Indications for 24-hour gastric pH monitoring with single and multiple probes in clinical research and practice

Gastric Mixing During Food Digestion: Mechanisms and Applications

Gastric mixing is a complex process that is governed by meal properties, such as food buffering capacity, physical properties, and the rate of breakdown as well as physiological factors, such as the rate of gastric secretions, gastric emptying, and gastric motility. Gastric mixing processes have been studied through the use of experimental and computational methods. Gastric mixing impacts the intragastric pH distribution and residence time in the stomach for ingested materials. Development of a fundamental understanding of the advective and diffusion processes and their roles in gastric mixing will be important in furthering our understanding of food breakdown, microbial survival, and drug dissolution during gastric digestion.

Gastric emptying rate and chyme characteristics for cooked brown and white rice meals in vivo

BACKGROUND

Rice structure is important to rice grain and starch breakdown during digestion. The objective of this study was to determine the gastric emptying and rice composition during gastric digestion of cooked brown and white medium-grain (Calrose variety) rice using the growing pig as a model for the adult human.

RESULTS

Brown and white rice did not show significantly different gastric emptying rates of dry matter or starch, but brown rice had slower protein emptying (P < 0.05). Moisture content was greater and pH was lower in the distal stomach compared to the proximal stomach (P < 0.0001), and varied with time (P < 0.0001). The mechanism of physical breakdown for brown and white rice varied. Brown rice exhibited an accumulation of bran layer fragments in the distal stomach, quantified by lower starch and higher protein content.

CONCLUSION

The quantity of gastric secretions observed after a brown or white rice meal may be related to the meal buffering capacity, and are accumulated in the distal stomach. The delayed rate of protein emptying in brown rice compared to white rice was most likely due to the accumulation of bran layers in the stomach.

Prevalence and clinical picture of gastroesophageal prolapse in gastroesophageal reflux disease

The prevalence of gastroesophageal (GE) mucosal prolapse in patients with gastroesophageal reflux disease (GERD) was investigated as well as the clinical profile and treatment outcome of these patients. Of the patients who were referred to our service between 1980 and 2008, those patients who received a complete diagnostic work-up, and were successively treated and followed up at our center with interviews, radiology studies, endoscopy, and, when indicated, esophageal manometry and pH recording were selected. The prevalence of GE prolapse in GERD patients was 13.5% (70/516) (40 males and 30 females with a median age of 48, interquartile range 38-57). All patients had dysphagia and reflux symptoms, and 98% (69/70) had epigastric or retrosternal pain. Belching decreased the intensity or resolved the pain in 70% (49/70) of the cases, gross esophagitis was documented in 90% (63/70) of the cases, and hiatus hernias were observed in 62% (43/70) of the cases. GE prolapse in GERD patients was accompanied by more severe pain (P < 0.05) usually associated with belching, more severe esophagitis, and dysphagia (P < 0.05). A fundoplication was offered to 100% of the patients and was accepted by 56% (39/70) (median follow up 60 months, interquartile range 54-72), which included two Collis-Nissen techniques for true short esophagus. Patients who did not accept surgery were medically treated (median follow up 60 months, interquartile range 21-72). Persistent pain was reported in 98% (30/31) of medical cases, belching was reported in 45% (14/31), and GERD symptoms and esophagitis were reported in 81% (25/31). After surgery, pain was resolved in 98% (38/39) of the operative cases, and 79% (31/39) of them were free of GERD symptoms and esophagitis. GE prolapse has a relatively low prevalence in GERD patients. It is characterized by epigastric or retrosternal pain, and the need to belch to attenuate or resolve the pain. The pain is allegedly a result of the mechanical consequences of prolapse of the gastric mucosa into the esophagus.

Prevalence of pathological duodenogastric reflux and the relationship between duodenogastric and duodenogastrooesophageal reflux in chronic gastrooesophageal reflux disease

The role of duodenogastric reflux in gastrooesophageal reflux disease is still controversial.

AIMS

(i) To determine the prevalence of pathological duodenogastric reflux (DGR) in gastrooesophageal reflux disease patients and (ii) to define the relationship between DGR and duodenogastrooesophageal reflux.

METHODS

We evaluated 92 patients referred for investigation of recurrent reflux symptoms after proton pump inhibitors (PPI) therapy. All the patients filled out symptom questionnaires and underwent endoscopy, oesophageal manometry and combined oesophagogastric pH and bilirubin monitoring.

RESULTS

Endoscopy divided the 92 patients into four groups (group I: 25 nonoesophagitis patients, group II: 26 patients with grade A-B oesophagitis, group III: 21 patients with grade C-D oesophagitis and group IV: 20 patients with Barrett's oesophagus. Twenty-four of the 92 patients (26%) showed pathological DGR. Abnormal oesophageal bilirubin exposure was observed in 62 of the 92 patients (67.4%). Of the 62 patients with abnormal oesophageal bilimetry, 15 (24.2%) patients simultaneously showed pathological DGR. The gastric bilirubin exposure in patients with abnormal oesophageal, Bilitec tests did not differ from that in patients with normal oesophageal bilimetry (P>0.05). A weak correlation between oesophageal and gastric bilirubin exposure, both expressed as a percentage of time, was found (r=0.28; P<0.01).

CONCLUSION

Pathological DGR is present in a little more than a quarter of patients with recurrent reflux and dyspeptic symptoms after PPI therapy. Excessive DGR is not a prerequisite for pathological oesophageal exposure to duodenal contents. Gastric bilirubin monitoring may be useful to choose the best surgical treatment for patients with reflux and dyspeptic symptoms refractory to PPI.

Gastric longitudinal shortening may occur during gastric phase III activities in man

BACKGROUND AND AIM

The aim of this study was to determine whether the gastric longitudinal shortening occurs during the gastric phase III in man.

METHODS

Intragastric pH and gastroduodenal motility were simultaneously measured by means of a 24-h ambulatory recording system in 14 healthy volunteers. In nine subjects (group A), the catheter assembly was endoscopically clipped to the gastric mucosa with the middle transducer and the distal pH sensor in the antrum. In the remaining five subjects (group B), measurements were performed without securing the assembly.

RESULTS

In 23 of the 25 gastrointestinal interdigestive migrating complexes in group A, the distal and middle transducers showed characteristic duodenal contractions (11-12 c.p.m.). Neutralization was noted at the distal pH sensor. Similar phenomena were observed during all 15 gastrointestinal interdigestive migrating complexes in group B. The catheter assemblies escaped into the duodenum despite the fact that they were secured to the stomach. This may be explained by gastric longitudinal shortening during gastric phase III activities.

CONCLUSIONS

Studies of intragastric physiology with test catheters must take the effect of gastric longitudinal shortening during phase III into consideration.

[Reflux esophagitis]

Gastroesophageal reflux disease (GERD) is one of the most prevalent diseases in the industrialized countries. Approximately 15-25% of adults suffer from reflux symptoms, characterized mainly by heartburn and/or regurgitation. Currently, antisecretory medication with proton pump inhibitors (PPI) or antireflux surgery are the established options for GERD-treatment. PPI are the therapeutic gold standard in acute, long-term or on-demand therapy of GERD. Since PPI do not restore the antireflux barrier but merely suppress acid secretion a life-long tablet adherence is required in most cases. In view of limitations of PPI and the potential risks of laparoscopic surgery, several endoscopic antireflux techniques were developed and may evolve as a valuable third option. However, so far objective long-term data are lacking for choosing the appropriate patient who will benefit most from endoluminal antireflux therapy.

Clinical relevance of esophageal and gastric pH measurements in patients with gastro-esophageal reflux disease (GERD)

BACKGROUND

Gastro-esophageal reflux disease (GERD) is a highly prevalent disease caused by the exposure of the esophagus to refluxed gastric contents. Proton pump inhibitors (PPIs) are the mainstay of current treatment. At present, the assessment of the efficacy of different PPIs in the treatment of GERD employs two measures: esophageal and gastric pH monitoring. Esophageal pH monitoring is the most accurate method of detecting reflux episodes and, therefore, its role as a diagnostic modality is well accepted. Gastric pH monitoring, on the other hand, is an accurate measure of gastric acid pH, but its relevance to patients with GERD is questionable, since recordings correlate poorly with esophageal acid exposure.

OBJECTIVE

This paper reviews (based on a Medline literature search, 1980-2004) the clinical relevance of esophageal and gastric pH measurements in both the management of GERD and in the evaluation of the efficacy of PPI therapy.

FINDINGS AND CONCLUSIONS

Evidence presented suggests that the assessment of esophageal pH yields data of greater relevance to patients with GERD than does data from gastric pH. This largely arises from the fact that esophageal pH monitoring assesses the pH of the refluxate and the frequency of reflux episodes at the mucosal site affected by the disease. The use of esophageal pH monitoring is recommended in patients who fail to present with endoscopic evidence of esophagitis, those with extra-esophageal symptoms, those who have failed traditional anti-reflux therapies, and those who are potential candidates for anti-reflux surgery. In recent years, the technique has benefited from the development of a wireless pH probe, and there is also an increasing body of evidence supporting its use in combination with other emerging technologies, such as Bilitec monitoring and multichannel intraluminal impedance. Such an approach is anticipated to aid both the diagnosis of GERD and the characterization of gastro-esophageal reflux (GER) in these patients.

Ambulatory gastric pH monitoring: proper probe placement and normal values

BACKGROUND

Gastric acid production may persist while patients are treated with proton pump inhibitors. Twenty-four-hour intragastric pH monitoring is being used to identify gastric acid in the stomach while on medical therapy.

AIM

To identify the optimal region of the stomach to demonstrate the presence of gastric acid.

METHOD

Probe locations confirmed with fluoroscopy after placement and prior to removal. In experiment 1, five volunteers underwent simultaneous, 24-h gastro-oesophageal pH monitoring with the pH sensors located in the gastric antrum, body, fundus and distal oesophagus. In experiment 2, five volunteers underwent simultaneous 24-h pH monitoring with sensors located side by side in the gastric fundus assessing the reproducibility of gastric pH in this region. In experiment 3, 35 volunteers underwent 24-h pH monitoring with pH sensors located in the distal oesophagus and gastric fundus. The mean percentage time for which pH < 4 was calculated for total, upright, and supine time periods.

RESULTS

pH profiles for the gastric fundus and body are similar-the mean percentage total time for which pH < 4 was 92.2% and 90.1%, respectively (P=N.S.). These values are significantly different from the antrum; pH < 4=54.6% (P < 0.01). pH values from the gastric fundus are highly reproducible (linear regression P= 0.004, r(2)=0.96). The normal values (mean +/- 95th percentile) for percentage time gastric pH < 4 in the fundus were: total 95.6 +/- 1.5%, upright 94.8 +/- 1.8%, and supine 96.5 +/- 2.3%.

CONCLUSION

The fundus is the optimal location to evaluate the presence of gastric acid; pH values are highly reproducible in this area. Normal values for percentage time gastric pH < 4 for a healthy population are now defined.

The extent of duodenogastric reflux in gastro-oesophageal reflux disease

BACKGROUND

It is known that duodenogastro-oesophageal reflux (DGOR) increases with worsening gastro-oesophageal reflux disease (GORD). It is unclear whether this is accompanied by increasing duodenogastric reflux (DGR).

OBJECTIVE

To investigate the extent of DGR in a control group and 66 patients with GORD, using the technique of ambulatory gastric bilirubin monitoring.

METHODS

Sixty-six patients with reflux symptoms (30 grade 0 or 1 oesophagitis (group 1), 16 grade 2 or 3 oesophagitis (group 2), 20 Barrett's oesophagus (group 3)) and 17 healthy controls were studied. All underwent oesophageal manometry followed by 24-h ambulatory oesophageal and gastric pH monitoring and gastric bilirubin monitoring.

RESULTS

Median per cent total oesophageal acid exposure (pH < 4) was significantly less in the control group (0.6%) than in group 1 (2.8%, P< 0.05) and groups 2 and 3 (7.5% and 7.8% respectively, P< 0.001). There was no significant difference between any group in median per cent total time gastric pH was greater than 4. There was no significant difference in median per cent total gastric bilirubin exposure (absorbance > 0.14) between any group. However, in each group gastric bilirubin exposure was greater in the supine position than the upright position, being significantly greater in the control group (P< 0.05) and group 1 (P < 0.001).

CONCLUSIONS

Gastric bilirubin exposure is similar across the spectrum of GORD severity. It is greater in the supine than in the upright position.

Comparison of zafirlukast (Accolate) absorption after oral and colonic administration in humans

PURPOSE

This study characterized the gastrointestinal (GI) absorption of zafirlukast after oral and colonic administration in humans.

METHODS

Five healthy subjects received zafirlukast solution (40 mg) orally and via an oroenteric tube into the colon in a randomized, crossover fashion. Two additional subjects were dosed into the distal ileum. Serial blood samples were obtained and plasma concentrations were quantitated by HPLC.

RESULTS

Mean +/- SD pharmacokinetic parameters after oral vs. colonic administration were: AUC infinity of 2076 +/- 548 vs. 602 +/- 373 ng x h/mL, respectively, and Cmax of 697 +/- 314 vs. 194 +/- 316 ng/mL, respectively. Mean colon:oral AUCalpha and Cmax were 0.29 and 0.30, respectively. Median tmax values were 2.0 and 1.35 hr after oral and colonic administration. First-order absorption rate constants (Ka and Kac) were estimated from a two-compartment model with first-order elimination. Kac:Ka was <0.5 in 4 of the 5 subjects dosed in the colon.

CONCLUSIONS

Zafirlukast was absorbed at multiple sites in the GI tract. The rate and extent of zafirlukast absorption was less after colonic than oral administration. Zafirlukast was significantly absorbed in the distal ileum. This study demonstrated that gamma scintigraphy, digital radiography, and fluoroscopy can be used to track the movement and confirm the location of the oroenteric tube in the GI tract.

Fiberoptic technique for 24-hour bile reflux monitoring. Standards and normal values for gastric monitoring

Physiologic bile reflux was assessed in 27 in vivo test with healthy volunteers to define a standardized protocol and normal values for 24-hour enterogastric bile reflux monitoring (protocol with supine, upright, and meal phases and a free diet avoiding alcohol, smoking, and coffee, evaluation with different thresholds of absorbance units: 0.14, 0.25). In vitro tests with bile-sodium solutions demonstrated a linear dependence of absorbance for bilirubin up to 600 mumol/liter (range of the fiberoptic device: 0.0-1.0). Fluids and food might interfere with absorbances below 0.25 (exception: coffee). In vivo bile often remains in the stomach for more than 1 hr; these events were defined as reflux episodes. The upper limits for physiologic bile reflux are a percentage of total time of bile reflux of 28.2% and an average absorbance during a reflux episode of 0.62 (95th percentile with threshold 0.25). Comparing bile with pH monitoring (absorbance > 0.25 and/or pH > 4), an increase of bilirubin was found most frequently with constant pH (45%) or an increase of pH with constant bilirubin (36%). The hypothesis was drawn that bile and duodenal or pancreatic secretions may separately contribute to duodenogastric reflux.

The origin of nocturnal intragastric pH rises in healthy subjects

BACKGROUND

Duodenogastric reflux (DGR) can produce transient increases in gastric luminal pH. It has been proposed that intragastric pH-metry is a reliable method for the detection of DGR. Our aim was to test the hypothesis that nocturnal increases in antral pH are due solely to DGR.

METHODS

Gastric pH was monitored overnight using two glass pH electrodes, one in the antrum adjacent to the tip of a nasogastric tube and one in the corpus. Scheduled antral aspirations were performed hourly to determine base-line concentrations of total bile acids (TBA; a marker of DGR) and thiocyanate (SCN; a marker of swallowed saliva). Additional, triggered aspirations were performed if antral pH exceeded 3.0 for 1 min or more (PHAP; period of high antral pH). TBA and SCN were considered to be increased if they exceeded the 90th percentile of values determined in scheduled aspirates (TBA, 0.88 mM; SCN, 0.67 mM).

RESULTS

In 28 of the 62 samples whose aspiration was triggered by a PHAP the pH was less than 3.0, and the sample was not considered to be representative. In the remaining 34 samples the antral luminal pH and the sample pH were concordant; TBA alone was increased in 6 samples, SCN alone was increased in 6 samples, and TBA and SCN were both increased in another 3 samples. Thus, DGR and swallowed saliva alone or in combination accounted for only 15 (45%) of the PHAP in which adequate gastric samples were obtained.

CONCLUSION

Samples of gastric antral contents often do not reflect accurately the acidity of gastric fluid in contact with a luminal antral pH electrode. Nocturnal increases in antral pH, detected by a luminal electrode, are frequently due to mechanisms other than duodenogastric reflux or swallowed saliva. Thus, antral pH-metry is not suitable for monitoring the occurrence of duodenogastric reflux.

MRI evaluation of potential gastrointestinal contrast media

Diluted ProHance [Gd(HP-DO3A), Squibb Diagnostics, Princeton, NJ], Sustacal (Meadjohnson, Evansville, IN), a nutritional drink, and a ProHance/Sustacal mixture have been investigated as potential oral contrast agents. At 2 T, T1-weighted (SE 500/20) images demonstrated hyperintense (positive) signal enhancement of rat GI tracts within 10 min after the ingestion of 2.0 mM Gd(HP-DO3A) or 2.0 mM ProHance/Sustacal. T2-weighted (SE 3000/80) images demonstrated hypointense (negative) signal intensity within 10 min after ingestion of 10 mM ProHance. Medical imaging applications of these oral contrast media are feasible.