Belching Disorders and Rumination Syndrome: A Literature Review

Belching is an ordinary phenomenon that practically everyone experiences in everyday life. However, it can be bothersome when excessive. On the other hand, rumination is not physiological for human being and causes regurgitation and/or vomiting as a result of bringing up food from the stomach to the mouth. Excessive belching and rumination can impair quality of life [1‒3], and according to Rome IV, these conditions are classified as belching disorders and rumination syndrome (RS). Belching disorders are further classified into excessive gastric belching (GB) and supragastric belching (SGB). Although excessive SGB and RS are discrete entities that cause different symptoms, they have two main characteristics in common as follows: (1) gastroesophageal reflux disease (GERD)-like symptoms and (2) behavioral nature. It has been increasingly recognized that patients with excessive SGB and/or RS are frequently regarded as having refractory GERD [4, 5]. As a consequence, inappropriate therapy is given to not insignificant part of such patients, which leads to unsatisfactory treatment outcome. In this review, we summarized literature pertaining to these behavioral disorders in Rome IV about definition, epidemiology, pathophysiology, diagnosis, and treatment.

Belching is defined as an audible escape of air through the pharynx [2]. On the basis of the pattern of air movement, belching can be classified into two types: GB and SGB. The air in GB rises from the stomach whereas, in SGB, the air comes from the esophagus. Although both types can be seen in healthy asymptomatic subjects, belching can be considered as a disorder when excessive and bothersome. The diagnostic criteria of excessive GB or SGB in Rome IV require bothersome (i.e., severe enough to impact on usual activities) belching more than 3 days a week regardless of its type. The criteria must be fulfilled for the last 3 months with symptom onset at least 6 months before diagnosis.

RS is defined as repetitive, effortless regurgitation of recently ingested food into the mouth followed by rechewing and re-swallowing or expulsion of the food bolus. The following two items need to be fulfilled for the diagnosis of RS in Rome IV: (1) persistent or recurrent regurgitation of recently ingested food into the mouth with subsequent spitting or re-mastication and swallowing, and (2) regurgitation is not preceded by retching. Unlike excessive GB and SGB, there is no statement about symptom frequency in the diagnostic criteria.

Few studies reported the prevalence of belching disorders or RS in general population. A large internet survey has been recently conducted for general population in 26 countries including over 54,000 people. The study found that the global prevalence of belching disorders and RS are 1% and 2.8%, respectively [6]. The prevalence of both disorders tended to be slightly female dominant. Our previous study showed that 6.1% of approximately 2,000 Japanese subjects at health check-up rated the frequency of their belching as often or always [7]. These frequent belching was associated with functional dyspepsia (FD), coexisting heartburn, anxiety/depression, and sleep disturbance. It should be noted that the prevalence of each excessive GB and SGB could not be evaluated on internet survey.

The aforementioned prevalence data about RS was unexpectedly high because RS had been previously thought as related to intellectual disability. Eating disorders including bulimia nervosa are known to overlap with RS. There was a regional difference in RS prevalence as highest in Brazil (5.5%) followed by Japan (4–4.3%) and lowest in Singapore (1.7%) [3]. Risk factors for RS were female, high BMI, and psychiatric comorbidities such as depression, and anxiety.

There must be an overlap between excessive SGB and RS as some RS patients use SGB to ruminate gastric contents. However, little is known about its epidemiological data.

GB is a gaseous gastroesophageal reflux. This is a physiological mechanism in which the swallowed air accumulated in the proximal stomach is emitted through transient lower esophageal sphincter relaxation (TLESR) [8]. TLESR is a vago-vagal reflex to the distension of the proximal stomach as bilateral vagotomy can abolish TLESR. The stretch stimulation is transmitted through vagal afferent nerves to the solitary nucleus in the medulla oblongata, followed by activation of efferent vagal pathway that results in releasing nitric oxide and vasoactive intestinal peptide to relax the LES.

SGB is a behavior where air sacked or swallowed from the mouth comes down into the esophagus, immediately followed by expelling it using abdominal straining. In air sucking type, this air movement starts with the diaphragmatic contraction that creates negative pressure in the esophagus. Subsequent relaxation of the upper esophageal sphincter with epiglottis closure lets air flow into the esophagus from the pharynx due to the pressure gradient. The air hardly enters the stomach through the LES in contrast to GB. Ultimately, the intraesophageal air is expelled orally with abdominal straining that increases gastric and esophageal pressure. In air-swallowing type, patients initially push air down to the esophagus using the pharyngeal pump [8].

Rumination regurgitates gastric contents using the abdominal compression, in which not only the anterior abdominal wall muscle but also the intercostals contract simultaneously to generate great pressure gradient between the esophagus and the stomach. Decreased LES pressure and pseudo-hiatal hernia can be seen during the retrograde flow.

Excessive SGB and RS are probably not congenital. Little is known about the exact mechanism that leads patients to acquiring these behaviors at some point although stressful life events might be a trigger for it. Several studies assume that uncomfortable bodily sensation plays an important role in excessive SGB and RS because these behaviors seem to be utilized to relieve discomfort. For instance, some excessive SGB patients with bloating believe that belching can emit the gas in the abdomen although it is not the case. Most patients with excessive SGB can recognize warning symptoms (e.g., throat, chest, or abdominal discomfort) before SGB commences [9]. Similarly, RS patients often suffer from concomitant epigastric pain or bloating that might be attributable to enhanced visceral pain perception, poor postprandial accommodation of the stomach, and lower esophageal sphincter relaxation. Rumination might be a result of countermove to abdominal discomfort (i.e., putting a strain on the abdomen).

Excessive SGB and RS can mimic true GERD as patients with the behavioral disorders often complain about predominant reflux symptoms. SGB can cause reflux symptoms by (1) inducing gastroesophageal reflux and/or (2) SGB-induced esophageal distension. The mechanism about the former has not been elucidated yet although excessive SGB sometimes results in pathological esophageal acid exposure. Needless to say, regurgitation in RS occurs due to retrograde liquid flow similar to GERD albeit driven by voluntary abdominal muscle contraction. Since proton pump inhibitors (PPIs) prescribed for reflux symptoms do not cease these behaviors, patients with excessive SGB and RS can be misdiagnosed as having PPI-refractory GERD.

Yadlapati et al. [4] using postprandial high-resolution impedance manometry (HRIM) identified pathological SGB and rumination in as much as 42% and 20% of patients with PPI-refractory reflux symptoms, respectively. In our previous study, off-PPI impedance-pH monitoring (MII-pH) found the prevalence of pathological SGB (>13 episodes/24 h) as 37.7% in non-erosive reflux disease (i.e., acid exposure time >6%), 39.7% in reflux hypersensitivity (RH) (i.e., acid exposure time <4% and positive reflux-symptom association) and 22% in functional heartburn (i.e., acid exposure time <4% and negative reflux-symptom association). Whilst 9.5% of RH and 1.3% of non-erosive reflux disease patients had RS. Importantly, both excessive SGB and rumination were related to approximately 40% of typical reflux symptoms (i.e., heartburn, regurgitation, and/or chest pain) in RH [5].

Both belching disorders and RS are related to FD. That seems reasonable because part of patients performs the behaviors to relieve abdominal discomfort. In fact, up to 80% of FD patients have belching symptom [10] and frequency of belching positively correlates to the prevalence of FD [7]. More interestingly, belching in FD is related to postprandial distress syndrome rather than epigastric pain syndrome. Tack et al. [11] found higher sensitivity to gastric dilatation in FD patients with concomitant belching symptom than without. Further study is required to elucidate whether FD is associated specifically with excessive SGB.

Zand Irani et al. [12] found RS overlaps with FD 3.83 times more likely than expected by chance. In clinical practice, overlapped FD often requires treatment apart from one for belching disorders and/or RS.

Belching disorders overlap with 8.2% (26/319) of IBS patients [13]. Obekli et al. [14] showed that IBS had increased episodes of SGBs compared to healthy volunteers whereas no difference was found in those of GBs.

Patients with globus had higher prevalence of pathological SGB and aerophagia than GERD patients [15].

In medical interview, it is possible to find a clue about the type of belching from patients. Kessing et al. [16] found the number of SGBs rather than GBs determines the severity of belching symptoms in patients with GERD. It indicates that patients who predominantly complain about belching symptoms are likely to have excessive SGB. Moreover, patients with excessive SGB often continue belching even during medical interview, but suddenly stop when speaking or distracted. Without these features, it would be challenging to distinguish excessive SGB from GB precisely. Twenty-four-hour MII-pH is a gold standard to diagnose belching disorders (Fig. 1). MII-pH measures movement of air and/or liquid in the esophagus, whereby GB is visualized as impedance rise retrogradely transmitting from the distal to proximal channel whilst SGB can be identified as V-shaped impedance rise. A previous study suggests that SGB >13 episodes/24 h is pathological [17]. However, it depends on the patient how many SGBs are considered as bothersome.

Meticulous history taking can diagnose RS given the diagnostic criteria in Rome IV. However, it would be challenging to distinguish RS from true GERD specifically when patients have concomitant disrupted anti-reflux barrier. Regurgitation-predominant GERD patients often require fundoplication whereas such surgical intervention is not strongly recommended for RS as a first-line treatment; hence, the diagnosis sometimes needs to be objectively confirmed for appropriate management. The crucial difference between the RS and GERD is whether the reflux is induced by abdominal compression. Simultaneous recording of pressure and impedance is therefore essential for precise diagnosis. There is no standardized protocol for postprandial recording of HRIM where we normally record for approximately 15 min after patients finish eating test meals (cornflakes with 200-mL milk). In rumination, the increase of intragastric pressure, i.e., the abdominal compression, precedes retrograde flow reaching to the proximal esophagus in the trace (Fig. 1). Kessing et al. [18] classified rumination into three types as follows: (1) primary rumination: an abdominal pressure increase precedes the retrograde flow, (2) secondary rumination: the increase in abdominal pressure occurs after the onset of a reflux event, and (3) SGB-associated rumination: an abdominal pressure increase by a SGB precedes the retrograde flow. They proposed >30 mm Hg as the threshold for intragastric pressure preceding reflux to distinguish rumination from GERD. Another study suggests gastro-sphincteric pressure gradient ≥2 mm Hg can increase the diagnostic yield [19].

Postprandial HRIM is a gold standard for diagnosis of RS. On the other hand, HRIM is not routinely performed even in tertiary centers and for this reason practitioners normally need to consider the possibility of RS in advance to offer HRIM. Nonetheless, some potential RS patients can be missed. In this context, characteristic reflux pattern in off-PPI MII-pH, which is an ordinary test for reflux patients, would help clinicians to identify unrecognized RS patients. Our previous study found that RS patients compared to GERD had more reflux episodes with higher proximal extent [20]. In addition, RS patients showed closer reflux-symptom association (i.e., higher symptom index during 1-h postprandial periods) than GERD. In fact, RS patients often mark reflux symptoms immediately after reflux episodes. These findings led to proposing criteria for detection of potential RS patients, which consists of two MII-pH parameters calculated within 1-h postprandial periods as follows: (1) >3 non-acid reflux episodes and (2) symptom index >60%. In patients with regurgitation-predominant reflux, RS can be diagnosed with sensitivity of 91.7% and 58% and specificity of 78.6% and 93% when either one or both of the criteria are fulfilled, respectively.

Proposed therapeutic algorithms for each condition are shown in Figure 2.

Given the mechanism of GBs, treatment should be aimed to reduce air swallowing and gas refluxes through TLESRs.

Eating habit modification (e.g., eat slowly and avoid carbonated drinks) might be able to reduce the air swallowing. In addition, diaphragmatic breathing might be effective [2].

For reduction of TLESRs, pharmaceutical and surgical options are available. Gamma-aminobutyric acid receptor type B receptor agonist, baclofen, can increase basal LES pressure, and reduce the number of TLESRs. A randomized controlled trial by Cossentino et al. [21] showed baclofen improves belching symptom, esophageal acid exposure time, and reflux episodes in patients with GERD. Interestingly, baclofen also has a suppressive effect on swallowing rate that might contribute to improvement of aerophagia. However, side effects of baclofen including sleepiness and dizziness might limit its use in clinical practice.

A systematic review showed that PPIs can improve belching symptoms the most among dyspeptic symptoms in GERD [22]. Several other drugs have been shown effective for belching symptom in FD as follows: rifaximin, acotiamide (acetylcholinesterase inhibitor), rebamipide (mucosal protective agents), and famotidine (H2 receptor antagonist).

Laparoscopic fundoplication (LPF) can reduce the number of GBs without any effect on air swallows in which 360° LPF is more efficient than 270° LPF [23]. As a result, 270° LPF causes less gas bloating and flatulence postoperatively compared to 360° LPF. However, it should be noted that the number of SGBs can increase after both types of LFP possibly due to inability to vent the air in the stomach through the tightened EGJ. Endoscopic augmentation of the anti-reflux barrier might be a possible option for excessive GB.

Changing behavioral patterns should be a reasonable way to treat behavioral disorders. In fact, cognitive behavioral therapy (CBT) has been established as the first-line therapy for both excessive SGB and RS [9, 24]. Speech therapy is one type of CBT, which includes normalizing a complex movement of tongue, larynx, and upper esophageal sphincter. One of the advantages of such psychological intervention is to cause few adverse events. On the other hand, CBT requires dedicated psychologists and for this reason access to CBT might be limited by local expertise.

For excessive SGB, CBT or speech therapy can improve not only belching symptoms but also an objective number of SGBs in 50–80% of patients [25]. In addition, CBT can diminish esophageal acid exposure when excessive SGB induces pathological acid refluxes [9]. CBT and speech therapy basically share the common concept. For RS, CBT with diaphragmatic breathing using electromyography-guided biofeedback decreased rumination episodes by approximately 70% [24]. The effect of CBT lasts at least 6–12 months.

CBT is normally composed of several sessions that consist of two main components: cognitive and behavioral parts. In cognitive part, clinicians explain the mechanisms of SGBs and/or RS so that patients can understand those conditions are consequence of an unconscious but voluntary behavior. Subsequently, they help patients to recognize warning signs (e.g., abdominal, chest, or throat discomfort) before SGBs and/or rumination occur. In addition, patients need to change their way of thinking that such behaviors are helpful to relieve uncomfortable bodily sensation. In behavioral part, patients learn gentle diaphragmatic breathing to physically stop SGB and/or rumination. For SGB, mouth opening/tongue position can be added to diaphragmatic breathing, which makes it more difficult to swallow air into the esophagus. In detail, the mouth is held moderately open, and the tip of the tongue is placed behind the top front teeth while breathing through the mouth. A previous study found that success factors about CBT for excessive SGB are a small number of SGBs, low hypervigilance and high CBT proficiency (i.e., possible to identify a warning signal, good acceptance, and adherence to CBT) [26].

Baclofen can improve both excessive SGB and RS although only a couple of studies involving a few patients support its efficacy. In a previous placebo-controlled, double-blind, cross-over study, postprandial HRIM found that 2-week baclofen administration (10 mg three times a day) significantly reduced the number of rumination episodes as well as regurgitation symptom. It was almost the case in SGB episodes, but the treatment effect did not reach statistically significance probably due to small sample size [27]. This positive effect of baclofen on RS is likely to be attributed to increase of LES pressure. Robles et al. [28] reported that combination of diaphragmatic breathing and tricyclic antidepressants such as nortriptyline, amitriptyline, or doxepin achieved symptom improvement in 90.9% of patients with RS. This study suggests that tricyclic antidepressants have an additional therapeutic effect on CBT.

It could be rationale to perform fundoplication for patients with predominant secondary rumination (i.e., rumination occurring during gastroesophageal reflux) because the reduction of reflux might lessen the chance of rumination. Oelschlager et al. [29] reported 5 cases of RS successfully treated with Nissen fundoplication. Another RS case with delayed gastric emptying was relieved by subtotal gastrectomy with Roux-en-Y reconstruction [30]. However, there is lack of evidence about indication of surgery for RS. Endoscopic anti-reflux procedure might be a possible treatment for RS.

Belching disorders and RS are not rare conditions. Patients with PPI-refractory reflux symptoms should be paid careful attention as for the possibility of two behavioral disorders, excessive SGB and RS. Although objective diagnostic criteria have been well established, there has still been unmet medical needs for treatment. Overlap with other disorders of gut-brain interactions and eating disorders often needs a holistic approach. Further study is required to develop more effective management for belching disorders and RS.

The authors have no conflicts of interest to declare regarding this manuscript.

The authors have no funding to declare regarding this manuscript.

A.S. contributed to conducting literature search and drafting the manuscript and approval of the final version and Y.F. contributed to editing the manuscript critically and approval of the final version.