Ursodeoxycholic acid treatment of LPAC presenting as post cholecystectomy pain: rationale and design of a randomised trial

Introduction

Gallstone disease is common. The prevalence of gallstones in Western countries is approximately 20%, and about a fifth of these patients become symptomatic (1-3), Cholecystectomy is the standard management for symptomatic gallstones (4-6). However, post cholecystectomy pain occurs in up to 33% of operations (7). Investigation and management of recurrent biliary pain with normal imaging can be challenging.

Low phospholipid associated cholelithiasis (LPAC) is a recently described syndrome that is an under-recognized and under-diagnosed cause of post cholecystectomy biliary pain (8). The prevalence of LPAC is not well defined but has been estimated to be about 1% of patients presenting for cholecystectomy (9).

LPAC is characterised by the reduced secretion of phosphatidylcholine into bile and is often associated with loss of function variants of the adenosine triphosphate binding cassette, subfamily B, member 4 (ABCB4) gene.

ABCB4 is a phospholipid translocator located on the biliary canalicular membrane of the hepatocytes and transports phosphatidylcholine into bile. Phospholipids associate with simple bile salt micelles to form mixed micelles containing both phospholipids and bile salts. This association strongly reduces the concentration of toxic bile salt monomers and simple micelles, protecting the hepatocyte membrane from dissolution (10,11). Variants of the gene encoding ABCB4 may impair transport of phosphatidylcholine reducing the concentration of phospholipids in bile. The unrestrained toxicity of bile acids leads to inflammation of hepatocytes and cholestatic liver disease. The formation of mixed micelles also increases the solubility of cholesterol in bile. Impaired phospholipid transport increases cholesterol saturation supporting the formation of cholesterol crystals and stones (12).

ABCB4 variants are associated with a broad overlapping spectrum of phenotypes of liver diseases related to the degree of impairment of phospholipid transport. These range from transient neonatal cholestasis, contraceptive induced cholestasis, intrahepatic cholestasis of pregnancy (ICP), LPAC, adult cholestatic liver disease and cirrhosis, and progressive familial intrahepatic cholestasis type 3 (PFIC type 3) (13). LPAC is usually associated with heterozygous ABCB4 genetic variants with mild to moderate severity on the clinical spectrum.

In 2001 Rosmorduc et al. investigated six patients with atypical intrahepatic stones and found low biliary phospholipid concentrations and variants of the gene encoding for ABCB4 (14). The clinical syndrome of LPAC was defined in a subsequent case control study as the presence of at least two of the following clinical criteria (15):

• Biliary symptoms before the age of 40 years.
• Recurrence of symptoms after cholecystectomy.
• Detection of intrahepatic intrahepatic stones or echogenic foci.

This is a very broad definition and includes all patients with post cholecystectomy pain under the age of 40 years. At the time these criteria were recognised as sensitive but not specific. Diagnostic certainty increases if typical imaging findings are seen on ultrasound or if genotyping identifies a known variant. Known variants are only identified in approximately 50% of cases of LPAC (9,15-18).

As more cases of LPAC have been reported, the diagnostic criteria have evolved. Additions that expand the initial diagnostic criteria include a family history of cholecystectomy before 40 years of age, and a personal or family history of other phenotypes of ABCB4 gene variants. ICP was reported in 42% of women with LPAC and a history of pregnancy (9).

More information has also been published about the spectrum of clinical features in LPAC. Compared with initial descriptions macroscopic intrahepatic stones are less frequent, 43%, and a subgroup of 10–15% of patients present with large uni or multifocal spindle-shaped dilations of the intrahepatic ducts filled with cholesterol and soft pigment stones. A small number of LPAC patients present with established chronic cholestatic liver disease and are at risk of progression to cirrhosis and end stage liver failure.

A subgroup with clinically milder LPAC has been more frequently recognized. These patients present with post cholecystectomy biliary pain with normal imaging or minimal changes on ultrasound. The episodes of biliary pain are often associated with transiently abnormal liver function tests (LFTs). Participants in the trial will be selected from this subgroup.

Ursodeoxycholic acid (UDCA; 3α,7β-dihydroxy-5β-cholanoate), a native hydrophilic bile acid forming about 3% of the bile acid pool, was first used to dissolve cholesterol gallstones (19). UDCA has also been used to treat cholestatic liver diseases initially based on the hypothesis that treatment replaces endogenous cytotoxic bile salts with UDCA which is a much less toxic bile salt (20,21). Several other mechanisms of action have been described more recently. UDCA stimulates the secretion of bile acids and phospholipids by upregulating the expression of the apical membrane transporters like ABCB11 and ABCB4 on the hepatocytes (22). The increase in phospholipid concentration in bile facilitates the solubilisation of cholesterol in bile and eventually the dissolution of cholesterol crystals and stones (23,24). UDCA also boosts the innate immune system within the biliary tree which suppresses biliary inflammatory and prevents phospholipid degradation (25). UDCA inhibits bile acid induced apoptosis by stabilizing the mitochondrial and hepatocyte membrane, increasing the hepatocyte defenses against oxidative stress (26).

Animal studies support the role of UDCA in treatment of LPAC. In Abcb4 knockout mice, UDCA treatment reduces liver damage and intrahepatic stone formation (27).

UDCA has been used to successfully treat other phenotypes of ABCB4 gene variants including PFIC3, ICP and drug induced liver disease (28). PFIC3 is associated homozygous or compound heterozygous ABCB4 gene variants and severe reductions in phospholipid levels in bile. Symptoms occur in the first year of life, cirrhosis in childhood and about 50% require liver transplantation. Treatment with UDCA 20–30 mg/kg/day improves liver function and delays progression in some patients (29).

The European Association for the Study of the Liver (EASL) advises UDCA treatment for LPAC but qualifies this advice with the recommendation that a randomized trial should be performed (6). UDCA treatment of more severe LPAC is well established. Case series report dissolution of intrahepatic stones and improvement in dilated intrahepatic ducts and chronic liver disease. Episodes of biliary pain are also reported to improve, however pain is a more subjective outcome. The placebo response of a sham sphincterotomy in the EPISOD trial was 47%. The placebo response in earlier trials of UDCA in post cholecystectomy pain was between 30 % and 52% (30,31). A randomized trial is the most reliable method to assess the efficacy of UDCA treatment of LPAC in patients presenting with episodes of post cholecystectomy biliary pain.

The Ursodeoxycholic acid in LPAC Treating Recurrent Abdominal (ULTRA) pain trial aims to determine whether UDCA reduces episodes of biliary pain and improves quality of life, in post cholecystectomy patients with LPAC and minimal or no abnormalities on imaging. The primary endpoint is the number of episodes of biliary pain. Quality of life, as measured by validated questionnaires, is a secondary endpoint. We present the protocol in accordance with the SPIRIT reporting checklist (available at https://tgh.amegroups.com/article/view/10.21037/tgh-24-127/rc) (32).

Methods

Study design

ULTRA Pain study is an investigator-initiated, double-blind randomised, placebo-controlled, Phase 3 crossover trial assessing the efficacy of UDCA treatment of post cholecystectomy pain in patients with LPAC. Patients presenting with difficult to manage episodes of biliary pain and diagnosed with LPAC, meeting other eligibility criteria, will be invited to participate in the trial. After informed consent, participants will be randomly assigned to receive UDCA 10 mg/kg/day for 1 year followed by a matched placebo for 1 year, separated by a washout period of 2 weeks, or vice versa. The study will be conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study protocol was granted ethical approval from Melbourne Health Human Research and Ethics Committee HREC (No. HREC/55994/MH-2019). This trial is registered with the Australian New Zealand Clinical Trials Registry (ANZCTR) (ACTRN12621000450819). Figure 1 depicts a flow diagram of the study design.

Figure 1 Study flow diagram. LPAC, low phospholipid associated cholelithiasis.

Study setting and participants

Adult participants will be recruited from a specialised gastroenterology outpatient clinic at the Royal Melbourne Hospital and from referrals from other hospitals. Eligible patients will be initially seen and screened by a gastroenterologist involved in the research project, to discuss their potential involvement in the trial and be provided with a participant information. Informed consent will then be obtained by a medically qualified site investigator trained in Good Clinical Practice.

Inclusion criteria

The study population is patients presenting with post cholecystectomy pain diagnosed with mild LPAC. Those with intrahepatic macroscopic stones or dilated intrahepatic bile ducts or chronic liver disease will be excluded. Entry criteria are as follows:

• Patients aged ≥18 years with a cholecystectomy, performed more than 6 months ago, presenting with 2 or more episodes of biliary pain in the last 12 months:
  • Typical biliary pain is defined by the Rome IV criteria (33). These specify biliary pain is located in the epigastrium and/or right upper quadrant and is experienced at least 2–3 days per month. However it is our experience that LPAC patients will not experience biliary pain this frequently hence the criteria has been modified to allow less frequent episodes (2 or more episodes per year).
• Two or more of the following criteria that are characteristic of LPAC:
  • Age less than 40 years at onset of symptoms.
  • Imaging features consistent with LPAC identified on a targeted liver ultrasound performed by an experienced hepatobiliary subspecialist radiologist: intrahepatic echogenic foci in a position consistent with biliary tree, intrahepatic microlithiasis or sludge.
  • Family history of cholecystectomy before 40 years of age, family history of other ABCB4 gene variant phenotypes including ICP, or a personal history of ICP.
  • Evidence of transiently abnormal LFTs corresponding with episodes of biliary pain.
• Access to a telephone.
• Must be able to speak, read, and write English.
• Signed and dated informed consent.

Exclusion criteria

• Stone in the common bile duct on imaging.
• Intrahepatic macroscopic stones, dilated intrahepatic bile ducts, and cholestatic liver disease.
• Known history of primary sclerosing cholangitis, primary biliary cholangitis, colitis, Crohn’s disease, cystic fibrosis, chronic liver disease.
• Presence of a significant psychiatric disorder.
• Pregnancy: women who are pregnant or are planning a pregnancy within 2 years at the time of screening.
• Any functional bowel disorders.
• Any use of regular narcotics.
• Inability to comply with study procedures and agents.
• Any significant medical illness that would interfere with study participation.
• Any condition that, in the investigator’s opinion, makes the subject unsuitable for study participation.
• Recent treatment with UDCA.

Randomisation

Patients will be randomised by a predetermined schedule (in 4 blocks of 6) created prior to study commencement by the trial statistician. There will be no stratification. The sequence of treatment allocations will be concealed to staff undertaking the randomisation. Randomisation will be associated with a bottle number for each participant that links to the corresponding allocated study dose (blinded), in accordance with randomisation. All prescriptions will be dispensed from a clinical trials pharmacy.

Blinding

Both the participants and clinicians will be blinded to treatment, matching placebos will be used in the control arm. The treating physician will be aware of dose level of the study medication but not the treatment itself.

Emergency unblinding will only be performed if it is necessary to ensure the safety of the participant. Situations that may warrant unblinding include pregnancy and a serious adverse drug reaction.

Intervention and monitoring

Participants will be randomised to UDCA or placebo with a crossover at 1 year and change over period of 2 weeks between the cross over. The dose of trial medication 10 mg/kg daily may be titrated upwards for persisting episodes of biliary pain to a maximum of 20 mg/kg daily at the discretion of the treating clinician. Diarrhoea is an occasional side effect. If diarrhoea is not responsive to regular treatment (fluids and anti-diarrhoea drugs) and is possibly related to the study drug, the trial medication can be down titrated to 5 mg/kg and slowly increased as tolerated.

Clinical review will be performed every 3 months by trial clinicians and will include completion of quality of life questionnaires and blood tests. Participants will be given request forms for blood tests, to be performed within 24–48 hours of each episode of pain, including LFTs, full blood examination (FBE), urea, electrolytes and creatinine (UEC), serum lipase, and C-reactive protein (CRP). Episodes of biliary pain may be treated with glyceryl trinitrate (GTN) spray and hyoscine butylbromide (Buscopan) as required. Participants with severe refractory biliary pain will be assessed in the Emergency department. Participants will also undergo liver US monitoring every 12 months.

Table 1 outlines the schedule of assessments.

Adherence

Compliance with medication will be assessed by a pill count performed by Pharmacy at each clinical review.

Primary outcome

The primary outcome is the number of episodes of biliary pain.

Secondary outcomes

Secondary outcomes include:

• Number of episodes of biliary pain associated with transiently abnormal LFTs.
• Number of episodes of biliary pain in participants with findings on ultrasound examination typical of LPAC.

Quality of life scores and patient reported outcomes including the Recurrent Abdominal Pain Intensity and Disability (RAPID) score (34) (Figure 2), the Hospital Anxiety and Depression Scale (HADS) (35) and both SF-36 (v1) and EQ-5D-5L (36,37).

Figure 2 RAPID questionnaire. RAPID, Recurrent Abdominal Pain Intensity and Disability.

Adverse events

UDCA is well tolerated with diarrhoea the major side effect, reported in up to 3% of patients (38). Nausea, vomiting and rarely urticaria have also been reported. A review of 24 randomised trials, over 3,000 patients, of UDCA for liver disease found that adverse effects were limited to minor gastrointestinal complaints (39).

Study monitor and safety

An independent medical monitor has been appointed to monitor the safety of participants and oversee the adverse events, withdrawals, and safety including adverse events. Adverse events will be reported as stipulated under the NHMRC Safety Monitoring and Reporting and Clinical Trials involving Therapeutic Products. An independent monitor has been employed to regularly review the trial processes and data integrity.

Data analysis

Sample size calculations and statistical method

We powered this study and based our sample size calculation on the number of patients needed to assess our primary outcome: number of episodes of biliary pain per year. In our previous cohort of LPAC patients, it was noted that the mean frequency of biliary pain was 3 episodes per year, with a standard deviation (SD) of 1. Based upon these figures, we would expect that UDCA would reduce the frequency of binary pain to a mean [SD] of 2 [1] episodes per year, a difference of one standard deviation. Using the methods for powering crossover designs discussed by Julious (40), and conservatively assuming a medium (41) correlation between pre and post-test of 0.30, a power of 90% and a 2-sided alpha of 0.05, a total of 17 patients would be required, rounding up to a total of 18 patients or 9 patients receiving treatment A then treatment B and 9 patients receiving B then A. Crossover studies typically require fewer subjects compared to parallel clinical trials given that inter-group variance is less, indeed Julious (40) shows that the total sample size required for a crossover study is typically very similar to that required for one arm of a parallel group study . Conservatively allowing for 25% attrition, a target of 18/0.75=24 patients will be recruited.

The assessment of the primary endpoint, the reduction in number of episodes of biliary pain, will begin 1 month after the beginning of treatment and continue over the next 11 months. With the changeover gap of 2 weeks this will provide an effective washout period of 6 weeks.

The trial will be advertised at local hospital meetings to aid enrolment.

An intention-to-treat analysis will be performed in accordance with CONSORT guidelines to provide an assessment of the impact of the treatment (42,43). Regression methods appropriate to the type of primary or secondary outcome, such as linear regression for continuous outcome or Poisson or negative binomial regression if found to be skewed, or binary logistic regression for binary outcomes will be employed. Alpha or level of statistical significance will be set to P<0.05 and 95% confidence intervals will be reported throughout. No adjustments for multiple testing will be made for secondary outcomes given their exploratory nature. The trial is not powered to detect secondary outcomes with a greater than 80% probability.

Statistical analysis will be undertaken by a trial statistician using standard statistical software.

Data management

Data will be entered for trial purposes to a secure validated clinical data management system (REDCap^TM) with password protection. Only study clinicians will have the password and ability to access these files. All research data including the Investigator Site File will be kept in a secure, locked location on-site at the hospital and all electronic data will be kept on at the hospital server and REDCap^TM for a minimum of 5 years. Participants will be identified by unique study identifier, date of birth and initials. All information collected including patient clinical, background, and family history will be allocated a unique re-identifiable code.

Screening, baseline, trial entry, medical history and study discontinuation will be recorded in patient’s medical records at their study site and this will form the source data. Only deidentified data will be statistically analysed. The data will be entered into the REDCap^TM system by site staff. Follow up data will be collected by the site personnel via clinics or participant phone calls and correspondence with relevant healthcare providers. This information will be retained in clinical notes held at the research sites and this will form the source data.

All data will be handled, computerised and stored in accordance with the Data Protection Act 1998. Key study findings will be published in peer-reviewed journals as well as presented at national and international conferences.

Discussion

The ULTRA Pain study is the first randomised trial to assess the efficacy of UDCA treatment of episodes of post cholecystectomy biliary pain in LPAC.

There is a broad spectrum of clinical severity in the LPAC syndrome. This trial will study patients with mild LPAC as judged by no or minimal changes on liver ultrasound imaging. Those with macroscopic intrahepatic stones, dilated ducts, or chronic cholestatic liver disease will be excluded. This patient population typically presents post cholecystectomy with difficult to manage recurrent episodes of biliary pain.

Post cholecystectomy pain is a common clinical problem, and the recently described LPAC syndrome is an under-recognised and under-diagnosed cause (44). The clinical presentation of LPAC is similar to that of functional biliary sphincter disorder, onset less than 40 years of age, predominantly females, seen several years after cholecystectomy with recurrent biliary pain often associated with transiently abnormal LFTs. Making the distinction between these two diagnoses facilitates appropriate investigation and management. Level 1 evidence supporting the value of UDCA treatment would raise awareness of LPAC and the existence of an effective treatment.

The milder forms of LPAC generally have a benign clinical course (45). The major clinical problem, recurrent episodes of biliary pain, has been chosen as the trial primary endpoint. Distinguishing biliary from other causes of pain post cholecystectomy can be difficult. The Rome IV classification has been used to define biliary pain in this trial. The association of transiently abnormal LFTs with pain confirms a biliary origin, although this is reported to occur in 47% of LPAC patients (9). In our experience transiently elevated LFTs associated with pain occur more frequently, 93% of patients, and a reduction in the number of episodes has been chosen as a secondary endpoint that is less liable to subjective bias than self-reported episodes of pain.

The EPISOD study is a randomised sham-controlled study that assessed whether patients with SOD presenting with episodes of post cholecystectomy pain responded to sphincter ablation and whether the outcomes were predicted by pain patterns, the presence of other functional GI or psychosocial problems (46). The outcomes were assessed with a scoring scale specifically developed and validated to measure the intensity and disability associated with episodes of biliary pain, the RAPID score. The RAPID score will be used to assess biliary pain in our study and a reduction in the RAPID score is a secondary outcome. The EPISOD study also used well-established psychological questionnaires to assess initial psychosocial comorbidity and the response to treatment. Our study uses identical questionnaires and improvement in scores is a secondary outcome.

Improvement in quality of life and mental health, as measured by validated questionnaires, will also be a secondary endpoint. In the clinical setting, many LPAC patients have reported how their severe biliary pain has affected their quality of life and mental health. We hypothesise that by improving biliary pain, UDCA will also improve the quality of life and mental health of LPAC patients. We have included these objective validated questionnaires to assess this. These measures have not been reported in the literature and will be novel. Emotional function will be assessed by the HADS, a 14-question tool comprising of seven questions for the assessment of depression in medical patients, and seven questions assessing anxiety (39). Quality of life will be measured by both SF-36 and EQ-5D-5L (41,42). The inclusion of these questionnaires, also used in the EPISOD trial, will facilitate comparison of the two studies.

The diagnosis of LPAC syndrome has been defined using Rosmorduc’s original three criteria with the addition of a family history of cholecystectomy before 40 years of age or a family or personal history of other ABCB4 phenotypes to make the definition more specific. Finding typical changes of LPAC on liver ultrasound examination strengthens the diagnosis however imaging may be normal. A secondary analysis will be performed on the subgroup of participants with characteristic findings of LPAC on ultrasound imaging.

The presence of a known variant of the ABCB4 gene will confirm the diagnosis of LPAC. However, genotyping is expensive and variants are identified in only approximately 50% of LPAC patients (9,15-18). Genotyping will not be performed prospectively in this trial.

After commencement of treatment the concentration of UDCA in the bile acid pool increases from 3% to 40–60% over one week (47). Subsequent to the initiation of our randomised control study, evidence has shown the onset of the clinical effect of UDCA, a reduction in the frequency of episodes of biliary pain, begins a mean of 3–4 weeks after treatment commences (44). The assessment of the primary endpoint, the reduction in number of episodes of biliary pain, will begin 4 weeks after the beginning of treatment and continue over the next 11 months.

The results of this trial will not necessarily be applicable to all LPAC patients with biliary pain. Those with intact gallbladders with stones or macroscopic intrahepatic stones may have a different cause for their pain, including cholecystitis and cholangitis.

LPAC is an under-diagnosed cause of post cholecystectomy pain. The results of this trial will provide level 1 evidence on the efficacy of UDCA treatment and will raise awareness of the importance of LPAC in the differential diagnosis of difficult to manage post cholecystectomy biliary pain.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the SPIRIT reporting checklist. Available at https://tgh.amegroups.com/article/view/10.21037/tgh-24-127/rc

Peer Review File: Available at https://tgh.amegroups.com/article/view/10.21037/tgh-24-127/prf

Funding: This study is funded by internal research funds supported by the Jreissati Pancreatic Centre, Epworth HealthCare.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tgh.amegroups.com/article/view/10.21037/tgh-24-127/coif). A.T. is in receipt of the 2020 GESA - Olympus Endoscopy Fellowship as part of a PhD stipend. All authors report funding from the Jreissati Pancreatic Centre, Epworth HealthCare. The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study will be conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was granted ethical approval from the Melbourne Health Human Research and Ethics Committee (HREC) (No. HREC/55994/MH-2019). Informed consent will be obtained from the participants in this study.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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