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Page 2 of 11 Fontan et al. Mini-invasive Surg 2020;4:29 I http://dx.doi.org/10.20517/2574-1225.2020.09

The United States is among the countries with the highest rates: more than 30% of adults are currently
[1,2]
obese, with rates up to 40% in some regions of the country . Multiple comorbidities have been associated
with obesity, and gastro-esophageal reflux disease (GERD) is one of the most common. Interestingly, the
incidence of GERD in the United States general population oscillates around 15%, whereas among obese
[3,4]
patients it ranges from 22% to 70% .

METHODS
A PubMed search was carried out to identify relevant references to include in this literature review. Two
senior surgeons, among the authors of this manuscript, reviewed and selected the references among a vast
list of available titles.

GERD definition
In 2006, an international group composed of experts in the field of reflux disease achieved consensus
on definitions and classifications regarding GERD. Their aim was to establish a universally accepted
terminology that could bridge cultures and simplify management, and to initiate collaborative research
[5]
studies to assist physicians, patients, and regulatory agencies . GERD was defined as a digestive disorder
secondary to persistent gastric contents rising into the esophagus, which can result in a constellation of
symptoms and/or complications from chronic acidic exposure. Evidence of troublesome mild symptoms
occurring two or more days a week, or moderate/severe symptoms occurring more than once per week
were defined as characteristic presentations that could serve for diagnosis.

GERD symptoms can be divided into two categories: typical and atypical. Heartburn, regurgitation,
and dysphagia are known as typical symptoms, whereas chest pain, globus sensation, belching, nausea,
[6]
wheezing, cough, and hoarseness are considered atypical symptoms .
Of note, up to 70% of patients with heartburn symptoms have normal endoscopy. Of those, 50% have
abnormal pH tests and thus belong to the non-erosive reflux disease group of patients. The remaining
[7]
50% can be divided into functional heartburn and reflux hypersensitivity . These functional esophageal
disorders are characterized by the presence of chronic typical heartburn symptoms attributed to the
esophagus without evidence of inflammatory, anatomic, motor, or metabolic disorders as the underlying
etiology. Together, these presentations account for 90% of the heartburn patients who fail proton pump
[8]
inhibitor (PPI) therapy at optimal doses . It is important to identify this subset of patients, as the usual
management of these conditions differs from classic heartburn patients. The current approach to these
patients begins with assurance about the nature of their disorder, followed by neuromodulators which are
[9]
the cornerstone of therapy .

GERD pathophysiology
There are many elements that contribute to the anatomic anti-reflux barriers. The lower esophageal
sphincter (LES), the angle of His, the crural diaphragm, phreno-esophageal ligament, and the gastric
sling fibers are some of the key components. LES structure and length, anatomic position (including a
fundamental intrabdominal portion), innervation, and hormonal control all contribute to its normal
function. The LES is not an annular sphincter, but rather formed by two muscle fiber bundles, which have
synergistic actions: the “clasp” and the “oblique” muscular fibers. These muscular bundles of approximately
3-cm width cover an area that starts 1.5 cm above the angle of His and ascends to form part of the distal
end of the esophagus. These gastric sling fibers form a natural wrap with two arms that extend downwards
by running parallel to the lesser curvature [10,11] . Excitatory and inhibitory neurons affect local sphincter
tone by regulating the duration and frequency of transient LES relaxations, thereby facilitating intermittent
[12]
passage of food into the stomach while preventing reflux back into the esophagus . The crural diaphragm,
which forms the esophageal hiatus and encircles the proximal LES, in addition to the angle of His, helps to