HM+Dor fundoplication is generally considered as the operative procedure of choice for esophageal achalasia. Post treatment complications include persistent or recurrent dysphagia, and gastroesophageal (G-R) reflux with related complications. One of the goals of instrumental follow-up in these patients is to evaluate silent reflux which can be present in up to 20% of patients.Aim of the present study was to characterize reflux events after HM + Dor in patients treated for achalasia, using MII-pH monitoringSeventeen consecutive patients who underwent HM+Dor fundoplication for achalasia (9 female; median age 39 (range 24-77 yrs;) underwent a clinical and physiopathological (esophageal stationary manometry and MII-pH impedance) evaluation after a median of 24 months after surgery (range 6-109). All patients were asymptomatic for acid reflux and none was on antisecretory therapy. Three patients reported persistent dysphagia for solid at follow up (Eckardt 2). Median Eckardt score was 7 (range 2-11) and 1 (0-3) respectively before and after surgery (p: 0.0001). Mean pressure of lower esophageal sphincter was 37 mm Hg (SD + 19,6) and 9,2 mm Hg (SD + 4,1) before and after HM. All but one had a residual pLes < 4 mmHg. The MII -pH data after HM + Dor in achalasia patients are reported in Table.Esophageal acid exposure is in the normal range after surgery in this cohort of patients. We found a pathological number of non acid reflux, mainly in patients complaining of residual dysphagia (Fisher’s exact test p<0,05), in spite of a normal bolus clearance time.Conclusions: Dor fundoplication is a valid option after HM for achalasia to prevent G-R reflux. In these patients reflux events are mostly non acid and may be positively correlated with dysphagia. More data are needed to confirm the role of MII pH in patients with motility disorder.

MII -pH	Median	Range
Esophageal total acid exposure (%)	0.003	0 - 0.4
Number of reflux events	60.5	20 - 263
Number of acid reflux events	1.5	0.25 - 107
Number of non acid reflux events	58	20 - 156
Bolus clearance time (s)	12	3 - 32