Intestinal tone and gas motion

Characterization of Simultaneous Pressure Waves as Biomarkers for Colonic Motility Assessed by High-Resolution Colonic Manometry

Simultaneous pressure waves (SPWs) in manometry recordings of the human colon have been associated with gas expulsion. Our hypothesis was that the SPW might be a critical component of most colonic motor functions, and hence might act as a biomarker for healthy colon motility. To that end, we performed high-resolution colonic manometry (HRCM), for the first time using an 84-sensor (1 cm spaced) water-perfused catheter, in 17 healthy volunteers. Intraluminal pressure patterns were recorded during baseline, proximal and rectal balloon distention, after a meal and following proximal and rectal luminal bisacodyl administration. Quantification was performed using software, based on Image J, developed during this study. Gas expulsion was always associated with SPWs, furthermore, SPWs were associated with water or balloon expulsion. SPWs were prominently emerging at the termination of proximal high amplitude propagating pressure waves (HAPWs); we termed this motor pattern HAPW-SPWs; hence, SPWs were often not a pan-colonic event. SPWs and HAPW-SPWs were observed at baseline with SPW amplitudes of 12.0 ± 8.5 mmHg and 20.2 ± 7.2 mmHg respectively. The SPW occurrence and amplitude significantly increased in response to meal, balloon distention and luminal bisacodyl, associated with 50.3% anal sphincter relaxation at baseline, which significantly increased to 59.0% after a meal, and 69.1% after bisacodyl. Often, full relaxation was achieved. The SPWs associated with gas expulsion had a significantly higher amplitude compared to SPWs without gas expulsion. SPWs could be seen to consist of clusters of high frequency pressure waves, likely associated with a cluster of fast propagating, circular muscle contractions. SPWs were occasionally observed in a highly rhythmic pattern at 1.8 ± 1.2 cycles/min. Unlike HAPWs, the SPWs did not obliterate haustral boundaries thereby explaining how gas can be expelled while solid content can remain restrained by the haustral boundaries. In conclusion, the SPW may become a biomarker for normal gas transit, the gastrocolonic reflex and extrinsic neural reflexes. The SPW assessment reveals coordination of activities in the colon, rectum and anal sphincters. SPWs may become of diagnostic value in patients with colonic dysmotility.

[Bloating]

Bloating is one of the most common and troublesome problems in a large proportion of patients with gastrointestinal disorders but the mechanism is not completely understood. Several factors, including gas-producing intestinal microbiota, disturbed handling of intestinal gas, visceral hypersensitivity, abnormal viscero-somatic responses, fermentable diet, and psychological factors, have been suggested as mechanisms. For an assessment, thorough medical history-taking and physical examination are the first steps. On the other hand, organic disorders should always be considered first for a differential diagnosis. The therapeutic options available are considered challenging and still limited in clinical practice. The treatment strategy may include diet modification, pharmacologic approach, psychiatric approach, biofeedback, etc. Further studies will be needed to explore the variable mechanism of bloating and develop an efficient treatment.

A new proposed mechanism of action for gastric bypass surgery: Air hypothesis

Roux-en-Y gastric bypass (RYGB) surgery is one of the most effective treatments for obesity and type II diabetes. RYGB was originally believed to work by mechanically restricting caloric intake or causing macronutrient malabsorption. However, such mechanical effects play no role in the remarkable efficacy of gastric bypass. Instead, mounting evidence shows that altered neuroendocrine signaling is responsible for the weight reducing effects of RYGB. The exact mechanism of this surgical response is still a mystery. Here, we propose that RYGB leads to weight loss primarily by inducing a functional shift in the gut microbiome, manifested by a relative expansion of aerobic bacteria numbers in the colon. We point to compelling evidence that gastric bypass changes the function of the microbiome by disrupting intestinal gas homeostasis, causing excessive transit of swallowed air (oxygen) into the colon.

Effect of prucalopride on intestinal gas tolerance in patients with functional bowel disorders and constipation

BACKGROUND AND AIM

Patients with functional bowel disorders develop gas retention and symptoms in response to intestinal gas loads that are well tolerated by healthy subjects. Stimulation of 5HT-4 receptors in the gut has both prokinetic and antinociceptive effects. The aim of this study is to determine the effect of prucalopride, a highly selective 5HT-4 agonist, on gas transit and tolerance in women with functional bowel disorders complaining of constipation.

METHODS

Twenty-four women with functional bowel disorders complaining of constipation were included in the study. Patients were studied twice on separate days in a cross-over design. On each study day, an intestinal gas challenge test was performed. During the five previous days, prucalopride (2 mg/day) or placebo was administered. Abdominal symptoms, stool frequency, and stool consistency were recorded during the treatment period on daily questionnaires.

RESULTS

During the gas challenge test, prucalopride did not decrease the volume of gas retained in the subset of patients who had significant gas retention (≥ 200 mL) while on placebo. However, in those patients who had increased symptoms during the gas test (≥ 3 on a 0 to 6 scale) when on placebo, prucalopride did significantly reduce the perception of symptoms (2.3 ± 0.5 mean score vs 3.5 ± 0.3 on placebo; P = 0.045). During the treatment period with prucalopride, patients exhibited an increase in the total number of bowel movements and decreased stool consistency compared with placebo.

CONCLUSION

Prucalopride reduces abdominal symptoms without modifying gas retention when patients with functional bowel disorders are challenged with the gas transit and tolerance test. European Clinical Trials Database (EudraCT2011-006354-86).

Bloating and Abdominal Distension: Old Misconceptions and Current Knowledge

Bloating, as a symptom and abdominal distension, as a sign, are both common functional-type complaints and challenging to manage effectively. Individual patients may weight differently the impact of bloating and distension on their well-being. Complaints may range from chronic highly distressing pain to simply annoying and unfashionable protrusion of the abdomen. To avoid mishaps, organic bloating, and distension should always be considered first and appropriated assessed. Functional bloating and distension often present in association with other manifestations of irritable bowel syndrome or functional dyspepsia and in that context patients tend to regard them as most troublesome. A mechanism-based management bloating and distension should be ideal but elucidating key operational mechanisms in individual patients is not always feasible. Some clues may be gathered through a detailed dietary history, by assessing bowel movement frequency and stool consistency and special imaging technique to measure abdominal shape during episodes of distension. In severe, protracted cases it may be appropriate to refer the patient to a specialized center where motility, visceral sensitivity, and abdominal muscle activity in response to intraluminal stimuli may be measured. Therapeutic resources focussed upon presumed or demonstrated pathogenetic mechanism include dietary modification, microbiome modulation, promoting gas evacuation, attenuating visceral perception, and controlling abdominal wall muscle activity via biofeedback.

Effect of selective CCK1 receptor antagonism on accommodation and tolerance of intestinal gas in functional gut disorders

BACKGROUND

Participants with functional gut disorders develop gas retention and symptoms in response to intestinal gas loads that are well tolerated by healthy subjects. To determine the role of cholecystokinin (CCK1 ) receptors on gas transit and tolerance in women with functional gut disorders.

METHODS

In 12 healthy women, and 24 women with functional gut disorders (12 dyspepsia and 12 constipation-predominant irritable bowel syndrome) gas was infused into the jejunum at 12 mL/min for 3 h with simultaneous duodenal lipid infusion (intralipid 1 kcal/min), while measuring anal gas evacuation and abdominal symptoms on a 0-6 score scale. Triple-blind paired studies during iv infusion of dexloxiglumide (2.5 mg/kg bolus plus 5 mg/kg h continuous infusion), a selective CCK1 inhibitor, or saline (control) were performed in random order.

RESULTS

During saline infusion participants with functional gut disorders developed significantly greater gas retention and abdominal symptoms than healthy subjects (394 ± 40 mL vs 265 ± 35 mL and 2.8 ± 0.3 vs 1.9 ± 0.4 highest abdominal symptom score, respectively; P < 0.05 for both). Dexloxiglumide increased gas retention in both groups (514 ± 35 mL and 439 ± 60 mL, respectively; P = 0.033 vs saline for both); however, despite the larger retention, dexloxiglumide reduced abdominal symptoms (2.3 ± 0.2 score and 0.8 ± 0.3 score, respectively; P = 0.05 vs saline for both). Post-hoc analysis showed that, the decrease in abdominal symptoms was more pronounced in those participants with functional gut disorders with higher basal abdominal symptoms than in the rest (P = 0.037).

CONCLUSION

Inhibition of CCK1 receptors by dexloxiglumide increases intestinal gas retention and reduces abdominal symptoms in response to by intestinal gas loads. European Clinical Trials Database (EudraCT 2005-003338-16).

Bloating and functional gastro-intestinal disorders: Where are we and where are we going?

Bloating is one of the most common and bothersome symptoms complained by a large proportion of patients. This symptom has been described with various definitions, such as sensation of a distended abdomen or an abdominal tension or even excessive gas in the abdomen, although bloating should probably be defined as the feeling (e.g. a subjective sensation) of increased pressure within the abdomen. It is usually associated with functional gastrointestinal disorders, like irritable bowel syndrome, but when bloating is not part of another functional bowel or gastrointestinal disorder it is included as an independent entity in Rome III criteria named functional bloating. In terms of diagnosis, major difficulties are due to the lack of measurable parameters to assess and grade this symptom. In addition, it is still unclear to what extent the individual patient complaint of subjective bloating correlates with the objective evidence of abdominal distension. In fact, despite its clinical, social and economic relevance, bloating lacks a clear pathophysiology explanation, and an effective management endorsement, turning this common symptom into a true challenge for both patients and clinicians. Different theories on bloating etiology call into questions an increased luminal contents (gas, stools, liquid or fat) and/or an impaired abdominal empting and/or an altered intra-abdominal volume displacement (abdomino-phrenic theory) and/or an increased perception of intestinal stimuli with a subsequent use of empirical treatments (diet modifications, antibiotics and/or probiotics, prokinetic drugs, antispasmodics, gas reducing agents and tricyclic antidepressants). In this review, our aim was to review the latest knowledge on bloating physiopathology and therapeutic options trying to shed lights on those processes where a clinician could intervene to modify disease course.

Colonic gas transit in patients with bloating: the effect of an electromechanical stimulator of the abdominal wall

BACKGROUND

The aim of our study was to evaluate gas retention, abdominal symptoms and changes in girth circumference in females with bloating using an active or sham abdominal wall mechanical stimulation.

METHODS

In 14 female patients, complaining of bloating (11 with irritable bowel syndrome and 3 with functional bloating according to the Rome III criteria) a gas mixture was continuously infused into the colon for 1 h (accommodation period). Abdominal perception and girth were measured. At the beginning of the 30-min period of free rectal gas evacuation (clearance period), an electromechanical device was positioned on the abdominal wall of all patients. The patients were randomly assigned to an active or a sham stimulation protocol group. Gas retention, perception and abdominal distension were measured at the end of the clearance period.

RESULTS

All patients tolerated the volume (1,440 ml) of gas infused into the colon. Abdominal perception and girth measurements was similar in both groups during the accommodation period. At the end of the clearance, the perception score and the girth changes in the active and sham stimulation groups were similar (2.8 ± 2.0 vs. 1.4 ± 1.2, p = 0.2 and 4.9 ± 4.5 vs. 2.8 ± 2.3 mm, p = 0.3 active vs. sham, respectively). Furthermore, the mechanical stimulation of the abdominal wall did not significantly reduce gas retention (495 ± 101 ml vs. 566 ± 55, active vs. sham, p = 0.1).

CONCLUSIONS

An external mechanical massage of the abdominal wall did not improve intestinal gas transit, abdominal perception and abdominal distension in our female patients complaining of functional bloating.

Effects on gastrointestinal transit and antroduodenojejunal manometry after gut-directed hypnotherapy in irritable bowel syndrome (IBS)

BACKGROUND

Gut-directed hypnotherapy is an effective treatment in irritable bowel syndrome (IBS) but little is known about the mechanisms of action. In this study we aimed to investigate the effects on gastrointestinal motility when treating IBS with gut-directed hypnotherapy.

METHODS

We randomized 90 patients with IBS, refractory to standard management to receive gut-directed hypnotherapy 1 h/week for 12 weeks or supportive treatment for the same time period. Eighty-one subjects (40 hypnotherapy, 41 controls) could be evaluated by one or more of the following investigations, both before and after the intervention: gastric emptying time, small bowel transit time, colonic transit time, and antroduodenojejunal manometry.

RESULTS

No significant differences in gastric emptying time, small bowel transit time, or colonic transit time was found when comparing the baseline and post-intervention measurements in the hypnotherapy group or in the control group. The same was true concerning the results of the antroduodenojejunal manometry. However, there was a numerical trend toward a higher number of migrating motor complexes at manometry and an accelerated gastric emptying time after hypnotherapy that did not reach statistical significance.

CONCLUSIONS

In this study, we were not able to find evidence for long-standing effects on gastrointestinal motility as a mediator of the effects on IBS when treating the condition with gut-directed hypnotherapy. Further research to understand the mechanism of action is needed.

Methods for the assessment of small-bowel and colonic transit

Transit assessment of the small intestine and colon is relevant in the study of physiology, pathophysiology, and pharmacodynamics, and there is increasing use of small-bowel and colonic transit measurements in clinical practice as well. The main methods that are applied in clinical practice are substrate-hydrogen breath tests for small-bowel transit and radiopaque markers for colonic transit. Over the past 2-3 decades, scintigraphy has become the preferred standard in research studies, particularly for studies of pathophysiology and pharmacodynamics. New approaches include experimental stable isotope measurement of orocecal transit and the recently approved method using a wireless motility capsule that is validated as an accurate measurement of small-bowel and colonic transit.

Accommodation of the abdomen to its content: integrated abdomino-thoracic response

BACKGROUND

  We previously showed that changes in intra-abdominal content induce a volume-dependent muscular response of the anterior abdominal wall and the diaphragm. We aimed to determine the contribution of the thorax to abdominal accommodation and the influence of the intra-abdominal expansion rate.

METHODS

  Gas (1440 mL total load) was infused into the colon of nine healthy subjects, while abdomino-thoracic perimeters (by tape measure), electromyography (EMG) activity of the diaphragm (via six ring electrodes over an esophageal tube in the hiatus), intercostals and anterior abdominal wall (via five pairs of surface electrodes) and the position of the diaphragm by ultrasonography were measured. Infusion rates of 24, 48, and 96 mL min(-1) were tested on separate days.

KEY RESULTS

  Gas infusion induced anterior abdominal wall contraction (18 ± 1% EMG increment; P < 0.001) with relatively modest girth increment (4.9 ± 0.9 mm; P = 0.001), diaphragmatic relaxation (by 15 ± 1%; P < 0.001) with cephalad displacement (by 23 ± 6 mm; P = 0.005), and intercostal contraction (by 19 ± 2%; P < 0.001) with increased thoracic perimeter (by 2.0 ± 0.5 mm; P = 0.009). Responses were similar with the three infusion rates.

CONCLUSIONS & INFERENCES

  Accommodation of intra-abdominal loads involves a volume-related integrated abdomino-thoracic response regardless of the expansion rate.

The dysfunctional gut

After many decades debating whether the clinical manifestations of patients with functional digestive symptoms originate "in their minds" or "in their guts," arguments remain strong on both sides of the controversy. However, advances in understanding of gut physiology and pathophysiology, and persuasive evidence on the bidirectionality of the regulatory traffic between the enteric and central nervous systems, are helping to characterize clinical situations in which we can legitimately speak of gut dysfunction, as opposed to others where symptoms are not associated with apparent or detectable gut disturbances and may truly represent somatization of an affective disorder. In this review, we describe available clinically applicable technology, albeit in specialized clinical research units, that may be used to discern whether or not challenging patients have gut sensory or motor disturbances. The practical yield of applying such methods to diagnostic investigation may be substantial, because it establishes a plausible mechanism of disease that may be used in patient management and patient persuasion, to remove uncertainties and to prevent futile repetition of conventional diagnostic tests. By evolving from symptom analysis to mechanism-based diagnosis, our gastroenterology community may progress toward the goal of delivering the full diagnostic spectrum from altered morphology to disturbed function.

[Abdominal bloating: an up-to-date]

Bloating is a common symptom, especially in women. In the clinical practice, it remains a therapeutic challenge. Since recently, its pathophysiology is better understood: an impaired transit of gas (particularly in the small bowel) or a visceral hypersensitivity leading to the induction of an abdominal discomfort despite a normal volume of gas are two of the main causes, far more frequent than an excessive production of gas. Moreover, bloating can be related to abnormal viscera-somatic reflexes promoting both an abdomino-phrenic dyssynergia and the relaxation of the muscles of the abdominal wall. From a therapeutic point of view, the efficacy of the gas absorbants remains to be more documented. Besides the treatment of a constipation and the avoidance of nutrients either highly fermentable or rich in fructose, other therapeutic options include prokinetics and drugs acting on visceral sensitivity. Probiotics are another promising option. In some centers, a non pharmacological therapeutic approach, mainly based on hypnosis, is discussed.

Bloating and distention in irritable bowel syndrome: the role of visceral sensation

BACKGROUND & AIMS

Abdominal bloating is an extremely intrusive symptom of irritable bowel syndrome (IBS) that is not always accompanied by an increase in abdominal girth (distention), raising the possibility that these 2 features of the condition may not share a common pathophysiology. A number of mechanisms have been postulated for bloating and distention, but the role of visceral sensation, which is often abnormal in IBS, has not been previously investigated, and this study aimed to address this question.

METHODS

Abdominal girth measured by ambulatory abdominal inductance plethysmography and bloating severity was recorded over 24 hours in 39 IBS-constipation (ages, 18-73 years) and 29 IBS-diarrhea patients (ages, 20-59 years) meeting Rome II criteria. Within 1 week, rectal sensory thresholds were assessed with a barostat using the ascending method of limits and tracking.

RESULTS

IBS patients who suffered with bloating alone had lower thresholds for pain (P = .005), desire to defecate (P = .044), and first sensation (P = .07) compared with those who had concomitant distention irrespective of bowel habit. When patients were grouped according to sensory threshold, hyposensitive individuals had distention significantly more than those with hypersensitivity (P = .001), and this was observed more in the constipation subgroup. Static and dynamic compliance did not differ among any of the groups.

CONCLUSIONS

The symptom of bloating alone is associated with visceral hypersensitivity, suggesting that the pathogenesis of bloating and distention may not be the same. Consequently, treatment approaches may have to be different, and measuring visceral sensation could have utility in choosing the right therapeutic modality.

Small intestinal motility

PURPOSE OF REVIEW

To review recently published studies presenting novel and relevant information on small intestinal motility.

RECENT FINDINGS

The reviewed studies covered a variety of topics with several themes emerging. Our understanding of the influence of systemic disorders, intestinal and extraintestinal infections and enteric bacteria on digestive motor function continues to involve. Elegant and important new studies have been published that better define the physiology of intestinal gas handling along with the genesis of symptoms commonly attributed to excessive intestinal gas. While interest in small intestinal bacterial overgrowth in irritable bowel syndrome continues, the utility and specificity of lactulose hydrogen breath testing is yet again questioned and further data are needed before the practice of routinely prescribing antibiotics to patients with irritable bowel syndrome can be endorsed.

SUMMARY

Small intestinal motility remains an understudied area. Recent publications provide additional new information related to physiology and pathophysiology of small bowel motility. These findings should be of interest to clinician and investigator alike.

Irritable bowel syndrome and bloating

Gaseous symptoms in irritable bowel syndrome (IBS) including eructation, flatulence, and bloating occur as a consequence of excess gas production, altered gas transit, abnormal perception of normal amounts of gas within the gastrointestinal tract, or dysfunctional somatic muscle activity in the abdominal wall. Because of the prominence of gaseous complaints in IBS, recent investigations have focussed on new insights into pathogenesis and novel therapies of bloating. The evaluation of the IBS patient with unexplained gas and bloating relies on careful exclusion of organic disease with further characterisation of the underlying condition with directed functional testing. Treatment of gaseous symptomatology in IBS should be targeted to pathophysiologic defects whenever possible. Available therapies include lifestyle alterations, dietary modifications, enzyme preparations, adsorbents and agents which reduce surface tension, treatments that alter gut flora, and drugs that modulate gut transit.