The investigators aim to ascertain the effects of hiatal hernia repair and fundoplication on the distensibility of the esophagogastric junction (EGJ) as measured by FLIP topography/impedance planimetry. The investigators also aim to assess for any correlation between values of EGJ distensibility and GERD related quality of life (QOL) and dysphagia scores.

Patients referred for antireflux surgery and/or hiatal hernia repair will be considered for enrollment. Standard preoperative evaluation will include esophagogastroduodenoscopy (EGD) to assess for intraluminal pathology including esophagitis, columnar lined esophagus suggestive of Barrett's esophagus, intraluminal masses, and to measure hernia size. Patients will also undergo preoperative high resolution esophageal manometry testing with impedance as clinically indicated to evaluate esophageal motility as assessed by standardized Chicago Classification V3. Manometry will occasionally be avoided in patients with paraesophageal hernias without substantial dysphagia or those not amenable to manometry, with appropriate upper gastrointestinal radiology imaging (UGI), who will be having partial fundoplications. UGI is also a routine preoperative evaluation. Furthermore, pH testing for evaluation of acid reflux will be performed in patients without LA grade C or D esophagitis, paraesophageal hernia, or pathologic confirmation of Barrett's esophagus.

Patients appropriate for enrollment will be consented in the office setting. Preoperative baseline evaluations of symptom severity will be assessed via the GERD-HRQL survey and Mayo Dysphagia Questionnaire. Surgery will be scheduled and patients will undergo intraoperative impedance planimetry with EndoFLIP obtaining measurements of the cross-sectional area, balloon pressure, minimum diameter, compliance, length of high pressure segment, and distensibility index of the EGJ using an 8cm EndoFLIP balloon. Sequential assessments will be performed to 30ml and 40ml for up to a minute for each volume of distension. An initial baseline measurement will be obtained after establishment of pneumoperitoneum. A second measurement will occur following hiatal dissection and mobilization but prior to crural closure. Two additional measurements will be obtained after hiatal closure and after fundoplication.

No adjustment will be made to the surgical procedure based on EndoFLIP results, as the operating surgeon will not be informed of the measured values. The EndoFLIP catheters and generator will be provided by Medtronic, at no cost to the patient. Medtronic will also cover the fees associated with the EndoFLIP procedure (CPT 91040 is used).

Postoperative clinical care will proceed as per standard protocol for foregut surgery, with 1 additional office visit. Reports of postoperative symptomatology and quality of life will be performed, via GERD-HRQL and Mayo Dysphagia Questionnaire during follow up clinic appointments at 2 weeks and 6 weeks postoperative, and with additional long-term follow-up of at 6 months. Long-term follow-up will again assess for quality of life symptoms via GERD-HRQL and the Mayo Dysphagia Questionnaire. The 6 month follow-up visit is not typical practice and the patients cost for this visit will be covered by Medtronic. Per standard clinical care, recurrence of symptoms or dysphagia at any point may lead to additional postoperative testing, including UGI, EGD, pH testing, esophageal manometry, CT scan, or EndoFLIP. Postoperative GERD-HRQL and Mayo Dysphagia score results will be compared to intraoperative EndoFLIP measurements in interim and final analysis.

Inclusion Criteria:

• Patient undergoing hiatal hernia repair (types I-IV included) and fundoplication
• Absence of spastic esophageal disorders (i.e. jackhammer esophagus, achalasia types I-III) assessed by preoperative high-resolution manometry
• Adult patients ≥18 years
• Elective repairs

Exclusion Criteria:

• Redo hiatal hernia repairs
• Emergent repairs
• Patients with contraindication to surgery or endoscopy
• Patients with esophageal varices
• Cases with insufficient esophageal length in which fundoplication is unable to be performed or a Collis gastroplasty is required
• Connective tissue diseases such as scleroderma or lupus
• Diameter measurements less than 5 mm as the EF-325N catheter is not suitable