IJCRR - 14(8), April, 2022
Date of Publication: 19-Apr-2022
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A Study of Anatomical Variations of Extrahepatic Biliary System by Pre-operative Magnetic Resonance Cholangio-Pancreatography and that Encountered during Laparoscopic Cholecystectomy: A Prospective Observational Study
Author: Chhikara Amit, Gupta Anurakshat, Trehan Vikram, Mohan Hari
Abstract:Introduction: The variations in cystic duct anatomy are of considerable importance during surgical excision of the gallbladder (cholecystectomy). Preoperative MRCP assessment of possible anatomical variations helps the surgeon to formulate appropriate strategies and operative planning. Objective: To assess the usefulness of pre-operative MRCP assessment of anatomical variations of the extra-hepatic biliary tree in surgical planning and validate the MRCP findings with surgical findings. Material and Method: A total 120 patients of ultrasonography-proven gallstone disease were included in the study, further evaluated preoperatively by magnetic resonance cholangiopancreatography for delineation of extra-hepatic biliary anatomy and was compared with findings during Laparoscopic Cholecystectomy performed in the same patients. Seven patients had frozen Calot's triangle per-operatively and were excluded from the study. Results: The majority of patients were in the age group of 51-60 years (28.4%) and females (85.84%). on MRCP, Posterior insertion of the Cystic duct was noted in 58.41% of patients, Lateral insertion in 35.39% of patients while on per-operatively Posterior insertion was noted in 50.44% and lateral insertion in 38.94 % patients. Most common intra-op complication was Bile spill in 19.4% of patients, a Stone spill in 9.7% patients and there was no bile duct injury noted. Conclusion: There is a definitive role of magnetic resonance cholangiopancreatography prior to laparoscopic cholecystectomy in gallstone disease for precisely delineating the extrahepatic biliary tree anatomy and predicting difficult surgery thus helping the surgeon to be prepared for the eventualities during surgery and to prevent biliary injury. However, still intra-op picture can vary and overall, there is a reduction in patient morbidity.
Keywords: Extra-hepatic Biliary Anatomy, Pre-operative MRCP, Cystic duct insertion, Laparoscopic Cholecystectomy, Biliary injury
The cystic duct drains the gallbladder into the common bile duct. In adults, it is usually between 2 and 4 cm long and has a luminal diameter of 2–3 mm.1 Cystic duct unite with the common hepatic duct in a variable fashion to form the common bile duct. Anatomic variants of the cystic duct insertion into the extrahepatic bile duct are:
(a) Right lateral insertion
(b) Anterior spiral insertion
(c) Posterior spiral insertion
(d) Low lateral insertion with a common sheath,
(e) Proximal insertion or low medial insertion.
The cystic duct joins the middle third of the combined lengths of the common hepatic and common bile ducts in most of the patients,2 but it may also drain by variable insertion into the distal common bile duct (CBD) usually joins the right lateral aspect by making oblique angle or run parallel with common hepatic duct in the free edge of the lesser omentum for a variable distance before merging.3 These variations of cystic duct anatomy are identified by preliminary cholangiogram of considerable importance to prevent biliary injury during cholecystectomy.
In adults, the common hepatic duct descends approximately 3 cm before being joined obliquely on its right by the cystic duct to form the common bile duct. In adults common bile duct divided into supraduodenal, gastroduodenal and pancreatic segments and is usually between 6 and 8 cm long and its luminal diameter, as measured by ultrasound, is no more than 7 mm.4 The supraduodenal segment of the common bile duct is the most accessible at surgery. Calot’s triangle, which is an isosceles triangle based on the common hepatic duct, with the cystic artery and cystic duct forming its sides.5 Understanding the variations in biliary and arterial anatomy as they relate to the triangle is of considerable importance during excision of the gallbladder in order to avoid injury to the common hepatic or common bile duct or right hepatic artery. 6,7 (Figure 1)
Extra-hepatic biliary system has wide anatomical variations which might have a detrimental role on the successful culmination of a Laparoscopic Cholecystectomy procedure. Although the incidence and frequency of these different anatomical variations vary substantially yet these anatomical variations from normal anatomy make the Laparoscopic Cholecystectomy procedure difficult and might result in biliary tract injury.7,8 Incidence of extra-hepatic biliary tree anatomical variations is seen less than 50%.9 Preoperative assessments of possible anatomical variations help the surgeon to formulate appropriate strategies and operative planning. Failure to recognize some of the clinically important variants may lead to complications. In recent years magnetic resonance cholangiopancreatography (MRCP) has come up as an optimal non-invasive imaging modality for the evaluation of anatomical variations of the extra-hepatic biliary tree. In the present study anatomical variations of the extrahepatic biliary system assessed by preoperative MRCP and that encountered during Laparoscopic Cholecystectomy
MATERIAL AND METHOD
Study type-This was a prospective observational study.
Study population- A total of 120 patients were included in the study.
Inclusion criteria- Patient aged 18 to 80 years of both sex, belonging to different socio-economic conditions and various geographical locations of India and who had ultrasonography proven symptomatic cholelithiasis were further evaluated preoperatively by magnetic resonance cholangiopancreatography for delineation of extra-hepatic biliary anatomy, underwent laparoscopic cholecystectomy.
Exclusion criteria- Patients who were unwilling to participate in the study, in which MRI was contraindicated, acute calculus cholecystitis, empyema gall bladder, pancreatitis and frozen Calot's triangle preoperatively were excluded from the study.
Place of study -This study was conducted at 7 Air Force Hospital Kanpur, India,
Duration of study- The study duration was from January 1, 2018, to December 31, 2018.
Objectives of study-
To find out by MRCP frequency and types of anatomical variations of the extra-hepatic biliary tree in patients supposed to undergo Laparoscopic Cholecystectomy.
To validate the MRCP findings with surgical findings.
To assess the usefulness of pre-operative MRCP assessment of anatomical variations of the extra-hepatic biliary tree in surgical planning.
Methodology: In the present study, 120 patients with ultrasonography-proven gallstone disease were further evaluated preoperatively by Magnetic Resonance Cholangiopancreatography using a Magnetic Resonance Image (MRI) unit on MRI scanner and images obtained by using Philips Achieva® 1.5 TESLA MRI. The MRCP images were evaluated by an experienced radiologist for the presence of different anatomical variations of the extra-hepatic biliary tree. Preoperative workup general blood picture, assessment of liver function test, renal function test and fitness for general anesthesia was done. Informed written consent was obtained from all the patients before the operative procedures. Participation in the study was entirely voluntary giving the patient right to withdraw from study whenever he/she wishes to do so.
This study was approved by the Institutional Ethical Committee (7AFH/24Apr/2018). Demographic information, personal and medical history was obtained. Preoperative MRCP for delineation of extra-hepatic biliary anatomy were noted. All the patients underwent Laparoscopic Cholecystectomy. Anatomic variations in extra-hepatic biliary tree were observed and recorded during the procedure. Seven patients had frozen Calot’s triangle per-operatively and were excluded from the study. Preoperative MRCP findings were compared with Laparoscopic Cholecystectomy findings in the same patients. Impact of MRCP assessment of extra-hepatic biliary tree variations was assessed with respect to reduction in intraoperative and postoperative complications.
Data Collection Method
The data was collected on a semi-structured questionnaire. Records of all the test reports are maintained. Observations were made under direct supervision. The data so collected were fed into the computer using MS Excel 2013 or compatible software.
The data was analyzed using Statistical Package for Social Sciences version 21.0 or above. Chi-square test, ANOVA and Independent Samples 't'-test was used for comparison of data. A p-value less than 0.05 was considered to indicate a statistically significant association. Sensitivity, Specificity, PPV, NPV and accuracy of MRCP were also assessed.
Age of the patients: Majority of patients were of age group 51-60 years (28.4%) followed by age groups 31-40 years and 41-50 years (20.3% each) and the mean age was 47.32±13.58 (Figure 2a).
Gender of patients: On the basis of their gender, the majority of patients were females (85.84%) followed by males (14.16%) (Figure2b).
Cystic duct and Common bile duct diameter: It was noted that mean cystic duct diameter in females was 1.60±0.79 mm and in males it was 1.35mm±0.44mm while mean CBD diameter in females was 5.88±1.67mm and in males it was 5.88±1.26mm (Table 1a, 1b).
Cystic duct insertion:
a) On MRCP: Posterior insertion was noted in 58.41% patients, lateral insertion in 35.39% patients, anterior insertion in 2.66% patients and medial insertion in 3.54% patients (Table 2a, Figure3).
b) On Per-operative: Posterior insertion was noted in 50.44% patients, lateral insertion in 38.94 % patients, anterior insertion in 9.74% patients and medial insertion in 0.88% patients (Table 2b, Figure 4).
MRCP was able to predict correct anatomical variation in 70 cases out of the 113 that were evaluated giving a rate of 61.94%. The errors in detection can be due to multiple causes like observer sensitivity, technical skill in image acquisition, stage of disease process leading to changes in nature of image and body characteristics of the patient. Each of these factors needs to be evaluated separately in future studies with larger sample size.
Table (Table 3a, 3b) analyses the usefulness of MRCP preoperatively to screen the cases planned for Laparoscopic Cholecystectomy. Considering Cystic duct insertion noted during preoperative MRCP and that noted intra-operatively, Lateral (a) and Posterior insertion(c) were the most common finding and considering these findings to be normal, Anterior (b) and Medial insertion(d) were considered as anatomical variation and the following results were obtained.
Intra-op complications: Most common intra-op complication was bile spill in 19.4% of patients, stone spill in 9.7% of patients and vascular injury (cystic artery) during dissection in 7.96% patients. No bile duct injury, trocar injury, bowel injury or port site bleeding was noted (Table 4).
Operative time: Time taken for performing laparoscopic cholecystectomy was less than 60 minutes in 82(72.56%) cases and more than 60 minutes of operative time in 31(27.43%) cases.
The frequency and types of extrahepatic biliary tree anatomical variations is quite high and owing to these variations, there is difficulty during operative procedures and often there is a high incidence of intra-operative and postoperative complications. In recent years, Magnetic Resonance Cholangiopancreatography (MRCP) has emerged as a useful modality to assess these variations non-invasively prior to surgery itself. The present study was conducted to assess the usefulness of pre-operative MRCP, assessment of frequency and types of anatomical variations of the extra-hepatic biliary tree in patients supposed to undergo Laparoscopic Cholecystectomy and compare with surgical findings.
In a study by Al Ghamdi A S et al. 10, the mean age was 41 years (range 10-100 years) in the age group 31-40 years while in the present study the mean age was 47 years (range 22-76) with the highest incidence was in 6th decade. The youngest male was 22 years old and the female 24 years. In a study by Sakorafas et al.11 female genders was associated with a higher prevalence, 16% compared to 9% for males. IJ Beckingham12 studied that the female gender carried twice the risk of gallstone disease as compared to men, which was especially prominent at young age, mainly because of hormonal factors. Present study results correlated with their findings with a female: male ratio of 6.06: 1 (97 females vs 16 males). In present study mean cystic duct diameter was 1.60 mm with a SD of 0.79mm in females and in males it was noted to be 1.35 mm with a SD of 0.44mm.No other study in the past has noted this particular parameter. This may be due to the non-availability of detailed MRCP findings or due to the non-availability of expertise. Kim H J et al.,13 in a study of normal structure, variations and anomalies of the pancreaticobiliary ducts found that the mean maximal and mid-portion diameters (mm) of the common bile duct were 6.4mm (1.8) and 5.5mm (1.7) respectively while dilated CBD was described to have an association with difficult surgery and conversion to open surgery by Liu et al.14 In present study, mean diameter of CBD in females was 5.88 mm with an SD of 1.67 mm and in males it was noted to be 5.88 mm with an SD of 1.26mm. In a study by Sarawagi R et al.,15 the accuracy of MRCP evaluated in the diagnosis of anatomic variants of biliary tree in 224 patients, MRCP demonstrated the cystic duct in 198 patients, including a low cystic duct insertion in 18 patients (9%) and a parallel course of the cystic and hepatic ducts in 7.5% patients. There were three common variants in the anatomy of the cystic duct region: low cystic duct insertion with distal third of the CBD (9%); medial insertion, where the cystic duct drains into the left side of CBD (10-17%); and a parallel course and less angular entry into CBD (1.5-25%). In the present study, patterns of cystic duct insertion noted during preoperative MRCP were lateral insertion in 35.40%, posterior insertion in 58.41%, anterior insertion in 2.65% and medial insertion in 3.54% of patients. When these patients were taken up for Laparoscopic Cholecystectomy, the intra-operative patterns of cystic duct insertion were found to be a lateral insertion in 38.93%, posterior insertion in 50.44%, anterior insertion in 9.73% and medial insertion in 0.88% patients. In this study it was tried to analyze the usefulness of MRCP preoperatively to assess the extrahepatic biliary tree anatomy for the case planned for Laparoscopic Cholecystectomy. To calculate the results, intraoperative findings have been used as Gold Standard. The sensitivity of MRCP was 97.12% with a 95% confidence interval (91.8%-99.4%). This implies that the sensitivity of MRCP was at least 91.8%, which was quite high and the chances of missing a case of anatomical variation were low, thus making MRCP a useful imaging modality for preoperative assessment of anatomical variations. The specificity was 44.4% with 95% confidence interval (13.7%-78%). The specificity was low which implies that there were fair chances of false-positive cases where MRCP highlights a variation, which actually was not present. However, this is clinically not very important as this would mean taking more precautions during surgery which is never a bad idea in such cases. I J Beckingham12 in his study found that biliary tree injury with laparoscopic cholecystectomy was 0.2 – 0.4 % as compared to 0.1% with open cholecystectomy while in the present study, there were no bile duct injuries. This may be attributed to the fact that centre has highly trained senior faculty and each patient had undergone extensive pre-operative evaluation which was far beyond the standard of care. Al Ghamdi A S et al.,10 in the study of 751 patients, the mean operative time was 65.52 minutes, seven patients (0.93%) converted to Open Cholecystectomy (OC) and mortalities of 02 patients (0.26%). In present study, the mean operative time was 54.13±25.71min and there was no conversion or mortality. In view of the smaller sample size in study group, the difference in mortality rates was also not statistically significant.
The present study attempts to determine the role of magnetic resonance imaging and magnetic resonance cholangiopancreatography prior to laparoscopic cholecystectomy in gallstone disease. However, laparoscopic cholecystectomy carries a higher risk of injury to biliary tree than conventional surgery. Significant number of these injuries is caused by variations in the biliary tree anatomy. By precisely delineating the biliary tree anatomy, magnetic resonance imaging and magnetic resonance cholangiopancreatography can assist the surgeons in predicting difficult surgery thus helping the surgeon to be prepared for the eventualities during surgery and to prevent biliary injury. However still intra-op picture can vary and overall, there is a reduction in patient morbidity.
Authors acknowledge the immense help received from the scholars whose articles are cited and included in references of this manuscript. The authors are also grateful to authors / editors / publishers of all those articles, journals and books from where the literature for this article has been reviewed and discussed. The authors also thank to all the participants who have participated in the study.
Source of Funding: NIL
Conflict of interest: NIL
Ethical committee clearance: IEC No. (7AFH/24Apr/2018).
Study conception, Design of methodology & Intellectual content: Dr. Amit Chhikara,
Dr. Anurakshat Gupta
Acquisition, Analysis and Interpretation of data: Dr. Amit Chhikara, Dr. Hari Mohan.
Drafting, Review, Editing of the manuscript: Dr. Hari Mohan, Dr.Vikram Trehan.
Critical revision & Final approval: Dr.Anurakshat Gupta, Dr.Vikram Trehan.
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