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Measurements of bile salt reflux are influenced by the method of collecting gastric juice
GASTROENTEROLOGY
1985:89:1338-41
Measurements of Bile Salt Reflux Are Influenced by the Method of Collecting Gastric Juice STEFAN A. MULLER-LISSNER, CHRISTINE FRAASS Medizinische
Klinik
Innenstadt,
University
with the technical of Munich,
Conventional gastric analysis by continuous aspiration and Q marker technique that allows the stomach to retain its volume were compared with respect to the measured rates of gastric secretion and bile salt reflux in 10 fasting subjects. In marker technique studies, the stomach contained 35.7 -C 3.3 ml (mean + SEM) and emptied at a rate of 4.1% 2 0.4% per minute. Secretion rates of volume and acid were similar in studies using continuous aspiration and in marker technique studies. In contrast, the bile salt reflux rate was significantly higher when continuous aspiration was performed (0.89 ? 0.11 vs. 0.38 2 0.06 pmollmin, pCO.01). Gastric bile salt concentrations were also higher (765 t 48 vs. 366 2 67 PmollL, p < 0.01). This may be due to changes in the gastroduodenal pressure gradient induced by evacuating the stomach. It is concluded that measurements of bile salt reflux are influenced by the
method
of collecfing
gastric juice.
Continuous gastric aspiration with intermittent suction is the technique used most for the study of gastric secretion of volume and acid (1). It is also often used to measure reflux of duodenal contents (2-4). As the normal stomach is never really empty, continuous aspiration may interfere with upper digestive physiology. In the present study, conventional gastric aspiration was compared with a marker technique that avoids disturbances of normal gastric function as far as possible. Received October 2, 1984. Accepted May 24, 198.5. Address requests for reprints to: Stefan A. Miiller-Lissner,
M.D.. Medizinische Klinik Innenstadt 1, D-8000 Munich 2, Federal
Department of Gastroenterology, der UniversitBt, Ziemssenstrasse Republic of Germany. This work was supported by Deutsche
Forschungsgemeinschaft
Grant No. Mu 62911-3. 0 1985 by the American Gastroenterological 0016-5085185153.30
Association
assistance
of
Germany
Material
and Methods
The experiments
were started at 8:30 Ah1 after an overnight fast. A nasogastric tube with an air vent (Salem sump tube, Ch 14) was positioned with its tip in the most dependent part of the stomach under fluoroscopic control. The subject then lay down on the left side and remained in this position throughout the experiment in both study designs. Design
1
An automatic pump with intermittent suction was used (Egnell, Sweden, No. 17). Maximal suction pressure was -50 mmHg. Residual gastric contents were aspirated over 15 min and discarded. Subsequently, gastric juice was aspirated over 4 h and pooled in 30-min fractions. Design
2
Fifteen minutes were allowed for the subject to get accustomed to the tube. Then gastric contents were rapidly aspirated manually with a SO-ml syringe. The volume was measured by differential weighing in preweighed glass containers. An equal volume of marker solution was instilled into the stomach. It consisted of polyethylene glycol 4000 (PEG), 200 g/L in normal saline. The time between the beginning of aspiration and the end of instillation was 3 min. Twenty-seven minutes later, the following procedure was performed during 3 min. The stomach was evacuated with a syringe, the volume of the aspirate was measured, and after thorough mixing a s-ml sample was taken. Five milliliters of the marker solution was added and mixed with the gastric juice. The marker concentration of the mixture (c,) was calculated from the volumes and marker concentrations of the aspirate (V,,, c,) and the added marker solution (V, = 5 ml, c,), respectively, using the following equation: c,,1 = Ic,,(V,, - 5) + 5c,w,,. The mixture was reinstilled into the stomach. This procedure was repeated every 30 min over a period of 4 h. Assay
Procedures
In the samples, acidity was determined by titration with 0.05 N NaOH to pH 7.0. Total bile salt concentration
December 1985
BILE SALT REFLUX
ml
1339
ments. For this purpose, three specimens of native gastric juice with different bile salt concentrations were mixed 1:l with solutions of PEG in saline of varying concentrations (Table l), and bile salt concentrations were determined.
100 ..
Results Validation 0
so
instilled
100 ml
Figure 1. Validation of gastric aspiration. The volume instilled is compared with the volume aspirated from the stomach as calculated from marker recovery. Identity line is shown.
Recovery of instilled marker was 92.8% 5 1.1% and was independent of the volume instilled (Figure 1). The presence of PEG did not affect the measured bile salt concentrations (Table 1).
Gastric was determined enzymatically (5). In the samples of design 2 studies, PEG concentration was measured (6). Calculations In design 1 studies, the aspirated volumes were assumed to equal the rate of gastric volume secretion. The rates of gastric acid secretion and bile salt reflux were calculated by multiplying their respective concentrations in the samples with the volume secretion rate. Ia design 2 studies, the rates of fractional gastric emptying, gastric voltime emptying, gastric secretion of voldme and acid, and bile salt reflux were calculated from the volumes and the concentrations of PEG, acid, and bile salts, respectively, using exponential equations previously published (7,B). Appropriate corrections were made for acid and bile salts lost by the sampling procedure. In both designs the volume secretion rate includes refluxed duodenal volume. Means for each study were calculated from fractions 5 through 8 (1.54 h) because, after 1.5h, turnover of gastric contents is nearly complete and hence the marker solution has been replaced, by fresh gastric juice (see Results). Group means are given with SEM. Statistical comparisons were made with the Wilcoxon test for paired data. Probability values below 0.05 were considered to be significant.
Subjects Studied Ten young (21-31 yr old) healthy volunteers, 3 women and 7 men, were studied according to each study design in randomized order. The time elapsed between the two experiments was at least 3 days. The study protocol had been approved by the local ethical committee.
Validation
Studies
Volume
Emptying
In design 2 studies, mean total gastric volume was 35.7 2 3.3 ml (range 14.3-96.0 ml). The mean fractional gastric emptying rate amounted to 4.1% t 0.4% per minute. This corresponds to 1.2 3fr 0.3 ml emptied per minute. After 90 min, 3.3% ? 0.5% of the starting gastric contents were still present in the stomach; the rest consisted of fresh gastric juice. Gastric volume and the emptying rate showed no specific time-course and were steady during the 4 h of the experiment. Gastric Secretion Gastric secretion rates were similar in both study designs. Volume secretion rates are shown in Figure 2. Acid secretion was 49 + 11 pmol/min in design 1 studies and 56 ? 14 pmol/min in design 2 studies.
Bile Salts Both gastric bile salt concentrations and bile salt reflux rates were higher in design 1 studies, when the stomach was kept empty, studies, when gastric juice remained (Figures 2 and 3).
Table
than in design 2 in the stomach
1. Validation of Accuracy of Bile Salt Measurements in Three Different Specimens Gastric Juice in the Presence of Polyethylene Glvcol
Studies
Completeness of gastric aspiration was tested in 15 experiments. Volumes of 15, 30, 50, or 100 ml of saline labeled with PEG were instilled into the stomach. Within 3 min the stomach was evacuated by manual aspiration with a 50-ml syringe. The concentration of PEG in the aspirates was measured and the percentage of recovered marker was calculated. In vitro tests were performed to determine whether PEG would affect bile salt measure-
and
of
Bile salt concentration for specimen: PEG (s/L)
1
2
3
0 5 50 100
94 94 82 94
540 516 551 528
2009 1996 1972 2009
PEG, polyethylene glycol. Measured given in micromoles per liter.
bile salt concentrations
are
1340
GASTROENTEROLOGY
MijLLER-LIS’SNER
Vol. 89, No. 6
Discussion The usual way to analyze gastric secretion is (1). When to perform continuous gastric aspiration bile constituents or a duodenal marker are measured in the aspirate, the method can also be used for the quantificatjon of duodenogastric reflux (2-4,9). The results become slightly more accurate when the stomach is perfused with a marker (1). However, whether marker perfusion is performed or npt, the stomach is always kept empty during the study. As even a fasting stomach normally is not empty, gastric physiology may be disturbed by this procedure. An alternative approach that allows the stomach to retain its volume is to label the gastric contents with a nonabsorbable marker.‘The decrease of the amount of marker in gastric contents over time allows the quantification of pyloric loss of gastric contents (i.e., gastric emptying). The dilution of gastric marker occurring simultaneously allows the calculation of the amount of marker-free fluid entering the stomach (i.e., secretions and reflux). This method depends on determinations of total gastric volume at specified intervals. This can be done by either a marker dilution technique (7,8,10) or by direct measurement of th’e completely aspirated and subsequently reinjected volume. The marker dilution technique may be subject to large errors (11). Therefore, direct volume measurement with external intermixing of the marker was chosen. Gastric secretory rates of both volume and acid were similar whether continuous aspiration or the marker technique was used. This is not astonishing, as intragastric acidity is not expected to be changed by aspirating the stomach. Feedback by gastrin should therefore not be affected. In addition, fasting
ml Ii%
mM
2
1. 0
Design 2 Figure
urn01 iiii
1
2. Individual means of volume secretion rates (left), gastric bile salt concentrations (middle]. and bile salt reflux rates (right). Each subject is represented by one symbol. Horizontal bars give the group means. Whereas secretion rates are similar in the two types of study, bile salt concentration and reflux rate are higher in design 1 studies (both p < 0.01).
0 10 Amol
05
01 0 Figure
1
z
3
h
3. Time-course of gastric bile salt concentrations (upper graph) and bile salt reflux rates (lower graph] in design 1 studies (O---O) and design 2 studies (G-O). Mean 2 SEM.*p < 0.05.
gastric volume is below the threshold of stimulation of secretion by fundic distention (12). Different degrees of duodenogastric reflux in the two designs are also not expected to cause differences of measured volume secretion rates, as duodenogastric volume reflux can be estimated to be less than one-tenth of gastric volume secretion (13,14). The trend toward lower acid secretion in design 1, however, could be due to a higher degree of neutralization by refluxed bicarbonate. In contrast to the secretion rates, reflux rates of bile acids and-in consequence-gastric bile acid concentrations were significantly different between cantinuous aspiration and marker technique studies (Figures 2 and 3). This difference could either be due to an increase of reflux by continuous aspiration or a decrease of reflux by the marker technique. Gastroduodenal flow is determined by the gastroduodenal pressure gradient and inversely related to the flow resistance between stomach and duodenum. As the resistance for liquids is low, the pressure gradient is the main determinant for flow (15). A small reduction in gastric pressure, e.g., by gastric evacuation, may therefore significantly affect gastroduodenal flow of liquids and hence increase duodenogastric reflux. This view is corroborated by findings of other authors who showed an increase of duodenogastric reflux with increasing duodenal perfusion rate (3), which is also expected to change the gastroduodenal pressure gradient. This speaks in favor of an iqcreased reflux during continuous aspiration. Bile reflux then may have been overestimated even in the marker technique studies, as the intermittent evacuation of the stomach for volume measurement could have provoked short pulses of reflux. An alternative
December
BILE SALT REFLUX
1985
explanation also seems possible. Between two volume measurements, when the stomach contains its spontaneous irolume, refluxed material may not mix well with the gastric juice but remain in the distal antrum. It then could be cleared more rapidly from the stomach than the rest of gastric contends and hence escape assessinent. The transpyloric flow from the duodenum then would have been uhderestimated. Continuous Aspiration, in contrast, leads to thorough in vitro mixing of all material present in the stomach. If this explanation is true, however, the marker technique is obvibusly the more accurate with respect to the resulting bile salt concentrations to which the gastric &cosa isekposed. It has been claimed that reflux of duodenal contents is related tb the phases of the migrating motor complex (4). Bedatise in the present study no pressure measurements were performed, one may specuiate that the observed differences might be due to different numbers of activity fronts dtiring measurements. It is, however, very unlikely that during a 4-h stu,dy such a bias would occur because the migrating motor complex cyc,le length is -1.5 h (16j. On the other hand, the relation between reflux and the migrating motor complex was found when continuous gastric aspiration and duodenal perfusion were performed. Bile salt reflux rate was not directly measured and the reported gastric bile salt concedtrations in designs without continuous gastric aspiration and without duodenal perfusion can be explained by cyclic changes irl gastric secretion and hence by dilution (4). The relation of reflux to the migrating motor complex, therefore, has not been proved. In conclusion, this paper shows that the measurements of bile salt reflux are inflbenced by the method of collecting gastric juice. Gastric secretion remains unchanged. Gastric bile salt concentration at least may be reflected more accurately when a marker technique is used.
1341
Refel;ences 1. Baron Jc. Clinical tests of gastric secretion. London: Macmillan, 1978. 2. Fisher ir, Cohen S. Physiological characteristics of the human pyloric sphincter. Gastroenterology 1973;64:67-75. 3. Gustke RF, Varma RR. Soergel KH. Gastric reflux during perfusion of the proximal small bowel. Gastroenterolog] 1970;59;850-5. 4. Keane FB, Dimagno EP. Malagelada JI?. Duodenogastric reflux in humans: its relationship to fasting antroduodenal motility and gristric, pancreatic, and biliary secretion. Gastroenterology 1981;81:726-31. 5. Talalay p. Enzymatic analysis of steroid hormones. Methods Biochem Anal 1960;8:119-43. 6. Buxtoi TB, Crockett JK. Moore WL, Moore WL Jr, Rissing JP. Protein precipitation by acetone for the analysis of polyethylene glycol (PEG). Gastroenterology 1980:79:35-!I. 7. Dubois A, van Ettrdewegh P. Gardner JLj, Gastric: emptying and secretion in Zollinge-Ellison svndrorne. J Clin Invest 1977:59:255-63. 8. Miiller-Lissner SA. Fimmel CJ. Sonnentlerg A, et al. Novel approach to quantify duoclenogastric retlux in healthy volunulcer. Gut 1983: teers and in patients with type I gastric 24:510-8. 9. Go VLW. Hofmann AF. Summerskill WHJ. Simultaneous measure,nients of total pancreatic, biliary. and gastric outputs in man using a prrfusion technique. Gastroenterology 1970; 58:321-8. 10. George JD. New clinical method for measuring the rate of gastric emptying: the double sampling test meal. Gut 1968:9:i37-42. 11. Hurwitz A. Measuring gastric. volumes by dye dilution. Gut 1981;22:85-93. 12. GriJtzingor II. Bergegard S. Olbc L. Thr, effect of fundic distension on gastric: acid socrtttion in man. Gut 1977: 18:105-11. 13. Dimagno EP. Hendricks JC. Go L’LW. Dozois RR. Relationship among canine fasting pancreatic and biliiry secretions, pancreatic duct pressure. and duodrnal phase 111motor activityBoldyreff revisited. Dig Dis Sci 1979:24:fi8!)-93. 14. Miiller-Lissner SA. Fraass C. Dissociation of duodenogastric marker reflux and bile salt retlux. Dig dis Sci 1985:30:733-8. 15. Kelly KA. blotitity of the stomach and pastroduodenal junction. In: Johnson LK. ed. Physiology of the gastrointestinal tract. New York: Ravim, 1981:393-410. 16. Summers KW. Anuras S. Gretln I. leiunal manomc~try patterns in health. partial intestinal obstruction. alld pseudoobstruction. Gastrbentorology 1983:85:1290-300
1985:89:1338-41
Measurements of Bile Salt Reflux Are Influenced by the Method of Collecting Gastric Juice STEFAN A. MULLER-LISSNER, CHRISTINE FRAASS Medizinische
Klinik
Innenstadt,
University
with the technical of Munich,
Conventional gastric analysis by continuous aspiration and Q marker technique that allows the stomach to retain its volume were compared with respect to the measured rates of gastric secretion and bile salt reflux in 10 fasting subjects. In marker technique studies, the stomach contained 35.7 -C 3.3 ml (mean + SEM) and emptied at a rate of 4.1% 2 0.4% per minute. Secretion rates of volume and acid were similar in studies using continuous aspiration and in marker technique studies. In contrast, the bile salt reflux rate was significantly higher when continuous aspiration was performed (0.89 ? 0.11 vs. 0.38 2 0.06 pmollmin, pCO.01). Gastric bile salt concentrations were also higher (765 t 48 vs. 366 2 67 PmollL, p < 0.01). This may be due to changes in the gastroduodenal pressure gradient induced by evacuating the stomach. It is concluded that measurements of bile salt reflux are influenced by the
method
of collecfing
gastric juice.
Continuous gastric aspiration with intermittent suction is the technique used most for the study of gastric secretion of volume and acid (1). It is also often used to measure reflux of duodenal contents (2-4). As the normal stomach is never really empty, continuous aspiration may interfere with upper digestive physiology. In the present study, conventional gastric aspiration was compared with a marker technique that avoids disturbances of normal gastric function as far as possible. Received October 2, 1984. Accepted May 24, 198.5. Address requests for reprints to: Stefan A. Miiller-Lissner,
M.D.. Medizinische Klinik Innenstadt 1, D-8000 Munich 2, Federal
Department of Gastroenterology, der UniversitBt, Ziemssenstrasse Republic of Germany. This work was supported by Deutsche
Forschungsgemeinschaft
Grant No. Mu 62911-3. 0 1985 by the American Gastroenterological 0016-5085185153.30
Association
assistance
of
Germany
Material
and Methods
The experiments
were started at 8:30 Ah1 after an overnight fast. A nasogastric tube with an air vent (Salem sump tube, Ch 14) was positioned with its tip in the most dependent part of the stomach under fluoroscopic control. The subject then lay down on the left side and remained in this position throughout the experiment in both study designs. Design
1
An automatic pump with intermittent suction was used (Egnell, Sweden, No. 17). Maximal suction pressure was -50 mmHg. Residual gastric contents were aspirated over 15 min and discarded. Subsequently, gastric juice was aspirated over 4 h and pooled in 30-min fractions. Design
2
Fifteen minutes were allowed for the subject to get accustomed to the tube. Then gastric contents were rapidly aspirated manually with a SO-ml syringe. The volume was measured by differential weighing in preweighed glass containers. An equal volume of marker solution was instilled into the stomach. It consisted of polyethylene glycol 4000 (PEG), 200 g/L in normal saline. The time between the beginning of aspiration and the end of instillation was 3 min. Twenty-seven minutes later, the following procedure was performed during 3 min. The stomach was evacuated with a syringe, the volume of the aspirate was measured, and after thorough mixing a s-ml sample was taken. Five milliliters of the marker solution was added and mixed with the gastric juice. The marker concentration of the mixture (c,) was calculated from the volumes and marker concentrations of the aspirate (V,,, c,) and the added marker solution (V, = 5 ml, c,), respectively, using the following equation: c,,1 = Ic,,(V,, - 5) + 5c,w,,. The mixture was reinstilled into the stomach. This procedure was repeated every 30 min over a period of 4 h. Assay
Procedures
In the samples, acidity was determined by titration with 0.05 N NaOH to pH 7.0. Total bile salt concentration
December 1985
BILE SALT REFLUX
ml
1339
ments. For this purpose, three specimens of native gastric juice with different bile salt concentrations were mixed 1:l with solutions of PEG in saline of varying concentrations (Table l), and bile salt concentrations were determined.
100 ..
Results Validation 0
so
instilled
100 ml
Figure 1. Validation of gastric aspiration. The volume instilled is compared with the volume aspirated from the stomach as calculated from marker recovery. Identity line is shown.
Recovery of instilled marker was 92.8% 5 1.1% and was independent of the volume instilled (Figure 1). The presence of PEG did not affect the measured bile salt concentrations (Table 1).
Gastric was determined enzymatically (5). In the samples of design 2 studies, PEG concentration was measured (6). Calculations In design 1 studies, the aspirated volumes were assumed to equal the rate of gastric volume secretion. The rates of gastric acid secretion and bile salt reflux were calculated by multiplying their respective concentrations in the samples with the volume secretion rate. Ia design 2 studies, the rates of fractional gastric emptying, gastric voltime emptying, gastric secretion of voldme and acid, and bile salt reflux were calculated from the volumes and the concentrations of PEG, acid, and bile salts, respectively, using exponential equations previously published (7,B). Appropriate corrections were made for acid and bile salts lost by the sampling procedure. In both designs the volume secretion rate includes refluxed duodenal volume. Means for each study were calculated from fractions 5 through 8 (1.54 h) because, after 1.5h, turnover of gastric contents is nearly complete and hence the marker solution has been replaced, by fresh gastric juice (see Results). Group means are given with SEM. Statistical comparisons were made with the Wilcoxon test for paired data. Probability values below 0.05 were considered to be significant.
Subjects Studied Ten young (21-31 yr old) healthy volunteers, 3 women and 7 men, were studied according to each study design in randomized order. The time elapsed between the two experiments was at least 3 days. The study protocol had been approved by the local ethical committee.
Validation
Studies
Volume
Emptying
In design 2 studies, mean total gastric volume was 35.7 2 3.3 ml (range 14.3-96.0 ml). The mean fractional gastric emptying rate amounted to 4.1% t 0.4% per minute. This corresponds to 1.2 3fr 0.3 ml emptied per minute. After 90 min, 3.3% ? 0.5% of the starting gastric contents were still present in the stomach; the rest consisted of fresh gastric juice. Gastric volume and the emptying rate showed no specific time-course and were steady during the 4 h of the experiment. Gastric Secretion Gastric secretion rates were similar in both study designs. Volume secretion rates are shown in Figure 2. Acid secretion was 49 + 11 pmol/min in design 1 studies and 56 ? 14 pmol/min in design 2 studies.
Bile Salts Both gastric bile salt concentrations and bile salt reflux rates were higher in design 1 studies, when the stomach was kept empty, studies, when gastric juice remained (Figures 2 and 3).
Table
than in design 2 in the stomach
1. Validation of Accuracy of Bile Salt Measurements in Three Different Specimens Gastric Juice in the Presence of Polyethylene Glvcol
Studies
Completeness of gastric aspiration was tested in 15 experiments. Volumes of 15, 30, 50, or 100 ml of saline labeled with PEG were instilled into the stomach. Within 3 min the stomach was evacuated by manual aspiration with a 50-ml syringe. The concentration of PEG in the aspirates was measured and the percentage of recovered marker was calculated. In vitro tests were performed to determine whether PEG would affect bile salt measure-
and
of
Bile salt concentration for specimen: PEG (s/L)
1
2
3
0 5 50 100
94 94 82 94
540 516 551 528
2009 1996 1972 2009
PEG, polyethylene glycol. Measured given in micromoles per liter.
bile salt concentrations
are
1340
GASTROENTEROLOGY
MijLLER-LIS’SNER
Vol. 89, No. 6
Discussion The usual way to analyze gastric secretion is (1). When to perform continuous gastric aspiration bile constituents or a duodenal marker are measured in the aspirate, the method can also be used for the quantificatjon of duodenogastric reflux (2-4,9). The results become slightly more accurate when the stomach is perfused with a marker (1). However, whether marker perfusion is performed or npt, the stomach is always kept empty during the study. As even a fasting stomach normally is not empty, gastric physiology may be disturbed by this procedure. An alternative approach that allows the stomach to retain its volume is to label the gastric contents with a nonabsorbable marker.‘The decrease of the amount of marker in gastric contents over time allows the quantification of pyloric loss of gastric contents (i.e., gastric emptying). The dilution of gastric marker occurring simultaneously allows the calculation of the amount of marker-free fluid entering the stomach (i.e., secretions and reflux). This method depends on determinations of total gastric volume at specified intervals. This can be done by either a marker dilution technique (7,8,10) or by direct measurement of th’e completely aspirated and subsequently reinjected volume. The marker dilution technique may be subject to large errors (11). Therefore, direct volume measurement with external intermixing of the marker was chosen. Gastric secretory rates of both volume and acid were similar whether continuous aspiration or the marker technique was used. This is not astonishing, as intragastric acidity is not expected to be changed by aspirating the stomach. Feedback by gastrin should therefore not be affected. In addition, fasting
ml Ii%
mM
2
1. 0
Design 2 Figure
urn01 iiii
1
2. Individual means of volume secretion rates (left), gastric bile salt concentrations (middle]. and bile salt reflux rates (right). Each subject is represented by one symbol. Horizontal bars give the group means. Whereas secretion rates are similar in the two types of study, bile salt concentration and reflux rate are higher in design 1 studies (both p < 0.01).
0 10 Amol
05
01 0 Figure
1
z
3
h
3. Time-course of gastric bile salt concentrations (upper graph) and bile salt reflux rates (lower graph] in design 1 studies (O---O) and design 2 studies (G-O). Mean 2 SEM.*p < 0.05.
gastric volume is below the threshold of stimulation of secretion by fundic distention (12). Different degrees of duodenogastric reflux in the two designs are also not expected to cause differences of measured volume secretion rates, as duodenogastric volume reflux can be estimated to be less than one-tenth of gastric volume secretion (13,14). The trend toward lower acid secretion in design 1, however, could be due to a higher degree of neutralization by refluxed bicarbonate. In contrast to the secretion rates, reflux rates of bile acids and-in consequence-gastric bile acid concentrations were significantly different between cantinuous aspiration and marker technique studies (Figures 2 and 3). This difference could either be due to an increase of reflux by continuous aspiration or a decrease of reflux by the marker technique. Gastroduodenal flow is determined by the gastroduodenal pressure gradient and inversely related to the flow resistance between stomach and duodenum. As the resistance for liquids is low, the pressure gradient is the main determinant for flow (15). A small reduction in gastric pressure, e.g., by gastric evacuation, may therefore significantly affect gastroduodenal flow of liquids and hence increase duodenogastric reflux. This view is corroborated by findings of other authors who showed an increase of duodenogastric reflux with increasing duodenal perfusion rate (3), which is also expected to change the gastroduodenal pressure gradient. This speaks in favor of an iqcreased reflux during continuous aspiration. Bile reflux then may have been overestimated even in the marker technique studies, as the intermittent evacuation of the stomach for volume measurement could have provoked short pulses of reflux. An alternative
December
BILE SALT REFLUX
1985
explanation also seems possible. Between two volume measurements, when the stomach contains its spontaneous irolume, refluxed material may not mix well with the gastric juice but remain in the distal antrum. It then could be cleared more rapidly from the stomach than the rest of gastric contends and hence escape assessinent. The transpyloric flow from the duodenum then would have been uhderestimated. Continuous Aspiration, in contrast, leads to thorough in vitro mixing of all material present in the stomach. If this explanation is true, however, the marker technique is obvibusly the more accurate with respect to the resulting bile salt concentrations to which the gastric &cosa isekposed. It has been claimed that reflux of duodenal contents is related tb the phases of the migrating motor complex (4). Bedatise in the present study no pressure measurements were performed, one may specuiate that the observed differences might be due to different numbers of activity fronts dtiring measurements. It is, however, very unlikely that during a 4-h stu,dy such a bias would occur because the migrating motor complex cyc,le length is -1.5 h (16j. On the other hand, the relation between reflux and the migrating motor complex was found when continuous gastric aspiration and duodenal perfusion were performed. Bile salt reflux rate was not directly measured and the reported gastric bile salt concedtrations in designs without continuous gastric aspiration and without duodenal perfusion can be explained by cyclic changes irl gastric secretion and hence by dilution (4). The relation of reflux to the migrating motor complex, therefore, has not been proved. In conclusion, this paper shows that the measurements of bile salt reflux are inflbenced by the method of collecting gastric juice. Gastric secretion remains unchanged. Gastric bile salt concentration at least may be reflected more accurately when a marker technique is used.
1341
Refel;ences 1. Baron Jc. Clinical tests of gastric secretion. London: Macmillan, 1978. 2. Fisher ir, Cohen S. Physiological characteristics of the human pyloric sphincter. Gastroenterology 1973;64:67-75. 3. Gustke RF, Varma RR. Soergel KH. Gastric reflux during perfusion of the proximal small bowel. Gastroenterolog] 1970;59;850-5. 4. Keane FB, Dimagno EP. Malagelada JI?. Duodenogastric reflux in humans: its relationship to fasting antroduodenal motility and gristric, pancreatic, and biliary secretion. Gastroenterology 1981;81:726-31. 5. Talalay p. Enzymatic analysis of steroid hormones. Methods Biochem Anal 1960;8:119-43. 6. Buxtoi TB, Crockett JK. Moore WL, Moore WL Jr, Rissing JP. Protein precipitation by acetone for the analysis of polyethylene glycol (PEG). Gastroenterology 1980:79:35-!I. 7. Dubois A, van Ettrdewegh P. Gardner JLj, Gastric: emptying and secretion in Zollinge-Ellison svndrorne. J Clin Invest 1977:59:255-63. 8. Miiller-Lissner SA. Fimmel CJ. Sonnentlerg A, et al. Novel approach to quantify duoclenogastric retlux in healthy volunulcer. Gut 1983: teers and in patients with type I gastric 24:510-8. 9. Go VLW. Hofmann AF. Summerskill WHJ. Simultaneous measure,nients of total pancreatic, biliary. and gastric outputs in man using a prrfusion technique. Gastroenterology 1970; 58:321-8. 10. George JD. New clinical method for measuring the rate of gastric emptying: the double sampling test meal. Gut 1968:9:i37-42. 11. Hurwitz A. Measuring gastric. volumes by dye dilution. Gut 1981;22:85-93. 12. GriJtzingor II. Bergegard S. Olbc L. Thr, effect of fundic distension on gastric: acid socrtttion in man. Gut 1977: 18:105-11. 13. Dimagno EP. Hendricks JC. Go L’LW. Dozois RR. Relationship among canine fasting pancreatic and biliiry secretions, pancreatic duct pressure. and duodrnal phase 111motor activityBoldyreff revisited. Dig Dis Sci 1979:24:fi8!)-93. 14. Miiller-Lissner SA. Fraass C. Dissociation of duodenogastric marker reflux and bile salt retlux. Dig dis Sci 1985:30:733-8. 15. Kelly KA. blotitity of the stomach and pastroduodenal junction. In: Johnson LK. ed. Physiology of the gastrointestinal tract. New York: Ravim, 1981:393-410. 16. Summers KW. Anuras S. Gretln I. leiunal manomc~try patterns in health. partial intestinal obstruction. alld pseudoobstruction. Gastrbentorology 1983:85:1290-300