Affiliations
doi: 10.29271/jcpsppg.2025.01.59ABSTRACT
Objective: To determine the diagnostic accuracy of the preoperative ultrasound scoring system (USS) in predicting the occurrence of a difficult laparoscopic cholecystectomy (LC), using perioperative findings as a comparative standard.
Study Design: A cross-sectional study.
Place and Duration of the Study: Department of General Surgery, Railway General Hospital, Rawalpindi, Pakistan, from July 2024 to January 2025.
Methodology: A total of 220 patients, aged between 18 and 70 years, undergoing LC for symptomatic gallbladder disease, were included in the study using a non-probability consecutive sampling technique. The sample size was calculated using the WHO sample size calculator. The patients underwent history taking and examination, followed by ultrasound score calculation using the USS. This score was used to predict the difficulty of LC. Perioperative findings, showing the difficulty of surgery, were compared with the prediction of the USS. Results were analysed using SPSS version 29.
Results: Out of 220 patients, 39 patients (17.7%) scored 5 or higher using the USS. Among these, 31 underwent difficult cholecystectomy according to the operational definitions, showing a positive predictive value (PPV) of 79.4%. Amongst the remaining 181 patients, who scored less than 5 on the USS, 11 (6.07%) had a difficult cholecystectomy. The results show a specificity of 95.5% for the USS and a sensitivity of 73.8%.
Conclusion: The USS demonstrates good diagnostic accuracy (91.3%) for predicting difficult LC, with a high specificity (95.5%) but a moderate sensitivity (73.8%). While promising as a predictive tool, multicentre validation studies are needed before routine clinical implementation.
Key Words: Accuracy, Laparoscopic cholecystectomy, Ultrasound scoring system, Cholecystectomy.
INTRODUCTION
Laparoscopic cholecystectomy (LC) has revolutionised the management of gallstone disease due to its minimally invasive qualities, reduced postoperative pain, shorter hospital stays, and faster recovery times compared to traditional open surgery.1 However, the success of this procedure is highly dependent on the surgeon's skills and experience, as well as the anatomical variations encountered during the surgery.2 Preoperative identification of factors that may contribute to surgical difficulty can help surgeons prepare adequately and choose the most appropriate surgical approach.2
Ultrasonography, a widely available and non-invasive imaging technique, has become an essential tool in the preoperative assessment of patients undergoing LC.3 It provides detailed information about gallbladder pathology, such as the presence of gallstones, gallbladder wall thickness, presence of pericholecystic fluid, and anatomical variations.3 These sonographic findings have been associated with increased surgical complexity, longer operative times, higher conversion rates to open surgery, and an increased risk of intraoperative complications.3,4 While several different studies have been conducted on the sensitivity, specificity, and diagnostic accuracy of the aforementioned ultrasonological parameters in isolation,3,4 the utility of grouping these ultrasonological features into a scoring system to predict a difficult laparoscopic procedure has received little attention. Siddiqui et al. formulated the preoperative ultrasound scoring system (USS), which, with a cut-off of >5, had a sensitivity of 80.7%, and a specificity of 91.7% for correctly identifying difficult procedures, keeping peroperative findings as a comparative standard, which accounted for 27.7% of their study sample.5 To the best of the authors’ knowledge, this is the only study to determine the utility of sonological findings alone in this setting. Pal et al. conducted a similar study on a scoring system that incorporated ultrasound findings with clinical ones and determined that their score had a sensitivity of 88.2% and a specificity of 73.8% in detecting difficult cases only.6
By conducting a comprehensive analysis of sonographic findings and their correlation with the perioperative difficulty of LC, this research aimed to determine the diagnostic validity of the USS as a predictive model that can assist surgeons in anticipating the challenges they may face during the procedure. Such a predictive tool could guide surgeons in selecting appropriate surgical strategies, including patient selection, trocar placement, and operative techniques, ultimately improving patient outcomes and reducing the risk of complications. Furthermore, the use of sonographic findings to predict surgical difficulty could aid in the development of standardised guidelines for preoperative assessment, enhancing the overall quality and consistency of care provided to patients undergoing LC.
This study aimed to determine the diagnostic accuracy of the preoperative USS in predicting the occurrence of a difficult LC, keeping perioperative findings as a comparative standard.
METHODOLOGY
This study was conducted at the Department of General Surgery, Railway General Hospital, Rawalpindi, Pakistan, from July 2024 to January 2025. Two hundred twenty patients, aged between 18 and 70 years, undergoing LC for symptomatic gallbladder disease (acute cholecystitis, cholelithiasis, or symptomatic polyps) were included in the study using a non-probability consecutive sampling technique. The sample size was calculated by using the WHO sample size calculator for sensitivity and specificity at 95% confidence level, taking an expected sensitivity of 80.7%,5 a specificity of 91.7%,5 anticipated proportion of disease 27.7%,5 and desired precision as 10%. Patients suffering from complications of gallstone disease, those requiring emergency surgery, and those who were pregnant were excluded from the study.
Ethical approval was obtained from the Ethical Review Board of the General Hospital (Riphah/lRC/24/1042; Dated: 26th March 2024), and written informed consent was taken from all participants before the study was conducted. All participants underwent a clinical session upon enrolment in the study, which consisted of history taking, examination, and documentation of pertinent demographic data. The height, weight, and body mass index (BMI) of all patients were recorded. This was followed by an ultrasound examination, which was performed by a consultant radiologist with a minimum of five years' post- fellowship experience. All ultrasounds were performed with the patients fasting for at least eight hours. Patients were assessed for gallbladder wall thickness (measured at the anterior wall adjacent to the liver), transverse diameter of the gallbladder, presence of the pericholecystic fluid collections, mobility (movement of stones with change in posture) and number of gallstones (well-defined, multi-planar intraluminal echogenic lesion with posterior acoustic shadowing), the diameter of the common bile duct, and the size of the liver. All patients were scored according to the USS (Table I).
A score of 5 or greater on USS is considered to be predictive of the occurrence of a difficult LC.5
A laparoscopic surgery was considered to be difficult if any of the following occurred during surgery:5 total operative time greater than 60 minutes, occurrence of biliary leakage, occurrence of injury to the cystic duct or cystic artery, and conversion to open cholecystectomy.
All patients underwent laparoscopic surgery as per their individual plan, within 24 hours of the sonological examination. The surgery was performed by a consultant surgeon with a minimum post-fellowship experience of five years in laparoscopic surgery under general anaesthesia. The operating surgeon analysed the case based on the parameters set for a difficult LC as per operational definitions. All patients received standard postoperative care and follow-up.
Whether the USS predicted the occurrence of a difficult LC procedure and whether the LC was difficult as per peroperative findings or not were measured as frequency and percentage, and these parameters were used to determine true positive, false positive, true negative, and false negative cases. A table was constructed to calculate the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of the USS in predicting a difficult laparoscopic procedure. SPSS version 29 was used for data analysis. Descriptive statistics were calculated for all variables, and the data were presented as tables.
RESULTS
Out of 220 patients, 39 (17.7%) scored ≥5 on the USS. Among these, 31 patients underwent difficult cholecystectomy, yielding a PPV of 79.4%. In contrast, among the remaining 181 patients who scored <5 on the USS, 11 (6.1%) experienced a difficult cholecystectomy (Table II). A total of 170 patients were correctly identified by the USS as not undergoing difficult cholecystectomy, corresponding to a NPV of 93.9%. However, 8 (3.6%) patients scored ≥5 but did not undergo a difficult cholecystectomy. Overall, the USS demonstrated a sensitivity of 73.8%, a specificity of 95.5%, and a diagnostic accuracy of 91.3% (Table II).
Stratified analysis demonstrated that the USS had better sensitivity and overall diagnostic accuracy in patients aged >50 years compared to those ≤50 years. Males showed higher sensitivity, specificity, and PPV than females, indicating more reliable performance of the USS in this subgroup. Similarly, diagnostic accuracy was superior in patients with BMI >30 kg/m2, where USS achieved perfect sensitivity and NPV. Overall, USS maintained diagnostic accuracy above 90% across all strata, confirming its robustness as a preoperative predictive tool (Table III).
Table I: Ultrasound scoring system (USS).
|
Scores |
Ultrasound parameters |
|
2 |
Gallbladder wall thickness ≥4 mm |
|
2 |
Transverse diameter of gallbladder ≥5 cm |
|
2 |
Presence of impacted stones |
|
2 |
Common bile duct diameter >6 mm |
|
1 |
Presence of pericholecystic collection |
|
1 |
Number of stones >1 |
|
1 |
Liver size ≥15.5 cm |
Table II: Diagnostic accuracy of USS in predicting difficult LC.
|
USS predictions |
Difficult LC n (%) |
Not Difficult LC n (%) |
Sensitivity |
Specificity |
PPV |
NPV |
Accuracy |
|
Difficult LC (USS +) |
TP = 31 (79.4) |
FP = 8 (20.6) |
73.8 |
95.5 |
79.4 |
93.9 |
91.3 |
|
Not Difficult LC (USS –) |
FN = 11 (6.1) |
TN = 170 (93.9) |
|||||
|
USS: Ultrasound scoring system; LC: Laparoscopic cholecystectomy; TP: True positive; FN: False negative; FP: False positive; TN: True negative; PPV: Positive predictive value; NPV: Negative predictive value |
|||||||
Table III: Stratification of diagnostic accuracy by age, gender, and BMI.
|
Groups |
TP |
FP |
FN |
TN |
Sensitivity % |
Specificity |
PPV |
NPV |
Accuracy |
|
Age ≤50 years (n = 32) |
2 (100.0) |
0 (0.0) |
2 (6.7) |
28 (93.3) |
50.0 |
100.0 |
100.0 |
93.3 |
93.8 |
|
Age >50 years (n = 188) |
29 (78.4) |
8 (21.6) |
9 (6.0) |
142 (94.0) |
76.3 |
94.7 |
78.4 |
94.0 |
91.0 |
|
Male (n = 127) |
19 (86.4) |
3 (13.6) |
4 (3.8) |
101 (96.2) |
82.6 |
97.1 |
86.4 |
96.2 |
94.5 |
|
Female (n = 93) |
12 (70.6) |
5 (29.4) |
7 (9.2) |
69 (90.8) |
63.2 |
93.2 |
70.6 |
90.8 |
87.1 |
|
BMI ≤30 (n = 180) |
24 (77.4) |
7 (22.6) |
11 (7.4) |
138 (92.6) |
68.6 |
95.2 |
77.4 |
92.6 |
90.0 |
|
BMI >30 (n = 40) |
7 (87.5) |
1 (12.5) |
0 (0.0) |
32 (100.0) |
100.0 |
97.0 |
87.5 |
100.0 |
97.5 |
|
TP: True-positive; FN: False-negative; FP: False-positive; TN: True-negative; PPV: Positive productive value; NPV: Negative predictive value. |
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DISCUSSION
This study evaluated the diagnostic accuracy of the USS in predicting difficult LC in 220 patients, achieving an overall diagnostic accuracy of 91.3%. This indicates that the USS can be a valuable tool for assessing the difficulty of LC. This is also supported by the research conducted by Jalil et al.7
The sensitivity of 73.8% in this study was lower than the original Siddiqui et al.’s study (80.7%), while maintaining a comparable specificity (95.5% vs. 91.7%). This performance variation may reflect several factors: differences in patient populations, institutional protocols, and surgeon experience levels. Recent validation studies emphasise that difficult cholecystectomies are associated with worse surgical outcomes, and the standardisation and use of predictive scores for difficult cholecystectomies must be implemented to improve surgical outcomes through more meticulous planning when scheduling procedures.2 A 2023 diagnostic trial comparing multiple scoring systems found significant variability in performance across different clinical settings, highlighting the challenges of developing universally applicable predictive models.8
Pal et al. reported different performance metrics with their combined clinical-USS, achieving a sensitivity and a specificity of 88.2% and 73.8%, respectively, for predicting easy cases,6 demonstrating the ongoing challenge of optimising predictive accuracy. Ary Wibowo et al. in their cross- sectional study emphasised that LC has become the preferred method due to its advantages over open cholecystectomy,9 however, noted continued challenges in preoperative difficulty prediction.
The observed prevalence of high USS scores (17.7%) in the present cohort was lower than anticipated based on the reference study (27.7%), potentially reflecting differences in disease severity patterns or referral practices. This lower prevalence contributed to wider confidence intervals for the sensitivity estimates but aligns with the realistic clinical scenario where most cholecystectomies are routine procedures.
This study identified eight false-positive cases (20.6% of high USS scores), representing patients predicted to have difficult procedures but underwent routine surgery. These cases highlight a significant limitation of ultrasound-based assessment in detecting all factors contributing to surgical complexity. Recent literature emphasises that multiple scores have been created to predict difficult cholecystectomy, but there is no consensus on which to use, indicating that ultrasound parameters alone may be insufficient for comprehensive difficulty prediction.
More concerning were the 11 false-negative cases (26.2% of actual difficult cases), where the USS failed to predict surgical difficulty. This represents a substantial proportion of cases where surgeons would be unprepared for operative challenges. Similar to the assessment of Ghadhban10 and Karim et al.,11 these findings improve the quality of surgical care provided to the patients. The operating surgeon is able to plan the surgery according to the difficulty indicated by the USS.12,13 This not only allows the surgeon to prepare for adverse perioperative circumstances, it is also a safer and effective way to provide surgical care.14
The diagnostic accuracy of the USS is defined as its ability to distinguish between patients who will have a difficult laparoscopic procedure and patients who will not have a difficult laparoscopic procedure.15 This study has shown the diagnostic accuracy of the USS to be 91.3%. This is comparable with the study done by Abdelhamid et al.16 The importance of preoperative assessment of difficult cholecystectomy has been made evident by many researchers.17,18 Many patients have suffered the consequences of unanticipated preoperative difficulty.19 The results of this study have shown that using the USS preoperatively can correctly predict perioperative difficulty in most cases. Therefore, the USS can play a valuable role in reducing operative time and perioperative complications.20,21
The diagnostic accuracy of 91.3% should be interpreted cautiously, given these limitations and the lack of external validation, as the study has several important limitations that affect the interpretation of results. The accuracy of sonographic findings is highly dependent on the skills and experience of the radiologist or sonographer performing the examination, which can introduce variability in data interpretation. Ultrasound may not capture all the factors that contribute to operative difficulty (e.g., intra-abdominal adhesions, patient comorbidities, and surgeon’s experience). Operating surgeons were not blinded to the USS results, which may have introduced assessment bias in difficulty evaluation.
CONCLUSION
This study highlights the importance of the USS and its potential benefit in predicting the operative difficulty of LC. However, due to the limitations of ultrasound and the multifactorial nature of operative difficulty, sonographic prediction should complement, rather than replace, clinical judgement. Further multicentre, prospective studies with larger sample sizes are recommended to validate and refine these predictive models.
ETHICAL APPROVAL:
Ethical approval was obtained from the Ethical Review Board of the Railway General Hospital, Rawalpindi, Pakistan (Riphah/lRC/24/1042; Dated: 26th March 2024).
PATIENTS’ CONSENT:
Informed written consent was taken from all participants.
COMPETING INTEREST:
The author declared no conflict of interest.
AUTHORS’ CONTRIBUTION:
RN: Conception, design of the work, acquisition, analysis, and interpretation of the data.
OSK: Drafting of the work and critical revision of the manuscript for important intellectual content.
JAH: Final approval of the version to be published.
NS: Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or inte-grity of any part of the work are appropriately investigated and resolved.
All authors approved the final version of the manuscript to be published.
REFERENCES