Purpose of review
Supragastric belching has recently gained recognition as a belching disorder of behavioral origin which can be accurately diagnosed on esophageal impedance monitoring. Its contribution to numerous other gastrointestinal disorders is beginning to be appreciated. Improved knowledge of its pathophysiology has enabled identification of therapeutic goals, some of which have been subject to formal study and demonstrated good outcomes. This review sets out to present and discuss new findings related to the improved understanding of the relationship between supragastric belching and other gastrointestinal disorders as well as fresh concepts in terms of management.
Recent findings
Supragastric belching is now shown to be associated with globus, as well as reflux symptoms in PPI non-responders. Patients with supragastric belching experience higher frequency of belching events if they have concurrent esophageal hypomotility. Gum chewing and sleeve gastrectomy have no impact on supragastric belching. Pediatric studies suggest an overlap with aerophagia that is not observed in adults. Successful treatments trialed recently include psychoeducation and behavioral therapy delivered by a health psychologist with expertise in gastroenterology.
Summary
With the foreseeable increase in recognition and diagnosis of pathological supragastric belching, there is a clear need to better understand its pathophysiology, especially in terms of its emerging importance in relation to other gastrointestinal disorders. Further study is justified to uncover additional therapeutic options for this benign but disabling condition.
Keywords: belching, burping, eructation, supragastric, impedance
Introduction
Belching occurs in all people as part of normal behavior. Those with repetitive, troublesome belching often exhibit a specific belch pattern known as supragastric belching. Excessive supragastric belching is considered pathological[1]. The prevalence of supragastric belching has recently been estimated at 3.4% among a tertiary referral population for investigation of upper gastrointestinal complaints[2**], although this figure is set to increase with growing awareness of the condition.
PATHOPHYSIOLOGY
The advent in the 1990s of esophageal impedance monitoring facilitated the dynamic tracking of liquid and air movement within the esophagus and their direction of travel. Over the last 12 years, this technique has enabled clinicians to identify two distinct types of belching: supragastric belching and gastric belching (see Figure 1 (a) and (b)). In supragastric belching, air enters and leaves the esophagus rapidly without reaching the stomach[3]. In contrast, gastric belching involves reflex-mediated involuntary venting of gastric air via transient relaxation of the lower esophageal sphincter (TLESR), and is largely a physiological occurrence to decompress the stomach and prevent downstream intestinal distension[1].
In supragastric belching, two mechanisms of esophageal air entry have been identified using high resolution manometry (HRM) with combined impedance (HRM-Z): 'air-suction' and 'air-injection'. The commoner 'air-suction' mechanism involves diaphragmatic movement in the aboral direction to create negative intrathoracic pressure, as seen in deep inspiration. The less common 'air-injection' is driven by pharyngeal contraction and the resultant increase in pharyngeal pressure initiates air influx into the esophagus[3'5*]. Both processes lead to a sudden increase in abdominal and esophageal pressure, causing immediate displacement of esophageal air orally. This expulsion of air is perceived as an audible belch[5*].
Of note, both mechanisms start with contraction of striated muscle ' diaphragmatic muscle in the first method, pharyngeal muscle in the second. Moreover, upper esophageal sphincter (UES) relaxation occurs prior to esophageal air influx in supragastric belching. In gastric belches, UES relaxation is a late, reflexive response to gaseous distension of the distal esophagus[5*].
PATHOGENESIS
Organic factors rarely underlie supragastric belching[6]. It is thought that supragastric belching is psychogenic in etiology and starts as an involuntary action to alleviate an unpleasant retrosternal or intra-abdominal sensation[4,7] that becomes ingrained behavior over time. This hypothesis is corroborated by a case report of de novo supragastric belching in pregnancy which resolved after delivery[8].
Cessation of supragastric belching during speech[5*,6], distraction[4] and sleep[9] all support the concept of a self-induced behavioral phenomenon. To illustrate this point, the ability to belch at will is sometimes employed by clinicians in front of patients with supragastric belching[3]. Gum chewing has recently been shown to have no impact on supragastric belching[10**].
Supragastric belching is associated with significant reduction in quality of life with distressing psychosocial repercussions. However the present literature base lacks consensus as to the coexistence of anxiety disorders and depression[11,12].
CLINICAL EVALUATION AND DIAGNOSTIC APPROACH
Patients who exhibit spells of excessive belching during their consultation invariably suffer from supragastric belching[5,13*], and may belch up to 20 times per minute[1,14]. Data are conflicting as to whether supragastric belching tends to exist in isolation[1] or alongside other gastrointestinal symptoms[2]. Nevertheless routine questioning about other symptoms is advisable. The presence of weight loss, pain, dysphagia, heartburn or regurgitation may point towards other organic diseases and would merit further diagnostic evaluation[13*].
History alone may often clinch the diagnosis. Nonetheless impedance monitoring is the gold standard diagnostic modality as it provides objective evidence of supragastric belching events[13*]. The impedancometric appearance of a supragastric belch has been defined by Bredenoord et al in their seminal 2004 paper as a rapid antegrade movement of gas (impedance '1000''), followed by its quick retrograde expulsion with a return to baseline impedance[3] (figure 1 (a)).
Pathological supragastric belching has been defined as >13 events per 24 hours[2**]. Afflicted patients normally far exceed this threshold (mean 101 events per 24 hours, range 17-510)[2**]. The sheer number of belching events in those with supragastric belching remains high even when compared to patients troubled by gastric belching (average 239 versus 59.5 events/day)[15]. The seasoned physiologist may spot-diagnose pathological supragastric belching on initial panoramic overview of impedance traces, based on characteristic daytime density of symptom markers and impedance 'spikes' of intra-esophageal air movement, notably absent during sleep[9] (figure 2(c)). Shorter measurement periods may suffice to reveal preponderance of supragastric belching ' in another paper which described truncated impedance monitoring of 90 minutes, the median number of belching events captured for patients with gastric belching was 1, compared to 36 for those with supragastric belching[4].
HRM is not routinely used in clinical practice to diagnose supragastric belching, but HRM-Z can be helpful in distinguishing between supragastric belching, gastric belching and rumination syndrome[13*].
SUPRAGASTRIC BELCHING AND OTHER GASTROINTESTINAL CONDITIONS
Supragastric belching has historically been confused with aerophagia, and to a lesser extent, reflux disease and other functional upper gastrointestinal conditions. Improved understanding of the pathophysiology underlying the different conditions has aided more accurate phenotyping of a heterogeneous patient group. In addition, supragastric belching has also been observed to coexist with other gastrointestinal conditions, and considerable headway has been made in the last decade in terms of clarifying the relationship between supragastric belching and these other disorders.
Aerophagia
Supragastric belching is frequently conflated with aerophagia, but the two conditions are not equivalent[16]. Aerophagia (Greek for 'air eating') is defined as the act of excessively swallowing air which is then transported by esophageal peristalsis to the stomach[3,17]. Such peristalsis is absent in supragastric belching. Furthermore, air influx in supragastric belching is completed within one second but takes several seconds in aerophagia[7] (figure 1(a) and (c)). Clinically, aerophagic patients tend to present with bloating, distension and flatulence[18]. Repetitive belching is not the predominant feature in aerophagia.
Rumination
Rumination syndrome is a functional disorder involving persistent or recurrent effortless regurgitation of recently ingested food into the mouth[19]. In certain individuals, supragastric belching has been shown to contribute to rumination syndrome, wherein a supragastric belch is followed quickly by abdominal strain, prompting retrograde flow of gastric contents into the esophagus[5*,20,21]. In a study utilizing HRM-Z measurements, 3 of 12 patients with rumination syndrome were observed to display this pattern of supragastric belch-induced rumination events[20].
Globus
Globus, or the sensation of a lump or tightness in the throat, is a symptom of unclear aetiology. A 2016 prospective Finnish study aimed to address this question by comparing patients with functional globus with controls with typical reflux symptoms. The major difference between groups was the significantly higher incidence of supragastric belching in those with globus, which led to the authors' proposal that globus may be a consequence of supragastric belching[22**].
Gastro-esophageal reflux disease (GERD)
GERD and supragastric belching can occur in tandem. GERD patients frequently report belching alongside typical symptoms of heartburn and regurgitation[7,23]. Likewise, 95% of patients with supragastric belching experience heartburn and regurgitation, nearly half of whom have pathological acid reflux[2**]. The sensation of heartburn in the absence of pathological acid reflux may be a consequence of pure gastric reflux, or gaseous distension of the esophagus as seen in supragastric belching[16,24].
While liquid reflux events occur in patients with supragastric and gastric belching at similar rates[15,25], the symptom burden is much higher for the supragastric belching group as two studies proved in 2015. They perceive both reflux and belching symptoms more readily and intensely[25,26**], and experience a higher frequency of belches[2**].
Two distinct patterns of supragastric belch-reflux association have been described. Up to 30% of all supragastric belching immediately precedes and thus plausibly elicits reflux[7,25]. This may explain refractoriness to proton pump inhibitors (PPIs), since acid suppression will not alter the genesis of supragastric belch-induced reflux[26**]. Less frequently (in 18%) supragastric belching occurs 4-10 seconds after a reflux episode begins, and is postulated to be a response to reflux-induced esophageal discomfort[7].
Esophageal hypomotility
A retrospective study of 100 patients with supragastric belching identified 44 with esophageal hypomotility (31 with dysphagia). This subgroup had significantly higher frequency of supragastric belches compared to the remainder of the cohort[2**] even when pathological acid exposure time was accounted for. Another paper showed slight differences in bolus transit between patients with supragastric belching and normal controls without differences in motility[27]. Beyond this, the relationship between supragastric belching and hypomotility remains unclear.
Gastric surgery
Gas-related symptoms are a known complication of antireflux surgery. The evidence surrounding perioperative frequency of supragastric belches is limited and inconsistent thus far. A 2011 study by Broeders et al showed a marked post-operative increase in supragastric belches at 6-month follow-up, suggesting the subconscious development of supragastric belching as a compensatory but futile mechanism to vent gastric air[28]. A 2013 report on a larger cohort by the same group reported no ultimate difference in pre- and post-operative frequency of supragastric belches[29]. Nonetheless both studies showed a significant decrease in reflux-induced supragastric belching[28,29]. The type of fundoplication (anterior 180'' versus 360''[30]; 270'' versus 360''[31]) appears to have no bearing on frequency of supragastric belching or reflux associated with supragastric belching.
A 2016 paper prospectively investigating belching frequency after sleeve gastrectomy found no significant change in the total number of supragastric belches at 3-month follow-up compared to pre-surgery baseline[32**].
Supragastric belching in pediatric patients
While excessive belching is known to occur in children[33,34], formal study into this area has only gained momentum in recent years. Two small impedance-based studies of symptomatic children in Canada[35] and Europe[36*] observed a significant overlap of aerophagia and supragastric belching compared to controls with normal studies. This is distinct from adults where the two entities seldom converge. Further research into this area is warranted.
TREATMENT
Fundamental to successful treatment of pathological supragastric belching is a careful explanation to the patient of its behavioral origin[5] (a strategy referred to as 'psychoeducation' by Riehl et al[37**]), and dispelling expectations of an underlying organic disorder. Subsequent therapeutic approaches revolve around behavioral modification and deconditioning from supragastric belching.
Speech therapy has been used in an open label study of 11 patients by Hemmink et al. A 10-session protocol combining explanation, glottis training, breathing and vocal exercises resulted in improvement in self-reported symptom frequency and intensity[38].
Biofeedback therapy with impedance or HRM monitoring facilitates symptom correlation with real-time visual input and aids patient understanding and motivation[3], although prolonged catheterisation may be poorly tolerated and thus hinder patient compliance.
Both speech and biofeedback therapy are time-intensive and therefore have yet to be widely adopted as routine management options. This may explain the paucity of data demonstrating clinical effectiveness outside of research settings.
Behavioral therapy appears to be simpler to administer, and has the most varied evidence base thus far. Riehl et al advocate a 2-session protocol, based on their pilot study of a health psychologist delivering psychoeducation and instructions on relaxed open-mouth breathing. This strategy resulted in 75% symptom improvement at 3 months[37**]. Even brief office-based interventions by clinicians can yield promising results, producing 80% complete resolution of supragastric belching at 1 month in Katzka's pilot of 5 patients taught sustained glottal opening[39], and complete resolution in 3 of 6 patients at 5 months' follow-up in a small UK study[21]. Hypnotherapy has also been anecdotally used to treat belching disorders[40].
All the above treatment strategies have yet to be studied in patients with supragastric belching and concomitant GERD or rumination. They also require highly specialist therapists familiar with the minutiae of supragastric belching and the different functional gastrointestinal disorders to adapt their therapeutic approach as necessary[1].
Pharmaceutical options for pure supragastric belching are limited at present to baclofen. Baclofen is a GABAB agonist which minimises reflux by increasing basal lower esophageal sphincter pressure and reducing TLESRs[41'44]. A small 2012 trial by Blondeau et al[45] and a 2014 Swedish case report of a therapy-refractory patient[46*] both described good outcomes with baclofen. The latter paper reported usage of baclofen in conjunction with pregabalin, and postulated that this combination produced a synergistic effect by reducing mechanosensitivity and chemosensitivity at the oesophagogastric junction. Wider uptake of baclofen for treating supragastric belching ' and reflux disorders in general ' has been hampered by excessive sedation and other unpleasant central nervous system and autonomic side effects. Alternatives in the form of lesogaberan and arbaclofen placarbil have yielded modest results at best[47,48] and further development has been abandoned.
Conclusion
Supragastric belching is a belching disorder of behavioral origin affecting both children and adults. The mainstay of diagnosis is esophageal impedance monitoring. The extent of the association between supragastric belching and numerous other gastrointestinal disorders is beginning to be clarified. Patient education combined with behavioral therapy currently has the best evidence in terms of treatment options. Further study is warranted to elucidate other therapeutic strategies for this benign but disabling condition.
KEY POINTS
' Supragastric belching is now understood as a belching disorder of behavioral origin. The mainstay of diagnosis is esophageal impedance monitoring.
' Supragastric belching is known to be associated with, and may be contributory to, GERD and rumination syndrome.
' New studies have sought to clarify the relationship between supragastric belching and other gastrointestinal complaints. Supragastric belching is now shown to be associated with globus, as well as reflux symptoms in PPI non-responders. Patients with supragastric belching also have higher frequency of belching events if they have concurrent esophageal hypomotility. Gum chewing and sleeve gastrectomy do not appear to have any bearing on supragastric belching. Recent research in children suggests an overlap between supragastric belching and aerophagia that is not observed in adults.
' Psychoeducation and behavioral therapy delivered by a health psychologist specializing in gastroenterology shows promise in treatment of supragastric belching. Baclofen used with pregabalin may be an effective pharmaceutical strategy.