Intraoperative ultrasound enhancing safety of key steps in complex laparoscopic cholecystectomy: a single-blinded randomized controlled trial.

Since Philippe Mouret performed the world’s first laparoscopic cholecystectomy (LC) in 1987, this procedure has become the standard surgery for treating benign gallbladder diseases (BGBD) such as stones and polyps due to its advantages of minimal invasiveness and rapid recovery [ 1 – 4 ] . The first LC in China was reported in 1991 in Qujing, Yunnan Province [ 5 ] . Currently, LC has been widely adopted in hospitals of all levels across this country, even township hospitals in economically underdeveloped areas. Although LC has emerged as the most routine laparoscopic procedure, its safety continues to be subject to numerous challenges. First, the incidence of biliary injury ranges from 0.08 to 0.3% [ 6 , 7 ] , frequently accompanied by blood supply damage of the biliary tracts, resulting in more severe consequences than those of open surgery. Second, the occurrence rate of stones in the residual gallbladder or cystic duct (CD) ranges between 2.5 and 16%. Occasionally, residual stones (RS) may be found in the common bile duct (CBD) after LC surgery, with a prevalence ranging from 2 to 5% [ 8 , 9 ] . Most of the patients with RS require secondary surgical intervention for persistent abdominal pain. The main reasons for RS include failure to diagnose CD/CBD stones preoperatively, biliary variations, and blind adoption of bailout procedures such as partial cholecystectomy [ 10 – 12 ] . In addition, the management of incidental gallbladder cancer (IGBC), with an incidence rate of 0.6–0.9%, is an inevitable challenge [ 13 ]. IGBC is more prevalent among patients with a history of recurrent acute cholecystitis, comprising 35–60% of all gallbladder cancer (GBC) [ 14 ] . Roughly 30% of LC cases experience intraoperative iatrogenic rupture (IIR) of the gallbladder wall (GBW), with pneumoperitoneum facilitating trocar site and peritoneal implantation metastasis [ 15 – 17 ] . Intraoperative ultrasonography (IOUS) is a widely utilized equipment in hepatobiliary surgery, offering advantages such as convenience, non-invasiveness, and reusability. IOUS is considered a viable alternative to traditional intraoperative cholangiography [ 18 ] . The application of IOUS during LC has enabled 91% of challenging cases to avoid conversion to open surgery [ 19 ] . The present prospective randomized controlled study aims to validate the role of IOUS during the full process of LC, including managing the Calot’s triangle, guiding the selection of suitable approaches for isolating the gallbladder from the liver, and diagnosing residual stones. The authors declared that AI and AI-supported technologies were not used in the present research and manuscript development. The work has been reported in line with the Transparency In The reporting of Artificial Intelligence (TITAN) criteria [ 20 ] .

The present study prospectively enrolled patients who underwent LC in the Department of Hepatobiliary Surgery of Shanghai Tenth People’s Hospital from May 2024 to May 2025. The study was approved by the Clinical Trial Ethics Committee (Ethics Authorization Number: 24K20), and all of the participants provided written informed consent before enrollment. This research adhered to the CONsolidated Standards Of Reporting Trials (CONSORT) guidelines [ 21 ] . It followed the ethical principles outlined in the “Regulations for Ethical Review of Biomedical Research Involving Human Participants” issued by the National Health Commission of China (2016), “Declaration of Helsinki (2013),” and the “International Ethical Guidelines for Biomedical Research Involving Human Subjects (2002).” This study was registered with the Chinese Clinical Trial Registry ( https://www.chictr.org.cn/ ), number ChiCTR2500105540. The study protocol and ethical approval could be accessed on the above website. Data supporting this study would be available from (Electronic Data Capture: China National Center for Bioinformation) at ( https://ngdc.cncb.ac.cn/gsub/ ) following a 12-month embargo. The inclusion criteria for patients were as follows: (1) prior to admission, the patient was diagnosed via ultrasound with benign gallbladder conditions, such as gallstones, gallbladder polyps, and gallbladder adenomyomatosis; (2) age: ≥18 and ≤90 years old; (3) preoperative diagnosis of BGBD, and patients who were able to tolerate LC; and (4) patients who met the conditions for IOUS examination. Exclusion criteria: (1) patients with significant organ or systemic comorbidities who could not tolerate general anesthesia or LC; (2) patients with severe, unmanageable mental illness, inability to cooperate with diagnostic and therapeutic activities, or a history of drug use, severe alcoholism, or substance abuse that might affect the normal conduct of the trial; (3) patients with a preoperative diagnosis of gallbladder cancer or high suspicion of malignancy; and (4) patients who did not meet the conditions for IOUS scanning of the gallbladder or hepatoduodenal ligament due to severe intra-abdominal adhesions or other reasons. HIGHLIGHTS The utilization of IOUS during LC enhances the safety of the following crucial procedures: Identify adherent gastrointestinal tracts within the surgical field. Diagnose CD stones. The integration of IOUS with GB-RADS helps in guiding the selection of safe dissection approaches for GBW and preventing IIR for cases with a risk of canceration. The utilization of IOUS during LC enhances the safety of the following crucial procedures: Identify adherent gastrointestinal tracts within the surgical field. Diagnose CD stones. The integration of IOUS with GB-RADS helps in guiding the selection of safe dissection approaches for GBW and preventing IIR for cases with a risk of canceration. Upon hospital admission, patients provided informed consent and underwent randomization. After screening based on predefined inclusion and exclusion criteria, patients were randomly assigned to the IOUS group and the control group in a 1:1 ratio using a random sequence generated by a computer program immediately after admission. The specific steps of the randomization procedure were as follows: (1) sample numbering: The study participants were sequentially numbered from 1 to the last patient; (2) random number assignment: Using the rand () function in Excel software, an independent uniformly distributed random number in the [0, 1) interval was generated for each number; and (3) sorting and grouping: all random numbers were sorted in descending order, with the first half of participants assigned to the experimental group and the remaining half to the control group. Randomization was concealed using the sequentially numbered, opaque, sealed envelopes (SNOSE) technique. Allocation was conducted consecutively by a research nurse before the start of the procedure. Patients were unaware of the intervention (Fig. 1 ). Figure 1. Consolidated Standards of Reporting Trials (CONSORT) flow diagram of this study. Consolidated Standards of Reporting Trials (CONSORT) flow diagram of this study. Following randomization, patients underwent preoperative assessments, which included symptom inquiry, physical examination, complete blood count, C-reactive protein test, liver function tests, and enhanced magnetic resonance cholangiopancreatography (MRCP) or CT scans. LCs were performed by two experienced senior surgeons, and the surgeon in charge has held ultrasound technician certification and conducts over 350 cases of medium- to large-scale hepatobiliary surgeries annually, employing IOUS for guidance. All of the IOUS images were independently interpreted and diagnosed by two highly experienced, senior-level ultrasound specialists, who offered recommendations to guide the surgeon’s operational decisions. After general anesthesia, patients were kept in the reverse Trendelenburg position with a left lateral tilt of 30°. The observation port was placed at the lower margin of the umbilical fossa, 10 mm in size. For patients with previous surgical incisions below the umbilicus, the placement location of the first observation port trocar was selected at the upper margin of the umbilicus. The insufflator was connected to maintain a constant intra-abdominal pressure of 12–14 mmHg. A 10 mm main operation hole and a 5 mm auxiliary hole were made 2 cm below the xiphoid process and at 2–3 cm below the projection point of the abdominal wall of the gallbladder fundus, respectively. Before starting the operation, the “Surgical Difficulty Grading System (SDGS)” was employed to evaluate the inflammation in the gallbladder, Calot’s triangle, and the region of the hepatoduodenal ligament [ 19 ] . In general, the Calot’s triangle was dissected first, followed by the ligation of the cystic artery (CA) and CD after achieving a critical view of safety (CVS). If it was deemed unsafe to dissect the triangle due to inflammation or fibrosis, a fundus-first approach or bailout procedure would be employed. After the management of the Calot’s triangle, the gallbladder was dissected from the liver bed. In the control group, LC was performed according to standard operating procedures, without using any other imaging techniques similar to IOUS for assisting surgery. Patients routinely underwent palpation of the CD using forceps before its disconnection. Those with positive palpation results or stones detected at the proximal end of the disconnected stump of CD were treated using the cystic duct micro-incision (CDMI) technique [ 22 ] , which entailed making a transverse incision in the CD to half of its diameter, followed by compression from the CBD towards the neck of the gallbladder to expel any potential sedimented stones or flocculent material through the small incision. In the IOUS group, the probe (BK medical Ultra View 2202 or SonoScape LAP7) was inserted into the abdominal cavity through the subxiphoid trocar (main operation hole), and the following steps were performed in sequence: (1) differentiate whether there were adherent gastrointestinal structures in the operative field. The presence of adhesion was verified via the observation port and then used IOUS as an adjunct; (2) trace the confluence of the CD and (common hepatic duct) CHD to diagnose CD stones. For patients exhibiting typical imaging characteristics of gallstones, such as hyperechoic foci with acoustic shadowing in the CD, exposure of the confluence between CD and CHD was achieved. Subsequently, the CDMI technique was employed. Once no additional stones could be expelled or extracted via the CD, IOUS should be employed again to scan the stump of the CD and the entire length of the CBD, ensuring there were no residual stones; and (3) scan the GBW to evaluate its echo characteristics (Fig. 2 ). The IOUS images of the GBW were graded based on the modified international expert consensus of the Gallbladder Reporting and Data System (GB-RADS) [ 23 ] . Given the reported limited discriminative power of GB-RADS classifications in differentiating GBC [ 24 ] , we did not strictly rely on GB-RADS for intraoperative GBC diagnosis. Instead, we utilized this system to guide the dissection of GBW, thereby reducing the occurrence of IIR. For patients classified as GB-RADS grade 1 and 2A, we adopt the subserosal approach (SA). For GB-RADS grade 2B patients, we use the cystic plate approach (CPA), and for grade 2C patients, we employ the liver bed approach (LBA) (Table 1 ). With the exception of whether IOUS was used, all other steps in the LC surgery procedure remained the same for both groups of patients. Figure 2. Confirmation of the structures at the confluence of the CD and CHD. (A) prior to dissecting the Calot triangle, scan from the ventral side and trace the convergence pattern of CD and CHD. (B) After achieving CVS, re-scan to confirm the convergence pattern of CD and CHD. (C–E) IOUS images depicting the entire process of the CD converging into the CHD. The yellow triangle indicated the CD, the green arrow indicated the CHD, and the white arrow indicated the CBD formed by the junction of CD and CHD. CD, cystic duct; CHD, common hepatic duct; CVS, critical view of safety; CBD, common bile duct. Table 1 Selection of surgical approach of gallbladder wall dissection based on GB-RADS. GB-RADS IOUS characteristics Surgical approaches 1 Adequate gallbladder distension, wall thickness ≤ 3 mm Subserosa 2A Symmetric circumferential thickening without intramural changes Subserosa 2B Symmetric circumferential thickening with multiple intramural changes Cystic plate 2C Focal thickening with intramural changes Liver bed GB-RADS, Gallbladder Reporting and Data System; IOUS, intraoperative ultrasonography. Subserosa approach: between the inner (SS-IL) and outer layer of the subserosa (SS-OL). Cystic plate approach: between Laennec’s membrane of the liver parenchyma and the cystic plate. Liver bed: combined liver bed resection. Confirmation of the structures at the confluence of the CD and CHD. (A) prior to dissecting the Calot triangle, scan from the ventral side and trace the convergence pattern of CD and CHD. (B) After achieving CVS, re-scan to confirm the convergence pattern of CD and CHD. (C–E) IOUS images depicting the entire process of the CD converging into the CHD. The yellow triangle indicated the CD, the green arrow indicated the CHD, and the white arrow indicated the CBD formed by the junction of CD and CHD. Selection of surgical approach of gallbladder wall dissection based on GB-RADS. GB-RADS, Gallbladder Reporting and Data System; IOUS, intraoperative ultrasonography. Subserosa approach: between the inner (SS-IL) and outer layer of the subserosa (SS-OL). Cystic plate approach: between Laennec’s membrane of the liver parenchyma and the cystic plate. Liver bed: combined liver bed resection. After gallbladder removal, the specimen was extracted via the trocar below the xiphoid process utilizing a retrieval bag. A drainage tube was inserted through Winslow’s foramen routinely. The patients were fed with liquid 6 h after the operation. The routine blood test, liver function, and serum pancreatic amylase were examined on the first day after the operation, and patients were given a low-fat semi-liquid diet. All perioperative complications were graded according to the Clavian–Dindo classification. The pathological diagnosis of the gallbladder specimens was conducted independently by two highly experienced, senior pathologists. The patient underwent three outpatient follow-up visits after LC: at 2 weeks, 3 months, and 5 months postoperatively. The follow-up content included consultation, physical examination, and liver function tests such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (AKP), gamma glutamyl transpeptidase (γ-GT), direct bilirubin (D-bil), total bilirubin (T-bil), and abdominal ultrasound. For patients with significant complaints of abdominal pain or abnormally elevated bilirubin levels accompanied by bile duct dilation, MRCP was performed. The primary aim of this study was to assess the following outcomes between the IOUS group and control group: (1) confirmation rate of the confluence pattern of CD/CHD, (2) diagnostic rate of CD stones, (3) rate of IIR of GBW, and (4) rate of gastrointestinal injury and gastrointestinal tract cauterization by energy devices. Secondary outcomes encompassed postoperative complications such as bleeding, bile leakage, abdominal infection, and length of hospital stay. If severe intraoperative bleeding, bile leakage, gallbladder rupture, or biliary tract injury occurs in the IOUS group, the experiment will be terminated. In this study, our primary focus was on whether IOUS could effectively diagnose CD stones and whether it was feasible to guide the selection of an appropriate approach to the GBW through the use of IOUS. This was due to the fact that, in both of the aforementioned aspects, the diagnostic performance of current preoperative routine imaging examinations is less than ideal. According to reports, the sensitivity of MRCP in detecting CD stones is relatively low at approximately 75% [ 25 , 26 ] . When it comes to suspicious carcinomatous changes in the gallbladder, the typical ultrasound manifestation is the disappearance of the multi-layered structure of the GBW. The sensitivity of percutaneous high-resolution ultrasound in detecting such changes stands at only approximately 64.3% [ 27 ] . Assuming that IOUS could enhance the sensitivity of the aforementioned indicators by 20%, and given a type I error probability α  = 0.05 and a power of 80%, the calculated expected sample sizes for diagnosing CD stones and distinguishing the structural hierarchy of the GBW were 49 and 74 cases for each group, respectively. Taking into account a 5% dropout rate, the final determined sample size was 76 per group, respectively. The sample size was calculated using the tool provided at the website “ https://clincalc.com/stats/samplesize.aspx .” Categorical variables were expressed as proportions, and continuous variables were presented as mean (SD) or median (IQR) based on the normality of their distribution. Count data were analyzed using the chi-square test or the Fisher’s exact test for proportions, and continuous variable data were assessed using independent t -tests or Mann–Whitney U tests. A P -value < 0.05 was defined as statistically significant. All statistical tests were conducted using IBM SPSS 25.0.

A total of 155 patients fulfilled the enrollment criteria. Due to that, 3 patients declined to participate in this study, leaving a final total of 152 patients who underwent randomization. All enrolled patients successfully completed the study without any loss to follow-up. The baseline characteristics of the study population were outlined in Table 2 . Table 2 Baseline characteristics of study participants. Parameters Total ( n = 152) IOUS ( n = 76) Control ( n = 76) P Gender 0.504  Male 58 (38.16) 27 (35.53) 31 (40.79)  Female 94 (61.84) 49 (64.47) 45 (59.21) Age (years) 62.0 (50.0; 68.0) 61.5 (53.8; 68.0) 64 (50.0; 67.0) 0.884 Chief complaint 0.164  Asymptomatic 16 (10.52) 9 (11.84) 7 (9.21)  Acute abdominal pain 26 (17.11) 17 (22.37) 9 (11.84)  Chronic abdominal pain 110 (72.37) 50 (65.79) 60 (79.45) Inflammation indicators  White blood cell (10 9 /L) 5.82 (4.86; 7.11) 5.74 (4.82; 7.28) 6.05 (5.03; 6.89) 0.947  NEUT (%) 60.8 (54.8; 69.2) 60.8 (56.5; 69.1) 62.0 (54.1; 69.4) 0.730  C-reactive protein (μg/L) 2.18 (1.01; 3.81) 2.34 (1.17; 3.59) 1.71 (0.86; 4.10) 0.648 Liver function indicators  ALT (U/L) 22.0 (14.9; 34.9) 23.9 (17.4; 44.5) 21.1 (13.5; 30.6) 0.009  AST (U/L) 20.2 (16.6; 25.7) 21.8 (17.1; 33.3) 19.2 (15.9; 22.2) 0.002  TBIL (μmol/L) 12.3 (9.70; 17.9) 12.3 (10.3; 17.7) 12.5 (9.17; 18.0) 0.841  DBIL (μmol/L) 3.80 (3.00; 5.43) 3.90 (2.98; 5.55) 3.75 (3.00; 5.32) 0.753  AKP (U/L) 72.0 (59.0; 91.4) 74.4 (58.8; 101) 70.7 (59.7; 87.7) 0.376  γ-GT (U/L) 29.1 (18.2; 60.1) 31.6 (17.3; 88.3) 27.4 (18.9; 43.5) 0.149  Albumin (g/L) 44.5 (42.3; 45.9) 44.5 (42.1; 45.9) 44.2 (42.6; 45.9) 0.835 Serum pancreatic amylase (U/L) 55.6 (46.5; 69.3) 56.0 (47.8; 71.5) 54.5 (46.0; 68.2) 0.371 Preoperative diagnosis 0.643  Stones in GB only 126 (82.90) 64 (84.21) 62 (81.58)  Stones in both GB and CBD 7 (4.61) 4 (5.26) 3 (3.95)  GB polyp 12 (7.89) 4 (5.26) 8 (10.52)  GB adenomyosis 6 (3.95) 3 (3.95) 3 (3.95)  Residual GB 1 (0.66) 1 (1.32) 0 (0.00) Gallbladder size (cm) 6.8 (6.1, 7.8) 6.8 (5.9, 8.2) 6.8 (6.4, 7.5) 0.751 GBW thickening (>3 mm) 0.064  Yes 134 (88.16) 72 (94.74) 64 (84.20)  No 18 (11.84) 4 (5.26) 12 (15.80) Gallstones ( N = 134) ( N = 69) ( N = 65)  Duration of illness 16.00 (2.00; 66.20) 12.00 (2.00; 60.00) 24.00 (2.00; 84.00) 0.527  Multiple stone 98 (73.13) 53 (76.81) 45 (69.23) 0.427  Diameter of the largest stone (cm) 1.40 (1.00; 2.10) 1.50 (1.00; 2.40) 1.30 (0.80; 1.80) 0.091  Stone incarceration in the GB neck 10 (7.46) 5 (7.25) 5 (7.69) 1.000 History of acute cholecystitis 40 (29.85) 22 (31.88) 18 (27.69) 0.733 PTGBD before cholecystectomy 11 (8.21) 8 (11.59) 3 (4.61) 0.248 GB polyp and adenomyosis ( N = 18) ( N = 7) ( N = 11)  Duration of illness 4.50 (1.00; 24.00) 2.00 (1.00; 13.50) 12.00 (1.00; 30.00) 0.406  Multiple polyps and adenomyosis 10 (55.56) 2 (28.57) 8 (72.73) 0.145  Diameter of the largest polyp and adenomyosis (cm) 1.00 (0.72; 1.20) 1.30 (1.10; 1.50) 0.90 (0.70; 1.00) 0.025 Special imaging findings  Abnormal biliary confluence or variation 12 (8.96) 6 (8.70) 6 (9.23) 1.000 IOUS, intraoperative ultrasonography; GB, gallbladder; CBD, common bile duct; GBW, gallbladder wall; PTGBD, percutaneous transhepatic gallbladder drainage; ALT, alanine aminotransferase; AST, aspartate aminotransferase; AKP, alkaline phosphatase; γ-GT, γ-glutamyl transpeptidase; D-bil, direct bilirubin; T-bil, total bilirubin. Baseline characteristics of study participants. IOUS, intraoperative ultrasonography; GB, gallbladder; CBD, common bile duct; GBW, gallbladder wall; PTGBD, percutaneous transhepatic gallbladder drainage; ALT, alanine aminotransferase; AST, aspartate aminotransferase; AKP, alkaline phosphatase; γ-GT, γ-glutamyl transpeptidase; D-bil, direct bilirubin; T-bil, total bilirubin. Based on the assessment results of the “SDGS,” the number of patients classified as SDGS-A, B, and C levels in the two groups was 33 and 38, 37 and 34, and 6 and 4 cases, respectively. No significant difference in surgical difficulty was observed between the two groups ( P = 0.601) (Table 3 ). Table 3 Evaluation of inflammation and surgical difficulty between the two groups. Grade A Grade B Grade C 0 1 2 3 4 5 6 IOUS 0 (0.00) 33 (43.42) 27 (35.52) 10 (13.16) 4 (5.26) 2 (2.63) 0 (0.00) Control 0 (0.00) 38 (50.00) 29 (38.16) 5 (6.58) 2 (2.63) 2 (2.63) 0 (0.00) IOUS, intraoperative ultrasonography. Evaluation of inflammation and surgical difficulty between the two groups. IOUS, intraoperative ultrasonography. As shown in Table 4 , there were no differences observed between the two groups in terms of operative duration, intraoperative blood loss, conversion rate to open cholecystectomy, surgical method, achievement rate of CVS, postoperative complications, length of postoperative hospital stay, and abdominal drainage volume ( P > 0.05). Table 4 Comparison of surgical outcomes between the two groups. Parameters Total ( n = 152) IOUS ( n = 76) Control ( n = 76) P Operative duration (min) 69.0 (55.00; 101.00) 79.00 (55.00; 109.00) 67.00 (56.00; 80.00) 0.132 Intraoperative blood loss (mL) 10.00 (10.00, 20.00) 10.00 (10.00, 30.00) 10.00 (10.00, 20.00) 0.073 Rate of conversion to open surgery ( n (%)) 1 (0.66) 1 (1.67) 0 (0.00) 1.000 Operative method of LC ( n (%)) 0.053  Simple cholecystectomy 141 (92.76) 70 (92.11) 71 (93.42)  Subtotal cholecystectomy 4 (2.63) 0 (0.00) 4 (5.26)  Fenestrating 1 (0.65) 0 (0.00) 1 (1.31)  Reconstituting 0 (0.00) 0 (0.00) 0 (0.00)  Preserve the entire posterior GBW 3 (1.97) 0 (0.00) 3 (3.95)  Cholecystectomy combined with liver parenchyma 6 (3.95) 5 (6.58) 1 (1.31)  LCBDE 1 (0.65) 1 (1.31) 0 (0.00) Timing for LC in acute cholecystitis ( N = 26) ( N = 17) ( N = 9) 0.683  Urgent (prompt surgery) 15 9 6  Delayed with a history of PTGBD 11 8 3 Achieving CVS ( n (%)) 148 (97.37) 73 (96.05) 75 (98.68) 0.620 Stone confirmed in CD specimen ( n (%)) 8 (5.26) 3 (3.95) 5 (6.58) 0.468 Stone confirmed before CD transected 4 (50.00%) 3 (100.00%) 1 (20.00%) 0.143  Diagnosis of CD stone by palpation before transection 2 (20.00) 1 (33.33) 1 (20.00)  Diagnosis of CD stone by IOUS before transection N/A 3 (100.00) N/A N/A Confirm the confluence pattern of CD 78 (51.32) 75 (98.68) 3 (3.94) 0.001 Management of GBW ( n (%))  Approaches for GBW 0.009  Subserosal 131 (86.18) 58 (76.32) 73 (96.05)  Cystic plate 15 (9.87) 13 (17.11) 2 (2.63)  Liver bed approach 6 (3.95) 5 (6.58) 1 (1.32) IIR of GBW 16 (10.53) 3 (3.95) 13 (17.11) 0.017 Detected CBD stone intraoperatively 1 (0.66) 1 (1.67) 0 (0.00) 1.000 Rupture of adherent GI serosa ( n (%)) 2 (1.32) 1 (1.67) 1 (1.67) 1.000 GI cauterization by energy devices ( n (%)) 3 (1.97) 0 (0.00) 3 (3.94) 0.080 Postoperative complications ( n (%)) 2 (1.32) 2 (2.63) 0 (0.00) 0.188  Bile leakage 0 (0.00) 0 (0.00) 0 (0.00) N/A  Bleeding 0 (0.00) 0 (0.00) 0 (0.00) N/A  Abdominal infection or abscess 2 (1.32) 2 (2.63) 0 (0.00) 0.497  Residual stone in CD 0 (0.00) 0 (0.00) 0 (0.00) N/A  Residual stone in the CBD requiring ERCP treatment 0 (0.00) 0 (0.00) 0 (0.00) N/A  Wound infection 0 (0.00) 0 (0.00) 0 (0.00) N/A Length of postoperative hospitalization ( d ) 2.00 (2.00; 3.00) 2.00 (2.00; 3.00) 2.00 (2.00; 3.00) 0.547 Postoperative drainage volume (ml) 25.0 (15.80; 37.50) 22.90 (15.20; 37.80) 25.00 (17.10; 37.50) 0.592 Pathological diagnosis ( n (%))  Chronic cholecystitis 123 (80.92) 60 (78.95) 63 (82.89) 0.679  Acute cholecystitis and acute exacerbation of chronic cholecystitis 26 (17.10) 17 (22.37) 9 (11.84) 0.131  Cholesterol polyp 21 (13.82) 9 (11.84) 12 (15.79) 0.638  GB adenoma 2 (0.66) 0 (0.00) 2 (2.63) 0.496  Xanthogranuloma 2 (1.32) 2 (2.63) 0 (0.00) 0.496  Rokitansky–Aschoff sinuses 27 (17.76) 10 (13.16) 17 (22.37) 0.203  GB adenomyosis 43 (28.29%) 24 (31.58%) 19 (25.00%) 0.471  Atypical hyperplasia 13 (8.55) 8 (10.53) 5 (6.58) 0.562  Mild 9 (5.92) 6 (7.89) 3 (3.94)  Moderate 3 (1.97) 2 (2.64) 1 (1.32)  Severe 1 (0.66) 0 (0.00) 1 (1.32) IGBC 1 (0.66) 1 (1.32) 0 (0.00) 1.000 IOUS, intraoperative ultrasonography; LC, laparoscopic cholecystectomy; CVS, critical view of safety; CD, cystic duct; GB, gallbladder; GBW, gallbladder wall; CBD, common bile duct; GI, gastrointestinal tract; ERCP, endoscopic retrograde cholangiopancreatography; IGBC, incidental gallbladder carcinoma; PTGBD, percutaneous transhepatic gallbladder drainage. Comparison of surgical outcomes between the two groups. IOUS, intraoperative ultrasonography; LC, laparoscopic cholecystectomy; CVS, critical view of safety; CD, cystic duct; GB, gallbladder; GBW, gallbladder wall; CBD, common bile duct; GI, gastrointestinal tract; ERCP, endoscopic retrograde cholangiopancreatography; IGBC, incidental gallbladder carcinoma; PTGBD, percutaneous transhepatic gallbladder drainage. Among the enrolled patients in this study, a total of eight cases were ultimately diagnosed with CD stones (three cases in the IOUS group and five cases in the control group). In the control group, MRCP diagnosed only one patient with incarcerated CD stones measuring 5.5 mm in diameter, along with CD dilation. Several months prior to admission, this patient presented with “obvious upper abdominal pain” and was diagnosed with acute cholecystitis and underwent PTGBD. During LC, the stone was clearly diagnosed by palpating the CD. On the other hand, the remaining patients (three cases in the IOUS group and four cases in the control group), whose MRCP showed no evidence of stones or dilation of CD. Additionally, these patients also exhibited no abdominal pain. The final pathological examination revealed that their CD stones that MRCP failed to detect were either tiny stones with diameters of less than 4 mm or thick, dense bile sludge that was not easily flowable. We cannot rule out the possibility that these small stones fell into the CBD from the gallbladder during the surgery. The diagnostic rate of CD stones for the IOUS group was higher than that for the control group (100.00 vs. 20.00%), but not statistically significant ( P = 0.143) (Supplemental Digital Content Video 1, available at: http://links.lww.com/JS9/G494 ). The confirmation rate of the CD confluence pattern in the IOUS group was significantly higher compared to the control group (98.68 vs. 3.94%, P = 0.001) (Fig. 2 ). IOUS clearly demonstrated the morphology of multiple GBW layers under different levels of inflammation, and its application effectively reduced the occurrence of IIR (3.95 vs. 17.11%, P = 0.017). Furthermore, although statistically insignificant, IOUS helped in differentiating adherent gastrointestinal tissues in surgical areas, thereby preventing them from cauterization by energy devices (Fig. 3 ). Figure 3. IOUS scanning for identifying adherent intestinal loops. (A) IOUS scanning of the Calot’s triangle area; (B) IOUS revealed the adherent duodenum ventral to the junction of the CD, CHD, and CBD (within the yellow-lined area), showing the intestinal wall structure and gas in the intestinal lumen; (C) IOUS scanning adhesion beneath the liver; and (D) IOUS indicated the presence of the gallbladder beneath the omentum. *Gas in the intestinal lumen; white triangle indicates the junction part of CD with CBD; white arrow indicates endoscopic nasobiliary drainage (ENBD) tube in CBD.IOUS, intraoperative ultrasound; CD, cystic duct; CHD, common hepatic duct; CBD, common bile duct. IOUS scanning for identifying adherent intestinal loops. (A) IOUS scanning of the Calot’s triangle area; (B) IOUS revealed the adherent duodenum ventral to the junction of the CD, CHD, and CBD (within the yellow-lined area), showing the intestinal wall structure and gas in the intestinal lumen; (C) IOUS scanning adhesion beneath the liver; and (D) IOUS indicated the presence of the gallbladder beneath the omentum. For the IOUS group, the ultrasound images of the GBW were classified based on the modified GB-RADS system. There were 5, 53, 14, and 4 patients in GB-RADS 1 (Fig. 4 ), 2A (Fig. 5 ), 2B (Fig. 6 ), and 2C (Fig. 7 ) subgroups, respectively. Figure 4. IOUS findings and surgical approach for GBW of GB-RADS 1. (A) MRI image of the gallbladder; (B) IOUS image indicated thin GBW with clearly identifiable boundaries between SS-IL and SS-OL, as well as between the gallbladder and the liver; (C) dissection of the GBW utilizing the SA; and (D) pathology revealed distinct layers of the GBW. IOUS, intraoperative ultrasound; M, mucosa; MP, muscularis propria; SS-IL, inner layer of subserosa; SS-OL, outer layer of subserosa; GBW, gallbladder wall; GB-RADS, Gallbladder Reporting and Data System; SA, subserosal approach. Figure 5. IOUS findings and surgical approach for GBW of GB-RADS 2A. (A) MRI imaging of the gallbladder; (B) IOUS imaging of the GBW indicated thickening, distinguishable SS-IL and SS-OL, as well as a distinct boundary between gallbladder and the liver; (C) dissection of the GBW was performed using the SA; and (D) pathology revealed clearly defined layers of tissue within the GBW. IOUS, intraoperative ultrasound; M, mucosa; MP, muscularis propria; SS-IL, inner layer of subserosa; SS-OL, outer layer of subserosa; GBW, gallbladder wall; GB-RADS, Gallbladder Reporting and Data System; SA, subserosal approach. Figure 6. IOUS findings and surgical approach for GBW of GB-RADS 2B. (A) MRI imaging of the gallbladder; (B) IOUS imaging revealed thickening of the GBW, with indistinct demarcation between SS-IL and SS-OL (*) in certain areas; the boundary between GBW and liver remained clear; hyperechoic nodule was visible within the GBW; (C) GBW dissection was performed using the CPA; (D) Pathology indicated unclear demarcation between SS-IL and SS-OL in the GBW, accompanied by partial mucosal shedding. Black arrows indicated the Laennec’s capsule; (E) inflammatory granuloma (1); (F) inflammatory polyp (2); (G) extensive fibrous tissue was visible adjacent to the inflammatory polyp; and (H–I) mild atypical hyperplasia is observed in some area in the mucosa (Fig. 6I showed enlarged view of the area enclosed by the red box in Fig. 6H). IOUS, intraoperative ultrasound; SS-IL, inner layer of subserosa; SS-OL, outer layer of subserosa; GBW, gallbladder wall; GB-RADS, Gallbladder Reporting and Data System; CPA, cystic plate approach. Figure 7. IOUS findings and surgical approach for GBW of GB-RADS 2C. (A) CT enhancement of the patient’s gallbladder reveals irregular thickening of the GBW accompanied by low-density areas; (B) IOUS imaging indicated an intact mucosal line, irregular thickening of the gallbladder, and indistinct echoes between the GBW and liver parenchyma (*); (C) gallbladder resection via LBA (#); (D–E) pathology revealed significant thickening of the GBW, xanthogranulomatous cholecystitis, and marked fibrosis in SS-IL and SS-OL with poorly defined layers; and (F–G) the SS-OL and hepatic bed parenchyma (Fig. 7E showed enlarged view of the area enclosed by the red box in Fig. 7D) have poorly defined layers, consistent with the IOUS findings (Fig. 7G showed enlarged view of the area enclosed by the red box in Fig. 7F). IOUS, intraoperative ultrasound; SS-IL, inner layer of subserosa; SS-OL, outer layer of subserosa; GBW, gallbladder wall; GB-RADS, Gallbladder Reporting and Data System; LBA, liver bed approach. IOUS findings and surgical approach for GBW of GB-RADS 1. (A) MRI image of the gallbladder; (B) IOUS image indicated thin GBW with clearly identifiable boundaries between SS-IL and SS-OL, as well as between the gallbladder and the liver; (C) dissection of the GBW utilizing the SA; and (D) pathology revealed distinct layers of the GBW. IOUS findings and surgical approach for GBW of GB-RADS 2A. (A) MRI imaging of the gallbladder; (B) IOUS imaging of the GBW indicated thickening, distinguishable SS-IL and SS-OL, as well as a distinct boundary between gallbladder and the liver; (C) dissection of the GBW was performed using the SA; and (D) pathology revealed clearly defined layers of tissue within the GBW. IOUS findings and surgical approach for GBW of GB-RADS 2B. (A) MRI imaging of the gallbladder; (B) IOUS imaging revealed thickening of the GBW, with indistinct demarcation between SS-IL and SS-OL (*) in certain areas; the boundary between GBW and liver remained clear; hyperechoic nodule was visible within the GBW; (C) GBW dissection was performed using the CPA; (D) Pathology indicated unclear demarcation between SS-IL and SS-OL in the GBW, accompanied by partial mucosal shedding. Black arrows indicated the Laennec’s capsule; (E) inflammatory granuloma (1); (F) inflammatory polyp (2); (G) extensive fibrous tissue was visible adjacent to the inflammatory polyp; and (H–I) mild atypical hyperplasia is observed in some area in the mucosa (Fig. 6I showed enlarged view of the area enclosed by the red box in Fig. 6H). IOUS findings and surgical approach for GBW of GB-RADS 2C. (A) CT enhancement of the patient’s gallbladder reveals irregular thickening of the GBW accompanied by low-density areas; (B) IOUS imaging indicated an intact mucosal line, irregular thickening of the gallbladder, and indistinct echoes between the GBW and liver parenchyma (*); (C) gallbladder resection via LBA (#); (D–E) pathology revealed significant thickening of the GBW, xanthogranulomatous cholecystitis, and marked fibrosis in SS-IL and SS-OL with poorly defined layers; and (F–G) the SS-OL and hepatic bed parenchyma (Fig. 7E showed enlarged view of the area enclosed by the red box in Fig. 7D) have poorly defined layers, consistent with the IOUS findings (Fig. 7G showed enlarged view of the area enclosed by the red box in Fig. 7F). The proportion of patients with atypical hyperplasia classified under GB-RADS grades 2B and 2C was notably higher when compared with those with GB-RADS grades 2A and 1 ( P = 0.002) (Table 5 ). Table 5 Comparisons of GB-RADS grading results between chronic cholecystitis and dysplasia. GB-RADS score Definitions and descriptions Chronic cholecystitis without atypical hyperplasia Atypical hyperplasia P 1 Adequate gallbladder distension 4 0 0.002 Wall thickness ≤ 3 mm 2 2A Symmetric circumferential thickening without intramural changes 44 2 2B Symmetric circumferential thickening with multiple intramural changes 7 5 2C Focal thickening with intramural changes at bedside 1 1 GB-RADS, Gallbladder Reporting and Data System. Comparisons of GB-RADS grading results between chronic cholecystitis and dysplasia. GB-RADS, Gallbladder Reporting and Data System. Based on the original IOUS video recordings, we determined the average durations required for scanning the GBW, the CD, and CHD confluence, and the entire length of the CBD using IOUS, which were 61.87 ± 8.34, 27.15 ± 6.98, and 61.45 ± 11.21 s, respectively. Consequently, when compared to the control group, the average additional surgery time attributed to the use of IOUS in the experimental group was merely 202.5 ± 22.08 s. This increase was virtually insignificant when compared to the total duration of the LC surgery. The follow-up results indicated that none of the patients exhibited significant abdominal pain or jaundice symptoms. Specifically, only four patients showed mild elevations in bilirubin, AKP, and γ-GT levels, accompanied by ultrasound findings of bile duct dilation (diameter ranging from 1.2 to 1.4 cm). All of these patients had pre-existing mildly elevated bilirubin before surgery. MRCP did not reveal any residual stones or CBD stones, leading us to diagnose cholestasis.

In China, patients with BGBD typically exhibit characteristics such as long disease duration, recurrent acute inflammation, and poor surgical compliance, all lead to severe adhesions or fibrosis, significantly increasing the difficulty of LC. Besides, there is also a significantly increased risk of GBC that warrants vigilance. Our data demonstrated that IOUS held significant practical values in confirming adherent gastrointestinal tract, tracking the course and confluence patterns of CD/CHD, diagnosing CD stones, and guiding the selection of suitable surgical approaches for GBW dissection. For patients with a history of prior abdominal surgery, how to avoid adherent gastrointestinal tracts when placing the observation trocar safely is the first challenge of LC. The normal abdominal cavity is a sealed environment devoid of air, whereas the contents of the intestines consist of a mixture of liquid, gas, and solid substances. In this study, we lifted abdominal wall and performed ultrasound scanning around the site selected for trocar placement, the absence of adhesions in the abdominal cavity was characterized by a black anechoic area; whereas, in cases where adhesions involved the omentum or intestinal loops, the ultrasound image showed heterogeneous mixed echoes, with the omentum and intestinal walls appearing as hypoechoic regions and the hyperechoic areas being caused by gas within the intestinal lumen, respectively (Fig. 8 ). Figure 8. Evaluate adhesion status beneath the abdominal wall in the region designated for the placement of the observation port trocar by utilizing ultrasound. (A) Lift the abdominal wall and then perform ultrasound scanning around the site selected for trocar placement; (B) IOUS imaging of adherent mesentery (*) beneath the abdominal wall. The area between the two yellow curves was peritoneum; and (C) intraoperative photograph of dense adherent mesentery beneath the abdominal wall. Black arrows indicated the scar of the previous right hemicolectomy; the black triangle indicated the umbilicus. Evaluate adhesion status beneath the abdominal wall in the region designated for the placement of the observation port trocar by utilizing ultrasound. (A) Lift the abdominal wall and then perform ultrasound scanning around the site selected for trocar placement; (B) IOUS imaging of adherent mesentery (*) beneath the abdominal wall. The area between the two yellow curves was peritoneum; and (C) intraoperative photograph of dense adherent mesentery beneath the abdominal wall. Black arrows indicated the scar of the previous right hemicolectomy; the black triangle indicated the umbilicus. Achieving CVS is an ideal goal for dissecting the Calot’s triangle safely. However, inflammation, fibrosis, and scar formation pose technical obstacles to achieving CVS and are key factors contributing to bile duct injury [ 28 ] . Bailout procedures (BP) like partial cholecystectomy might effectively prevent biliary tract injuries; however, blindly expanding the indications of BP might increase the occurrence of complications such as residual stones, biliary leaks, and abdominal abscesses [ 29 ] . Our results indicated that IOUS could clearly trace the course of intra- and extrahepatic bile ducts, especially in cases where there were variations. IOUS effectively guided the surgeons to determine the appropriate position for the CD division. It was reported that IOUS achieved high accuracy rates in identifying various bile duct structures, including intrahepatic bile ducts (95.7–100%), confluence of the left and right hepatic ducts (88.6–97.1%), CHD (98.9–92%), CBD (88.6–100%), the confluence part of CD and CHD junction (91.4–100%), and intra-pancreatic segment of CBD (73.8–98.3%) [ 30 ] . Additionally, IOUS exhibited a high vascular identification rate ranging from 89.3 to 100% in the porta hepatis and Calot’s triangle regions [ 18 , 31 – 33 ] . The proportion of patients requiring reoperation due to residual gallbladder accounts for 0.25–0.53% of all individuals who have undergone cholecystectomy. Additionally, residual gallbladder cancer is also not uncommon [ 34 – 36 ] . For CD stones, due to the diagnostic rates of conventional ultrasound and MRCP being only 66.67% and 65–75% [ 37 ] , respectively, in most cases, the presence of stones can only be determined by palpating the CD with surgical instruments during operations. Our findings indicated that IOUS might be more efficacious in the following two scenarios: (1) When preoperative imaging revealed small stones in the neck of the gallbladder that carried a risk of migrating into the CBD during the LC procedure. (2) The presence of a substantial amount of sediment-like calculi in the gallbladder. Drawing on our prior surgical experience, we frequently encounter situations where preoperative imaging fails to detect any stones in CD, yet stones are unexpectedly discovered at the transected CD stump during LC surgery. These sediment-like calculi are typically soft in texture and hard to detect through palpation with forceps. The two aforementioned types of stones might remain undetected in preoperative MRCP, or they might migrate into CD during the process of gallbladder traction [ 38 ] . Indiscriminately incising the CD for diagnostic exploration of stones might elevate the risks of biliary injury and bile leakage. Compared with MRCP, IOUS may offer advantages of enabling real-time, repeated diagnostic assessments both before and after the transection of the CD, thus confirming that there are no residual stones in either the CD or the stump or the CBD. As the “gold standard” for intraoperative assessment of biliary anatomy, intraoperative cholangiography offers the benefits of real-time visualization and excellent reproducibility. Compared with IOUS, it features a shorter learning curve and can fully delineate the entire biliary tree on a single radiographic image. Moreover, when cannulation is successful, it remains unaffected by abdominal adhesions, providing distinct advantages in diagnosing distal bile duct stones. However, intraoperative cholangiography often necessitates bile duct incision, thereby increasing the risk of patient trauma and potential bile leakage. Additionally, it requires the use of X-ray equipment, which poses radiation hazards. The prevention of IGBC is a significant challenge that each surgeon who performing LC has to confront. Histologically, GBW is composed of layers including the mucosa, muscularis propria, subserosa, and serosa (absent on the liver bed side). The subserosal layer can be further divided into the inner layer (SS-IL) and the outer layer (SS-OL). In normal or mildly inflamed GBW, the histological gap between SS-IL and SS-OL represents the suitable plane for removing the gallbladder from the liver bed. When early carcinogenesis occurs, the structure of the mucosal layer is initially disrupted. The IOUS probe boasts a frequency exceeding 10 MHz, enabling it to clearly differentiate each layer of GBW [ 39 ] . The ultrasound imaging of normal GBW exhibits a distinctive “sandwich-like” layered echogenicity: the innermost thin mucosa and the outermost layer (comprising SS-OL and serosal layer) appear hyperechoic, whereas the intervening layers, which include the muscularis propria and subserosal SS-IL, are hypoechoic, facilitating easy differentiation. The echo boundary between GBW and liver parenchyma is also distinctly clear. It is noteworthy that patients with a history of acute cholecystitis have a significantly higher risk of IGBC [ 9 ]. In this study, there were 17.10% (26 cases) of the enrolled patients presented with acute exacerbations of chronic cholecystitis. Among them, those with atypical hyperplasia accounted for 23.07%, significantly higher than the 4.06% observed in patients with chronic inflammation only. Prolonged inflammation and fibrosis might result in the disappearance of the SS-IL and SS-OL gaps, making it challenging for surgeons to discern planes during LC. Consequently, they might resort to a bailout procedure such as partial cholecystectomy, which readily leads to IIR of the GBW, thereby elevating the risk of tumor dissemination. GB-RADS was a recently introduced ultrasound-based system designed for assessing GBW thickness and stratifying canceration risks. Due to factors such as intestinal adhesions affecting the observation, GB-RADS based on body surface ultrasound scanning was not applicable to patients with acute cholecystitis, abdominal adherence, or obesity. IOUS effectively avoids the above issues by directly scanning within the abdominal cavity when utilizing GB-RADS [ 23 ] . Two crucial conditions for preventing IGBC were as follows: (1) the basic condition was avoiding IIR; and then (2) selecting an oncological safe plane for GBW dissection. These were especially important for GB-RADS 2B/2C patients, among whom more atypical hyperplasia cases were diagnosed than GB-RADS 1/2A patients, according to our data. For patients with GB-RADS grades 1 and 2A, we employed the SA. Upon IOUS examination, the innermost mucosal layer of the GBW was visible as a thin, continuous hyperechoic layer. The SS-OL, on the other hand, demonstrated a uniform “fine granular” or “reticulated” hyperechoic pattern characteristic of adipose tissue, with distinct boundaries separating it from the intervening SS-IL and the hypoechoic muscularis propria. One patient diagnosed with carcinoma in situ was evaluated as GB-RADS 2A. The patient underwent GBW stripping via SA without IIR, and postoperative pathology confirmed negative surgical margins (Fig. 9 ). This suggested that the risk of gallbladder carcinogenesis should be taken seriously starting from GB-RADS 2A. Figure 9. IOUS findings and surgical approach for carcinoma in situ (GB-RADS 2A). (A) MRI of the gallbladder (T1); (B) MRI of the gallbladder revealed impacted stones in the gallbladder neck (yellow triangle); (C) IOUS imagery of the GBW demonstrated stones in the neck, with a distinct echogenic delineation between SS-IL and SS-OL (yellow triangle), and a relatively clear boundary between the GBW and the liver; and (D–E) dissection of the gallbladder utilizing the SA and pathological indicated a clear demarcation between SS-IL and SS-OL within the GBW, accompanied by partial infiltration of the in situ carcinoma into Rokitansky–Aschoff sinuses (Fig. 8 E showed enlarged view of the area enclosed by the red box in Fig. 8 D). SA, subserosal approach. IOUS findings and surgical approach for carcinoma in situ (GB-RADS 2A). (A) MRI of the gallbladder (T1); (B) MRI of the gallbladder revealed impacted stones in the gallbladder neck (yellow triangle); (C) IOUS imagery of the GBW demonstrated stones in the neck, with a distinct echogenic delineation between SS-IL and SS-OL (yellow triangle), and a relatively clear boundary between the GBW and the liver; and (D–E) dissection of the gallbladder utilizing the SA and pathological indicated a clear demarcation between SS-IL and SS-OL within the GBW, accompanied by partial infiltration of the in situ carcinoma into Rokitansky–Aschoff sinuses (Fig. 8 E showed enlarged view of the area enclosed by the red box in Fig. 8 D). SA, subserosal approach. IOUS manifestations for patients with GB-RADS 2B were as follows: based on diffuse thickening of GBW, there were notable intramural hyperechoic foci and/or cysts visible. Specifically, intramural cysts represented the ultrasonic appearance of Rokitansky–Aschoff sinuses, whereas hyperechoic foci corresponded to cholesterol deposits or intramural calcifications within these sinuses [ 40 ] . Upon further observation, it was found that although the hyperechoic features within the SS-OL of GB-RADS 2B patients were still distinctly present, there was a transition from “fine granular” or “reticulated” patterns to a more compact “linear” strong echo (Fig. 6 ). Meanwhile, the echogenicity of the muscularis propria and SS-IL was notably increased as moderate echogenicity, in contrast to the hypoechoic features seen in patients with GB-RADS grade 1 or grade 2A. Pathological examination revealed an increase in fibrous tissue throughout the layers of the GBW, with the delineation between SS-IL and OL being somewhat obscured. In actual procedures, forcibly dissecting SS-IL and OL could readily result in IIR. Given this, for patients with GB-RADS 2B, it was deemed more suitable to dissect the gallbladder via CPA. Patients with GB-RADS 2C classification exhibited focal thickening of the GBW. We found that all patients with a pathological diagnosis of xanthogranulomatous cholecystitis belonged to the GB-RADS 2C category. Among these patients, the normal loose spaces between the SS-IL and SS-OL, as well as between the SS-OL and the liver bed, were all absent, accompanied by proliferation of fibroblasts in the outer membrane. Therefore, our center employed the LBA, which involved partial resection of the liver parenchyma adjacent to the gallbladder, effectively preventing the occurrence of IIR. In the present study, a total of 14 patients (9.2% of all enrolled cases) exhibited significant thickening of the GBW, loss of normal histological layers, and postoperative pathological examination indicated atypical hyperplasia or carcinoma in situ . In the IOUS group, only three cases (3.95%) experienced IIR during GBW dissection, and all had mild inflammation with a GBW thickness of 2–3 mm. IIR was caused by instrument clamping and traction of the gallbladder and did not involve cases of atypical hyperplasia or carcinogenesis. In the control group, 13 cases (17.11%) experienced IIR of the GBW, among which 4 patients exhibited significant thickening of the GBW accompanied by atypical hyperplasia due to an inability to accurately grasp the dissection layer. The difference between the two groups was statistically significant ( P = 0.017). Although the data presented in Table 4 indicated that reducing the IIR of GBW did not significantly alter the incidence rates of various complications, such as abdominal infections and abscesses, nor did it shorten the hospital stay, we believe that the clinical significance of selecting the GBW approach guided by IOUS lies in improving the integrity of the GBW and oncological safety. In the vast majority of cases, patients with easily manageable Calot’s triangle and clear histological layers of the GBW, LC surgery does not require the assistance of IOUS. The findings of this study indicate that surgeons may safely employ IOUS to facilitate LC surgery during the diagnosis and extraction of CD stones, as well as in scenarios involving abnormal thickening of the GBW. The present study had the following limitations: (1) stones in Hartmann’s pouch, neck, or CD posed a challenge in safely managing the Calot’s Triangle and dissecting the posterior wall of the gallbladder. The acoustic shadow cast caused by these stones impaired the visualization of the confluence location of the CD/CHD via IOUS which might have a high risk of atypical hyperplasia and even carcinogenesis. For such patients, if there was a suspicion of potential malignancy before surgery, we would prioritize the use of the CPA or LBA. (2) Similarly, acoustic shadows of filling-type gallstones also reduced the diagnostic efficacy of IOUS for the entire GBW scanning. In response, we contemplate whether approaches such as intraperitoneal fluid infusion to create an artificial acoustic window could potentially enhance the diagnostic capabilities. (3) Prolonged inflammation leading to mucosal shedding, as well as early-stage GBC, can both exhibit as discontinuity of the mucosal line when observed under IOUS. Future research might benefit from the incorporation of contrast-enhanced ultrasound, thereby enhancing the accuracy of IOUS in both diagnosing early cancers and guiding approaches for GBW dissection. (4) It would be preferable to further increase the sample size. (5) Since this study was a single-center study, the technical reproducibility of IOUS in general surgical settings might be limited. We suggest that the learning curve of IOUS might be shortened to some extent by inviting ultrasound specialists to participate in the team’s surgeries. In China, the application of IOUS in assisting hepatobiliary surgeries is still in its early stages of widespread adoption. Given the substantial population suffering from gallbladder diseases, there is considerable promise for the widespread adoption and application of IOUS in LC surgeries. During this process, enhancing communication among various hepatobiliary surgery centers and close collaboration with ultrasound physicians may offer an effective approach to shorten the learning curve for surgeons in mastering IOUS.

IOUS is helpful in assisting intraoperative diagnosis and the extraction of CD stones. The integration of IOUS with GB-RADS offered significant value in guiding the selection of safe dissection approaches for GBW and in preventing IIR for cases with a risk of canceration. Consequently, we advocate for the application of IOUS in LC for selected BGBD patients with the above complicated conditions.