Periodic gallbladder contraction maintains bile acid circulation during the fasting period: a canine study

Gall bladder ejection fractions in dogs investigated for chronic altered appetite: 14 cases (2015-2017)

OBJECTIVES

To determine if gall bladder dysmotility occurs in dogs investigated for chronic altered appetite and to determine if gall bladder dysmotility warrants further investigation as a contributing factor to altered appetite.

MATERIALS AND METHODS

Case series of dogs investigated for chronic gastrointestinal disease. Gastrointestinal clinical signs were assessed before and after a 6-week hydrolysed protein diet. Gall bladder ejection fractions were determined at the end of the 6-week hydrolysed protein diet as part of an investigation that included a full blood cell count, biochemistry, abdominal X-rays and ultrasound. The gall bladder ejections fraction results of dogs with normal appetite were compared to dogs with general inappetence and dogs with diurnal inappetence in the morning.

RESULTS

In this retrospective case series of 14 dogs, altered appetite was the most frequent and persistent clinical sign associated with chronic gastrointestinal disease. Nine dogs had suboptimal gall bladder function and this occurred in dogs with, and without, gravity-dependent biliary sludge. Gall bladder function and volumes of dogs in this study were comparable to those of dogs with nongravity-dependent gall bladder sludge or gall bladder mucoceles in other studies. There was an observable difference in gall bladder ejection fractions between groups defined by appetite but no statistically significant difference was present. Small sample sizes meant the effect size was large.

CLINICAL SIGNIFICANCE

Gall bladder dysmotility and distension can occur in the absence of gall bladder sludge and mucocoeles in younger dogs. Gall bladder dysmotility requires further investigation as a potential contributing factor to altered appetite in dogs.

Effect of 6-8 weeks of oral ursodeoxycholic acid administration on serum concentrations of fasting and postprandial bile acids and biochemical analytes in healthy dogs

BACKGROUND

Ursodeoxycholic acid (UDCA) is commonly used for the treatment of hepatobiliary disease. UDCA is a bile acid that can be detected in the bile acid assay. Its effect on biochemical analytes is unknown.

OBJECTIVES

The aim of this study was to determine the effect of 6-8 weeks of UDCA administration on fasting and postprandial concentrations of serum bile acids (SBA), cholesterol, triglycerides, bilirubin, and liver enzyme activities in healthy dogs.

METHODS

Twenty healthy dogs received UDCA for 6-8 weeks. CBC, biochemistry profile, urinalysis, fasting and postprandial SBA, and hepatobiliary ultrasound examination were performed prior to starting UDCA (timepoint 0) and after 6-8 weeks of therapy, while animals were still receiving UDCA (timepoint 1). Timepoint 0 and timepoint 1 values were compared with a paired t-test. SBA were remeasured 72 hours after UDCA discontinuation.

RESULTS

Only mean fasting SBA at timepoint 1 increased significantly (P = .03) from timepoint 0 (2.26 μmol/L at time 0 and 3.81 μmol/L at time 1) but were not elevated above the normal reference interval (0-9 μmol/L). Two dogs had timepoint 1 fasting SBA above the reference interval (10 and 11.7 μmol/L). One dog had timepoint 1 postprandial SBA above the reference interval at 20.1 μmol/L (reference interval 0-17 μmol/L). Repeat SBA 72 hours after UDCA discontinuation were normal.

CONCLUSIONS

Long-term administration of UDCA to healthy dogs may increase fasting SBA above pretreatment values (typically within the reference interval). Long-term administration of UDCA to healthy dogs does not alter liver enzyme activities, and bilirubin, cholesterol, or triglyceride concentrations.

Effects of lorglumide and atropine on MgSO(4)-induced gallbladder emptying in conscious dogs

The aim of the study was to examine the possible involvement of cholecystokinin (by lorglumide) and cholinergic mechanisms (by atropine) in magnesium sulphate (MgSO(4))-induced gallbladder contraction of conscious dogs. The gallbladder (GB) volume was determined by ultrasonography. The optimal dose of 80 mg kg(-1)of MgSO(4)was determined from a MgSO(4)dose-response curve using doses of 10, 20,40, 80, 120 mg kg(-1). The largest dose of MgSO(4)was less effective than the optimal dose. Peak gallbladder contraction (32 per cent) was achieved at 30 minutes. Atropine (50 microg kg(-1)s.c.) or lorglumide (1 mg kg(-1)p.o.) fully prevented GB contraction. In conclusion, supraoptimal doses of MgSO(4)have a diminishing effect. The sustained contraction of the gallbladder in response to the optimal dose of MgSO(4)can be explained by an additive effect of the cholecystokinin release and a cholinergic trigger mechanism. Ultrasonography and MgSO(4)stimulation proved to be a valuable technique for examination of gallbladder motility.

Coordination of biliary and upper gastrointestinal motility in the fasted conscious pig

A chronic pig model was developed which permits the simultaneous measurement of integrated biliary motility as resistance to flow (CBD inflow), gallbladder, duodenal and gastric motility in addition to collection of venous blood samples for gut hormones estimations. Animals displayed a duodenal interdigestive cycle of 55.4 +/- 3.4 min (mean +/- SEM, n = 6), consisting of phase I, II and III (21.2 +/- 2.1, 70.5 +/- 2.0, 8.7 +/- 0.5% of the cycle, respectively). A gastric interdigestive cycle of 60.2 +/- 6.5 min (n = 4) was similarly demonstrated consisting of three phases which corresponded to the three duodenal phases. The gastric phases I, II and III comprised 26.3 +/- 3.0, 71.2 +/- 2.7 and 2.5 +/- 0.8% of the cycle, respectively. The gastric phase III immediately preceded the onset of the duodenal phase III. The gallbladder likewise displayed an interdigestive cycle of 54.5 +/- 7.2 min (n = 6) consisting of a quiescent period (37.2 +/- 3.7% of the cycle) corresponding temporally to duodenal phase III and phase I. This quiescent phase was followed by a period of rhythmic contractions (64.5 +/- 4.1% of the cycle) which corresponded temporally to duodenal phase II. The onset of the gallbladder quiescent period coincided with the onset of duodenal phase III. The CBD inflow similarly demonstrated an interdigestive cycle of 53.4 +/- 9.6 min (n = 4) duration, consisting of three phases. The initial phase was evident as a period of rapid inflow, the onset of which coincided with the onset of duodenal phase III and the gallbladder quiescent period, and occupied 12.0 +/- 0.8% of the cycle. The second phase which occupied 18.0 +/- 7.4% of the cycle, was typified as a period of declining inflow which reached a relatively stable level at a time corresponding to the end of duodenal phase I. The third phase consisted of the maintenance of the inflow rate achieved at the end of the previous phase (60% of maximum inflow), corresponding in onset and duration with duodenal phase II and occupied 70.0 +/- 8.6% of the cycle. Plasma motilin levels fluctuated in relation to the duodenal interdigestive cycle, peaking during phase III relative to phase I (36.9 +/- 8.5 vs 25.4 +/- 7.7 pg mL-1, respectively, n = 5, P < 0.05). Cholecystokinin levels did not fluctuate, remaining low (2.3 +/- 2.1 pM cholecystokinin octapeptide equivalents, n = 5) throughout the duodenal interdigestive cycle, but increased about two fold after ingestion of solid food. Feeding disrupted the gastric, duodenal, gallbladder and CBD inflow cycles.

Serum bile acids in companion animal medicine

Quantification of total serum bile acids is used as a method for appraising liver function and perfusion in contemporary small animal practice. This article provides a historical perspective and a comprehensive review of bile acid physiology, laboratory methodologies for bile acid quantification, and normal values published for total serum bile acids measured using the spectrophotometric enzymatic method and for serum bile acids measured using validated radioimmunoassay procedures. The variables influencing the enterohepatic circulation of bile acids and, consequently, the fasting and postprandial serum bile acid concentrations are discussed with the intent of clarifying the application of test results to clinical patients. A brief discussion of the therapeutic use of dehydrocholate and ursodeoxycholic acid in clinical patients is provided.

Opposite effects of cholestyramine and loxiglumide on gallbladder dynamics in humans

The aim of this study was to conduct dose-response studies of the effect of cholestyramine, alone or in combination with a test meal, on gallbladder emptying studied by ultrasonography in 31 healthy volunteers. The role of cholecystokinin in mediating the effects of cholestyramine was studied using the cholecystokinin-receptor antagonist loxiglumide. In the absence of a test meal, cholestyramine produced a dose-dependent decrease in gallbladder volume; minimal residual volumes were 30% (2 g), 55% (4 g), and 110% (12 g) of the minimal volume produced by a test meal alone. Gallbladder volume was still only 50% of the initial volume, 24 hours after ingestion of 12 g cholestyramine. Cholestyramine also enhanced gallbladder emptying in response to the test meal (n = 7). Oral loxiglumide strongly inhibited gallbladder evacuation in response to either test meal (n = 6) or cholestyramine alone (n = 6) but partially blocked gallbladder emptying when the resin was added to the test meal (n = 12). It is concluded that (a) cholestyramine alone or in combination with a test meal produces a marked decrease in gallbladder volume and (b) the action of the resin itself on gallbladder motor function appears to be mainly, but not solely, mediated by cholecystokinin through the disinhibition of the luminal feedback mechanism between bile salts and the endogenous release of cholecystokinin.

Fourier analysis of biliary and pancreatic excretion in man based on data obtained by a duodenal perfusion/aspiration technique

A standard duodenal perfusion/aspiration technique was used to continuously monitor biliary and pancreatic excretion in young healthy human subjects, and the excretory patterns were examined by Fourier power spectral analysis. Experiments were carried out in the fasting state, either without or during a continuous parenteral (i.v.) stimulation by secretin and the cholecystokinin analogue ceruletide. The duodenal content aspirated was either discarded after sampling or reinfused into the jejunum. In the fasting state, significant biliary and pancreatic excretion was detected, fluctuating with a periodicity of about 60 min. During parenteral infusion with ceruletide/secretin, to simulate a postprandial state, the rate of biliary and pancreatic excretion increased as compared with fasting levels alone (basal levels). A dominant period of about 60 min was still detected but second periods of approximately 45 min and approximately 95 min, respectively, were also observed. The peak power and the total power of the biliary excretion signals were reduced. Reinfusion of aspirated duodenal fluid into the intestine (jejunum) led to a further decrease in peak power and total power of the known biliary signals. Trypsin excretion into the duodenum revealed mainly insignificant changes in peak and total power upon hormone stimulation despite a definite increase in total amount of trypsin excreted. The results indicate that parenteral ceruletide/secretin stimulation has a stabilizing effect on biliary excretion in man, and that reinfusion of aspirated duodenal content into the intestine further stabilizes the excretion.

Preduodenal mechanisms in initiating gallbladder emptying in man

The existence of preduodenal phases of gallbladder emptying in normal volunteers was investigated by evaluating the effect of sham feeding a sandwich (chew and spit) (n = 15), the sight and smell of food followed by sham feeding a cooked meal (n = 15), and gastric distension (intragastric balloon tube) (n = 9) on gallbladder emptying and comparing these responses with those after ingestion of a standard meal (n = 14). A control group given no intestinal stimuli were studied to determine the frequency of spontaneous emptying during fasting (n = 18). 99mTc-EHIDA (2,6 diethylphenylcarbamoylmethyliminodiacetic acid) was used as the biliary tracer. The frequency of gallbladder emptying during fasting was 0.0045/min. Thus, in any 20 min period emptying occurred spontaneously in only about 1 in 11 volunteers. Significant emptying (greater than 5 per cent over 20 min) occurred in 8 out of 15 volunteers after sham feeding a sandwich (P less than 0.001 versus control), in 8 out of 15 volunteers after sham feeding a cooked meal (P = 1.0 versus sandwich sham feed, n.s.), in 6 out of 9 volunteers after gastric distension (P less than 0.001 versus control) and in 14 out of 14 volunteers after meal ingestion. The rate of emptying was significantly greater in the gastric distension and meal ingestion groups compared with other groups (P less than 0.05). However, the emptying rate after sham feeding was not significantly different from spontaneous gallbladder emptying (P greater than 0.05, n.s.). There was no significant difference in time to onset of emptying between the four stimulus groups (P greater than 0.05, n.s.). These results suggest that pre-duodenal stimuli can evoke gallbladder emptying in man, although the precise physiological significance of this phenomenon remains to be established.