Detecting biliary complications following liver transplantation with contrast-enhanced ultrasound

Abstract

Liver transplantation is the primary therapeutic choice for end-stage liver disease. Currently, biliary complications are among the main factors affecting the survival rate and quality of life of liver transplant recipients. Nevertheless, the clinical manifestations of biliary complications following liver transplantation are often non-specific, making early diagnosis and timely treatment crucial for improving patient outcomes. Ultrasound is the preferred imaging method following liver transplantation. Importantly, contrast-enhanced ultrasound, with the administration of contrast agents, can improve the resolution of biliary images and enable real-time, dynamic visualization of microcirculation perfusion in the biliary system and surrounding tissues. The present article describes the normal ultrasonic features of the biliary system following liver transplantation and briefly reviews the progress in the ultrasonic diagnosis of common biliary complications, including anastomotic biliary strictures, non-anastomotic biliary strictures, biliary leakage, biloma, and bile sludge/bile stone.

Key Words: Liver transplantation; Biliary complications; Biliary stricture; Biliary leakage; Contrast-enhanced ultrasound

Core Tip: The clinical manifestations of biliary complications after liver transplantation are typically non-specific. If not detected and treated in a timely manner, these complications can lead to a decline in the patient’s quality of life and may even impact the recipient’s survival rate. Ultrasound, as the preferred imaging method for post-liver transplantation, is highly effective in diagnosing both vascular and parenchymal liver complications. Contrast-enhanced ultrasound has been shown to improve contrast in the bile duct wall and for detecting micro-perfusion and is increasingly being implemented in clinical practice for assessing biliary complications post-liver transplantation.

INTRODUCTION

Liver transplantation is an effective treatment for end-stage liver disease. With advancements in surgical techniques and comprehensive perioperative management, the long-term survival rate of patients undergoing liver transplantation has steadily improved. Nonetheless, complications post-liver transplantation remain a significant challenge. Of note, the incidence of biliary complications can be as high as 40% early on[1,2], and these include biliary stricture, biliary leakage, biloma, and biliary sludge/biliary stone formation. The clinical manifestations of biliary complications after liver transplantation are heterogeneous and can range from being asymptomatic to presenting with symptoms such as jaundice, abdominal pain, and fever. Patients with biliary complications may require repeated treatments, leading to a poorer quality of life. Therefore, early diagnosis and timely intervention are crucial for improving patient outcomes. Ultrasound is the primary method for assessing biliary complications[3], making a comprehensive understanding of its characteristics and the development of new diagnostic methods clinically significant. As the main source of blood supply to the biliary system, the hepatic artery plays a crucial role in the risk of biliary complications, with its blood flow directly affecting patient outcomes[4]. Color Doppler flow imaging (CDFI) ultrasound techniques are widely used to assess the patency and blood flow status of the hepatic artery, providing information such as hepatic artery blood flow velocity, resistance index (RI), and acceleration time. However, CDFI can sometimes lead to false-positive or false-negative diagnoses. Contrast-enhanced ultrasound (CEUS) involves injecting an ultrasound contrast agent and the primary injection techniques include intravenous CEUS and trans-cavitary CEUS. Specifically, intravenous CEUS enhances blood flow signals in human tissues, allowing for a more accurate assessment of hepatic artery blood flow and improves diagnostic accuracy[5]. Besides, intravenous CEUS also enables the evaluation of microcirculatory perfusion in the bile duct wall. Moreover, intravenous CEUS can assess the microcirculatory perfusion of liver parenchyma, aiding in detecting the scope of biloma and providing crucial imaging information for clinical diagnosis and treatment. Xu et al[6] conducted a study involving 80 patients with obstructive jaundice who underwent simultaneous percutaneous transhepatic biliary drainage and intraductal bile CEUS (IB-CEUS). The findings demonstrated that IB-CEUS achieved a diagnostic accuracy rate of 96.3% for evaluating the degree of biliary obstruction. It can also be used to diagnose issues such as bile leakage and T-tube displacement, with imaging quality comparable to that of T-tube cholangiogram, making it one of the most direct and effective methods for diagnosing bile duct lesions. Low mechanical index imaging technology decreases acoustic energy, thereby minimizing damage to microbubbles. This enables real-time, continuous monitoring of the dynamic filling and diffusion of contrast agents within blood vessels and tissues. As a result, it significantly enhances the timeliness of hemodynamic assessment[7]. CEUS offers several notable advantages. Being radiation-free and devoid of operational complications, it enables real-time dynamic assessment and can be conveniently performed at the patient’s bedside. These features render it the favored option for postoperative screening and follow-up evaluations. Nevertheless, CEUS is not without its limitations. Factors such as obesity and intestinal gas can impede ultrasound scanning, and patient cooperation is essential for accurate results. Additionally, intravenous contrast imaging has restricted efficacy when it comes to visualizing deep bile ducts or complex anatomical structures, like the intrahepatic bile ducts. Moreover, the examination’s outcome is highly operator-dependent, necessitating that operators possess specific skills and undergo specialized training. Magnetic resonance cholangiopancreatography (MRCP), the most prevalent technique for detecting biliary complications, stands out for its non-invasive nature. It does not necessitate catheterization or the use of contrast agents, enabling a comprehensive evaluation of the intra and extrahepatic bile ducts. This allows for the detailed assessment of stenosis, dilation, or the presence of stones. However, due to its inherent limitations in spatial resolution, there is a risk of overlooking micro-stones (less than 3 mm in size) or mild stenosis. On the other hand, endoscopic retrograde cholangiopancreatography (ERCP) provides high-resolution imaging and uniquely combines diagnostic and therapeutic capabilities. Despite these advantages, ERCP is an invasive procedure, and the potential for post-ERCP complications, including pancreatitis, biliary infection, biliary bleeding, residual stones, and perforation, significantly restricts its widespread application.

Herein, we provide a comprehensive review of the common causes and clinical manifestations of bile duct complications post-liver transplantation and briefly summarize the advancements in ultrasound diagnosis of these complications.

NORMAL BILIARY TRACT

When studying the ultrasonic characteristics of biliary complications, it is essential to first understand the sonographic features of the normal biliary system after liver transplantation. In the early postoperative period (within one month), mild dilation of intrahepatic bile ducts may be observed, with thickened walls and enhanced echogenicity. The bile ducts at the porta hepatis exhibit poor or undifferentiated acoustic transmission and thickened walls. In the late postoperative period (after one month), intrahepatic bile ducts no longer show dilation, and the bile duct walls are no longer thickened. The bile duct lumen at the porta hepatis can be clearly identified, resembling the ultrasonic image of a healthy liver that has not undergone transplantation surgery[8].

Zeng et al[9] previously proposed an ultrasound diagnostic criterion for biliary lesions post-liver transplantation, with third-level bile ducts with a diameter greater than 2 mm or an intrahepatic bile duct diameter greater than one-third of the accompanying portal vein diameter being defined as bile duct dilation. The thickness of the bile duct wall is also an important observation indicator, with the standard for thickening referenced to the thickness of the accompanying portal vein wall; if it exceeds the thickness of the portal vein wall, it is considered thickened[10]. In normal healthy individuals, the bile duct wall exhibits mainly equal or high enhancement during the arterial phase and equal or low enhancement during the portal venous and delayed phases[11].

Anastomotic biliary strictures

Anastomotic biliary strictures (ABS) are defined as a solitary stenosis within 5 mm of the anastomotic site, with the stenosis typically being short in length. The incidence of ABS is 5% to 10%, and it can occur at any time following liver transplantation, although most cases arise between 5 to 8 months postoperatively[12]. The occurrence of ABS is associated with factors such as inadequate mucosal-mucosal anastomosis, surgical techniques, local tissue ischemia, bile duct fibrosis during healing, bile leakage, and infection. Clinical symptoms of ABS may include jaundice, fever, abdominal distension, ascites, and signs of peritoneal irritation postoperatively. Laboratory tests may reveal elevated liver function indicators, including gamma-glutamyl transpeptidase, alkaline phosphatase, alanine aminotransferase, direct bilirubin, and total bilirubin. In cases of biliary infection, there may also be an increase in white blood cells and neutrophils.

The typical ultrasound appearance of ABS is a regular and continuous dilation of the proximal common bile duct and intrahepatic bile ducts near the anastomosis, with smooth bile duct walls, no thickening of the walls, good acoustic transmission of the lumen, and localized stenosis of the bile duct anastomosis lumen (Figure 1). It was previously believed that two-dimensional ultrasound could not directly display the stenotic areas of the bile ducts and could not distinguish between ABS and non-ABS (NABS), with diagnosis primarily based on indirect signs. Indirect signs of NABS include intrahepatic bile duct dilation, thickening of the bile duct wall, and enhanced echogenicity[13-15]. Clevert et al[16] demonstrated that CEUS exhibits a high level of diagnostic accuracy in identifying biliary complications following liver transplantation. Intravenous CEUS can display the blood flow perfusion status of the common bile duct wall by intravenously injecting a microbubble contrast agent, showing the perfusion pattern of the bile duct wall in real time by comparing it with the blood flow perfusion of surrounding normal tissues. This technique allows for a clearer measurement of the internal diameter of the common bile duct and the identification of lesions causing stenosis. Meanwhile, trans-cavitary CEUS can also reveal intra-biliary anatomy by injecting the contrast agent into the bile duct drainage tube, clearly displaying the branching of the biliary tree and providing information about the position of the drainage tube and the intra-biliary environment. Combining intravenous CEUS and trans-cavitary CEUS offers a relatively comprehensive and clear view of the biliary anatomy. In the case of complete obstruction, intravenous CEUS would reveal an anechoic bile duct lumen that is completely filled or externally compressed and occluded by solid echogenicity, while trans-cavitary CEUS reveals a sudden cutoff of the ultrasonically filled bile duct lumen since the contrast agent cannot pass through that area. In the case of incomplete obstruction, intravenous CEUS shows incomplete occlusion of the local lumen, with visible and connected anechoic bile duct cavities. Meanwhile, for trans-cavitary CEUS, the ultrasound contrast agent-filled bile duct cavity would be incompletely occluded, allowing the contrast agent to pass through the convergence point into the other side of the bile duct cavity.

Figure 1 A 68-year-old male patient who had undergone piggyback liver transplantation for primary hepatocellular carcinoma was examined more than four months postoperatively. A: Two-dimensional ultrasound showed that the morphology and parenchymal echoes of the transplanted liver appeared normal, with no significant abnormalities. However, the intrahepatic and extrahepatic bile ducts were diffusely dilated, with the inner diameter of the widest part of the intrahepatic bile duct measuring 8.1 mm (indicated by the arrow); B: Intravenous contrast-enhanced ultrasound revealed Wedge-shaped stenosis at the common bile duct anastomosis and diffuse intrahepatic and extrahepatic bile duct dilation. Magnetic resonance cholangiopancreatography later confirmed the diagnosis of anastomotic biliary strictures. Frequency of ultrasonic probe: 3.5 MHz; Contrast agent: SonoVue^® (Bracco).

NABS

NABS is usually located at least 5 mm proximal to the anastomosis and is characterized by multiple stenoses of both intrahepatic and extrahepatic bile ducts, often accompanied by recurrent biliary sludge formation. The clinical manifestations of NABS can be absent or mild but may also include recurrent cholangitis.

De Jong et al[17] previously performed a histomorphological analysis of the periportal bile ducts in 42 recipients who underwent retransplantation. Their findings indicated that persistent hypoxia and inadequate regeneration of the bile ducts are key pathogenic mechanisms of NABS following transplantation. NABS encompasses a spectrum of bile duct lesions, ranging from mild local mucosal irregularities to widespread, diffuse stenosis of the bile ducts, resembling ischemic changes in the bile duct tree. As a result, NABS is also referred to as an ischemic-type biliary lesion (ITBL)[18]. ITBL can lead to diffuse ischemic necrosis of the bile duct wall, which is the primary cause of patient mortality following transplantation. Therefore, early diagnosis and timely symptomatic treatment are crucial. Routine ultrasound following liver transplantation is not effective in diagnosing ITBL, and other methods, such as X-ray cholangiography and MRCP, typically detect the disease only three months postoperatively, thereby missing the opportunity for early treatment[19]. Typical ultrasound findings of ITBL include irregular narrowing of the porta hepatis bile ducts, thickened and rough bile duct walls, and segmental irregular dilation of the intrahepatic bile ducts. Necrosis and shedding of bile duct epithelial cells lead to the accumulation of debris within the bile duct lumen, resulting in poor acoustic transmission on ultrasound. Hepatic artery stenosis or thrombosis is a common cause of early bile duct complications following transplantation[20,21]. Therefore, patients with ITBL should have their hepatic artery blood flow closely monitored. CDFI is considered an important and effective method for monitoring and diagnosing postoperative ITBL in patients who underwent liver transplantation[22]. Hepatic artery RI is a key indicator reflecting the status of hepatic artery blood flow, with a normal range of 0.55 to 0.80. A reduced intrahepatic artery RI indicates decreased hepatic perfusion, which can result in insufficient blood supply to the bile ducts, leading to ischemic injury[23] (Figure 2A).

Figure 2 A 46-year-old female patient who underwent liver transplantation due to liver failure. Three months postoperatively, an ultrasound examination revealed ischemia of the bile duct wall near the porta hepatis region. A: Color Doppler ultrasound indicated a reduced hepatic artery resistance index in the right hepatic artery; B: Intravenous contrast-enhanced ultrasound showed mild stenosis of the upper segment of the common bile duct, mild dilation of the intrahepatic bile ducts, and low perfusion of the bile duct wall arteries near the porta hepatis region during the arterial phase (indicated by the arrow).

In addition, intravenous CEUS can assess the microvascular perfusion of the bile duct wall[24], which may have significant value for both the diagnosis and prognosis evaluation of ITBL[25]. Intravenous CEUS of the hepatic portal bile duct wall in liver transplant patients[11] revealed that a normal porta hepatis bile duct wall shows higher or equal enhancement compared to the surrounding liver parenchyma during the arterial phase, and equal or lower enhancement during the portal venous and delayed phases, indicating good blood perfusion of the bile duct wall. In contrast, when intravenous CEUS shows low enhancement during the arterial and portal venous phases, it suggests poor blood perfusion of the bile duct wall (Figure 2B). If bile duct ischemia leads to bile duct wall necrosis, there will be no blood perfusion, and intravenous CEUS will show no enhancement in all phases (Figure 3). Notably, bile duct wall necrosis may be accompanied by ischemic changes in the liver parenchyma, which ultrasound angiography can identify as areas of low or no perfusion. CEUS offers qualitative diagnostic value for ITBL by monitoring the perfusion level of the porta hepatis bile duct wall, addressing the limitation of conventional ultrasound in diagnosing ITBL. When intravenous CEUS shows no enhancement in the porta hepatis bile duct wall, it suggests a poor prognosis and may serve as an indication for retransplantation[26].

Figure 3 A 57-year-old male patient who underwent liver transplantation due to liver failure. More than two months postoperatively, an ultrasound examination revealed necrosis of the bile duct wall near the porta hepatis region. A: Two-dimensional ultrasound revealed that morphology and parenchymal echoes of the transplanted liver showed no significant abnormalities. The common bile duct wall was edematous and thickened, measuring approximately 5.3 mm in thickness, with a narrowed lumen of about 2.3 mm (indicated by the arrow); B: Contrast-enhanced ultrasound revealed complete non-perfusion of the bile duct wall near the common bile duct anastomosis (indicated by the arrow).

Biliary leakage

The incidence of bile duct leakage after liver transplantation ranges from 2% to 25%[27], and it can occur at various sites, including the anastomosis, T-tube outlet, remnant cystic duct, Lushka bile duct, accessory bile duct, and the hepatic resection surface. The causes include displacement or dislodgement of the T-tube, incomplete sinus tract formation, prolonged storage time of the donor liver, bile duct injury, and postoperative hepatic artery thrombosis. In cases of small bile duct leakage, there may be no obvious clinical manifestations, leading to missed diagnosis. In contrast, large bile duct leakage can result in bile leakage into the abdominal cavity, causing biliary peritonitis, which presents with abdominal pain, high fever, and chills, to name a few. Of note, chronic accumulation of bile can also lead to the formation of biloma. When a biliary leakage occurs and an abdominal drainage tube is in place, yellow or yellow-green fluid may be observed in the draining tube. In cases of abdominal wall perforation, bile leakage from the wound may occasionally be seen. Prolonged, large-scale bile leakage can result in malnutrition, electrolyte disturbances, and other complications.

Most physicians believe that ultrasonic imaging of biliary leakage is difficult to distinguish from extrahepatic localized effusion and hematoma, and as a result, ultrasound alone cannot diagnose the condition. Ultrasonic imaging of a biliary leakage typically shows a clearly demarcated anechoic or hypoechoic area within the liver or at the porta hepatis region (Figure 4), with varying sizes and shapes depending on the specific case. When a biliary leakage is complicated by infection, punctate or flocculent echoes may be observed within the anechoic or hypoechoic areas. Intravenous CEUS shows no enhancement within the lesion, but mild enhancement may be seen at the margins[28] (Figure 4). Furthermore, observing the bile duct wall at the porta hepatis region using intravenous CEUS reveals poor microperfusion of the bile duct wall, indicating ischemia, which can aid in diagnosis.

Figure 4 A 60-year-old male patient who underwent liver transplantation for primary biliary cirrhosis. Twelve days postoperatively, an ultrasound examination revealed a biliary duct fistula. A and B: Two-dimensional ultrasound and color Doppler ultrasound showed that a large anechoic area with an irregular shape and good acoustic transmission was visible in the hepatic hilum, measuring approximately 200 mm × 46 mm, with no significant blood flow signals observed internally; C: Intravenous contrast-enhanced ultrasound showed no internal enhancement, with clear margins (indicated by the arrow); D: Endoscopic retrograde cholangiopancreatography showed that a catheter was successfully inserted, and a small amount of 10% Ultravist (Shering, Berlin, Germany) was injected. A narrow segment, approximately 8 mm long, was visible at the biliary duct anastomosis, and a fistula was observed in the intrahepatic biliary duct on the left side of the liver. The contrast agent infiltrated into the extrahepatic liver through the fistula (indicated by the arrow).

For patients with imaging findings suggesting cystic lesions both intra- and extrahepatically, percutaneous liver biopsy under ultrasound guidance can be performed. If the bilirubin concentration in the aspirate is higher than that in the serum, it suggests the possibility of biloma formation. Patients with biliary leakage require catheter drainage while awaiting fistula healing. Injecting a contrast agent through the drainage tube can help assess the morphology and course of the leakage, identify its location, and determine its communication with other bile ducts, thus monitoring the effectiveness of treatment while minimizing radiation exposure. MRCP failed to clearly identify the precise location of bile leakage. Conversely, CEUS was conducted by directly injecting a contrast agent through a percutaneous drainage tube inserted into the biliary effusion. This approach clearly visualized the contrast agent flowing from the effusion into the bile duct, thus confirming the presence of an intrahepatic leakage pathway[29]. Chopra et al[30] conducted a comparison of the overall imaging quality between CEUS cholangiography via the T-tube approach and conventional radiology. Their findings revealed no significant difference in the imaging quality achieved by these two techniques. Combined intravenous and trans-cavitary CEUS is an effective method for diagnosing biliary leakage after liver transplantation.

Biloma

Abnormal accumulation of bile outside the biliary system is referred to as a biloma. This form of intrahepatic bile tumor often results from severe ischemic injury to the intrahepatic bile ducts caused by impaired hepatic artery blood flow, leading to the destruction of the bile duct wall and subsequent bile leakage. The accumulated bile often causes necrosis and infection of local liver tissue, eventually forming encapsulated fluid that contains various tissue components[31].

Biloma appears as cystic anechoic, heterogeneous, or mixed echogenic lesions on ultrasound examination. When infected, small echogenic foci may be seen floating within the lesion, which is typically irregular in shape (Figure 5). The bile duct wall near the biloma may show irregular dilation, thickening, or roughness, potentially due to cholangitis or ischemia. Intravenous CEUS shows no enhancement within the lesion, although slight enhancement may be observed around its periphery. Most researchers agree that biloma can be challenging to distinguish from simple hepatic cysts and liver abscesses. Occasionally, partial cystic cavities may be seen communicating with the bile ducts during trans-cavitary CEUS, which can aid in diagnosis and treatment planning. The World Federation for Ultrasound in Medicine and Biology[32] recommends percutaneous cholangiography as a method to visualize the biliary tree. This can be achieved via drainage catheters, T-tubes that are inserted during surgery, or through endoscopic access. Ultrasound-guided puncture drainage is also useful for confirming biloma[32]. CEUS is an important tool for evaluating biloma after liver transplantation, providing crucial information about the morphology, size, location, and relationship of the lesion to the bile ducts.

Figure 5 A 30-year-old male patient, more than 4 months post-liver transplantation, presented with a one-week history of fever and diarrhea, followed by vomiting and impaired consciousness for two hours. A: Two-dimensional ultrasound showed multiple hypoechoic areas within the transplanted liver, suggestive of infarct foci; B: Color Doppler ultrasound showed that no arterial blood flow signals were observed in the hepatic artery course area, indicating hepatic artery occlusion; C: Intravenous contrast-enhanced ultrasound (CEUS) showed no visualization of the entire hepatic artery, consistent with hepatic artery occlusion; D: Intravenous CEUS indicated no enhancement in multiple hypoechoic areas within the liver, consistent with infarct foci; E: Magnetic resonance imaging revealed multiple hypoattenuating lesions within the liver, with an increase in number and size compared to previous scans, suggesting biloma and intrahepatic biliary duct dilation.

Biliary sludge/biliary stone formation

The incidence of biliary calculi after liver transplantation ranges from 0% to 30.5%[33], with an increased likelihood in cases of biliary stricture[34,35]. When biliary stricture occurs, bile stasis, necrotic shed biliary duct epithelial cells, and biliary tract infection contribute to the formation of biliary sludge, which, if further concentrated, may develop into biliary stones. The presence of biliary sludge or stones following liver transplantation is mainly associated with biliary stricture, biliary tract infection, ischemia-reperfusion injury, damage to the vascular plexus surrounding the biliary tract, insufficient biliary tract irrigation, and chronic rejection reactions[36]. Biliary sludge in the biliary tract appears as moderately echogenic or highly echogenic masses within the biliary duct lumen, which may be distributed either focally or diffusely. Biliary stones are typically highly echogenic, presenting as masses with clear margins and often accompanied by posterior acoustic shadows (Figure 6). In contrast, biliary sludge or sandy-like stones are generally moderately echogenic, appearing as linear or spindle-shaped masses with unclear margins and no acoustic shadows posteriorly. Ultrasound images of biliary sludge or stones after liver transplantation resemble those of general biliary sludge or stones, making early-stage detection and diagnosis relatively easier[37]. Early biliary tract space-occupying lesions often lack specific clinical characteristics, which can lead to confusion with biliary sludge or stones in the biliary tract. SonoVue^® microbubbles (1-10 μm diameter) predominantly distribute within the intravascular space during the arterial phase (10-30 seconds post-injection), allowing them to affect the microvascular flow in biliary tract space-occupying lesions. This enhances the diagnostic sensitivity, enabling a clear differentiation between the presence or absence of enhancement in the biliary duct. In conclusion, ultrasound plays a vital role in diagnosing biliary sludge and biliary stone formation, as well as in dynamically monitoring treatment efficacy.

Figure 6 Follow-up ultrasound examination of an 8-year-old girl who underwent split hepatic transplantation due to congenital biliary atresia. A: Ultrasound showed intrahepatic biliary duct dilation with a smooth biliary duct wall; B and C: Two-dimensional ultrasound showed that a high-echo mass approximately 12 mm × 6 mm in size was visible within the dilated intrahepatic biliary duct, with clear margins from the biliary duct wall and no posterior acoustic shadowing. Color Doppler ultrasound showed no significant color flow signals inside or around the high-echo mass; D: Magnetic resonance cholangiopancreatography showed intrahepatic biliary stones with biliary duct dilation.

CONCLUSION

With continued investigation into the pathogenesis of biliary complications following liver transplantation, the range of ultrasonic features indicative of these complications has expanded. Notably, the integration of conventional ultrasound with emerging technological advancements has significantly enhanced diagnostic accuracy. Intravenous CEUS provides detailed insights into the biliary wall’s blood supply, while trans-cavitary CEUS enables precise visualization of biliary morphology. These innovations have improved the detection of biliary complications, including ABS, NABS, biliary leakage, biloma, and biliary sludge/biliary stone formation. Compared to radiological methods, ultrasound offers a non-invasive, bedside-capable approach suitable for early postoperative evaluation. In summary, ultrasound stands out as the preferred imaging modality for post-liver transplantation assessment due to its portability, safety, non-invasiveness, and repeatability, offering accurate, real-time, and dynamic evaluation of transplanted livers. In the future, super-resolution ultrasound technology holds great promise for enhancing biliary imaging capabilities. By leveraging artificial intelligence technology, it will be possible to analyze dynamic blood flow parameters obtained from CEUS, such as the perfusion velocity and intensity of the biliary wall. Establishing a hemodynamic model of biliary tissues can significantly enhance the sensitivity to pathological changes, which facilitates the differentiation of ITBL from non-ITBL (e.g., infectious, calculous inflammations, etc.). This analysis can potentially enable the prediction of the progression of biliary complications, providing valuable insights for early intervention and improved patient management.