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Fasting gallbladder volume is increased in patients with Parkinson's disease

Open AccessPublished:April 30, 2021DOI:https://doi.org/10.1016/j.parkreldis.2021.04.027

      Highlights

      • A quarter of patients with PD have enlarged fasting gallbladder volume.
      • Patients with iRBD do not have enlarged fasting gallbladder volume.
      • Gallstone frequency was not increased in patients with PD or iRBD.
      • Biliary dysfunction may be an overlooked subject in PD research.

      Abstract

      Introduction

      Autonomic denervation in patients with Parkinson's disease (PD) and isolated REM-sleep behavior disorder (iRBD) could impede gallbladder function leading to increased fasting gallbladder volume (fGBV) and higher risk of gallstones. We aimed to determine fGBV in patients with PD, iRBD, and healthy controls (HCs).

      Methods

      We included 189 subjects; 100 patients with PD, 21 with iRBD, and 68 HCs. fGBV was determined from abdominal CT scans, and radiopaque gallstone frequency was evaluated.

      Results

      Median fGBV was 35.7 ml in patients with PD, 31.8 ml in iRBD, and 27.8 ml in HCs (Kruskal-Wallis test: P = 0.0055). Post-tests adjusted for multiple comparison revealed a significant group difference between patients with PD and HCs (P = 0.0038). In the PD group, 23% had enlarged fGBV (cut-off at mean + 2 x standard deviation (SD) in the HC group). No difference in fGBV was observed between iRBD and the other two groups. The total prevalence of gallstones was 6.4% with no differences between the three groups.

      Conclusion

      Almost a quarter of patients with PD in our cohort exhibited increased fGBV. This study illuminates a potentially overlooked topic in PD research and calls for more studies on biliary dysfunction.

      Keywords

      1. Introduction

      Many patients with Parkinson's disease (PD) exhibit autonomic dysfunction and bothersome gastrointestinal (GI) tract symptoms [
      • Fasano A.
      • Visanji N.P.
      • Liu L.W.
      • Lang A.E.
      • Pfeiffer R.F.
      Gastrointestinal dysfunction in Parkinson's disease.
      ]. Objective assessment of GI function shows that patients with PD have disturbed gastric emptying and increased small and large intestinal transit time [
      • Knudsen K.
      • Szwebs M.
      • Hansen A.K.
      • Borghammer P.
      Gastric emptying in Parkinson's disease - a mini-review.
      ,
      • Knudsen K.
      • Fedorova T.D.
      • Bekker A.C.
      • Iversen P.
      • Ostergaard K.
      • Krogh K.
      • Borghammer P.
      Objective colonic dysfunction is far more prevalent than subjective constipation in Parkinson's disease: a colon transit and volume study.
      ]. Furthermore, colonic transit time is tightly correlated with colon volume [
      • Knudsen K.
      • Fedorova T.D.
      • Bekker A.C.
      • Iversen P.
      • Ostergaard K.
      • Krogh K.
      • Borghammer P.
      Objective colonic dysfunction is far more prevalent than subjective constipation in Parkinson's disease: a colon transit and volume study.
      ]. The underlying pathophysiologic mechanism is not well established but thought to be caused partly by denervation of the parasympathetic neurons that promote intestinal peristalsis. Indeed, the dorsal motor nucleus of the vagus shows early and severe involvement in the majority of patients with PD [
      • Braak H.
      • Del Tredici K.
      • Rub U.
      • de Vos R.A.
      • Jansen Steur E.N.
      • Braak E.
      Staging of brain pathology related to sporadic Parkinson's disease.
      ].
      Possible gallbladder dysfunction has received little attention in PD research. Gallbladder motility and emptying are coordinated by a complex interplay of hormonal, paracrine, and neuronal mechanisms. Cholecystokinin, secreted from the duodenal mucosa, and vagal parasympathetic neurons work in concert to stimulate bile secretion through gallbladder contraction and sphincter Oddi relaxation. Sympathetic neurons to the gallbladder arise from the celiac ganglia and inhibit gallbladder emptying. Direct excitation of efferent vagal neurons promotes gall bladder motility [
      • Furukawa N.
      • Okada H.
      Effects of stimulation of the dorsal motor nucleus of the vagus on the extrahepatic biliary system in dogs.
      ]. Conversely, vagotomy can compromise gallbladder contractility, which was suggested as cause for the high prevalence of gallstones following gastrectomy including bilateral, truncal vagotomy [
      • Sapala M.A.
      • Sapala J.A.
      • Soto A.D.
      • Bouwman D.L.
      Cholelithiasis following subtotal gastric resection with truncal vagotomy.
      ]. One study evaluated contractility and gallstone development after total vagotomy and found two distinct patterns; one group had unchanged contractility and a low incidence of gallstone (2%), whereas the other group had significantly impaired gallbladder contraction and a much higher incidence of gallstone formation (20%) [
      • Ihasz M.
      • Griffith C.A.
      Gallstones after vagotomy.
      ]. In support, incomplete gallbladder emptying was reported in patients with reoccurrence of gallstones [
      • Berr F.
      • Mayer M.
      • Sackmann M.F.
      • Sauerbruch T.
      • Holl J.
      • Paumgartner G.
      Pathogenic factors in early recurrence of cholesterol gallstones.
      ].
      Gallstone patients generally have larger fasting gallbladder volume (fGBV) than healthy controls (HCs) [
      • Pauletzki J.
      • Cicala M.
      • Holl J.
      • Sauerbruch T.
      • Schafmayer A.
      • Paumgartner G.
      Correlation between gall bladder fasting volume and postprandial emptying in patients with gall stones and healthy controls.
      ]. In patients with diabetes, enlarged fGBV was observed in patients with symptomatic autonomic neuropathy [
      • Gaur C.
      • Mathur A.
      • Agarwal A.
      • Verma K.
      • Jain R.
      • Swaroop A.
      Diabetic autonomic neuropathy causing gall bladder dysfunction.
      ]. Furthermore, patients with diabetes have increased risk of gallstones and exhibit both an increased gallbladder filling rate and a reduced emptying rate; a sign of hypotonicity [
      • Shreiner D.P.
      • Sarva R.P.
      • Van Thiel D.
      • Yingvorapant N.
      Gallbladder function in diabetic patients.
      ]. Thus, a relationship seems to exist between gallbladder dysmotility, increased fGBV, and gallstone formation, which may be provoked by autonomic denervation.
      In PD, gallbladder dysmotility has been assessed by cholescintigraphy [
      • Cabuk M.
      • Balkan Aksoy N.
      • Sen F.
      • Emre U.
      • Savas Den Hartigh O.
      • Yoruk Atik D.
      • Kokturk F.
      Evaluation of gallbladder function in patients with Parkinson's disease by using cholescintigraphy.
      ]. Furthermore, an ultrasonography case-control study found a higher age-adjusted prevalence of gallstones among 91 patients with PD compared with 80 controls [
      • Modaine P.
      • Levy S.
      • Masmoudi K.
      • Capron D.
      • Votte A.
      • Josse C.
      • Capron J.P.
      Parkinson's disease: a new risk factor for gallstone disease?.
      ]. Recently, higher levels of secondary bile acids were demonstrated in the gut of patients with PD [
      • Li P.
      • Killinger B.A.
      • Ensink E.
      • Beddows I.
      • Yilmaz A.
      • Lubben N.
      • Lamp J.
      • Schilthuis M.
      • Vega I.E.
      • Woltjer R.
      • Pospisilik J.A.
      • Brundin P.
      • Brundin L.
      • Graham S.F.
      • Labrie V.
      Gut microbiota dysbiosis is associated with elevated bile acids in Parkinson's disease.
      ]. This may be a contribution factor in gallstone formation [
      • Berr F.
      • Mayer M.
      • Sackmann M.F.
      • Sauerbruch T.
      • Holl J.
      • Paumgartner G.
      Pathogenic factors in early recurrence of cholesterol gallstones.
      ]. The possibility of increased fGBV has not yet been explored in a PD population.
      In the present study we tested the hypothesis that patients with early-to-moderate disease stage PD have larger fGBV and a higher prevalence of radiopaque gallstones than HCs. We also included subjects with isolated REM-sleep behavior disorder (iRBD); a prodromal subtype of synucleinopathy known to exhibit severe autonomic denervation to the same degree as patients with PD [
      • Knudsen K.
      • Fedorova T.D.
      • Hansen A.K.
      • Sommerauer M.
      • Otto M.
      • Svendsen K.B.
      • Nahimi A.
      • Stokholm M.G.
      • Pavese N.
      • Beier C.P.
      • Brooks D.J.
      • Borghammer P.
      In-vivo staging of pathology in REM sleep behaviour disorder: a multimodality imaging case-control study.
      ]. Finally, we recently published a study proposing that PD comprises two subtypes. One that originates in the autonomic nervous system with early, severe damage of sympathetic and parasympathetic neurons (body-first PD), and one originating in the brain where the autonomic nervous system is relatively intact early in the disease course (brain-first PD) [
      • Horsager J.
      • Andersen K.B.
      • Knudsen K.
      • Skjaerbaek C.
      • Fedorova T.D.
      • Okkels N.
      • Schaeffer E.
      • Bonkat S.K.
      • Geday J.
      • Otto M.
      • Sommerauer M.
      • Danielsen E.H.
      • Bech E.
      • Kraft J.
      • Munk O.L.
      • Hansen S.D.
      • Pavese N.
      • Goder R.
      • Brooks D.J.
      • Berg D.
      • Borghammer P.
      Brain-first versus body-first Parkinson's disease: a multimodal imaging case-control study.
      ]. The 13 body-first patients and 24 brain-first patients from that study were included in a subgroup analysis.

      2. Methods

      2.1 Study population

      We included 189 abdominal CT scans from three previous [
      • Knudsen K.
      • Fedorova T.D.
      • Bekker A.C.
      • Iversen P.
      • Ostergaard K.
      • Krogh K.
      • Borghammer P.
      Objective colonic dysfunction is far more prevalent than subjective constipation in Parkinson's disease: a colon transit and volume study.
      ,
      • Knudsen K.
      • Fedorova T.D.
      • Hansen A.K.
      • Sommerauer M.
      • Otto M.
      • Svendsen K.B.
      • Nahimi A.
      • Stokholm M.G.
      • Pavese N.
      • Beier C.P.
      • Brooks D.J.
      • Borghammer P.
      In-vivo staging of pathology in REM sleep behaviour disorder: a multimodality imaging case-control study.
      ,
      • Horsager J.
      • Andersen K.B.
      • Knudsen K.
      • Skjaerbaek C.
      • Fedorova T.D.
      • Okkels N.
      • Schaeffer E.
      • Bonkat S.K.
      • Geday J.
      • Otto M.
      • Sommerauer M.
      • Danielsen E.H.
      • Bech E.
      • Kraft J.
      • Munk O.L.
      • Hansen S.D.
      • Pavese N.
      • Goder R.
      • Brooks D.J.
      • Berg D.
      • Borghammer P.
      Brain-first versus body-first Parkinson's disease: a multimodal imaging case-control study.
      ] and two on-going studies of patients with PD, iRBD and HCs. Patients with PD were diagnosed in accordance with MDS diagnostic criteria. Diagnosis of iRBD was confirmed with video-polysomnography and in accordance with International Classification of Sleep Disorders [
      • Knudsen K.
      • Fedorova T.D.
      • Hansen A.K.
      • Sommerauer M.
      • Otto M.
      • Svendsen K.B.
      • Nahimi A.
      • Stokholm M.G.
      • Pavese N.
      • Beier C.P.
      • Brooks D.J.
      • Borghammer P.
      In-vivo staging of pathology in REM sleep behaviour disorder: a multimodality imaging case-control study.
      ]. All participants were aged 50–85. Exclusion criteria were: previous intestinal surgery, current or previous gastrointestinal cancer, heart- or kidney failure, inflammatory bowel disease, neuropathies and diabetes. All subjects conformed to an identical fasting regimen; at least 6 h for solids and 4 h for liquids. All participants provided written informed consent in accordance with the Declaration of Helsinki. The study was approved by the Science Ethical Committees of the Central Denmark Region.

      2.2 CT protocols

      Three CT protocols were used: 1) semi-diagnostic scans with contrast enhancement and 1 mm slice thickness (PD = 59, iRBD = 21, HC = 31), 2) low-dose CT scans with contrast enhancement and 2 mm slice thickness (PD = 14, HC = 10), and 3) low-dose CT scan without contrast enhancement and 2 mm slice thickness (PD = 27, HC = 27). Semi-diagnostic scans were performed on a Siemens Biograph PET/CT or Siemens Biograph vision PET/CT (Siemens Healthcare, Erlangen, Germany). Low-dose CT scans were performed on Siemens Symbia T16 SPECT/CT system (Siemens Healthcare, Erlangen, Germany).

      2.3 VOI definition

      Regions-of-interest (ROIs) outlining the entire gallbladder on adjacent slices were summed to determine fGBV (Fig. 1). ROI definition was performed blinded to clinical status. Gallbladder lumen was inspected for radiopaque gallstones. All CT analyses were performed in PMOD 3.6 (PMOD, Zürich, Switzerland).
      Fig. 1
      Fig. 1CT scan of the abdomen. The green ROI outlines the gallbladder wall. Black arrow marks two gallstones. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

      2.4 Other measurements

      Radiopaque marker (ROM) and colon volume data from our previously published studies [
      • Knudsen K.
      • Fedorova T.D.
      • Bekker A.C.
      • Iversen P.
      • Ostergaard K.
      • Krogh K.
      • Borghammer P.
      Objective colonic dysfunction is far more prevalent than subjective constipation in Parkinson's disease: a colon transit and volume study.
      ,
      • Knudsen K.
      • Fedorova T.D.
      • Hansen A.K.
      • Sommerauer M.
      • Otto M.
      • Svendsen K.B.
      • Nahimi A.
      • Stokholm M.G.
      • Pavese N.
      • Beier C.P.
      • Brooks D.J.
      • Borghammer P.
      In-vivo staging of pathology in REM sleep behaviour disorder: a multimodality imaging case-control study.
      ,
      • Horsager J.
      • Andersen K.B.
      • Knudsen K.
      • Skjaerbaek C.
      • Fedorova T.D.
      • Okkels N.
      • Schaeffer E.
      • Bonkat S.K.
      • Geday J.
      • Otto M.
      • Sommerauer M.
      • Danielsen E.H.
      • Bech E.
      • Kraft J.
      • Munk O.L.
      • Hansen S.D.
      • Pavese N.
      • Goder R.
      • Brooks D.J.
      • Berg D.
      • Borghammer P.
      Brain-first versus body-first Parkinson's disease: a multimodal imaging case-control study.
      ] were used for comparison in the present study. In short, ROMs are ingested every morning for six days prior to CT scan, and the retained number of ROM estimates the colonic transit time. Colon volume was defined by outlining the entire colon on the CT scan, as previously explained [
      • Knudsen K.
      • Fedorova T.D.
      • Bekker A.C.
      • Iversen P.
      • Ostergaard K.
      • Krogh K.
      • Borghammer P.
      Objective colonic dysfunction is far more prevalent than subjective constipation in Parkinson's disease: a colon transit and volume study.
      ]. Body Mass Index (BMI) was calculated as (weight [kg]/(height [m])2) and body surface area (BSA) as (0.007184 x ((weight [kg])0.425 x (height [cm])0.725). Non-motor symptoms were assessed using SCOPA-AUT and NMSS. Gastrointestinal symptoms isolated were also assessed using ROME III constipation and nausea questionnaires. ROME III constipation questionnaire was available from all participants and some participants were interviewed with ROME III nausea questionnaire (HC = 39, PD = 72, iRBD 21), SCOPA-AUT (HC = 43, PD = 71, iRBD 21) and NMSS (HC = 15, PD = 41, iRBD = 21).

      2.5 Statistical analyses

      Statistical analyses were performed with GraphPad Prism 7.0 and Stata 13.1. Cholecystectomized participants were not included in fGBV analyses. Normality in distribution was assessed with Shapiro-Wilk tests. Group differences of categorical variables were investigated using Chi-squared tests. Group differences of continuous variables were tested with ANOVA or Kruskal-Wallis, as appropriate. Dunn's multiple comparison test was performed as post-tests in significant Kruskal-Wallis analyses and the adjusted P-values are presented. Subgroup analyses stratified by sex, presence of gallstones, and levodopa treatment were performed using t-tests or Mann-Whitney U tests, as appropriate. Spearman's rank correlation coefficients were calculated to explore correlations between fGBV and other variables (as fGBV data were not normally distributed). We built a multiple linear regression model with log-transformed fGBV data to explore possible confounders (sex, age, and BMI). P-values <0.05 were considered significant.

      3. Results

      3.1 Demographics and clinical information

      Demographic and clinical information is presented in Table 1. In the PD group, 65/100 received medication; 49 received levodopa and the remaining 16 received pramipexole (n = 7), pramipexole + rasagiline (n = 2), pramipexole + selegiline (n = 4), ropinirole (n = 1), ropinirole + rasagiline (n = 1), or ropinirole + selegiline (n = 1). There were no group differences in sex, age, BMI, or BSA. The total prevalence of radiopaque gallstones was 12/189 (6.3%). Furthermore, 8/189 (4.2%) were cholecystectomized. No group differences in frequency of gallstones or cholecystectomy were seen.
      Table 1Demographic and clinical information.
      HCPDiRBDP-value
      Sample size, n6810021
      Sex (male/female)42/2672/2817/40.17
      Age mean (SD)68.5 (7.5)66.7 (7.9)68.8 (8.7)0.26
      Disease duration [months] median (IQR)21.5 (4.8–63.5)
      UPDRS III median (IQR)21 (15–26)1 (0–2)<0.0001
      Hoehn and yahr stage I/II/III16/72/10
      LEDD [mg] median (IQR)600 (300–828)
      Gallstone (yes/no)4/647/931/200.91
      Cholecystectomy (yes/no)4/643/971/200.66
      BSA [m2] mean (SD)1.91 (0.2)1.96 (0.21)1.97 (0.16)0.30
      BMI [kg/m2]mean (SD)25.8 (3.5)25.8 (3.8)26.1 (3.6)0.94
      fGBV [ml] median (IQR)27.8 (21–39)35.7 (24–50)31.8 (27–40)0.0055
      Post-tests of fGBVHC vs PDPD vs iRBDiRBD vs HC
      Adjusted P-value0.00380.990.6
      BSA = body surface area, BMI = Body Mass Index, fGBV = fasting gallbladder volume, LEDD = Levodopa equivalent daily dose.
      We found a significant difference in fGBV between the three groups (P = 0.0055) (Fig. 2). Dunn's multiple comparison test revealed a significant difference in fGBV between patients with PD and HCs (adjusted P = 0.0038). The median fGBV was 7.9 ml (28.4%) larger in patients with PD than in HCs. No difference in fGBV was observed between PD and iRBD or between iRBD and HC. Using a cut-off score, defined as mean + 2 x SD of the HC group (53.82 ml), we found that 22/97 (23%) patients with PD had enlarged fGBV. This was only observed in 2/64 (3.1%) HCs and 1/21 (4.8%) iRBDs. Of the 22 PD patients with enlarged fGBV, 5 had gallstones. In the HC group, we found a significantly higher mean fGBV in male subjects (32.7 ml) than in female subjects (25.6 ml) (P = 0.02). This sex-dependent difference was not observed in the PD or iRBD group. In the PD group, patients with gallstones had significantly larger median fGBV (71.2 ml) than patients without gallstones (34.7 ml) (P = 0.0009). The same trend was observed in the HC group (38.8 ml vs 27.2 ml) and the iRBD group (40.1 ml vs 30.5 ml), but these trends were not statistically significant. There was a non-significant trend towards larger fGBV in the untreated patients with PD (median 44.9 ml) than in treated patients (median 32.8 ml) (P = 0.07). Body-first PD patients (with severe autonomic denervation) had larger median fGBV than brain-first PD patients (with a relatively intact autonomic nervous system), 54.9 ml vs 35.7 ml, but the difference fell just short of statistical significance (P = 0.054).
      Fig. 2
      Fig. 2A: The fasting gallbladder volume (fGBV) for healthy controls (HC, white circles), patients with Parkinson's disease (PD, black circles), and subjects with isolated REM-sleep behavior disorder (iRBD, grey circles). The medians and interquartile ranges are depicted with black lines. Dashed, horizontal line denotes the threshold for increased fGBV B: Patients with PD assigned to a brain-first subtype and a body-first subtype (see text for details). The “outlier” in the brain-first group had two gallstones.

      3.2 Correlations and adjustments

      In the total study population, fGBV was correlated with BMI (r = 0.34, P < 0.0001), BSA (r = 0.35, P < 0.0001), and height (r = 0.22, P = 0.0025). Colon volume data was available from 120 participants (PD = 73, iRBD = 21, HC = 26). A positive correlation was seen between colon volume and fGBV (r = 0.31, P = 0.0009). The correlation was also present in the PD group alone (r = 0.28, P = 0.02) (Fig. 3). The fGBV was not correlated with age, ROM (i.e. estimate of colonic transit time), disease duration in PD patients, or LEDD in treated PD patients. No correlation was found between fGBV and non-motor symptoms (SCOPA-AUT and NMSS, P > 0.6) or gastrointestinal symptoms separately (ROME III constipation, ROME III constipation question 9–15, ROME III nausea and NMSS gastrointestinal section, P > 0.3).
      Fig. 3
      Fig. 3Correlation between fGBV and colon volume in 73 patients with PD. Presented with linear regression line for visual purpose only. Spearman's rank correlation coefficient r = 0.28, P = 0.02.
      To explore potential influence of confounders on the between-group differences, multiple linear regression analyses were performed on log-transformed fGBV data. The difference between the PD and HC groups remained significant after sex-, age-, and BMI-adjustment (P < 0.004 for all three analyses).

      4. Discussion

      In the present study, we found that 23% of our PD cohort had increased fGBV, and the median fGBV in patients with PD was significantly larger than in HCs. It is worth noting that Fig. 2 suggests a bimodal distribution in the PD group, with most subjects having similar fGBV to that seen the HC group, but then a sizeable fraction of PD patients, whose gallbladders were clearly enlarged. Previous studies have shown that most patients with PD exhibit parasympathetic denervation in the gastrointestinal tract [
      • Horsager J.
      • Andersen K.B.
      • Knudsen K.
      • Skjaerbaek C.
      • Fedorova T.D.
      • Okkels N.
      • Schaeffer E.
      • Bonkat S.K.
      • Geday J.
      • Otto M.
      • Sommerauer M.
      • Danielsen E.H.
      • Bech E.
      • Kraft J.
      • Munk O.L.
      • Hansen S.D.
      • Pavese N.
      • Goder R.
      • Brooks D.J.
      • Berg D.
      • Borghammer P.
      Brain-first versus body-first Parkinson's disease: a multimodal imaging case-control study.
      ,
      • Fedorova T.D.
      • Seidelin L.B.
      • Knudsen K.
      • Schacht A.C.
      • Geday J.
      • Pavese N.
      • Brooks D.J.
      • Borghammer P.
      Decreased intestinal acetylcholinesterase in early Parkinson disease: an (11)C-donepezil PET study.
      ] and increased colon volume [
      • Knudsen K.
      • Fedorova T.D.
      • Bekker A.C.
      • Iversen P.
      • Ostergaard K.
      • Krogh K.
      • Borghammer P.
      Objective colonic dysfunction is far more prevalent than subjective constipation in Parkinson's disease: a colon transit and volume study.
      ]. Thus, we hypothesized that fGBV would be larger in the PD group. However, total elimination of parasympathetic innervation (vagotomy) only compromises gallbladder contractility in 50% of patients [
      • Ihasz M.
      • Griffith C.A.
      Gallstones after vagotomy.
      ]. Therefore, we did expect that some patients in the present study would have normal fGBV. One study even demonstrated no effect on gallbladder contractility after vagotomy [
      • Sandhya B.
      • Kate V.
      • Ananthakrishnan N.
      • Bhuvaneshwari V.
      • Koner B.C.
      Effect on gallbladder function subsequent to truncal vagotomy and gastrojejunostomy for chronic duodenal ulcer.
      ]. Furthermore, in liver-transplant recipients, fGBV did not increase, although both parasympathetic and sympathetic innervation are lost in the transplantation procedure [
      • Vezina W.C.
      • McAlister V.C.
      • Wall W.J.
      • Engel C.J.
      • Grant D.R.
      • Ghent C.N.
      • Hutton L.C.
      • King M.E.
      • Chey W.Y.
      Normal fasting volume and postprandial emptying of the denervated donor gallbladder in liver transplant recipients.
      ]. This could indicate that gallbladder dilation following vagotomy is caused by unopposed sympathetic relaxation of the gallbladder [
      • Vezina W.C.
      • McAlister V.C.
      • Wall W.J.
      • Engel C.J.
      • Grant D.R.
      • Ghent C.N.
      • Hutton L.C.
      • King M.E.
      • Chey W.Y.
      Normal fasting volume and postprandial emptying of the denervated donor gallbladder in liver transplant recipients.
      ]. This would suggest that parasympathetic denervation needs to be more severe than sympathetic denervation to cause gallbladder dilation. However, in PD both the sympathetic and parasympathetic systems undergo marked degeneration, and it is unclear whether one system shows earlier or more prominent involvement than the other.
      Another possible explanation of increased fGBV is sphincter Oddi dysfunction that theoretically could obstruct bile secretion leading to increased gallbladder filling. Truncal vagotomy eliminates physiological postprandial actions of the sphincter Oddi, i.e. increased amplitudes and decreased frequency of phasic waves [
      • Tanaka M.
      Function and dysfunction of the sphincter of Oddi.
      ]. However, one study of eleven patients with PD found sphincter Oddi basal pressure and contraction frequency within the normal range [
      • Hagenmuller F.
      • Classen M.
      Motility of Oddi's sphincter in Parkinson's disease, progressive systemic sclerosis, and achalasia.
      ]. Hormonal alterations in PD could also affect gallbladder function. Reduced pre- and postprandial plasma ghrelin levels have been documented in patients with PD [
      • Pietraszko W.
      • Furgala A.
      • Gorecka-Mazur A.
      • Kwinta B.
      • Kaszuba-Zwoinska J.
      • Polak J.
      • Fiszer U.
      • Gil K.
      • Krygowska-Wajs A.
      Assessments of plasma acyl-ghrelin levels in Parkinson's disease patients treated with deep brain stimulation.
      ,
      • Song N.
      • Wang W.
      • Jia F.
      • Du X.
      • Xie A.
      • He Q.
      • Shen X.
      • Zhang J.
      • Rogers J.T.
      • Xie J.
      • Jiang H.
      Assessments of plasma ghrelin levels in the early stages of Parkinson's disease.
      ], and low ghrelin levels are associated with gallstone disease [
      • Mendez-Sanchez N.
      • Ponciano-Rodriguez G.
      • Bermejo-Martinez L.
      • Villa A.R.
      • Chavez-Tapia N.C.
      • Zamora-Valdes D.
      • Pichardo-Bahena R.
      • Barredo-Prieto B.
      • Uribe-Ramos M.H.
      • Ramos M.H.
      • Baptista-Gonzalez H.A.
      • Uribe M.
      Low serum levels of ghrelin are associated with gallstone disease.
      ]. However, iRBD patients also exhibit low ghrelin levels [
      • Unger M.M.
      • Moller J.C.
      • Mankel K.
      • Eggert K.M.
      • Bohne K.
      • Bodden M.
      • Stiasny-Kolster K.
      • Kann P.H.
      • Mayer G.
      • Tebbe J.J.
      • Oertel W.H.
      Postprandial ghrelin response is reduced in patients with Parkinson's disease and idiopathic REM sleep behaviour disorder: a peripheral biomarker for early Parkinson's disease?.
      ], and we did not observe increased fGBV in this group. This argues against reduced ghrelin as cause for the observations in the present study.
      In the present study, we found a significant correlation between fGBV and colon volume. The average colon volume of iRBDs is increased compared to control subjects but not to the level of PD patients [
      • Horsager J.
      • Andersen K.B.
      • Knudsen K.
      • Skjaerbaek C.
      • Fedorova T.D.
      • Okkels N.
      • Schaeffer E.
      • Bonkat S.K.
      • Geday J.
      • Otto M.
      • Sommerauer M.
      • Danielsen E.H.
      • Bech E.
      • Kraft J.
      • Munk O.L.
      • Hansen S.D.
      • Pavese N.
      • Goder R.
      • Brooks D.J.
      • Berg D.
      • Borghammer P.
      Brain-first versus body-first Parkinson's disease: a multimodal imaging case-control study.
      ]. We observed the same pattern with fGBV in this study. However, no difference in colon volume was observed between patients with brain-first PD (with relatively intact autonomic nervous system) and iRBDs [
      • Horsager J.
      • Andersen K.B.
      • Knudsen K.
      • Skjaerbaek C.
      • Fedorova T.D.
      • Okkels N.
      • Schaeffer E.
      • Bonkat S.K.
      • Geday J.
      • Otto M.
      • Sommerauer M.
      • Danielsen E.H.
      • Bech E.
      • Kraft J.
      • Munk O.L.
      • Hansen S.D.
      • Pavese N.
      • Goder R.
      • Brooks D.J.
      • Berg D.
      • Borghammer P.
      Brain-first versus body-first Parkinson's disease: a multimodal imaging case-control study.
      ]. Furthermore, patients with body-first PD (with the most severe autonomic denervation) have a significantly larger colon volume than patients with brain-first PD and iRBDs. This could indicate the presence of a synergistic effect of dopaminergic and autonomic denervation on the colon volume and thus also on the fGBV. In support, unilateral lesioning of the substantia nigra in rats also leads to gastrointestinal dysfunction [
      • Zhu H.C.
      • Zhao J.
      • Luo C.Y.
      • Li Q.Q.
      Gastrointestinal dysfunction in a Parkinson's disease rat model and the changes of dopaminergic, nitric oxidergic, and cholinergic neurotransmitters in myenteric plexus.
      ].
      Dividing the PD group according to the presence or absence of gallstones, we found that patients with gallstones had a significantly higher fGBV than patients without gallstones. This effect was similar in the HC and iRBD group, although not to the same extent. Generally, gallstone patients have a higher fGBV than HCs [
      • Pauletzki J.
      • Cicala M.
      • Holl J.
      • Sauerbruch T.
      • Schafmayer A.
      • Paumgartner G.
      Correlation between gall bladder fasting volume and postprandial emptying in patients with gall stones and healthy controls.
      ]. This effect may harbor an inflammatory component as gallstone patients with cholecystitis exhibit incremental fGBV with more severe inflammation [
      • Huang S.M.
      • Yao C.C.
      • Pan H.
      • Hsiao K.M.
      • Yu J.K.
      • Lai T.J.
      • Huang S.D.
      Pathophysiological significance of gallbladder volume changes in gallstone diseases.
      ]. Peripheral levels of proinflammatory cytokines are higher in patients with PD than controls [
      • Qin X.Y.
      • Zhang S.P.
      • Cao C.
      • Loh Y.P.
      • Cheng Y.
      Aberrations in peripheral inflammatory cytokine levels in Parkinson disease: a systematic review and meta-analysis.
      ]. When gallstones evolve and subsequently are expelled in a patient with PD, an inflammatory response might be exacerbated, contributing to gallbladder dilation. Indeed, inflammation disturbs gallbladder wall function, generating an increased risk of gallstones, and the presence of gallstones increases gallbladder inflammation, creating a vicious cycle [
      • Rege R.V.
      Inflammatory cytokines alter human gallbladder epithelial cell absorption/secretion.
      ]. Interestingly, in the PD group we observed that 5/22 (23%) with enlarged fGBV had gallstones, whereas only 2/75 (3%) with fGBV in the normal range had gallstones. Furthermore, we might have underdiagnosed a substantial fraction of gallstones because ultrasound of the gallbladder was not available (see below).
      Medication effects could also be a potential explanation for increased gallbladder volume in patients with PD. However, we found no correlation between LEDD and fGBV. On the contrary, untreated patients had a larger median fGBV than treated patients, although this difference was not significant.
      In our HC group, the fGBV (27.8 ml) was in close agreement with one previous report of subjects aged >50 years [
      • Caroli-Bosc F.X.
      • Pugliese P.
      • Peten E.P.
      • Demarquay J.F.
      • Montet J.C.
      • Hastier P.
      • Staccini P.
      • Delmont J.P.
      Gallbladder volume in adults and its relationship to age, sex, body mass index, body surface area and gallstones.
      ]. Other studies have reported a smaller fGBV in healthy, younger subjects [
      • Pauletzki J.
      • Cicala M.
      • Holl J.
      • Sauerbruch T.
      • Schafmayer A.
      • Paumgartner G.
      Correlation between gall bladder fasting volume and postprandial emptying in patients with gall stones and healthy controls.
      ,
      • Huang S.M.
      • Yao C.C.
      • Pan H.
      • Hsiao K.M.
      • Yu J.K.
      • Lai T.J.
      • Huang S.D.
      Pathophysiological significance of gallbladder volume changes in gallstone diseases.
      ]. This could be explained by the younger population, as fGBV may be positively correlated with age [
      • Caroli-Bosc F.X.
      • Pugliese P.
      • Peten E.P.
      • Demarquay J.F.
      • Montet J.C.
      • Hastier P.
      • Staccini P.
      • Delmont J.P.
      Gallbladder volume in adults and its relationship to age, sex, body mass index, body surface area and gallstones.
      ]. Although fGBV was not correlated with age in the present study, it may be due to the small age range as only older subjects were studied here. The fGBV was correlated with BMI and BSA, which is in accordance with a previous study [
      • Caroli-Bosc F.X.
      • Pugliese P.
      • Peten E.P.
      • Demarquay J.F.
      • Montet J.C.
      • Hastier P.
      • Staccini P.
      • Delmont J.P.
      Gallbladder volume in adults and its relationship to age, sex, body mass index, body surface area and gallstones.
      ].
      We detected no difference in gallstone frequency between the groups. The total prevalence of gallstones in this study was only 6.3%. In a Danish population study on 3608 participants, with presumably similar dietary habits, the prevalence in subjects aged 60 was approximately twice as high [
      • Jorgensen T.
      Prevalence of gallstones in a Danish population.
      ]. However, 4.2% in our study were cholecystectomized, presumably due to gallstone disease, which may partly explain the low prevalence. Furthermore, CT scans have only a 39–75% sensitivity of detecting gallstones compared with ultrasound, since a fraction of gallstones are not radiopaque and therefore invisible on CT [
      • Benarroch-Gampel J.
      • Boyd C.A.
      • Sheffield K.M.
      • Townsend Jr., C.M.
      • Riall T.S.
      Overuse of CT in patients with complicated gallstone disease.
      ].
      This study has several limitations. The size of the iRBD group was small as mentioned above. Furthermore, all CT scans were performed in studies with different purposes than to estimate fGBV. Due to radiation exposure, it may not be advisable to perform abdominal CT scans in studies of the gallbladder. Ultrasound offers an alternative radiation-free examination of gallbladder volume and also has a higher sensitivity for detecting gallstones. This study is the first to use CT scans to estimate gallbladder volume. CT scans were performed using three different protocols. However, the gallbladder wall was easily discerned on all scans, and the difference in slice thickness could not have introduced a significant bias as 2 mm slice thickness is sufficient to get a precise fGBV estimate. A CT scan provides a clear, fixed image of the entire gallbladder as the Hounsfield units differs from the surrounding liver tissue (Fig. 1). Further, the volume definition is not influenced by geometrical distortions of the gallbladder. The sum-of-cylinder method is commonly used in ultrasound studies of the gallbladder, where gallbladder volume is calculated based on several cylinders along the longitudinal axis, sometimes including a correction factor if the gallbladder is curved [
      • Everson G.T.
      • Braverman D.Z.
      • Johnson M.L.
      • Kern Jr., F.
      A critical evaluation of real-time ultrasonography for the study of gallbladder volume and contraction.
      ]. Therefore, we argue that a CT scan provides a more precise fGBV estimate compared to the sum-of-cylinder method. In support, two studies of urinary bladder volume used CT scan as reference to evaluate accuracy of their ultrasound-derived estimates [
      • Mullaney L.
      • O'Shea E.
      • Dunne M.T.
      • Thirion P.G.
      • Armstrong J.G.
      A comparison of bladder volumes based on treatment planning CT and BladderScan(R) BVI 6100 ultrasound device in a prostate radiation therapy population.
      ,
      • Yoon H.I.
      • Chung Y.
      • Chang J.S.
      • Lee J.Y.
      • Park S.J.
      • Koom W.S.
      Evaluating variations of bladder volume using an ultrasound scanner in rectal cancer patients during chemoradiation: is protocol-based full bladder maintenance using a bladder scanner useful to maintain the bladder volume?.
      ]. All patients fasted for at least 6 h for solids and 4 h for liquids, but the exact fasting time was not registered. It is possible that fasting for, e.g., 12 h would dilate the gallbladder more. However, we have no reason to believe that there was an uneven distribution in the exact fasting time between the three groups. History of biliary pain was not assessed in the present study. It is possible that patients with enlarged fGBV were more likely to experience recurrent biliary pain; either due to gallstone disease or functional gallbladder dysfunction. The latter is defined as typical biliary pain in the upper right corner of the abdomen in the absence of gallstones or other structural abnormalities [
      • Cotton P.B.
      • Elta G.H.
      • Carter C.R.
      • Pasricha P.J.
      • Corazziari E.S.
      Rome IV. Gallbladder and Sphincter of Oddi Disorders.
      ]. Indeed, supportive diagnostic criteria for functional gallbladder dysfunction include decreased ejection fraction on cholescintigraphy as reported in one study of patients with PD [
      • Cabuk M.
      • Balkan Aksoy N.
      • Sen F.
      • Emre U.
      • Savas Den Hartigh O.
      • Yoruk Atik D.
      • Kokturk F.
      Evaluation of gallbladder function in patients with Parkinson's disease by using cholescintigraphy.
      ].
      Finally, post-prandial fGBV measures would have allowed for estimates of gallbladder contractility, but they were not performed in the present study. One MRI study of gastric motility found that the most significant difference between patients with PD and HCs was in the post-prandial state, i.e. when digestive demands are high [
      • Cho J.
      • Lee Y.J.
      • Kim Y.H.
      • Shin C.M.
      • Kim J.M.
      • Chang W.
      • Park J.H.
      Quantitative MRI evaluation of gastric motility in patients with Parkinson's disease: correlation of dyspeptic symptoms with volumetry and motility indices.
      ]. Thus, future gallbladder studies of patients with PD should include post-prandial gallbladder volume to get an estimate of contractility under high digestive demands.
      We conclude that fGBV is significantly larger in patients with PD than HCs. This difference was driven mainly by a quarter of our PD cohort who exhibited enlarged fGBV, whereas the remaining three quarters were closer to normal. Subjects with iRBD did not show increased fGBV. A mechanistic cause of gallbladder dilation in PD may be a synergistic effect of dopaminergic and autonomic denervation.

      Funding source

      The study was supported by the Lundbeck Foundation [grant number: R190-2014-4183 ]. The funding source had no role in any part of the study.

      Declaration of competing interest

      None.

      Acknowledgements

      None.

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