High-resolution versus conventional manometry for the diagnosis of small bowel motor dysfunction.

BACKGROUND: The diagnosis of small bowel motility disorders is performed by manometric evaluation of the contractile patterns of the small intestine. Conventional intestinal manometry systems include few pressure sensors at relatively long intervals. We have recently shown that high-resolution jejunal manometry, with multiple closely spaced recording sites, allows the analysis of propagation patterns of intestinal motility in healthy subjects that cannot be detected with conventional manometry. The objective of this pilot study was to explore the feasibility and diagnostic value of high-resolution intestinal manometry in patients with suspected small bowel dysmotility. METHODS: Prospective pilot study evaluating intestinal motility patterns in 16 consecutive patients (16-61 years; 11 women) with severe, chronic digestive symptoms referred for the evaluation of intestinal motility and in 18 healthy controls (21-38 years; 8 women). A 36-channel high-resolution manometry catheter was orally placed under radiological guidance in the jejunum. Intestinal motility was continuously recorded for 3 h fasting and 2 h after a 450 kcal meal. The manometric recordings were analyzed in two formats: (a) with the high-resolution data from 34 channels and (b) showing only the recordings from 5 channels separated by 7 cm intervals, mimicking a conventional manometry recording. KEY RESULTS: In the analysis mimicking conventional manometry, abnormal motility criteria were detected in six patients and in no healthy subject [bursts (n = 3), postprandial minute rhythm (n = 1) and myopathic pattern (n = 2)]. These classical dysmotility criteria were also detected by high-resolution manometry. High-resolution analysis detected one or more abnormal findings in seven additional patients that were not observed in any healthy subject, specifically: (a) abnormal propagation of Phase III (n = 3); (b) reduced propagated activity during Fasting Phase II (n = 4); (c) increased propagated activity during Fasting Phase II and postprandial phase (n = 1). CONCLUSIONS AND INFERENCES: This pilot study suggests that high-resolution intestinal manometry may improve the sensitivity of conventional manometry in the detection of intestinal motor dysfunction.

Non-anatomical intestinal transplantation.

INTRODUCTION: Intestinal transplantation is the only long-range treatment option for patients with intestinal failure. We report an exceptional case of isolated intestinal transplantation with the implant in a non-anatomical position. CLINICAL CASE: The patient was a thirty-eight-year-old man (60 kg weight, 180 cm height, 18.3 body mass index) with intestinal failure and home parenteral nutrition due to a short-bowel syndrome for which intestinal transplantation was indicated. The patient had a vascular malformation with the cava vein located left to the aorta, and the intestine was implanted with a 180 masculine rotation around the mesenteric axis, so that the implant s superior mesenteric artery and vein matched the recipient s cava and aorta. Postoperative follow-up was excellent and the patient was discharged after six weeks with a 10-kg gain in body weight. DISCUSSION: This non-anatomical intestinal implantation of the small bowel, previously unreported, offers technical advantages over other options. Adequate intestinal function represents a unique model to prove the viability of intestinal implants in a non-anatomical position.

Effects of meal palatability on postprandial sensations.

BACKGROUND: Food palatability has been shown to influence satiation and meal consumption; our aim was to determine its effects on postprandial satisfaction, ie digestive well-being (primary outcome), and homeostatic sensations (satiety, fullness). METHODS: Randomized, cross-over trial comparing the postprandial responses to conventional (potato-cheese cream followed by vanilla cream) vs unconventional test meals (mixture of both creams) with identical composition and physical characteristics (color, texture, consistency, temperature) but distinctively different palatability. In 22 non-obese healthy men sensations were measured on 10 cm scales before and during the 60-min postprandial period (-5 to +5 score scales for palatability, satiety, well-being, and mood, and 0-10 score scales for fullness and discomfort). Comparisons between meals were performed with a 2-way repeated measures ANCOVA with premeal data as co-variate. KEY RESULTS: As compared to the palatable conventional meal, the unconventional meal was rated unpalatable (-1.8 ± 0.4 score vs 2.8 ± 0.1 score potato cream and 2.9 ± 0.2 vanilla cream; P < .001 for both), induced significantly more fullness sensation [meal effect F (1, 19) = 7.389; P = .014] but had less effect on digestive well-being [meal effect F (1, 19) = 47.016; P < .001] and mood [meal-effect F (1, 19) = 6.609; P = .019]. The difference in satiety was not significantly different. CONCLUSION & INFERENCES: Meal palatability influences the postprandial experience: it bears a direct relation to the hedonic response (well-being/mood) but an inverse relation to homeostatic sensations (fullness). These relations could be applicable to influence eating behavior, because at equal conditions, more palatable meals induce less fullness but more satisfaction, and vice-versa.

Meal composition influences postprandial sensations independently of valence and gustation.

BACKGROUND: Palatability of meals with identical composition has been shown to influence postprandial sensations. Our aim was to determine to what extent meal composition influences postprandial sensations independently of palatability. METHODS: Randomized, crossover, double-blind trial comparing the postprandial responses to a low-fat vs a high-fat test meal, with the same physical and organoleptic characteristics (taste, smell, texture, color, and temperature). The test meal consisted in 150 g hummus containing either 17.7 g fat (low-fat) or 22.3 g fat (high-fat), 19.8 g toasts, 120 mL water and 50 g apple puree. In 12 non-obese healthy men, palatability, homeostatic sensations (hunger/satiety, fullness) and hedonic sensations (digestive well-being, mood) were measured on 10 cm scales before and during the 60-min postprandial period. Comparisons between meals were performed with a two-way repeated measures ANCOVA with premeal data as co-variate. KEY RESULTS: Both test meals were rated equally palatable (palatability scores 3.8 ± 0.3 low-fat, 3.3 ± 0.2 high-fat; P = .156). As compared to the high-fat meal, the low-fat meal induced more satisfaction (meal effect on well-being F(1,21) = 4.92; P = .038) and tended to improve mood (meal effect F(1,21) = 3.02; P = .064), and this was associated with a non-significant decrease in satiety (meal effect F(1,21) = 2.29; P = .145) and fullness (meal effect F(1,21) = 1.57; P = .224). CONCLUSIONS AND INFERENCES: The composition of meals with equal palatability influences postprandial satisfaction, even without significant impact on homeostatic sensations, although an effect on homeostatic sensations has not been excluded. These conditioning factors may have clinical implications in patients with impaired meal tolerance or meal-related symptoms.

Education of the postprandial experience by a sensory-cognitive intervention.

BACKGROUND: Ingestion of a meal induces homeostasis-related sensations (satiety/fullness) that have a hedonic dimension (satisfaction/mood). We have previously shown that a previous physiological intervention, a meal preload, influences the responses to a subsequent meal, specifically: it increases satiety/fullness and decreases satisfaction. We now wished to determine the differential effects of education on the homeostatic and hedonic postprandial experience. METHODS: Randomized, parallel study comparing the effect of real vs sham education on the responses to a probe meal. In two groups of healthy subjects (n = 14 each), homeostatic (satiety, fullness) and hedonic sensations (digestive well-being, mood) in response to a probe meal (250 mL soup, 25 g bread) were measured on 2 separate days before and after a single sensory-cognitive educational intervention (taste recognition test of supra- and sub-threshold tastands for real and sham education, respectively). KEY RESULTS: Before education, in both groups the probe meal induced homeostatic sensations (satiety, fullness) with a positive hedonic dimension (increased digestive well-being and mood). In contrast to sham education, real education enhanced both homeostatic and hedonic responses to the probe meal (P < .05 vs sham education for all). CONCLUSIONS AND INFERENCES: Education modifies the subjects' receptiveness and influences the responses to a meal, not only the hedonic postprandial experience, but also homeostatic sensations. Since homeostatic and hedonic responses are dissociable, education might be tailored to target different conditions.

Comparison between small bowel manometric patterns and full-thickness biopsy histopathology in severe intestinal dysmotility.

BACKGROUND: Intestinal manometry is the current standard for direct evaluation of small bowel dysmotility. Patients with abnormal motility can either be diagnosed of pseudo-obstruction when there are radiological findings mimicking mechanical intestinal obstruction or of enteric dysmotility when these findings are absent. The aim of the present study was to prospectively compare small bowel manometric abnormalities with histopathological findings in intestinal full-thickness biopsies in patients with severe dysmotility disorders. METHODS: We investigated 38 patients with intestinal manometry and a subsequent full-thickness intestinal biopsy. Manometric recordings were read by 4 investigators and a diagnostic consensus was obtained in 35 patients. Histopathological analysis, including specific immunohistochemical techniques of small bowel biopsies was performed and compared to manometric readings. KEY RESULTS: Patients with abnormal intestinal manometry had abnormal histopathological findings in 73% of cases. However, manometric patterns did not match with the specific neuromuscular abnormalities. Among patients with a neuropathic manometry pattern and abnormal histopathology, only 23% had an enteric neuropathy, whereas 62% had neuromuscular inflammation, and 15% an enteric myopathy. On the other hand, patients with a myopathic manometry pattern all had abnormal histopathology, however, none of them with signs of enteric myopathy. CONCLUSION & INFERENCES: Small bowel dysmotility detected by intestinal manometry is often associated with abnormal neuromuscular findings in full-thickness biopsies. However, there is no correlation between the specific manometric patterns and the histopathological findings.

Relation between cognitive and hedonic responses to a meal.

BACKGROUND: Ingestion of a meal induces cognitive and hedonic sensations and our aim was to determine the relation between both dimensions. METHODS: In three groups of healthy non-obese men (n=10 per group) three types of meals with equivalent levels of palatability were tested: a liquid meal, a solid-liquid low-calorie meal, and a solid-liquid high-calorie meal. The cognitive and hedonic responses were measured on 10-cm scales before and during the 30-minute postprandial period. KEY RESULTS: The liquid meal induced a relatively strong cognitive response with satiation (4.7±0.7 score increment), fullness (3.3±0.7 score increment), and inhibition of desire of eating a food of choice; in contrast, its impact on sensation of digestive well-being and satisfaction was not significant (0.7±0.7 score increment). The high-calorie solid-liquid meal, with larger volume load and caloric content, induced much lower satiation (2.4±0.8 score increment; P=.041 vs liquid meal) and fullness sensation (1.3±0.6 score increment; P=.031 vs liquid meal), but a markedly higher level of satisfaction (2.7±0.4 score increment; P=.021 vs liquid meal); the low-calorie mixed meal had less prominent effects with significantly lower satisfaction (1.0±0.4 score increment; P=.039 vs high-calorie meal). CONCLUSIONS AND INFERENCES: The cognitive (satiation, fullness) and hedonic responses (satisfaction) to meals with equivalent levels of palatability, that is, equally likable, are dissociable. The characteristics of meals in terms of satiation and rewarding power could be adapted to specific clinical targets, whether nutritional supplementation or restriction.

Appetite influences the responses to meal ingestion.

BACKGROUND: We have previously shown that the postprandial experience includes cognitive sensations, such as satiety and fullness, with a hedonic dimension involving digestive well-being and mood. Preload conditioning has been shown to modulate appetite and food consumption under certain conditions, but its effects on the responses to meal ingestion are not clear. We hypothesized that appetite modulation by preload conditioning has differential effects on the cognitive and the emotive responses to meal ingestion. METHODS: The effects of preload conditioning (ingestion of a low- vs a high-calorie breakfast) on appetite and on the cognitive and emotive responses to a comfort probe meal ingested 2 hours later (ham and cheese sandwich with orange juice; 300 mL, 425 Kcal) was tested in healthy subjects (n=12) in a cross-over design. Sensations were measured at regular intervals 15 minutes before and 60 minutes after the probe meal. KEY RESULTS: As compared to the low-calorie breakfast, the high-calorie breakfast reduced basal hunger sensation and influenced the responses to the subsequent probe meal: it increased satiety (4.3±0.2 score vs 2.7±0.2 score; P<.001) and fullness (5.4±0.5 score vs 3.1±0.5; P<.001), but reduced the expected postprandial experience of digestive well-being after a palatable meal (1.3±0.7 score vs 3.0±0.3; P=.045). CONCLUSION AND INFERENCES: Appetite modulation by preload conditioning has differential effects on the cognitive and emotive responses to a meal. Preload conditioning of the postprandial experience may be applicable to dietary planning and prevention of postprandial symptoms.

Brain networks associated with cognitive and hedonic responses to a meal.

BACKGROUND: We recently reported interrelated digestive, cognitive, and hedonic responses to a meal. The aim of this study was to identify brain networks related to the hedonic response to eating. METHODS: Thirty-eight healthy subjects (20-38 age range) were evaluated after a 5-hour fast and after ingestion of a test meal (juice and warm ham and cheese sandwich, 300 mL, 425 kcal). Perceptual and affective responses (satiety, abdominal fullness, digestive well-being, and positive mood), and resting scans of the brain using functional MRI (3T Trio, Siemens, Germany) were evaluated immediately before and after the test meal. A high-order group independent component analysis was performed to investigate ingestion-related changes in the intrinsic connectivity of brain networks, with a focus on thalamic and insular networks. KEY RESULTS: Ingestion induced satiation (3.3±0.4 score increase; P<.001) and abdominal fullness (2.4±0.3 score increase; P<.001). These sensations included an affective dimension involving digestive well-being (2.8±0.3 score increase; P<.001) and positive mood (1.8±0.2 score increase; P<.001). In general, thalamo-cortical connectivity increased with meal ingestion while insular-cortical connectivity mainly decreased. Furthermore, larger meal-induced changes (increase/decrease) in specific thalamic connections were associated with smaller changes in satiety/fullness. In contrast, a larger meal-induced decrease in insular-anterior cingulate cortex connectivity was associated with increased satiety, fullness, and digestive well-being. CONCLUSIONS AND INFERENCES: Perceptual and emotional responses to food intake are related to brain connectivity in defined functional networks. Brain imaging may provide objective biomarkers of subjective effects of meal ingestion.

Colonic gas homeostasis: Mechanisms of adaptation following HOST-G904 galactooligosaccharide use in humans.

BACKGROUND: We have shown that a galactooligosaccharide prebiotic administration (HOST-G904) initially increased intestinal gas production and this increase declined back to baseline after 2 week administration. Our aim was to determine the mechanism of microbiota adaptation; i.e., to determine whether the net reduction is due to decreased overall production or increased gas consumption. METHODS: In 10 healthy subjects, intestinal gas production and intraluminal disposal was measured before, at the beginning and after 2 week of HOST-G904 prebiotic administration. Anal gas was collected for 4 hour after a probe meal. Paired studies were performed without and with high-rate infusion of exogenous gas (24 mL/min) into the jejunum to wash-out the endogenous gas produced by bacterial fermentation. The exogenous gas infused was labeled (5% SF6 ) to calculate the proportion of endogenous gas evacuated. KEY RESULTS: The volume of intestinal gas produced i.e., endogenous gas washed-out, increased by 37% at the beginning of HOST-G904 administration (P=.049 vs preadministration) and decreased down to preadministration level after 2 week administration (P=.030 vs early administration). The proportion of gas eliminated from the lumen before reaching the anus tended to increase after 2-week administration (87±3% vs 78±5% preadministration; P=.098). CONCLUSIONS & INFERENCES: Adaptation to regular consumption of HOST-G904 prebiotic involves a shift in microbiota metabolism toward low-gas producing pathways, with a non-significant increase in gas-consuming activity. Hence, regular consumption of HOST-G904 regulates intestinal gas metabolism: less gas is produced and a somewhat larger proportion of it is consumed.

Colonic content: effect of diet, meals, and defecation.

BACKGROUND: The metabolic activity of colonic microbiota is influenced by diet; however, the relationship between metabolism and colonic content is not known. Our aim was to determine the effect of meals, defecation, and diet on colonic content. METHODS: In 10 healthy subjects, two abdominal MRI scans were acquired during fasting, 1 week apart, and after 3 days on low- and high-residue diets, respectively. With each diet, daily fecal output and the number of daytime anal gas evacuations were measured. On the first study day, a second scan was acquired 4 hours after a test meal (n=6) or after 4 hours with nil ingestion (n=4). On the second study day, a scan was also acquired after a spontaneous bowel movement. RESULTS: On the low-residue diet, daily fecal volume averaged 145 ± 15 mL; subjects passed 10.6 ± 1.6 daytime anal gas evacuations and, by the third day, non-gaseous colonic content was 479 ± 36 mL. The high-residue diet increased the three parameters to 16.5 ± 2.9 anal gas evacuations, 223 ± 19 mL fecal output, and 616 ± 55 mL non-gaseous colonic content (P<.05 vs low-residue diet for all). On the low-residue diet, non-gaseous content in the right colon had increased by 41 ± 11 mL, 4 hours after the test meal, whereas no significant change was observed after 4-hour fast (-15 ± 8 mL; P=.006 vs fed). Defecation significantly reduced the non-gaseous content in distal colonic segments. CONCLUSION & INFERENCES: Colonic content exhibits physiologic variations with an approximate 1/3 daily turnover produced by meals and defecation, superimposed over diet-related day-to-day variations.

Metabolic adaptation of colonic microbiota to galactooligosaccharides: a proof-of-concept-study.

BACKGROUND: Prebiotics have been shown to reduce abdominal symptoms in patients with functional gut disorders, despite that they are fermented by colonic bacteria and may induce gas-related symptoms. AIM: To investigate changes in the metabolic activity of gut microbiota induced by a recognised prebiotic. METHODS: Healthy subjects (n = 20) were given a prebiotic (2.8 g/day HOST-G904, HOST Therabiomics, Jersey, Channel Islands) for 3 weeks. During 3-day periods immediately before, at the beginning and at the end of the administration subjects were put on a standard diet (low fibre diet supplemented with one portion of high fibre foods) and the following outcomes were measured: (i) number of daytime gas evacuations for 2 days by means of an event marker; (ii) volume of gas evacuated via a rectal tube during 4 h after a test meal; and (iii) microbiota composition by faecal Illumina MiSeq sequencing. RESULTS: At the beginning of administration, HOST-G904 significantly increased the number of daily anal gas evacuations (18 ± 2 vs. 12 ± 1 pre-administration; P < 0.001) and the volume of gas evacuated after the test meal (236 ± 23 mL vs. 160 ± 17 mL pre-administration; P = 0.006). However, after 3 weeks of administration, these effects diminished (11 ± 2 daily evacuations, 169 ± 23 mL gas evacuation). At day 21, relative abundance of butyrate producers (Lachnospiraceae) correlated inversely with the volume of gas evacuated (r = -0.52; P = 0.02). CONCLUSION: The availability of substrates induces an adaptation of the colonic microbiota activity in bacterial metabolism, which produces less gas and associated issues. Clinical trials.gov NCT02618239.

Effects of scFOS on the composition of fecal microbiota and anxiety in patients with irritable bowel syndrome: a randomized, double blind, placebo controlled study.

BACKGROUND: Short-chain fructooligosaccharides (scFOS) have beneficial effects in subjects with minor digestive complaints, but the potential mechanisms involved have not been elucidated. The aim of the study was to evaluate changes in rectal sensitivity related to the clinical effects of scFOS in a selected group of patients with irritable bowel syndrome (IBS) and rectal hypersensitivity. METHODS: In 79 IBS patients (defined by Rome III criteria) with rectal hypersensitivity (defined as discomfort threshold ≤44 g) a parallel, placebo-controlled, randomized, and double-blind study was performed to assess the effects of dietary supplementation (5 g d-1 ) with scFOS vs placebo for 4 weeks on rectal sensitivity (primary outcome: tolerance to increasing wall tension applied by a tensostat), clinical outcomes (IBS, anxiety/depression and quality of life scores) and composition of fecal microbiota. KEY RESULTS: Rectal discomfort threshold, and IBS and quality of life scores, significantly improved during treatment, but in a similar manner in both scFOS and placebo groups; a post-hoc analysis showed that the effect of scFOS on rectal sensitivity was more pronounced in constipation-predominant-IBS patients (P=.051 vs placebo). Contrary with placebo, scFOS significantly reduced anxiety scores and increased fecal Bifidobacteria (P<.05 for both) without modifying other bacterial groups. CONCLUSIONS & INTERFENCES: The effect of scFOS on anxiety may be related to modulation of the gut microbiota; demonstration of effects of scFOS on rectal sensitivity may require higher doses and may depend on the IBS subgroup.

Intestinal sensitivity testing by transmucosal electrical nerve stimulation: stimulus parameters to induce conscious perception.

Intestinal sensitivity can be tested using transmucosal electrical nerve stimulation. The aim of this study was to establish the stimulus characteristics that determine perception. In six healthy subjects constant current electrical stimuli were applied via an intrajejunal bipolar electrode while measuring perception. Intensity-response tests with stimuli trains of various frequencies (5 and 100 Hz) and pulse durations (50 and 1000 mus) were performed. All stimuli within the broad range tested induced similar-type abdominal sensations, but the intensity of the stimuli to produce perception differed depending on both pulse duration and frequency. A 20-fold increase in pulse duration decreased the intensity of perceived stimuli by a factor of 0.34 +/- 0.04 (P < 0.05); a similar increase in pulse frequency decreased the intensity by a 0.63 +/- 0.07 factor (P < 0.05). When the frequency and duration concomitantly increased, the stimulus intensity decreased by the product of both factors (0.22 +/- 0.04). Transmucosal electrical nerve stimulation of the intestine induces perception within a broad range of stimuli. However, the intensity of the stimuli required to activate sensory pathways is primarily weighted by the duration rather than by the frequency of the pulses.

Colonic content in health and its relation to functional gut symptoms.

BACKGROUND: Gut content may be determinant in the generation of digestive symptoms, particularly in patients with impaired gut function and hypersensitivity. Since the relation of intraluminal gas to symptoms is only partial, we hypothesized that non-gaseous component may play a decisive role. METHODS: Abdominal computed tomography scans were evaluated in healthy subjects during fasting and after a meal (n = 15) and in patients with functional gut disorders during basal conditions (when they were feeling well) and during an episode of abdominal distension (n = 15). Colonic content and distribution were measured by an original analysis program. KEY RESULTS: In healthy subjects both gaseous (87 ± 24 mL) and non-gaseous colonic content (714 ± 34 mL) were uniformly distributed along the colon. In the early postprandial period gas volume increased (by 46 ± 23 mL), but non-gaseous content did not, although a partial caudad displacement from the descending to the pelvic colon was observed. No differences in colonic content were detected between patients and healthy subjects. Symptoms were associated with discrete increments in gas volume. However, no consistent differences in non-gaseous content were detected in patients between asymptomatic periods and during episodes of abdominal distension. CONCLUSIONS & INFERENCES: In patients with functional gut disorders, abdominal distension is not related to changes in non-gaseous colonic content. Hence, other factors, such as intestinal hypersensitivity and poor tolerance of small increases in luminal gas may be involved.

Cognitive and hedonic responses to meal ingestion correlate with changes in circulating metabolites.

BACKGROUND: We have previously shown that meal ingestion induces cognitive perception (sensations) with a hedonic dimension (well-being) that depends on the characteristics of the meal and the appropriateness of the digestive response. The aim of the present study is to identify metabolomic biomarkers of the cognitive response to meal ingestion. METHODS: In 18 healthy subjects, the response to a test meal (Edanec, 1 kcal/mL) ingested until maximum satiation (50 mL/min) was assessed. Perception measurements and blood samples were taken before, at the end of the meal, and 20 min after ingestion. The cognitive response and the hedonic dimension were measured on 10 cm scales. Metabolomic analysis was performed using nuclear magnetic resonance (NMR) spectroscopy and values of triglycerides, insulin, peptide YY (PYY), and glucagon-like peptide-1 (GLP-1) were determined using conventional laboratory techniques. KEY RESULTS: Ingestion up to maximum satiation induced sensation of fullness and decreased digestive well-being. The total amount ingested by each subject correlated with the basal sensation of hunger, but not with other sensations or blood metabolite levels. Immediately after ingestion, satiation correlated with an increase in glucose (R = 0.49; p = 0.038) and valine levels (R = 0.48; p = 0.043). Twenty-minutes after finalizing ingestion, triglyceride levels had significantly increased which correlated with the recovery in well-being (R = 0.48; p = 0.046) and the decrease in desire to eat a food of choice (R = -0.56; p = 0.016). The increase in lipids inversely correlated with abdominal discomfort (R = -0.51; p = 0.032). CONCLUSIONS & INFERENCES: Cognitive and hedonic responses to meal ingestion correlate with changes in circulating metabolites, which may serve as objective biomarkers of perception.

Toxic megacolon in typhoid fever.

A 40-year-old man with bacteriologically documented typhoid fever who was receiving correct antibiotic treatment developed toxic megacolon. Because of progressive clinical deterioration, the patient underwent surgical treatment, with quick postoperative improvement while receiving antibiotics and total parenteral nutrition.

Accumulative effect of food residues on intestinal gas production.

BACKGROUND: As mean transit time in the colon is longer than the interval between meals, several consecutive meal loads accumulate, and contribute to colonic biomass. Our aim was to determine the summation effect of fermentable food residues on intestinal gas production. METHODS: In eight healthy subjects, the volume of endogenous intestinal gas produced in the intestine over a 4-h period was measured by means of a wash-out technique, using an exogenous gas infusion into the jejunum (24 mL/min) and collection of the effluent via a rectal Foley catheter. The exogenous gas infused was labeled (5% SF6 ) to calculate the proportion of endogenous intestinal gas evacuated. In each subject, four experiments were performed ≥1 week apart combining a 1-day high- or low-flatulogenic diet with a test meal or fast. KEY RESULTS: Basal conditions: on the low-flatulogenic diet, intestinal gas production during fasting over the 4-h study period was 609 ± 63 mL. Effect of diet: during fasting, intestinal gas production on the high-flatulogenic diet was 370 ± 146 mL greater than on the low-flatulogenic diet (p = 0.040). Effect of test meal: on the low-flatulogenic diet, intestinal gas production after the test meal was 681 ± 114 mL greater than during fasting (p = 0.001); a similar effect was observed on the high-flatulogenic diet (599 ± 174 mL more intestinal gas production after the test meal than during fasting; p = 0.021). CONCLUSIONS & INFERENCES: Our data demonstrate temporal summation effects of food residues on intestinal gas production. Hence, intestinal gas production depends on pre-existing and on recent colonic loads of fermentable foodstuffs.

Intestinal gas homeostasis: disposal pathways.

BACKGROUND: Patients with functional gut disorders frequently complain of gas-related symptoms, but the role of intestinal gas in this context is not clear, because intestinal gas homeostasis is incompletely understood. Our aim was to compare the proportion of the gas produced by colonic fermentation that is evacuated per anus and that eliminated via alternative pathways. METHODS: In 20 healthy subjects, gas evacuated per anus was collected for 4 h after a standard flatulogenic test meal. Paired studies were performed without and with high-rate infusion of exogenous gas (24 mL/min) into the jejunum to wash-out of the gut the endogenous gas produced by bacterial fermentation. The exogenous gas infused was labeled (5% SF6) to calculate the proportion of endogenous gas evacuated. KEY RESULTS: In the experiments with gaseous wash-out, 1817 ± 139 mL of endogenous gas was produced over the 4-h study period. However, in the experiments without wash-out (basal conditions), 376 ± 43 mL were evacuated, indicating that only 23 ± 3% of the gas produced was finally eliminated per anus, while the rest (77 ± 3%) had been previously eliminated via alternative pathways. CONCLUSIONS & INFERENCES: Intestinal gas homeostasis is a highly dynamic process by which a large proportion of the gas produced by bacterial fermentation of meal residues is rapidly absorbed into the blood and/or metabolized by gas-consuming microorganisms, and only a relatively modest proportion is eliminated per anus. These data contribute to clarify the complex dynamics of intestinal gas and may help interpret the pathophysiology of gas-related symptoms.