Background: HM + Dor fundoplication is generally accepted as the operative procedure of choice for achalasia. Post treatment failures included persistent or recurrent dysphagia, and gastroesophageal reflux with related complications (Barrett's esophagus and adenocarcinoma). Objective follow-up is thus required in those patients, in whom more than 20% are silent reflux.The aim of the study was to characterize reflux events after HM + Dor in achalasia patients, using 24 hour-pH impedance recordings.
Methods: eleven consecutive achalasia patients (five female; median age 42 (range 27-77 yrs;) underwent a clinical and physiopathological evaluation (esophageal stationary manometry and MII-pH impedance) after a median of 66 months from surgery.
Results: All patients were asymptomatic for reflux and none was on antisecretory therapy. Three patients reported recurrent dysphagia for solid, without loosing weight . Median Eckardt score was 8 (range 3-11) and 2 (range 1-3) before and after surgery respectively (p: 0.0001). Mean pressure of lower esophageal sphincter (LES) was 35 mmHg (range 23-50) and 9 mmHg (range 6-15) before and after HM (p: 0.0008). All patients but one had a residual pressure of Les < 4 mmHg. The MII - 24 hours pH data after HM + Dor in achalasia patients are reported in Table.The mean number of reflux events were 87 (range 20-254), 11of these were acid and 76 non acid. The latter were prevalent in those patients complaining of residual dysphagia, in spite a normal median bolus clearance time.
Conclusions: HM with Dor fundoplication is a valid choice in achalasia to prevent G-R reflux. Esophageal acid exposure was in the normal range after surgery in this cohort of patients, also in the long term follow-up. Reflux events are mostly non acid and may be positively correlated with dysphagia. More data are need to confirm the role of MII pH in patients with a motility disorder.

MII -pH data (mean; SD)	total	upright	supine
Esophageal total acid exposure (%)	0.4 (1.15)	2.0 (5.06)	0.3 (0.87)
Esophageal total non acid exposure (%)	3.9 (1.91)	3.8 (1.98)	3.9 (3.7)
Median bolus clearance time (s)	11.7 (6.99)	10.9 (6.33)	16.4 (21.3)