The anatomy of the normal esophago-gastric junction showing the esophagus, stomach, diaphragm and the clasp and sling fibers (modified and reproduced with permission from ref. )
LES is a tonically contracted segment of the EGJ that together with the clasp and sling fibers of the gastric cardia form an integrated sphincter mechanism [2, 3]. LES anatomy is fascinating since a distinct anatomical sphincter with muscle thickening has not been clearly identified [2, 3, 6, 7]. Rather, manometric studies have shown the high-pressure zone in the lower esophagus [8, 9]. LES is not an annular sphincter but rather formed by two crossing muscle bundles, i.e. the semicircular “clasp” and the oblique “sling” muscular fibers derived from the oblique fibers of the stomach [2, 3, 6, 7, 10]. Closure of the EGJ appears to be due to contraction of these muscle bundles in conjunction with crural fibers of the diaphragm [7, 9, 11–16].
Another important anti-reflux structure is the gastroesophageal flap valve formed by a musculo-mucosal fold that maintains a pressure gradient between the stomach and lower esophagus to keep gastric contents away from the EGJ [3, 14, 17–21]. The sling fibers of the stomach located below the LES are associated with a valve mechanism whereby pressure in the gastric fundus creates a flap that presses against the lower end of the esophagus .
The gastroesophageal flap valve is located at the gastric cardia where it maintains the acute angle of His [7, 20].
Brasseur and co-workers described three distinct components of the barrier mechanism in the gastro-esophageal segment and how they can be differentiated. The components are the extrinsic crural sphincter and the intrinsic LES and sling/clasp muscle unit. Efficacy is maintained by a delicate interplay between the components .
Hiatus hernia is characterized by proximal displacement of the EGJ causing the intrinsic sphincter to lie proximal to the hiatus formed by the crural diaphragm  (Fig. 10.2). This is likely caused by rupture or weakening of the phreno-esophageal ligament . Patients with hiatus hernia have more reflux episodes and greater esophageal acid exposure than patients without hiatus hernia and they have more severe esophagitis . Furthermore, larger hiatal hernia is associated with a greater esophageal acid exposure and prolonged acid clearance times . This is likely a reflection of the remodeled mechanical properties of the barrier mechanism . Referring again to the work by Brasseur, hiatus hernia with its distinct mechano-morphometric changes disrupts the integrity of the physiological barrier mechanism .
Surgical or endoscopic fundoplication aims to restore the lost efficacy observed in herniation. The geometry of the EGJ and mechanically defect LES can be somewhat restored by antireflux surgery. The LES length and the FLAP valve are to some degree regenerated which increases the baseline LES pressure . In addition to the contribution to the pressure increase, the lengthened LES better resist the effect of gastric wall tension in opening the LES. This is complemented by the recreation of the FLAP valve which tends to occlude the lumen and increase pressure . If the wrap is defect or recurrence occur, then the full geometric-mechanical effect is not obtained and efficacy will be impaired.
10.3 Physiology of Esophago-Gastric Junction with Focus on LES Efficacy
From studies performed up to 20 years ago and summarized elegantly by reviews from Mittal & Balaban  and Kahrilas , it is evident that the core tenants of the barrier function at the EGJ are now well established. The thickened muscle area at the distal end of the esophagus represent the LES intrinsic barrier whereas the diaphragmatic hiatus, which is located as a narrow opening in the diaphragm where the distal esophagus exits the thoracic cavity and enters the abdominal cavity, represents an extrinsic barrier. Studies indicate that the proximal 2 cm of the 4 cm-long LES is where the so-called extrinsic “pinch cock” effect of the diaphragm overlaps the intrinsic circular valve effect of the LES . The physiology described in these reviews still forms the basis for surgical treatment options as mentioned in the recent review by Patti and coworkers .
The role of the LES at the EGJ has been quite well understood for a considerable time. In normal subjects the LES exerts a circular muscle force at the distal end of the esophagus just as it enters the stomach. This is part of the barrier that ensures stomach contents do not travel back into the esophagus. When swallowing is initiated the LES relaxes allowing ingested material to travel from the esophagus into the stomach . Much of our understanding of this comes from manometric studies. These type of studies were further enhanced in the 1970’s by Dent and co-workers, who using a variant of manometry known as the Dent sleeve, demonstrated that the LES relaxes at other times as well . These events are known as transient lower esophageal sphincter relaxations (TLESRs) . It has been shown that the number of transient relaxations is higher in patients suffering from GERD .
The more recent work of Miller and Brasseur used a very precise manometric pull-through technique concurrent with high frequency ultrasound and studied the high-pressure zone at the EGJ . Their aim was to separate and manometrically quantify in vivo the skeletal and smooth muscle components at the EGJ in an attempt to gather more physiological detail in the LES region. This was achieved using atropine in one group of healthy volunteers to suppress the cholinergic smooth muscle sphincter effect and cistracurium in another group to neuromuscularly block the crural sphincter. Hence, the muscle contributions could be studied separately. The main and significant finding from this study is that the pressure profiles generated by manometric pull-through of the region, if carried out with great precision and with the interventions above, can obtain more information on the physiology and function of the LES.
From this work new information that suggests the LES has two subcomponents is evident. The authors conclude that one component is a proximal smooth muscle component. They describe this as the lower esophageal circular muscle, which tends to move with the movement of the crural diaphragm component probably due to its attachment to the phreno-esophageal ligament. The other component is described as the smooth muscle component distal to the diaphragm and from ultrasound appeared to be located approximately at the position of the sling-clasp muscle fibers .
10.4 Laparoscopic Antireflux Surgery with Hiatal Repair Surgical Aspects
The anti-reflux effect of fundoplication was discovered after a 16-year follow-up of a patient with partial esophagectomy done using a fundoplication wrap around the anastomosis with the purpose of preventing leakage . It became the most commonly practiced effective surgical treatment for GERD. However, how the procedure has augmented the effect of the lower esophageal complex to act as a valve against reflux is still under discussion.
Fundoplication is shown to increase the nadir lower esophageal pressure [38, 39] and thereby better resists the intra-gastric pressure that produces reflux, while preserving its ability to relax (though less completely) upon wet swallows . While this increase in pressure is shown to be exerted by the gastric wrap in animal studies excluding the LES by myotomy , the fact that this new high pressure zone behaves similarly to the physiological LES is interpreted as improvement of the LES smooth muscles by some authors .
The relaxation pattern of the LES is also altered after fundoplication. Increased TLESR is found in many patients with GERD [42–45]. The relaxation is initiated by gastric cardiac distension, the most sensitive zone as shown in animal studies . The fundoplication wrap alters the distensibility at the region. Ireland and coworkers have demonstrated a significant decrease in TLESR frequency detected after fundoplication and gastroesophageal reflux associated with the episodes .
10.5 Recurrence of GERD and Hiatal Hernia Clinical Features
10.5.1 Clinical Features and Fundoplication Failures
The rate of long-term resumption of acid-reducing medication after fundoplication is shown to vary widely from 5.8 to 62%, with most reports showing a rate of <20% . Level I evidence showed a symptom resolution rate of 67% at 7-year follow up . Recurrence with new reflux symptoms usually indicates a breakdown of the fundoplication . A systematic review on surgical re-intervention after anti-reflux surgery showed that over 80% of failed procedure is due to disruption of the post-operative anatomy .
Upon symptom recurrence after fundoplication, the approach to investigate for indication of re-operation is similar to that for the primary procedure. Investigations aim to show objective evidence of acid reflux recurrence and to show the integrity of the previous repair. Most patients who received re-operations were worked up with endoscopy, fluoroscopy and/or pH monitoring studies . In particular, endoscopy and fluoroscopy help visualize the status of the wrap and hiatal repair.
A successful anti-reflux surgery comprises of a proper fundoplication and an intact hiatal hernia repair. Various types of fundoplication wrap disruptions have been described , according to the status of the wrap itself and the presence of any recurrence of the hiatus hernia. The wrap can be incompetent due to loosening or breakdown, or intact but slipped so part of the stomach is herniated through the wrap. Hiatus hernia may recur in any of the scenarios, and the wrap itself may also herniate through the diaphragm (Fig. 10.3).
Types of fundoplication failure (reproduced with permission from ref. ). (a) Complete or partial wrap disruption with or without recurrence of the hiatus hernia. (b) Hiatal herniation of the stomach via the intact fundoplication wrap. (c) Slippage of the wrap causing gastric herniation through the wrap only but not the diaphragm. (d) Hiatal herniation of the intact fundoplication wrap
10.5.2 Role of Fluoroscopy
Barium esophagography is a simple investigation that allows surgeons to assess the morphology of the wrap, albeit interpretation can be challenging even for radiologists unless full understanding of the surgical procedure itself is acquired . Double-contrast study is preferred. Three components can be observed: (1) the wrap, (2) hiatus hernia, and (3) presence of reflux. Barium esophagogram after fundoplication would show a smooth well-circumscribed filling defect at the gastric fundus surrounding the narrowed distal esophagus, located below the diaphragm. The wrap can occasionally be filled with barium contrast (Fig. 10.4). Normally, above the wrap would be the esophagus and below the stomach. A slipped wrap would show the presence of the gastric fundus above the wrap (Fig. 10.5). Noting the level of diaphragm, recurrence of hiatus hernia can be identified, even in the case of herniation of the whole wrap (Fig. 10.6). Occasionally, contrast reflux is observed during fluoroscopy, confirming the presence of an incompetent LES.
Barium esophagogram after fundoplication (reproduced with permission from ref. ) with the well-circumscribed filling defects seen around the narrowed distal esophagus, and a schematic diagram of the corresponding anatomy
Barium esophagogram showing a slipped wrap, indicated by the arrows, and part of the stomach is now above the wrap (reproduced with permission from ref. ). Schematic diagram of corresponding anatomy
Barium esophagogram showing herniation of the whole fundoplication wrap above the diaphragm (reproduced with permission from ref. ). The wrap is filled with contrast. Schematic diagram of corresponding anatomy
In the situation of reflux recurrence after fundoplication, endoscopy (esophagogastroduodenoscopy) is another important investigation. It plays the role of identifying failed procedure and ruling out any other organic causes of the new symptoms. Endoscopic features to identify a failed fundoplication was described by Jailwala and coworkers, including presence of esophagitis, ease of endoscope passage through the EGJ, location of wrap relative to diaphragmatic hiatus, location of the squamocolumnar junction and the appearance of the wrap .
A competent fundoplication should give an endoscopic appearance, upon retroflexion, a good seal around the endoscope by the wrap, and its resultant lengthened intra-abdominal portion of the LES.
Compared with barium esophagography, endoscopy is able to pick up 10–15% more structural abnormalities upon investigation for recurrence  whereas it is less informative upon workup for dysphagia. However, fluoroscopy is still recommended in the planning of revision surgery as an image guide to the relative anatomy of different structures.
10.5.3 Role of High-Resolution Impedance-Manometry
Invariably for type I sliding hernia, the LES has moved through the diaphragmatic hiatus and has herniated in the thoracic cavity . High-resolution manometry can identify what is sometimes referred to as the double hump or double high-pressure zone . This can be seen clearly in Fig. 10.7. Evaluating hernia size indirectly based on the distance between the double high-pressure zone on high-resolution manometry tracings is fast coming the accepted practice in clinics globally . This is very useful for general diagnosis and orientation of a hiatal hernia but it does not give precise information on structure and function. It is recommended as part of patient work up before surgery .
High resolution manometry tracing of a single swallow by a patient with a small size hiatal hernia. The hernia is indicated by the spacing between the green color suggesting a higher pressure where there is a squeeze present from the tone of the LES and the pinchcock effect of the diaphragmatic hiatus. The X-axis represents time, Y-axis is position in the esophagus and color represents pressure going from blue for low pressure through green toward red for high pressure. Precise values are not shown as this figure is for illustrative purposes only
As high-resolution manometry has evolved over the last 20 years so too has the concept of intraluminal impedance and the combined concept of high-resolution impedance manometry (HRIM). Studies have shown that intraluminal impedance provides a much better understanding of the solid, liquid or gaseous state of the refluxate . However, although the technique has proven to be a useful tool in this regard, and despite predictions on its development into clinical practice, this has not materialized. Arguably it will not be useful to help diagnose patients with hiatal hernia or the recurrence of GERD and hiatal hernia after antireflux surgery . This is mostly because repair of hiatal hernia by antireflux surgery alters biomechanical activity in the region of the EGJ. As intraluminal impedance does not provide objective measures of function, it cannot directly evaluate improvements in the junction barrier after surgery. Early information indicates that intraluminal impedance may have a role in assessing the acid pocket and this relates to the hypothesis that in patients with hiatal hernia the acid pocket may appear in the hiatus . Further studies need to be carried out to evaluate if using intraluminal impedance to assess the makeup of the refluxate in the hiatus and to assess if this is altered, improved, or eradicated after anti-reflux surgery or to determine recurrence.
Since the physiological concept of TLESR is widely accepted and can currently be more easily assessed using high-resolution manometry, its assessment role with respect to hiatal hernia patients is worth a mention . However, studies back in the year 2000 are conflicting. Van Herwaarden and coworkers claimed that TLESRs in patients with HH were comparible to those without HH and in the same year and journal Kahrilas and coworkers claimed TLESRs were increases in patients with GERD and hiatal hernia [62, 63]. However, there is no evidence from the literature of TLESR evaluation being important before or after antireflux surgery to evaluation efficacy. This of course makes some sense since very often it is not a lack of tone or pressure in the LES that is observed with hiatal hernia but a separation on the two main mechanism of the barrier, i.e. the LES and the crural diaphragm.
10.5.4 Role of the Functional Luminal Imaging Probe
New work using the functional luminal imaging probe (FLIP) to measure function in the region of the LES and the wider EGJ segment suggests it may have a role in antireflux surgery in general and in the evaluation of hiatal hernia in particular. In brief FLIP provides serial measures of cross-sectional areas inside a long bag and the lumen geometry and distensibility can be derived from the measurements.
De Haan and coworkers provided some insights into the role of FLIP in the evaluation of reflux surgery, Nissen and Toupet in a series of 75 patients (48 of which were redos). The authors suggested that there is ongoing variability in the outcomes of antireflux procedures despite their existence for more than 50 years. This has hampered the ability to assess adequately predictors of clinical and symptomatic outcomes. In their study they showed that the esophagogastric segment is less distensible after anti-reflux surgery and that Nissen procedures are less distensible than Toupet procedures. Based on this they suggested FLIP provides a method to tailor fundoplication distensibility by observing geometry and pressure intraoperatively. Although further studies are needed, this could help create more uniformity in technique, improve the long-term symptomatic outcomes and further minimize side effects .
It follows that enquiry into the role of FLIP as a distensibility technique may teach us something about the separation of the intrinsic effect of the LES and the extrinsic effect of the diaphragmatic hiatus when they are no longer co-located to form the EGJ.