the LES is only relevant in terms of when the esophageal diameter is displayed, and not for CSAs or esophagogastric junction (EGJ) distensibility. In addition, Massey questions the accuracy of the Endoflip device to measure distensibility at higher and lower CSAs, based on validation studies of an earlier prototype. With the current, commercially available Endoflip system, however, the accuracy to measure CSA values between balloon diameters of 5 and 25 mm is >99%.1Keating F. et al.Accuracy of the Endoflip functional luminal imaging probe.Surgical Endoscopy. 2009; 23: S287Google Scholar With a greater balloon diameter (>25 mm), the accuracy indeed decreases, a situation that can occur when the distal part of the balloon is positioned in the stomach when distended at the 50-mL balloon volume. However, as validated by Kwiatek et al,2Kwiatek M.A. et al.Gastrointest Endosc. 2010; 72: 272-278Abstract Full Text Full Text PDF PubMed Scopus (182) Google Scholar the EGJ is located at the minimal CSA, that is, at the waist of the balloon, implying that the balloon diameter used for EGJ distensibility did not exceed 25 mm, and is therefore well within the accuracy of the device. The last technical issue Massey raises concerns the impact of secondary peristalsis on measurements. Because Endoflip measurements are performed without sedation, secondary peristalsis can indeed occur. In our experience, secondary peristalsis is mainly a challenge in healthy volunteers, and is completely absent in patients with (treated) achalasia. Hence, although interference of contractile activity may indeed compromise Endoflip experiments in healthy subjects, we did not experience this as a methodologic issue in achalasia. Subsequently, Massey questions our conclusion that monitoring basal LES pressure is an insensitive method to assess therapeutic success. We completely agree that high-resolution manometry is more informative and may yield better parameters. However, to date, and especially at the time we performed our study, no such criteria have been validated, and therefore, the gold standard at that time, which was basal LES pressure > 10 mm Hg, was used. Irrespective, using high-resolution manometry, Pandolfino et al also detected abnormal distensibility assessed by Endoflip in 40% of patients with treated achalasia, even though high-resolution manometry revealed normal IRP.3Nicodeme F. et al.Does EGJ distensibility measured by endoflip aid in diagnosis or follow-up of achalasia patients? A comparison study with high resolution manometry and timed barium esophagogram.Gastroenterology. 2012; 142: S237Abstract Full Text PDF Google Scholar, 4Ruigh de A.A. et al.EGJ distensibility as a measure of treatment outcome in achalasia.Gastroenterology. 2012; 142: S95-S96Abstract Full Text PDF Google Scholar Hence, although we agree that one should be more creative and comprehensive in assessing the information already available with manometry, we are quite confident that based on our data, the new technique is superior. EndoFLIP Assessment of Achalasia Therapy: Interpreting the Distensibility Data Is a Bit of a StretchGastroenterologyVol. 144Issue 4PreviewIn the August 2012 issue of Gastroenterology Rohof et al1 report that, as measured by the EndoFLIP device, patients with achalasia have reduced distensibility of the lower esophageal sphincter (LES). They argue that this may result from fibrosis in the LES. Because resting LES pressure correlated poorly with outcome, they suggest that distensibility measurements or tests of esophageal emptying are preferred to manometry to assess the need for additional therapy. These conclusions require critical assumptions about the performance of the Endoflip device, the interpretation of distensibility measurements using EndoFLIP at the level of the LES in achalasia, and the appropriate parameters to measure on manometry. Full-Text PDF