Table 1.

Studies assessing esophageal motility.

No.	Author, year of publication, country	Type of study	Patients	Method of assessment/follow-up	Distance from pylorus/bougie size	Main findings of the study
1	Sioka, E. et al., 2017 [5], Greece	Prospective study	18	Esophageal manometry preoperatively and at median interval of 7 months	5 cm/36F	The lower esophageal sphincter (LES) total length decreased postoperatively (p = 0.002). The resting and residual pressures tended to decrease postoperatively (mean difference [95% confidence interval]: −4 [−8.3/0.2] mmHg, p = 0.060; −1.4 [−3/0.1] mmHg, p = 0.071, resp.). The amplitude pressure decreased from 95.7 ± 37.3 to 69.8 ± 26.3 mmHg at the upper border of LES (p = 0.014) and tended to decrease at the distal esophagus from 128.5 ± 30.1 to 112.1 ± 35.4 mmHg (p = 0.06) and midesophagus from 72.7 ± 34.5 to 49.4 ± 16.7 mmHg (p = 0.006). The peristaltic normal swallow percentage increased from 47.2 ± 36.8 to 82.8 ± 28% (p = 0.003). The postoperative regurgitation was strongly negatively correlated with LES total length (Spearman's r = −0.670). When groups were compared according to heartburn status, the statistical significance was observed between the groups of improvement and deterioration regarding postoperative residual pressure and postoperative relaxation (p < 0.002 and p < 0.002, resp.). With regard to regurgitation status, there was statistically significant difference between groups regarding preoperative amplitude pressure at the upper border of LES (p < 0.056). Patients developed decreased LES length and weakened LES pressure after LSG. Esophageal body peristalsis was also affected in terms of decreased amplitude pressure, especially at the upper border of LES. Nevertheless, body peristalsis was normalized postoperatively. LSG might not deteriorate heartburn. Regurgitation might increase following LSG due to shortening of LES length, particularly in patients with range of preoperative amplitude pressure at the upper border of LES of 38.9–92.6 mmHg.
2	Mion, F. et al., 2016 [7], France	Retrospective study	53	High-resolution impedance manometry Sleeve volume and diameter with CT scan Median follow-up at 11 months (1–50)	NR/NR	The increased intragastric pressure occurred very frequently in patients after SG (77%) and was not associated with any upper GI symptoms, specific esophageal manometric profile, or impedance reflux. Impedance reflux episodes were also frequently observed after SG (52%): they were significantly associated with gastroesophageal reflux (GER) symptoms and ineffective esophageal motility. The sleeve volume and diameters were also significantly smaller in patients with impedance reflux episodes (p < 0.01). SG significantly modified esophagogastric motility. The IIGP is frequent, not correlated to symptoms and should be regarded as a HRIM marker of SG. The impedance reflux episodes were also frequent, associated with GER symptoms and esophageal dysmotility. HRIM may thus have a clinical impact on the management of patients with upper GI symptoms after SG.
3	Rebecchi, F. et al., 2014 [8], Italy	Prospective clinical study	65	Clinically validated questionnaire, upper endoscopy, esophageal manometry, and 24-hour pH monitoring before and 24 months after LSG.	6 cm/36F	On the basis of preoperative 24-hour pH monitoring, patients were divided into group A (pathologic, n = 28) and group B (normal, n = 37). The symptoms improved in group A, with the gastroesophageal reflux disease symptom assessment scale score decreasing from 53.1 ± 10.5 to 13.1 ± 3.5 (p < 0.001). The DeMeester score and total acid exposure (% pH < 4) decreased in group A patients (DeMeester score from 39.5 ± 16.5 to 10.6 ± 5.8, p < 0.001; % pH < 4 from 10.2 ± 3.7 to 4.2 ± 2.6, p < 0.001). Real de novo GERD occurred in 5.4% of group B patients. No significant changes in the lower esophageal sphincter pressure and esophageal peristalsis amplitude were found in both groups. LSG improves symptoms and controls reflux in most morbidly obese patients with preoperative GERD. In obese patients without preoperative evidence of GERD, the occurrence of de novo reflux is uncommon. Therefore, LSG should be considered as an effective option for the surgical treatment of obese patients with GERD.
4	Gorodner, V. et al., 2015 [10], Argentina	Prospective study	14	Esophageal manometry (EM) and 24 h pH monitoring before and 1 year after LSG.	6 cm/36F	The lower esophageal sphincter (LES) length increased from 2.7 to 3.2 cm (p = NS), and LES pressure decreased from 17.1 to 12.4 mmHg (p ≤ 0.05). Preoperatively, LES was normotensive in 13 (93%) patients; postoperatively, LES was normal in 10 (71%) (p = NS). After LSG, the LESP significantly decreased
5	Burgerhart, J. S. et al., 2014 [11], Netherlands	Prospective study	20	Esophageal function tests (high-resolution manometry (HRM), 24-h pH/impedance metry) before and 3 months after LSG	6 cm/34F	Esophageal acid exposure significantly increased after sleeve gastrectomy: upright from 5.1 ± 4.4 to 12.6 ± 9.8% (p = 0.003), supine from 1.4 ± 2.4 to 11 ± 15% (p = 0.003) and total acid exposure from 4.1 ± 3.5 to 12 ± 10.4% (p = 0.004). The percentage of normal peristaltic contractions remained unchanged, but the distal contractile integral decreased after LSG from 2006.0 ± 1806.3 to 1537.4 ± 1671.8 mmHg · cm · s (p = 0.01). The lower esophageal sphincter (LES) pressure decreased from 18.3 ± 9.2 to 11.0 ± 7.0 mmHg (p = 0.02). After LSG, the patients have significantly higher esophageal acid exposure, which may well be due to a decrease in the LES resting pressure following the procedure.
6	Del Genio, J. et al., 2014 [9], Italy	Prospective study	25	High-resolution impedance manometry (HRiM) and combined 24 h pH and multichannel intraluminal impedance (MII-pH). Median follow-up at 13 months	NR/40F	Unchanged LES function, increased ineffective peristalsis, and incomplete bolus transit. MII-pH showed an increase of both acid exposure of the esophagus and number of nonacid reflux events in postprandial periods. Laparoscopic SG is an effective restrictive procedure that creates delayed esophageal emptying without impairing LES function. A correctly fashioned sleeve does not induce de novo GERD. Retrograde movements and increased acid exposure are probably due to stasis and postprandial regurgitation.
7	Kleidi, E. et al., 2013 [6], Greece	Prospective study	23	Esophageal manometry preoperatively and 6 weeks postoperatively	3-4 cm/34F	The LES total and abdominal lengths increased significantly postoperatively, whereas the contraction amplitude in the lower esophagus decreased. There was an increase in reflux symptoms postoperatively (p < 0.009). The approximation of the angle of His mostly from the operating surgeon resulted in an increased abdominal LES length (p < 0.01). The presence of esophageal tissue in the specimen correlated with the increased total GERD score (p < 0.05). LSG weakens the contraction amplitude of the lower esophagus, which may contribute to postoperative reflux deterioration. It also increases the total and the abdominal lengths of the LES, especially when the angle of His is mostly approximated. However, if this approximation leads to esophageal tissue excision, the reflux is again aggravated. Thus, stapling too close to the angle of His should be done cautiously.
8	Petersen, W. V. et al., 2012 [12], Germany	Prospective study	37 Group I (BMI = 19–25) 20 (control group) Group II (BMI = 42–65) 20 patients (8 months) Group III (BMI = 37–57) 17 patients (6 days)	Esophageal manometry	2 cm/35 Ch	Postoperatively, the LESP increased significantly, namely, from preoperative 8.4 to 21.2 mmHg in group II and from 11 to 24 mmHg (p < 0.0001) in group III. The tubular esophageal motility profits from LSG. The LSG significantly increased the lower esophageal pressure independent of weight loss after LSG and may protect obese patients from gastroesophageal reflux.
9	Braghetto, I. et al., 2010 [13], Chile	Prospective study	20	Esophageal manometry preoperatively, 6 months postoperatively	2 cm/32F	Preoperative mean LESP was 14.2 ± 5.8 mmHg. The postoperative manometry decreased in 17/20 (85%), with a mean value of 11.2 ± 5.7 mmHg (p = 0.01). Seven of them presented LESP of <12 mmHg and ten patients presented LESP of <6 mmHg after the operation. Furthermore, the abdominal length and total length of the high pressure zone at the esophagogastric junction were affected. A sleeve gastrectomy produces an important decrease in LES pressure, which can, in turn, cause the appearance of reflux symptoms and esophagitis after the operation due to a partial resection of the sling fibers during the gastrectomy.