Use Of Cholecystectomy Research Articles

Epidemiology of cholangiocarcinoma

Aim: We aimed to analyze temporal trends in mortality from intrahepatic (ICC) and extrahepatic (ECC) cholangiocarcinoma in selected countries worldwide. Methods: Official death certification data for ICC and ECC and populations estimates for 29 countries worldwide (17 from Europe, 8 from the Americas, and 4 from Australasia) and for Hong Kong Special Administrative Region of the People’s Republic of China (SAR), from 1995 to 2018, were extracted from the World Health Organization and the Pan American Health Organization databases. Age-standardized mortality rates were computed. A joinpoint regression analysis was performed. Results: In both sexes, ICC mortality rates increased in most countries considered, including the USA, the UK, and Australia; in some countries, including Italy and France, the increasing trends leveled off over the most recent years. In men, around 2016, the highest rates (1.7-2.3/100,000) were observed in Hong Kong SAR, Portugal, France, Spain, Australia, Austria, the UK, and Canada; Latin American countries and some eastern European countries had the lowest rates (0.2-0.8/100,000). A similar pattern was observed in women, but with lower rates (from 1.7/100,000 in Hong Kong SAR to 0.14/100,000 in Argentina). ECC mortality declined in most European and Australasian countries, but it tended to increase in Americas. In both sexes, rates were below 1/100,000 around 2016, with the only exceptions being Japan (2.6/100,000 men and 1.2/100,000 women) and Hungary (1.5/100,000 men and 1.1/100,000 women). Conclusion: ICC mortality increased in most areas of the world, likely due to increased prevalence of risk factors and improved cancer recognition and classification. ECC mortality fell in most countries, largely due to the widespread use of cholecystectomy.

National Trends in Cholecystectomy and Endoscopic Retrograde Cholangiopancreatography During Index Hospitalization for Mild Gallstone Pancreatitis.

Guidelines call for cholecystectomy during the index hospitalization for patients with gallstone pancreatitis. Therefore, the study sought to determine the trends for cholecystectomy and Endoscopic Retrograde Cholangiopancreatography (ERCP) for mild gallstone pancreatitis. A retrospective analysis of the 2010-2018 Nationwide Readmission Database (NRD) was performed to identify patients with mild gallstone pancreatitis. The primary aim was to identify the trends in the use of cholecystectomy in these patients, and the secondary aim was to assess if ERCP alone was protective against readmission. A total of 510,470 patients with mild gallstone pancreatitis were identified. There has been an increasing trend in ERCP use (25% in 2018 vs. 22% in 2010; p-0.001) and a decline in cholecystectomy (37% in 2018 vs. 46% in 2010; p-0.001) prior to discharge. Multivariate analysis revealed higher 30-day readmission for patients who underwent ERCP without cholecystectomy (odds ratio1.3; 95% confidence interval, 1.1-3.5) during the index admission. There has been a decline in the use of cholecystectomy during index hospitalization for mild gallstone pancreatitis. In addition, ERCP was not protective against 30-day readmission from mild gallstone pancreatitis.

A Clinical Decision Tool for Selection of Patients With Symptomatic Cholelithiasis for Cholecystectomy Based on Reduction of Pain and a Pain-Free State Following Surgery

There is currently no consensus on the indication for cholecystectomy in patients with uncomplicated gallstone disease. To report on the development and validation of a multivariable prediction model to better select patients for surgery. This study evaluates data from 2 multicenter prospective trials (the previously published Scrutinizing (In)efficient Use of Cholecystectomy: A Randomized Trial Concerning Variation in Practice [SECURE] and the Standardized Work-up for Symptomatic Cholecystolithiasis [Success] trial) collected from the outpatient clinics of 25 Dutch hospitals between April 2014 and June 2019 and including 1561 patients with symptomatic uncomplicated cholelithiasis, defined as gallstone disease without signs of complicated cholelithiasis (ie, biliary pancreatitis, cholangitis, common bile duct stones or cholecystitis). Data were analyzed from January 2020 to June 2020. Patient characteristics, comorbidity, surgical outcomes, pain, and symptoms measured at baseline and at 6 months' follow-up. A multivariable regression model to predict a pain-free state or a clinically relevant reduction in pain after surgery. Model performance was evaluated using calibration and discrimination. A total of 1561 patients were included (494 patients in 7 hospitals in the development cohort and 1067 patients in 24 hospitals in the validation cohort; 6 hospitals included patients in both cohorts). In the development cohort, 395 patients (80.0%) underwent cholecystectomy. After surgery, 225 patients (57.0%) reported that they were pain free and 295 (74.7%) reported a clinically relevant reduction in pain. A multivariable prediction model showed that increased age, no history of abdominal surgery, increased visual analog scale pain score at baseline, pain radiation to the back, pain reduction with simple analgesics, nausea, and no heartburn were independent predictors of clinically relevant pain reduction after cholecystectomy. After internal validation, good discrimination was found (C statistic, 0.80; 95% CI, 0.74-0.84) between patients with and without clinically relevant pain reduction. The model had very good overall calibration and minimal underestimation of the probability. External validation indicated a good discrimination between patients with and without clinically relevant pain reduction (C statistic, 0.74; 95% CI, 0.70-0.78) and fair calibration with some overestimation of probability by the model. The model validated in this study may help predict the probability of pain reduction after cholecystectomy and thus aid surgeons in deciding whether patients with uncomplicated cholelithiasis will benefit from cholecystectomy.

Corrosion and biocompatibility behaviours of microarc oxidation/phytic acid coated magnesium alloy clips for use in cholecystectomy in a rabbit model.

With the popularisation of laparoscopic cholecystectomy, ligation clips have been commonly used for ligating the cystic duct and cystic artery. However, non-degradable clips remain in the body long-term, which significantly increases the risk of the clip becoming detached. Thus, magnesium alloys have attracted tremendous attention owing to their biodegradability and good biocompatibility. However, the poor corrosion resistance hinders the clinical application of magnesium alloys with microarc oxidation/phytic acid (MAO/PA) composite coatings as protective coatings. Here, these alloys were used to hinder the rapid material degradation in aqueous solution. Electrochemical tests were conducted to evaluate the in vivo degradation behaviour in simulated body fluid (SBF) for Mg–Zn–Y–Nd alloys, and scanning electron microscopy (SEM) was used to observe the micromorphology of in vivo clip degradation. Cell toxicity, cell adhesion, and flow cytometry were performed in vitro to detect cytocompatibility. Biochemical detection of serum magnesium, serum creatinine (CREA), blood urea nitrogen (BUN), alanine transaminase (ALT), and alanine aminotransferase (AST), and haematoxylin–eosin (HE) staining of the heart, liver, and kidney tissues in vivo was conducted to determine the biocompatibility properties after surgery. Electrochemical measurements and SEM images revealed that the MAO/PA-coated magnesium alloy delayed corrosion in SBF. The apoptosis rate increased slightly with increased extract concentration. Nevertheless, MAO/PA-coated magnesium alloys still exhibited good cytocompatibility. No obvious abnormality was observed in the blood biochemical test or HE staining. Thus, MAO/PA-coated magnesium alloys exhibit better corrosion than bare magnesium. In addition, Mg–Zn–Y–Nd and MAO/PA-coated magnesium alloys exhibited no cytotoxicity, good adhesion, and biosafety.

A multicentre randomized non-inferiority trial comparing usual care to restrictive strategy for use of cholecystectomy in patients with gallstones and abdominal pain (SECURE trial)

Background: Cholecystectomy is the preferred treatment for symptomatic, uncomplicated gallstones. Usual care in patients with abdominal pain and gallstones is associated with practice variation and persistent abdominal pain in 10-41% of post-cholecystectomy patients. We scrutinized (in)efficient use of cholecystectomy by determining non-inferiority of a restrictive strategy with stepwise selection compared to current usual care for patients with abdominal pain and gallstones. Material & Methods: We randomly assigned patients with ultrasound proven gallstones and abdominal symptoms from 24 Dutch hospitals, to a restrictive strategy with stepwise selection for cholecystectomy or usual care. The primary endpoint was the proportion of patients being pain-free at 12 months' follow-up. A 5% non-inferiority margin was chosen, based on estimated clinical relevant difference. Secondary endpoints included: cholecystectomy rate, proportion of patients with gallstone related and surgical complications, patients' satisfaction, health status and time to pain-free. Results: Between 2014-2018, 1067 patients were included. At 12 months’ follow-up 298 of 530 patients (56.2%, 95% CI, 52.0%-60.4%) were pain-free in the restrictive strategy, compared to 321 of 537 patients (59.8%, 95% CI, 55.6%-63.8%) in usual care. Non-inferiority was not demonstrated as the lower limit of 95% confidence interval of pain-free patients exceeds the 5% non-inferiority margin. (pnon-inferiority = 0.316). The restrictive strategy resulted in a significantly lower cholecystectomy rate than usual care (67.7% versus 75.4%, p=0.005). Other secondary outcomes were comparable between groups: median time to pain-free (7.87 months versus 7.29 months, p=0.130), patient satisfaction with treatment outcome at 12 months’ follow-up (p=0.976), and patients’ health status over time (p=0.820). Overall, patients with preoperative biliary colics were more often pain-free after cholecystectomy (65.5% versus 57.4%, p=0.048). Conclusion: The restrictive strategy is associated with less cholecystectomies. However, suboptimal pain reduction in patients with gallstones and abdominal pain is seen in both usual care and following a restrictive strategy for selection for cholecystectomy.

Initial Experience With a New Robotic Surgical System for Cholecystectomy.

Background. Laparoscopic cholecystectomy has been the gold standard treatment for symptomatic cholelithiasis for more than 3 decades. Robotic techniques are gaining traction in surgery, and recently, the Senhance™ robotic system was introduced. The system offers advantages over other robotic systems such as improved ergonomics, haptic feedback, eye tracking, and usability of standard laparoscopic trocars and reusable instruments. The Senhance was evaluated to understand the feasibility, benefits, and drawbacks of its use in cholecystectomy. Study Design. A prospectively maintained database of the first 20 patients undergoing cholecystectomy with the Senhance was reviewed at a single hospital. Data including operative time, console time, set up time, and adverse events were collected, with clinical outcome and operative time as primary outcome measures. A cohort of 20 patients having laparoscopic cholecystectomy performed by the same surgeon was used as a comparator group. Results. The 2 groups had comparable demographic data (age, sex, and body mass index). In the Senhance group, 19 of the 20 procedures (95%) were completed robotically. The median (interquartile range) total operating, docking, and console times were 86.5 (60.5-106.5), 11.5 (9-13), and 30.8 (23.5-35) minutes, respectively. In the laparoscopic group, the median (interquartile range) operating time was 31.5 (26-41) minutes. Postoperatively, only one patient had a surgical complication, namely a wound infection treated with antibiotics. Conclusion. Our results suggest that Senhance-assisted cholecystectomy is safe, feasible, and effective, but currently has longer operative times. Further prospective and randomized trials are required to determine whether this approach can offer any other benefits over other minimally invasive surgical techniques.

Mo1935 – Use of Cholecystectomy Decreasing in Patients with Crohn's Disease

Mo1935 – Use of Cholecystectomy Decreasing in Patients with Crohn's Disease

Restrictive strategy versus usual care for cholecystectomy in patients with gallstones and abdominal pain (SECURE): a multicentre, randomised, parallel-arm, non-inferiority trial

International guidelines advise laparoscopic cholecystectomy to treat symptomatic, uncomplicated gallstones. Usual care regarding cholecystectomy is associated with practice variation and persistent post-cholecystectomy pain in 10-41% of patients. We aimed to compare the non-inferiority of a restrictive strategy with stepwise selection with usual care to assess (in)efficient use of cholecystectomy. We did a multicentre, randomised, parallel-arm, non-inferiority study in 24 academic and non-academic hospitals in the Netherlands. We enrolled patients aged 18-95 years with abdominal pain and ultrasound-proven gallstones or sludge. Patients were randomly assigned (1:1) to either usual care in which selection for cholecystectomy was left to the discretion of the surgeon, or a restrictive strategy with stepwise selection for cholecystectomy. For the restrictive strategy, cholecystectomy was advised for patients who fulfilled all five pre-specified criteria of the triage instrument: 1) severe pain attacks, 2) pain lasting 15-30 min or longer, 3) pain located in epigastrium or right upper quadrant, 4) pain radiating to the back, and 5) a positive pain response to simple analgesics. Randomisation was done with an online program, implemented into a web-based application using blocks of variable sizes, and stratified for centre (academic versus non-academic and a high vs low number of patients), sex, and body-mass index. Physicians and patients were masked for study-arm allocation until after completion of the triage instrument. The primary, non-inferiority, patient-reported endpoint was the proportion of patients who were pain-free at 12 months' follow-up, analysed by intention to treat and per protocol. A 5% non-inferiority margin was chosen, based on the estimated clinically relevant difference. Safety analyses were also done in the intention-to treat population. This trial is registered at the Netherlands National Trial Register, number NTR4022. Between Feb 5, 2014, and April 25, 2017, we included 1067 patients for analysis: 537 assigned to usual care and 530 to the restrictive strategy. At 12 months' follow-up 298 patients (56%; 95% CI, 52·0-60·4) were pain-free in the restrictive strategy group, compared with 321 patients (60%, 55·6-63·8) in usual care. Non-inferiority was not shown (difference 3·6%; one-sided 95% lower CI -8·6%; pnon-inferiority=0·316). According to a secondary endpoint analysis, the restrictive strategy resulted in significantly fewer cholecystectomies than usual care (358 [68%] of 529 vs 404 [75%] of 536; p=0·01). There were no between-group differences in trial-related gallstone complications (40 patients [8%] of 529 in usual care vs 38 [7%] of 536 in restrictive strategy; p=0·16) and surgical complications (74 [21%] of 358 vs 88 [22%] of 404, p=0·77), or in non-trial-related serious adverse events (27 [5%] of 529 vs 29 [5%] of 526). Suboptimal pain reduction in patients with gallstones and abdominal pain was noted with both usual care and following a restrictive strategy for selection for cholecystectomy. However, the restrictive strategy was associated with fewer cholecystectomies. The findings should encourage physicians involved in the care of patients with gallstones to rethink cholecystectomy, and to be more careful in advising a surgical approach in patients with gallstones and abdominal symptoms. The Netherlands Organization for Health Research and Development, and CZ healthcare insurance.

Benchtop and animal validation of a portable fluorescence microscopic imaging system for potential use in cholecystectomy

We propose a portable fluorescence microscopic imaging system (PFMS) for intraoperative display of biliary structure and prevention of iatrogenic injuries during cholecystectomy. The system consists of a light source module, a camera module, and a Raspberry Pi computer with an LCD. Indocyanine green (ICG) is used as a fluorescent contrast agent for experimental validation of the system. Fluorescence intensities of the ICG aqueous solution at different concentration levels are acquired by our PFMS and compared with those of a commercial Xenogen IVIS system. We study the fluorescence detection depth by superposing different thicknesses of chicken breast on an ICG-loaded agar phantom. We verify the technical feasibility for identifying potential iatrogenic injury in cholecystectomy using a rat model in vivo. The proposed PFMS system is portable, inexpensive, and suitable for deployment in resource-limited settings.

Emergent cholecystectomy is superior to percutaneous cholecystostomy tube placement in critically ill patients with emergent calculous cholecystitis

BackgroundThe role of percutaneous cholecystostomy (PC) is undefined in patients with multiple comorbidities presenting with emergent calculous cholecystitis (CC). This study compared outcomes between PC, laparoscopic (LC), and open cholecystectomy (OC). MethodsThe Vizient UHC database was queried for high-risk patients with CC who underwent PC, LC, OC, or laparoscopic converted to open cholecystectomy (CONV). Demographics, outcomes, mortality, length of stay (LOS), and direct cost were compared between the groups. ResultsLC was the most common approach with the lowest risk of death, complications, LOS, and cost. Complication risk was highest in OC. Nearly 20% of patients underwent PC. Complication rate, LOS, infection, aspiration pneumonia, and mortality were higher in PC. Direct cost was lowest in LC, followed by CONV, PC, and OC. ConclusionsEmergent cholecystectomy for CC in high-risk patients is safer and more cost effective than PC and this study supports the use of cholecystectomy as the primary treatment approach in these patients.

Analysis of gallstone disease after gastric cancer surgery.

The incidence rate of newly developed gallstone disease after gastrectomy for gastric cancer is thought to be higher than that in the general population. However, the presentation and management of these gallstones remain under debate, and the role of prophylactic cholecystectomy remains questionable. Data on adult patients who were diagnosed with gastric cancer and received gastrectomy between 2000 and 2011 were extracted from the Taiwan National Health Insurance Research Database. A patient was excluded if he or she had gallstone disease or received cholecystectomy before the index date. The incidence of newly developed gallstone disease and its subsequent management were recorded. Data were analyzed to evaluate the factors associated with gallstone development and treatment options. A total of 17,325 gastric cancer patients who underwent gastrectomy were eligible for analysis. During the follow-up period (mean 4.1years; median, 2.9years), 1280 (7.4%) patients developed gallstone disease and 560 (3.2%) patients subsequently underwent cholecystectomy. The in-hospital mortality for cholecystectomy was 1.8% (10/560). Development of gallstone disease was associated with older age, total gastrectomy, duodenal exclusion, diabetes, cirrhosis, and more comorbidities. Factors associated with the use of cholecystectomy to treat gallstone disease included younger age, fewer comorbidities, medical center admission, and presentation as cholecystitis. Although few patients required further gallbladder removal after gastrectomy for gastric malignancy, the increased mortality rate for subsequent cholecystectomy was worth noting. The decision to undergo prophylactic cholecystectomy might be individualized based upon patient characteristics and the surgeon's discretion.

Is cholecystectomy the treatment of choice for acute acalculous cholecystitis? A systematic review of the literature.

There is currently no consensus with regard to the use of cholecystectomy or percutaneous cholecystostomy as the therapy of choice for acute acalculous cholecystitis. The goal of this study was to review the scientific evidence on the management of these patients according to clinical and radiographic findings. A systematic review of the literature from 2000 to 2016 was performed. The databases of PubMed, Índice Médico Español, Cochrane Library and Embase were searched according to the following inclusion criteria: publication language (English or Spanish), adult patients, acalculous etiology and appropriate study design. A total of 1,013 articles were identified and ten articles were selected for review. These included five observational controlled studies and five case series which described the outcome of patients treated with percutaneous cholecystostomy and emergency cholecystectomy. No prospective or randomized studies were identified using the search criteria. The data from the literature and analysis of results suggested that percutaneous cholecystostomy may be a definitive therapy for acute acalculous cholecystitis with no need for subsequent elective cholecystectomy. Percutaneous cholecystostomy may be the first treatment option for patients with acute acalculous cholecystitis except in cases with a perforation or gallbladder gangrene. Patients at low surgical risk may benefit from cholecystectomy but both treatment options may be effective. Percutaneous cholecystostomy in patients with acute acalculous cholecystitis may be a definitive therapy with no need for a subsequent elective cholecystectomy. However, the overall quality of studies is low and the final recommendations should be considered with caution.

Regional variations in cholecystectomy rates in Sweden: impact on complications of gallstone disease

Objective There are considerable variations in cholecystectomy rates between countries, but it remains unsettled whether high cholecystectomy rates prevent future gallstone complications by reducing the gallstone prevalence. The aims of this study were to investigate the regional differences in cholecystectomy rates and their relation to the incidence of gallstone complications.Material and methods Nation-wide registry-based study of the total number of cholecystectomies in Sweden between 1998 and 2013. Data were obtained from the Swedish Inpatient Registry covering the entire population and subdivided for by the 21 different counties. Indications for the procedure were prospectively collected during the years 2006–2013 in the National Registry for Gallstone Surgery and ERCP. The detailed demography of the total number of patients undergoing cholecystectomy and its relation to the respective indications were analysed by linear regression.Results The annual rates of cholecystectomy in the Swedish counties ranged from 100 to 207 per 100,000 inhabitants, with a mean of 157 (95% CI 145–169). The majority of cholecystectomies were done in females based on the indication biliary colic, with a peak incidence in younger ages. Cholecystectomies performed due to gallstone complications, pancreatitis and cholecystitis, were mainly carried out in the older age groups. No significant relationship could be demonstrated between cholecystectomy rates in the different regions and the respective incidences of gallstone complications. Conclusions There are wide regional variations in cholecystectomy rates in Sweden. The present study does not give support that frequent use of cholecystectomy in uncomplicated gallstone disease prevents future gallstone complications.

Critical Reappraisal of Cholecystectomy in Patients with Asymptomatic Gallstones for Early Diagnosis and Removal of Dysplasia and Cancer

It has been known that chronic trauma and inflammation of gallbladder (GB) mucosa by gallstones (GS) can induce epithelial dysplasia, carcinoma in situ, and invasive cancer. This study was designed to investigate the usefulness of cholecystectomy in patients with asymptomatic GS for the early diagnosis and removal of dysplasia or cancer. From January 2004 to July 2008, the clinical records of 703 cases with GS who underwent cholecystectomy at Korea University Guro Hospital were reviewed, and the prevalence of dysplasia and cancer was analyzed. In symptomatic GS (542 cases) group, low grade dysplasia was found in 4 cases (0.74%) and high grade dysplasia in 1 case (0.18%). In asymptomatic GS (161 cases) group, low grade dysplasia was found in 4 cases (2.48%) and cancer in 2 cases (1.24%) (p=0.012 vs. symptomatic cases). Dysplasias in symptomatic GS group were not associated with polyps, but dysplasias and cancers in asymptomatic GS group were associated. Patients with asymptomatic GS and polyps were analyzed according to the size of polyps. In those (12 cases) with larger polyps (> or 1 cm), low grade dysplasia was found in 2 cases and cancer in 2 cases. And in those (12 cases) with smaller polyps (<1 cm), low grade dysplasia was found in 2 cases. Extending indication of prophylactic cholecystectomy in patients with asymptomatic GS without polyp to prevent GB dysplasia or cancer beyond the existing indication does not seem to be justifiable in Korea. However, further studies are needed in patients with asymptomatic GS and polyp of any size.

43: Routine cholecystectomy is not mandatory during surgery for the morbidly obese

Rapid weight loss is a risk factor for gallbladder disease. Despite this many bariatric patients do not develop gallbladder pathology. We report our single institution experience of 621 bariatric operations without the routine use of cholecystectomy.

Health-Related Quality of Life and Appropriateness of Cholecystectomy

To evaluate the relationship among appropriateness of the use of cholecystectomy and outcomes. The use of cholecystectomy varies widely across regions and countries. Explicit appropriateness criteria may help identify suitable candidates for this commonly performed procedure. This study evaluates the relationship among appropriateness of the use of cholecystectomy and outcomes. Prospective observational study in 6 public hospitals in Spain of all consecutive patients on waiting lists to undergo cholecystectomy for nonmalignant disease. Explicit appropriateness criteria for the use of cholecystectomy were developed by a panel of experts using the RAND appropriateness methodology and applied to recruited patients. Patients were asked to complete 2 questionnaires that measure health-related quality of life-the Short Form 36 (SF-36) and the Gastrointestinal Quality of Life Index (GIQLI)-before the intervention and 3 months after it. Patients judged as being appropriate candidates for cholecystectomy, using the panel's explicit appropriateness criteria, had greater improvements in the bodily pain, vitality, and social function domains of the SF-36 than those judged to be inappropriate candidates. They also demonstrated improvements in the GIQLI's physical impairment domain. Interventions judged as inappropriate were performed primarily among patients without symptoms of cholelithiasis. Those asymptomatic had a lower improvement in the bodily pain, social functioning, and physical summary scale of the SF-36 and in the symptomatology, physical impairment, and total score domains of the GIQLI. These results suggest a direct relationship between the application of explicit appropriateness criteria and better outcomes, as measured by health-related quality of life. They also indicate that patients without symptoms are not good candidates for cholecystectomy.

Incidence of cancer of the pancreas, extrahepatic bile duct and ampulla of Vater in the United States, before and after the introduction of laparoscopic cholecystectomy

Background: Some epidemiologic studies have identified cholecystectomy as a risk factor for pancreatic and biliary cancer. Methods: We compared the incidence of cancers of the pancreas, extrahepatic bile duct and ampulla of Vater before and after the widespread adoption of laparoscopic cholecystectomy in the United States in 1991, when the use of cholecystectomy increased dramatically. Results: Compared with 1980 to 1991, there was no increase in the incidence of cancer of the pancreas (adjusted incidence rate ratio [IRR] 0.97, 95% confidence interval [CI] 0.94 to 0.99) or extrahepatic bile duct (IRR 0.80, 95% CI 0.74 to 0.87) during 1992 to 1996. There was a small increase in the incidence of ampullary cancer (IRR 1.14, 95% CI 1.03 to 1.26). Conclusions: We did not find clear evidence of a short-term increase in the incidence of cancers of the pancreas, bile duct, and ampulla of Vater, that was attributable to the increased use of cholecystectomy.