Minimum standards of anorectal manometry.
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Anal Canal↗
Biomedical subjects
F Azpiroz
Publications and source records attributed to F Azpiroz.
Hypersensitivity in functional gastrointestinal disorders.
Patients with functional gastrointestinal disorders may have visceral sensory dysfunction so that physiological stimuli induce their symptoms. The clinical significance of altered perception-that is, its relation to clinical symptoms-remains unclear. Data indicate that sensory dysfunction is associated with altered reflex activity. Hence evidence of combined sensory-reflex dysfunction as a common pathophysiological mechanism in various functional gastrointestinal disorders would suggest that they are different forms of the same process. Altered reflex activity and altered conscious perception of gastrointestinal stimuli may combine to differing degrees, and their interaction may produce clinical symptoms.
Colonic Diseases, Functional↗
The rectum: a window to irritable bowel syndrome?
This report summarizes current concepts and information gathered to date about the rectum in the irritable bowel syndrome (IBS) that were presented at the 10th meeting of IBiS Club held in Leuven, Belgium. A working group of experts in the field of IBS discussed whether the rectum or the whole colon is the better site to test in IBS patients and provided suggestions for a number of areas where further advances are required.
Biopsy↗
Impaired transit and tolerance of intestinal gas in the irritable bowel syndrome.
BACKGROUND: Patients with irritable bowel syndrome (IBS) frequently complain of excessive gas but their fasting volume of intestinal gas is apparently normal. We hypothesised that the pathophysiological mechanism involved may be impairment of intestinal gas transit. AIM: To investigate intestinal gas transit and tolerance in IBS patients compared with healthy subjects. METHODS: A gas mixture (N(2), O(2), and CO(2) in venous proportions) was infused into the jejunum of 20 patients with IBS and 20 healthy controls at 12 ml/min for four hours. Gas evacuation, initially flatus from the anus (two hours) and then intrarectally (two hours), was continuously recorded. Symptom perception (0-6 scale) and abdominal distension were measured at 10 minute intervals. RESULTS: After two hours of external gas (flatus) collection, 18 of 20 IBS patients had developed gas retention (>400 ml), increased gastrointestinal symptoms (score >3), or abdominal distension (>3 mm girth increment) compared with only four of 20 control subjects. During intrarectal gas collection, 13 of 17 patients still exhibited abnormal responses. CONCLUSION: A large proportion of patients with IBS can be shown to have impaired transit and tolerance of intestinal gas loads. This anomaly may represent a possible mechanism of IBS symptoms, specifically pain and bloating.
Abdomen↗
Modification of small bowel mechanosensitivity by intestinal fat.
BACKGROUND: Lipids may exacerbate symptoms induced by gut stimuli. AIM: To determine the mechanism whereby fat exerts this effect. SUBJECTS: Twenty four healthy subjects were studied during fasting. METHODS: We measured perception (0-6 scale) in response to jejunal balloon distension and transmucosal electrical nerve stimulation; phasic stimuli (one minute) were randomly applied at five minute intervals during intestinal infusion (2 ml/min) of saline and then Intralipid 2 kcal/min (high fat; n=8 subjects), Intralipid 0.5 kcal/min (low fat; n=8), or saline (n=8). RESULTS: Intestinal lipids increased the perception of jejunal distension regardless of concentration (by 53% with high fat, 49% with low fat, and 17% with saline; p<0.05 for both fat loads). This effect could not be attributed to changes in intestinal compliance as intraballoon pressures remained unchanged during lipid infusion (2% change; NS). Sensitisation induced by lipids seemed to be specifically related to intestinal mechanoreceptors because electrical stimulation, which non-specifically activates gut afferents, was perceived equally during saline and lipid administration (10%, 11%, and 15% change during high fat, low fat, and saline, respectively; NS). CONCLUSION: Physiological amounts of lipids heighten intestinal sensitivity by modulating intestinal mechanoreceptor response.
Adult↗
Mechanisms of intestinal gas retention in humans: impaired propulsion versus obstructed evacuation.
To explore the clinical role of intestinal gas dynamics, we investigated two potential mechanisms of gas retention, defective propulsion and obstructed evacuation. In healthy subjects, a gas mixture was continuously infused into the jejunum (4 ml/min) 1) during a 2-h control period of spontaneous gas evacuation and 2) during a 2-h test period either with impaired gut propulsion caused by intravenous glucagon (n = 6) or with obstructed (self-restrained) anal evacuation (n = 10) while anal gas evacuation, symptom perception (0-6 scale), and abdominal girth were measured. Impaired gut propulsion and obstructed evacuation produced similar gas retention (558 +/- 68 ml and 407 +/- 85 ml, respectively, vs. 96 +/- 58 ml control; P < 0.05 for both) and abdominal distension (8 +/- 3 mm and 6 +/- 3 mm, respectively, vs. 1 +/- 1 mm control; P < 0.05 for both). However, obstructed evacuation increased symptom perception (2.3 +/- 0.6 score change; P < 0.05), whereas gas retention in the glucagon-induced hypotonic gut was virtually unperceived (-0.4 +/- 0.7 score change; not significant). In conclusion, the perception of intestinal gas accumulation depends on the mechanism of retention.
Adult↗
Potential pitfalls in the differential diagnosis of irritable bowel syndrome.
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Colonic Diseases, Functional↗
Nongastrointestinal disorders in the irritable bowel syndrome.
A large proportion of irritable bowel syndrome (IBS) patients also complain of other functional disorders, such as headache, noncardiac chest pain, low back pain, and dysuria. Some of these features, particularly headache, may have a negative influence on the outcome of IBS. In a large proportion of female IBS patients, sexual intercourse triggers the symptoms, and frequently IBS symptoms exacerbate during menses. These gynecological-type symptoms often mislead the patients to the gynecological clinic, which may imply unnecessary investigations and inappropriate treatments. The diagnostic criteria of the fibromyalgia syndrome include IBS, and hence, the apparent relationship of both syndromes is difficult to analyze. On the other hand, no convincing evidence has been produced to date to sustain an association between IBS and the chronic fatigue syndrome.
Adult↗
Gastric wall tension determines perception of gastric distention.
BACKGROUND & AIMS: The primary mechanism that originates symptoms in response to gastric distention remains undefined. The aim of this study was to determine which factor, whether intragastric volume, pressure, or wall tension, determines perception of gastric distention. METHODS: Healthy subjects underwent increasing gastric distentions (2-minute duration at 5-minute intervals) either at fixed pressure levels using a conventional barostat (n = 10) or at fixed tension levels using a newly developed computerized tensostat (n = 12); perception was scored by a 0-6 scale. Distentions were performed during basal conditions (intravenous saline) and during gastric relaxation by glucagon administration (4.8 microgram/kg intravenous bolus plus 9.6 microgram. kg-1. h-1 infusion). RESULTS: Isobaric distentions with the conventional barostat produced more intense perception during glucagon (95% +/- 40% higher; P < 0.05). However, the factor that determined higher perception could not be ascertained, because at the same pressure levels both intragastric volume and wall tension were greater during glucagon administration (174% +/- 56% and 34% +/- 8% greater, respectively; P < 0.05 vs. saline for both). The tensostat evidenced that perception was selectively related to tension, not to elongation; during glucagon administration, intragastric volumes were significantly larger (80% +/- 28% larger increase; P < 0.05), but perception of isotonic distentions remained the same (27% +/- 22%; nonsignificant change). CONCLUSIONS: Gastric wall tension, but not intragastric volume, determines perception of gastric distention, at least below nociception.
Adult↗
Principles of applied neurogastroenterology: physiology/motility-sensation.
Many of the symptoms characteristic of the functional gastrointestinal disorders (FGID) are consistent with dysfunction of the motor and/or sensory apparatus of the digestive tract. Those aspects of sensorimotor dysfunction most relevant to the FGID include alterations in: gut contractile activity; myoelectrical activity; tone and compliance; and transit, as well as an enhanced sensitivity to distension, in each region of the gastrointestinal tract. Assessment of these phenomena involves a number of techniques, some well established and others requiring further validation. Using such techniques, researchers have reported a wide range of alterations in sensory and in motor function in the FGID. Importantly, however, relationships between such dysfunction and symptoms have been relatively weak, and so the clinical relevance of the former remains unclear. Moreover, the proportions of patients in the various symptom subgroups who display dysfunction, and the extent and severity of their symptoms, require better characterization. On a positive note, progress is occurring on several fronts, especially in relation to functional dyspepsia and irritable bowel syndrome, and based on the data gathered to date, a number of areas where further advances are required can be highlighted.
Colonic Diseases, Functional↗
Dimensions of gut dysfunction in irritable bowel syndrome: altered sensory function.
Growing evidence suggests that symptoms in patients with irritable bowel syndrome (IBS) may be due to a visceral sensory dysfunction. Specifically, it has been shown that patients with IBS have hypersensitive responses to distension of the rectum, whereas their tolerance to somatic stimuli is normal or even increased. Furthermore, patients with IBS have hypersensitivity of the small bowel, which selectively affects mechanosensitive afferents, with normal perception of electrical stimulation of the gut. Sensory dysfunctions may also be associated with altered reflex activity, which may contribute to the clinical symptoms. Normally, a series of mechanisms at different strata of the nervous system modulate visceral afferent input and determine conscious perception. Conceivably, a dysfunction of these regulatory mechanisms may alter sensitivity in clinical conditions. To date, neither the origin nor the clinical significance of visceral hyperalgesia has been elucidated. However, it seems likely that the sensory and reflex dysfunctions of the gut in IBS may combine to different degrees, and their interaction may explain the clinical pleomorphism of the syndrome.
Colonic Diseases, Functional↗
Modulation of gut perception in humans by spatial summation phenomena.
1. We have recently shown that perception of intestinal stimuli increases by spatial summation phenomena. Our aim was to determine in humans whether intestinal perception depends on (a) the length of gut stimulated, and (b) the distance between stimuli. 2. In a first series of studies, we compared perception of isobaric intestinal distensions applied over a 3 cm segment and a 36 cm segment by means of two separate barostats (n = 8). In a second series of studies we compared perception of intestinal distensions applied simultaneously by two balloons sited 3, 12 or 48 cm apart (n = 6). 3. Distension of the 36 cm segment induced significantly greater perception than distension of the 3 cm intestinal segment (discomfort perceived at 20 +/- 2 mmHg and 31 +/- 2 mmHg, respectively; P < 0.05). Perception of intestinal balloon distension increased when a second stimulus was simultaneously applied, independently of the distance between the two balloons (the discomfort thresholds were 30 +/- 11, 20 +/- 6 and 28 +/- 7% lower with simultaneous distensions 3, 12 and 48 cm apart, respectively). 4. We conclude that perception of intestinal distension is determined by the extension of the field of stimulation, and the summation effect is similar whether adjacent or distant fields are stimulated.
Adult↗
Intestinal gas dynamics and tolerance in humans.
BACKGROUND & AIMS: Abdominal symptoms are often attributed to intestinal gas. In humans, gas production and composition have been previously investigated, but intestinal gas dynamics and tolerance remain virtually unknown. The aim of this study was to establish the relationship between intestinal gas loads, evacuation, perception of symptoms, and objective abdominal distention in healthy humans. METHODS: A dose-response study was performed in 46 healthy subjects; intestinal gas was infused for 3 hours (0, 1, 4, 12, and 30 mL/min), and anal gas evacuation, symptom perception, and abdominal distention were measured. A mixture of gases was infused in venous proportions to minimize diffusion. Anal gas recovery and calculations of gas retention were validated using sulfur hexafluoride as a nonabsorbable gaseous marker. RESULTS: At all of the infusion rates, gas evacuation rapidly equilibrated and paralleled gas infusion without significant differences in perception. Only 6 subjects retained >400 mL gas, and 5 of them developed abdominal distention and symptoms. By contrast, all but 4 of the 41 subjects without retention tolerated the gas loads without discomfort. CONCLUSIONS: Intestinal gas tolerance is normally high, because expeditious gas transit and evacuation prevent gas pooling and symptoms. When this protective mechanism is insufficient, gas retention occurs, and it causes abdominal symptoms and distention.
Abdomen↗
Endogenous cholecystokinin enhances postprandial gastroesophageal reflux in humans through extrasphincteric receptors.
BACKGROUND & AIMS: Exogenous cholecystokinin (CCK) decreases lower esophageal sphincter (LES) pressure and increases transient LES relaxations (TLESRs) in humans. The aims of this study were to determine whether endogenous CCK increases gastroesophageal reflux in humans and whether this is a direct effect on the LES. METHODS: Esophageal pH, LES pressure, and gallbladder volume were measured in 8 healthy volunteers after ingestion of a 181-kcal meal alone or adding 12 g cholestyramine to increase endogenous CCK release. In 7 additional volunteers, the effect of cholestyramine was studied during intravenous perfusion of saline or the CCK-A receptor antagonist loxiglumide. In circular LES strips from 9 transplant donors, we measured the effect of CCK-8 (10(-11) to 3 x 10(-8) mol/L) on basal tension and on electrical field-induced relaxation. RESULTS: Cholestyramine increased gallbladder emptying, reflux episodes, TLESRs, and time of esophageal pH of <4. Loxiglumide inhibited postprandial gallbladder emptying, reflux episodes, TLESRs, and time of pH of <4 and prevented the decrease in LES pressure induced by cholestyramine. In vitro, CCK-8 contracted LES strips through a tetrodotoxin-insensitive pathway but did not modify electrical field-induced LES relaxations. CONCLUSIONS: Endogenous CCK enhances postprandial gastroesophageal reflux in humans by increasing the rate of TLESRs and reduces postprandial LES pressure. These actions seem mediated by extrasphincteric CCK-A receptors that override a direct contractile effect of CCK on the LES muscle.
Adult↗
Gastric neurology: evolving concepts and techniques.
Gastric function is finely modulated by a series of neurological mechanisms, so that gastric digestion is normally not perceived. Alteration of these control mechanisms may lead to different situations, which are frequently associated with symptoms. An impaired tonic contraction of the proximal stomach, that is, an impaired gastric tone, results in gastroparesis. Patients with functional dyspepsia, and also patients with achalasia, have impaired meal accommodation of the stomach. Interestingly, patients with functional dyspepsia may also have a sensory dysfunction, and both dysfunctions could play a synergistic role. However, the sensory dysfunction in dyspepsia, particularly the types of afferent fibres affected, and the mechanisms of impaired accommodation, still remain to be characterized. Evaluation of gastric function has been approached using the barostat. However, the barostat has limitations and potential technical pitfalls that require proper attention. Meal ingestion induces a variety of reflexes and the net result is a relaxation of the stomach. However, gastric reflexes can be best evaluated with the stomach empty, when the stimuli are applied at a different site. Nevertheless, altered reflex responses may be difficult to interpret. For instance, absent or decreased relaxatory responses may equally correspond to a gastroparetic stomach without tone or to a dyspeptic stomach unable to relax. In this context, it may be important to measure basal tone. Distension of the stomach by means of the barostat has been also used to test gastric sensitivity. However, recent studies have shown that perception of gastric distension relays on stimulation of tension receptors; since wall tension depends on both pressure and volume, distension with the barostat may be difficult to standardize. Hopefully, a battery of tests may become available in the near future for a complete neuromuscular evaluation of the gut.
Gastrointestinal Motility↗
Perception and gut reflexes induced by stimulation of gastrointestinal thermoreceptors in humans.
1. Experimental studies in animals suggest the existence of thermoreceptors in the gastrointestinal tract. Our aim was to investigate the distribution and specificity of upper gut thermoreceptors in humans. 2. In healthy subjects, thermal stimulation of the stomach (n = 8) and the small intestine (n = 6) was produced by means of a thermostat, which recirculates water at adjusted temperatures through an ultrathin intraluminal bag. Progressively warm (42, 47 and 52 degrees C) and cold (32, 22 and 12 degrees C) stimuli of 3 min duration were alternately applied at 13 min intervals. Perception was scored on a scale of 0-6 and gastric tone responses were measured with a barostat. 3. Thermal stimuli induced specific responses: cold stimuli induced abdominal cold sensation and a reflex contraction of the stomach, whereas warm stimuli induced warm sensation and a reflex gastric relaxation. 4. Thermal stimuli induced similar stimulus-related perception in the stomach and small intestine (temperatures between 12 and 49.5 +/- 0.5 degrees C were tolerated). 5. The reflex responses were site specific. Warm and cold stimulation of the stomach induced gastric reflexes (76 +/- 26 ml isobaric expansion at 47 degrees C, and 68 +/- 10 ml contraction at 12 degrees C; P < 0.05 for both). However, only warm, not cold, stimulation of the intestine induced enterogastric reflexes. 6. These results indicate that in humans, warm and cold receptors are distributed along the gastrointestinal tract and project afferent input both into perception and reflex circuits with specific topographic organization.
Adult↗
Small bowel manometry.
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Gastrointestinal Motility↗
Gastric tone and the barostat: comprehend and compromise.
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Gastrointestinal Motility↗