<title>1. INTRODUCTION</title> <p>Breath hydrogen (H2)
measurements are widely used to detect carbohydrate malabsorption [##REF##5020434##1##–##REF##441681##7##]. Because
bacteria represent the sole source of gut H2, fasting breath H2 gas has been
used as a marker of colonic fermentation [##REF##1486849##8##, ##REF##6489700##9##]. If the fermentation occurs in
the stomach, H2 gas should be produced and released into the gastric lumen. Gastric
acid plays an important part in the prevention of bacterial colonization of the
stomach and the small intestine [##REF##5421079##10##, ##REF##1553853##11##]. 
Reduction of gastric acid secretion predisposes to infection with a
variety of organisms [##REF##3546004##12##–##REF##5711487##14##]. Intestinal
bacterial overgrowth during treatment with PPI was previously reported because
of an intragastric neutral pH [##REF##342548##15##–##REF##8307444##18##]. 
Atrophic gastritis is the most common cause of reduced gastric acid secretion and <italic>Helicobacter pylori</italic> (<italic>H.pylori</italic>) seems to be the commonest
cause of atrophic gastritis [##UREF##1##19##–##REF##7569761##22##]. Then we attempted to collect
endoscopically intraluminal gas from the stomach and the duodenum and analyze
the H2 concentration in order to determine the bacterial overgrowth in the
upper digestive tract.</p>
<title>2. PATIENTS AND METHODS</title> <title>2.1. Patients</title> <p>Studies were performed
in 647 consecutive patients undergoing upper endoscopy, 211 men and 436 women,
19 to 85 years old (mean 60.8 ± 12.9 years). Of the patients recruited in this study, women are
preponderant for one reason or another. None of the patients had a history of use
of PPI, H2-receptor antagonist, antibiotics, steroids, or nonsteroidal
anti-inflammatory drugs for a period of at least six months before the
investigation. Twenty patients had a previous Billroth- partial gastrectomy and were also excluded from
analysis.</p> <p>Blood samples for measurements of IgG antibody to <italic>H.pylori</italic> were taken prior to endoscopy.
Serum samples were also examined for <italic>H.pylori</italic> antibody by an enzyme-linked immunosorbent assay (ELISA) using the EPI HM-CAP
IgG (Enteric Products, Inc., NY) assays. All assays were performed in
accordance with manufacturer's instructions. The calculated ELISA is read as
positive if above 2.2.</p> <title>2.2. Collection of intraluminal gas samples</title> <p>Endoscopy was performed after a topical anesthesia gargle after a fasting period of more than
12 hours and without previous exercise. The patients were also requested to
brush their teeth in the evening, but not in the morning of, the study. All
patients ate meals of their own choice in the evening of the study. At the time
of endoscopic examination, we intubated the stomach without inflation by air,
and 20 mL of intragastric gas was collected through the biopsy channel using a
30 mL syringe. The first 5 mL was discarded for reduction of dead-space error. Once
the pylorus is located, the tip of the endoscope is advanced into the
descending portion of the duodenum. After that, 20 mL of intraduodenal gas was
collected again by the same way. Intragastric and intraduodenal hydrogen
concentrations were immediately measured by gaschromatography using Breath
Analyzer TGA-2000 (TERAMECS Co., Ltd., Kyoto)
and expressed in parts per million (ppm). Linear accuracy response range was 2
to 150 ppm. After collecting an intraduodenal gas sample, the endoscopist
inflated the stomach by air and observed the gastric mucosa. Operators
involved in the measurement of breath samples were blinded for age, sex, and
endoscopic diagnosis.</p> <title>2.3. Grading of atrophic gastritis</title> <p>In this study, atrophic gastritis was classified into four stages by observing the location of
the atrophic border in the stomach [##UREF##3##23##]; closed type and open type (O-1, O-2, and
O-3). For closed type, the atrophic borderline is located at the lesser
curvature. In the stage O-1, the atrophic borderline lies between the lesser
curvature and the anterior wall of the body. In the stage O-3, the atrophic
region spreads throughout the entire stomach. Stage O-2 is in-between O-1 and
O-3. Stages O-1 to O-3 constitute the advanced stages of atrophic gastritis.</p> <title>2.4. Statistical analysis</title> <p>Data of intragastric and intraduodenal hydrogen were presented as mean±SD (standard deviation). Comparisons of groups
were made using the unpaired <italic>t</italic>-test.
A <italic>P</italic> value of &lt;.05 was accepted as indicating statistical
significance.</p>
<title>3. RESULTS</title> <p>Endoscopic findings included gastric ulcer (51 patients), duodenal ulcer (24), 
gastric cancer (3),
and gastritis (569). All of patients with gastric ulcer, duodenal ulcer, and
gastric cancer had a positive result of <italic>H.pylori</italic> serology. Among 569 patients 
with gastritis, 389 were seropositive.</p> <p>Over all, intragastric
and intraduodenal hydrogen gases were detected in 566 (87.5%) and 524 (81.0%),
respectively. The mean values of intragastric and intraduodenal hydrogen gas were
8.5 ± 15.9 (0–219)
and 13.2 ± 58.0 (0–828)
ppm, respectively.</p> <p>Intragastric and
intraduodenal H2 values and characteristics of patients in relation to
endoscopic diagnosis are summarized in ##TAB##0##Table 1##. The duodenal 
ulcer group showed a significantly younger mean age than the other groups. The intragastric H2
level was the highest in gastritis group followed by the duodenal ulcer group,
and the gastric ulcer group. The intraduodenal H2 level was the highest in the
gastric ulcer group among three groups.</p> <p>Mean intragastric and
intraduodenal H2 concentrations at different stages of atrophic gastritis are
summarized in ##TAB##1##Table 2##. The mean levels of intragastric H2 gas in patients with
closed type, stages O-1, O-2, and O-3, were 10.5 ± 17.3 ppm, 7.4 ± 10.2 ppm, 8.0 ± 12.0 ppm, and 7.5 ± 17.0 ppm, respectively. The intragastric H2 level
was the highest in patients with gastric mucosa of closed type and was
significantly higher than in those with O-3 stage atrophic gastritis (<italic>P</italic> = .031). In contrast, the intraduodenal H2 level was the highest in patients with
O-3 stage atrophic gastritis among four groups. There was a progressive
increase with the progression of atrophic gastritis. The mean levels of
intraduodenal H2 in patients with closed type, stages O-1, O-2, and O-3, were
7.1 ± 12.7 ppm,
4.4 ± 8.2 ppm,
8.1 ± 18.5 ppm,
and 21.5 ± 86.1 ppm,
respectively. The maximum of intraduodenal H2 was 828 ppm and found in
74-year-old female with O-3 stage atrophic gastritis.</p>
<title>4. DISCUSSION</title> <p>Before the discovery of <italic>H.pylori</italic> infection in 1983 [##UREF##4##24##],
many investigators reported that an increased number of bacteria had been found
in the stomach in patients with achlorhydria or hypochlorhydria [##UREF##5##25##].
The type and numbers of microbial flora present in the stomach are affected by
gastric pH [##REF##4865576##26##–##REF##3129329##28##], and a rise in intragastric pH has often been
associated with an increased number of bacteria in gastric juice [##REF##4556018##29##–##UREF##7##31##]. Atrophic
gastritis is the most common cause of reduced gastric acid secretion.
Therefore, if atrophic gastritis is closely related to the gastric and intestinal
bacterial overgrowth, it is possible, we suggest,
that intragastric and intraduodenal hydrogen, reflecting the fermentation by
bacteria in the stomach and the duodenum, should be detected in subjects with
atrophic gastritis.</p> <p>The gold standard for
bacterial overgrowth, against which intraluminal gas analysis must be compared,
is gastric and duodenal fluid culture. Actually, the microbial flora, which is
dominated by <italic>Viridans streptococci</italic>, <italic>coaglase negative Staphylococci</italic>, <italic>Haemophilus sp</italic>., <italic>Neisseria spp</italic>., <italic>Lactobacillus
spp.</italic>, <italic>Candida spp</italic>., and <italic>Aspergillus spp</italic>. [##REF##7085070##32##, ##REF##1446855##33##], has been
demonstrated. However, the study of gastrointestinal flora by direct methods is
cumbersome, primary due to its inaccessible location. In addition, the results
of identification and quantification of microbes in samples from the
gastrointestinal tract are significantly influenced by difficulties in accurate
tube placement, contamination during insertion, delay between sampling and
inoculation of culture media, and inadequate anaerobic isolation techniques.</p> <p>In the present
study, of all 647 subjects, intragastric H2 was detected in 566 (87.5%) and
ranged from 1 to 219 ppm, whereas intraduodenal H2 was done in 524 (81.0%),
ranging from 1 to 828 ppm. This suggested that more than 80% of endoscoped
patients had H2-producing bacteria in the stomach or the jejunum. Moreover,
intraduodenal H2 levels were higher in patients with stage O-3 atrophic
gastritis than in other groups, and there was a progressive increase with the
progression of atrophic gastritis. In contrast, the intragastric H2 level was
the highest in patients with gastric mucosa of closed type and was significantly
higher than in those with O-3 stage atrophic gastritis. These results suggest
that extensive atrophic gastritis may be more closely related to bacterial
overgrowth in the jejunum, compared to that in the stomach.</p> <p>Fried et al. [##REF##8307444##18##]
reported that most of the bacteria identified from the duodenal aspirates
belonged to species colonizing the oral cavity and pharynx, suggesting a
descending route of colonization. Husebye et al. [##REF##1446855##33##] also reported that
fasting hypochlorhydria associated with gastric colonization of microbes
belonging to the oro- and nasopharyngeal flora is highly prevalent in healthy
old people. At the normal acidic gastric pH, it has been thought that the
stomach is sterile or contains swallowed organisms [##REF##2859649##34##]. Although the
pathogenesis of swallowed organisms is unknown, it is reasonable to suppose
from the results of our study that these oral bacteria should continuously
enter the stomach and produce H2 gas. Furthermore, it is likely that the
influence of hypochlorhydria on bacterial overgrowth in the proximal small
intestine is more pronounced, compared to that in the stomach.</p> <p>Few studies on intragastric
and intraduodenal H2 concentrations have been reported, and the clinical
features and pathogenesis of intraluminal H2 gas are not clear. Bacteria
represent the sole source of gut hydrogen, and H2 gas is produced at a rate of
4 L for every 12.5 g of undigested carbohydrate [##UREF##8##35##]. H2 gas is either absorbed
by diffusion or consumed by bacteria to reduce carbon dioxide to methane or acetate.
The intragastric H2 concentration was considered to reflect directly the
intragastric fermentation and the presence of H2-producing bacteria in the
stomach. Since the intragastric H2 level is not affected by absorption or
metabolism of H2 unlike a breath H2 level, a trace of H2 should be detected in
patients with intragastric fermentation.</p> <p>In summary, unexpectedly, intragastric and intraduodenal H2 was
detected in more than 80% of all subjects in this study, and the intraduodenal
H2 level was increased with the progression of atrophic gastritis. Although it
is unknown whether intraluminal fermentation is related to digestive diseases,
a large amount of intragastric and intraduodenal H2 may cause abdominal
symptoms. We have to make a further study to evaluate whether bacterial
overgrowth in the stomach or the proximal small intestine is associated with some
clinical symptoms or gastrointestinal diseases.</p>
<p>Recommended by Maria Eugenicos</p> <p>
<italic>Objective</italic>. Gastric acid plays an important part in the prevention of bacterial colonization of the gastrointestinal tract. If these bacteria have an ability of hydrogen (H2) fermentation, intraluminal H2 gas might be detected. We attempted to measure the intraluminal H2 concentrations to determine the bacterial overgrowth in the gastrointestinal tract. <italic>Patients and methods</italic>. Studies were performed in 647 consecutive patients undergoing upper endoscopy. At the time of endoscopic examination, we intubated
the stomach and the descending part of the duodenum without inflation by air, and 20 mL of intraluminal gas samples of both sites was collected through the biopsy channel. Intraluminal H2 concentrations were measured by gas chromatography. <italic>Results</italic>. Intragastric and intraduodenal H2 gas was detected in 566 (87.5%) and 524 (81.0%) patients, respectively. The mean
values of intragastric and intraduodenal H2 gas were 8.5 ± 15.9 and 13.2 ± 58.0 ppm, respectively. The intraduodenal H2 level was
increased with the progression of atrophic gastritis, whereas the intragastric H2 level was the highest in patients without atrophic gastritis. <italic>Conclusions</italic>. The intraduodenal hydrogen levels were increased with the progression of atrophic gastritis. It is likely that the influence of hypochlorhydria on bacterial overgrowth in the proximal small intestine is more pronounced, compared to that
in the stomach.
</p>
<table-wrap id="tab1" position="float"><label>Table 1</label><caption><p>Intragastric and intraduodenal hydrogen levels in relation to endoscopic findings.</p></caption><table frame="hsides" rules="groups"><thead><tr><th align="left" rowspan="1" colspan="1"/><th align="center" rowspan="1" colspan="1">Gastric ulcer</th><th align="center" rowspan="1" colspan="1">Duodenal ulcer</th><th align="center" rowspan="1" colspan="1">Gastritis</th></tr></thead><tbody><tr><td align="left" rowspan="1" colspan="1">Number of patients</td><td align="center" rowspan="1" colspan="1">51</td><td align="center" rowspan="1" colspan="1">24</td><td align="center" rowspan="1" colspan="1">569</td></tr><tr><td align="left" rowspan="1" colspan="1">Age</td><td align="center" rowspan="1" colspan="1">64.5 ± 13.5</td><td align="center" rowspan="1" colspan="1">44.8 ± 10.7</td><td align="center" rowspan="1" colspan="1">61.4 ± 12.5</td></tr><tr><td align="left" rowspan="1" colspan="1">Male/female</td><td align="center" rowspan="1" colspan="1">34/17</td><td align="center" rowspan="1" colspan="1">18/6</td><td align="center" rowspan="1" colspan="1">156/413</td></tr><tr><td align="center" colspan="4" rowspan="1">
<hr/>
</td></tr><tr><td align="left" rowspan="1" colspan="1">Stomach (ppm)</td><td align="center" rowspan="1" colspan="1">6.1 ± 8.9</td><td align="center" rowspan="1" colspan="1">6.5 ± 12.4</td><td align="center" rowspan="1" colspan="1">8.7 ± 16.5</td></tr><tr><td align="left" rowspan="1" colspan="1">
<italic>P</italic> values v.s.*</td><td align="center" rowspan="1" colspan="1">.13</td><td align="center" rowspan="1" colspan="1">.26</td><td align="center" rowspan="1" colspan="1">*</td></tr><tr><td align="left" rowspan="1" colspan="1">Duodenum(ppm)</td><td align="center" rowspan="1" colspan="1">22.2 ± 70.5</td><td align="center" rowspan="1" colspan="1">5.6 ± 6.8</td><td align="center" rowspan="1" colspan="1">12.8 ± 58.1</td></tr><tr><td align="left" rowspan="1" colspan="1">
<italic>P</italic> values v.s.**</td><td align="center" rowspan="1" colspan="1">.12</td><td align="center" rowspan="1" colspan="1">**</td><td align="center" rowspan="1" colspan="1">.27</td></tr></tbody></table></table-wrap> <table-wrap id="tab2" position="float"><label>Table 2</label><caption><p>Intragastric and intraduodenal hydrogen levels in relation to the grade of atrophic gastritis.</p></caption><table frame="hsides" rules="groups"><thead><tr><th align="left" rowspan="1" colspan="1"/><th align="center" rowspan="1" colspan="1">Closed type</th><th align="center" rowspan="1" colspan="1">O-1</th><th align="center" rowspan="1" colspan="1">O-2</th><th align="center" rowspan="1" colspan="1">O-3</th></tr></thead><tbody><tr><td align="left" rowspan="1" colspan="1">Number of patients</td><td align="center" rowspan="1" colspan="1">200</td><td align="center" rowspan="1" colspan="1">66</td><td align="center" rowspan="1" colspan="1">101</td><td align="center" rowspan="1" colspan="1">280</td></tr><tr><td align="left" rowspan="1" colspan="1">Age (mean ±SD)</td><td align="center" rowspan="1" colspan="1">55.3 ± 13.9</td><td align="center" rowspan="1" colspan="1">58.1 ± 13.6</td><td align="center" rowspan="1" colspan="1">59.1 ± 12.5</td><td align="center" rowspan="1" colspan="1">66.1 ± 9.8</td></tr><tr><td align="left" rowspan="1" colspan="1">Male/female</td><td align="center" rowspan="1" colspan="1">60/140</td><td align="center" rowspan="1" colspan="1">22/44</td><td align="center" rowspan="1" colspan="1">39/62</td><td align="center" rowspan="1" colspan="1">90/190</td></tr><tr><td align="center" colspan="5" rowspan="1">
<hr/>
</td></tr><tr><td align="left" rowspan="1" colspan="1">Stomach (ppm)</td><td align="center" rowspan="1" colspan="1">10.5 ± 17.3*</td><td align="center" rowspan="1" colspan="1">7.4 ± 10.2</td><td align="center" rowspan="1" colspan="1">8.0 ± 12.0</td><td align="center" rowspan="1" colspan="1">7.5 ± 17.0</td></tr><tr><td align="left" rowspan="1" colspan="1">
<italic>P</italic> values v.s.*</td><td align="center" rowspan="1" colspan="1">*</td><td align="center" rowspan="1" colspan="1">.085</td><td align="center" rowspan="1" colspan="1">.105</td><td align="center" rowspan="1" colspan="1">.031</td></tr><tr><td align="left" rowspan="1" colspan="1">Duodenum (ppm)</td><td align="center" rowspan="1" colspan="1">7.1 ± 12.7</td><td align="center" rowspan="1" colspan="1">4.4 ± 8.2</td><td align="center" rowspan="1" colspan="1">8.1 ± 18.5</td><td align="center" rowspan="1" colspan="1">21.5 ± 86.1</td></tr><tr><td align="left" rowspan="1" colspan="1">
<italic>P</italic> values v.s.**</td><td align="center" rowspan="1" colspan="1">.009</td><td align="center" rowspan="1" colspan="1">.055</td><td align="center" rowspan="1" colspan="1">.061</td><td align="center" rowspan="1" colspan="1">**</td></tr></tbody></table></table-wrap>
<inline-graphic xlink:href="GRP2008-584929.001.jpg"/>
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Gastroenterol Res Pract. 2008 Jun 16; 2008:584929