Endoscopic ultrasound (EUS) and intraductal ultrasound (IDUS) play very important roles in the field of biliary tract disease. Because of their excellent spatial resolution, the detection of small lesions and T- or N-staging of tumors have become possible. Additionally, contrast-enhanced EUS and the new imaging technique of detective flow imaging are reported to be useful for differential diagnosis. Furthermore, EUS-guided tissue acquisition is used not only for pathological diagnosis but also to collect tissue samples for cancer genome profiling. This review provides an overview of diagnosis utilizing the features and techniques of EUS and IDUS.

Detection of a common channel outside the duodenal wall is important in diagnosing pancreaticobiliary maljunction (PBM). The present study evaluated the utility of contrast-enhanced harmonic endoscopic ultrasonography (CH-EUS) in diagnosing PBM.

This single-center retrospective study enrolled 45 patients who were diagnosed with PBM or high confluence of pancreatobiliary ducts (HCPBD) between January 2007 and December 2021. The diagnostic sensitivities of contrast-enhanced computed tomography (CE-CT), magnetic resonance imaging (MRI), and CH-EUS for diagnosing PBM were analyzed. Imaging findings were evaluated by two reviewers blinded to the clinicopathological results.

Based on diagnostic criteria, 33 patients were diagnosed with PBM and 12 with HCPBD. Compared with the patients with HCPBD, those with PBM had significantly longer common channel (12.5 mm vs. 8.1 mm, P = 0.018) and common bile duct (13.0 mm vs. 8.6 mm, P = 0.049) lengths. The κ-coefficients for differentiating PBM and HCPBD were 0.871 between CE-CT and MRI, 0.330 between CE-CT and CH-EUS, and 0.611 between MRI and CH-EUS. The diagnostic sensitivity of CH-EUS (95.2%) was higher than that of CE-CT (83.3%) and MRI (82.8%), although the differences were not statistically significant.

CH-EUS may be useful for the diagnosis of PBM.

Gallbladder (GB) diseases represent various lesions including gallstones, cholesterol polyps, adenomyomatosis, and GB carcinoma. This review aims to summarize the role of endoscopic ultrasound (EUS) in the diagnosis of GB lesions. EUS provides high-resolution images that can improve the diagnosis of GB polypoid lesions, GB wall thickness, and GB carcinoma staging. Contrast-enhancing agents may be useful for the differential diagnosis of GB lesions, but the evidence of their effectiveness is still limited. Thus, further studies are required in this area to establish its usefulness. EUS combined with fine-needle aspiration has played an increasing role in providing a histological diagnosis of GB tumors in addition to GB wall thickness.

Although both radial- and convex-arrayed endoscopic ultrasonography (EUS) scopes are widely used for observational EUS examinations, there have been few comparative studies on their power of visualization. The aim of this study was to evaluate the capability of these EUS scopes for observation of the pancreatobiliary junction.

The rate of successful visualization of the pancreatobiliary junction was retrospectively compared between a radial-arrayed and a convex-arrayed echoendoscope, from a prospectively maintained database. Study periods were defined as January 2010 to December 2012 for the radial group, and February 2015 to October 2016 for the convex group because the respective scope was mainly used during those periods.

During the study period, 1,660 cases with radial EUS and 1,984 cases with convex EUS were recruited. The success rates of observation of the pancreatobiliary junction were 80.0% and 89.5%, respectively (p<0.0001).

The capability of visualization of the pancreatobiliary junction in observational EUS was found to be better with a convex-arrayed than with a radial-arrayed echoendoscope.

An increasing number of children are being diagnosed with pancreatitis and other pancreatic abnormalities. Dissemination of the information regarding existing imaging techniques and endoscopic modalities to diagnose and manage pancreatic disorders in children is sorely needed.

We conducted a review of the medical literature on the use of the following imaging and procedural modalities in pediatric pancreatology: transabdominal ultrasonography (TUS), computed tomography (CT), magnetic resonance imaging (MRI)/magnetic resonance cholangiopancreatography (MRCP), endoscopic ultrasonography (EUS), and endoscopic retrograde cholangiopancreatography (ERCP). Recommendations for current use and future research were identified.

TUS offers noninvasive images of the pancreas but has limitations to details of parenchyma and ductal structures. CT offers improved detail of pancreatic parenchyma, solid masses, and traumatic injuries, but requires relatively high levels of ionizing radiation and does not adequately assess ductal anatomy. MRI/MRCP offers detailed intrinsic tissue assessment and pancreatic ductal characterization, but requires longer image acquisition time and is relatively poor at imaging calcifications. EUS provides excellent evaluation of pancreatic parenchyma and ductal anatomy, but can be subjective and operator dependent and requires sedation or anesthesia. EUS offers the capacity to obtain tissue samples and drain fluid collections and ERCP offers the ability to improve drainage by performing sphincterotomy or placing pancreatic stents across duct injuries and strictures.

Various imaging modalities may be used in pediatric pancreatology, but TUS and MRI/MRCP are favored. Interventional therapeutic maneuvers primarily involve use of ERCP and EUS. Future research is necessary to optimize equipment, expertise, and appropriate indications.

There have been no clinical guidelines for the management of pancreaticobiliary maljunction (PBM). The Japanese Study Group on Pancreaticobiliary Maljunction (JSPBM) has proposed to establish clinical practice guidelines on how to deal with PBM, with the support of the Japan Biliary Association (JBA). Because the body of evidence-based literature is relatively small, we decided to create guidelines based on the consensus of experts, using the medical literature for reference. A total of 46 clinical questions (CQs) were considered by the members of the editorial committee responsible for the guidelines. The CQs covered distinct aspects of PBM: (1) Concepts and Pathophysiology (10 CQs); (2) Diagnosis (10 CQs); (3) Pancreatobiliary complications (9 CQs); and (4) Treatments and prognosis (17 CQs). Statements and comments for each CQ were prepared by the guidelines committee members and collaborating partners. The CQs were completed after review by members of the editorial committee, meetings of this committee, public comments on the homepages of the JSPBM and the JBA, public hearings, and assessment and approval by the guidelines evaluation board. PBM includes cases where the bile duct is dilated (PBM with biliary dilatation) and those in which it is not (PBM without biliary dilatation). In these guidelines, PBM with biliary dilatation is defined as being identical to congenital biliary dilatation of Todani type I (except for type Ib) and type IV-A, both of which are accompanied by PBM in almost all cases. These guidelines are created to provide assistance in the clinical practice of PBM management; their contents focus on clinical utility, and they include general information on PBM to make this disease more widely recognized.

Gallbladder cancer is among the organs examined in mass screening for cancer using ultrasonography; the reported prevalence of gallbladder cancer in such screening of a general population was 0.011%, while the prevalence of gallbladder polyps was reported as 4.3 to 6.9%. Endoscopic ultrasonography is useful for the differential diagnosis of gallbladder tumors detected by mass screening, as well as for estimating the depth of tumor invasion and detecting abnormal connections between pancreatobiliary ducts. While a systematic approach leading to diagnosis by endoscopic ultrasonography is useful, recent advances of contrast-enhanced ultrasonography are expected to establish it as a new modality for early detection. At our hospital, 7 of 26 patients with abnormal connections between pancreatobiliary ducts developed gallbladder carcinoma (23.1%), and 7 of 48 patients with gallbladder carcinoma had abnormal connections between pancreatobiliary ducts (12.5%). Serial observation in patients with gallstones and prophylactic surgery in patients with abnormal connections between pancreatobiliary ducts are necessary.

To estimate the detectability of anomalous connection in pancreatobiliary disease (ACPBD) cases, measuring gallbladder wall blood flow (GWBF).

In the retrospective study, we enrolled 42 subjects with gallbladder wall thickening. GWBF velocity was determined as an average value of the peak velocity of color signals on the gallbladder wall, three times in each case. Based on the findings on endoscopic ultrasonography (EUS) or endoscopic retrograde cholangiopancreatography (ERCP), the 42 subjects were divided into 11 cases with ACPBD and 31 cases without ACPBD. In the prospective study, the subjects were 92 cases with gallbladder wall thickening. Using the cut-off level of the flow velocity obtained in the retrospective study, the usefulness of measuring GWBF velocity in diagnosing ACPBD was evaluated.

In the retrospective study, imaging of GWBF was obtained in 40 of the 42 subjects. The mean GWBF velocity of the ACPBD cases was 29.4+/-3.9 cm/s (mean+/-SD), which was significantly different (P<0.0001; 95% CI 5.48-13.2) from that of the without ACPBD cases (20.1+/-5.9 cm/s). Based on this result, we prepared a receiver operating characteristic curve, and the cut-off level appropriate for diagnosing ACPBD was estimated to be 25 cm/s. In the prospective study, GWBF was detected in 86 of the 92 subjects. Based on the EUS or ERCP findings, the 92 subjects were divided into 15 cases with ACPBD and 77 cases without ACPBD. When a cut-off level of 25 cm/s was employed, ACPBD could be diagnosed with a sensitivity of 87.0% (13/15) and a specificity of 87.3% (62/71).

Measurement of GWBF velocity, which is less invasive and provides objective values, is very useful for diagnosing ACPBD prior to the development of malignant tumors in cases with gallbladder wall thickening.

It seems that EUS will most likely become the gold standard technique to diagnose chronic pancreatitis not diagnosed on plain radiography, standard transcutaneous sonography, or CT scanning. Because of its low risk and increased sensitivity, it will replace ERCP as a diagnostic test for this condition. Confirmation with cytology may be beneficial for indeterminate cases. EUS will also have an important role in determining the management of cystic lesions in the pancreas. EUS seems to be very effective in determining which cystic lesions have malignant potential. If a cyst appears malignant or produces symptoms, it requires resection and therefore does not require FNA. Prediction of the clinical course for cysts of indeterminate nature requires EUS-guided FNA and analysis of fluid. EUS, although quite accurate in diagnosing CBD stones, has a more limited role in diagnosis and management of stone disease because of current limitations of therapeutic maneuvers, which can be performed at the same time. In general, patients with probable CBD stones or sludge require therapeutic ERCP. Therefore, ERCP is the preferred initial test to diagnose and simultaneously treat these disorders. Patients with a low suspicion for CBD stones, or patients with relative contraindications to ERCP (i.e., pregnancy or bleeding disorders), can be evaluated first with EUS to determine whether further invasive treatment is required. EUS seems to be complementary to therapeutic ERCP for the aspiration and drainage of cysts and pseudocysts. Although celiac plexus nerve blocks using EUS-guided injection of neurolytic agents seems to be more effective than other nerve block techniques, surgical bypass or resection is likely to continue as the primary method of treatment of patients with pain from chronic pancreatitis or those who do not respond to endoscopic stenting when there is a dominant stricture that can be bypassed.

A frequent association of biliary tract carcinoma and anomalous pancreaticobiliary ductal union (APBD) is well recognized, especially gall-bladder carcinoma in undilated type APBD. However, little is known about the presence and incidence of adenomyomatosis (AMT) of the gall-bladder, a presumed premalignant lesion, in patients with APBD. This retrospective study was conducted to elucidate the clinical features and incidence of AMT in APBD patients with relation to undilated type and dilated type APBD. We reviewed the clinicopathological records of 30 patients with APBD (28 women and two men) encountered during the past 10 years. Among them, 22 patients underwent cholecystectomy and the resected specimens were subjected to histopathological examinations. Eleven cases of APBD patients were undilated type and 11 cases were dilated type. Adenomyomatosis was found in six (55%) of 11 undilated type and one (9%) of 11 dilated type, and fundal type was predominantly observed in six (86%) of seven AMT. An overall incidence of AMT in APBD patients was 32%. An undilated type of APBD is frequently associated with AMT and we believe, therefore, that clinicians should be aware of a possible coexistence of APBD and AMT.

An anomalous pancreaticobiliary ductal union (APBD) is a high-risk factor for biliary tract carcinoma, which often is not diagnosed before overt malignancy. The early detection of APBD is therefore clinically important. We evaluated the gallbladder wall in APBD patients with endoscopic ultrasonography.

Clinicopathologic features and ultrasonographic findings of the gallbladder in 33 consecutive patients with APBD between 1986 and 1995 were studied in relation to two subtypes of APBD, that is, undilated (n = 17) and dilated (n = 16). The gallbladder wall was evaluated with conventional ultrasonography and/or endoscopic ultrasonography. Histologic examinations of 25 resected gallbladders were made.

Fourteen of the seventeen patients with undilated type APBD (82%) had diffuse thickened gallbladder wall of 4 mm or more, whereas 5 of the 16 with dilated type (31%) had this finding (p < 0.01). The thickened gallbladder wall consisted sonographically of two layers: diffuse thickened inner hypoechoic layer and outer hyperechoic layer. Mucosal hyperplasia was histologically found in 8 of 9 cases (89%) with thickened inner hypoechoic layer on endoscopic ultrasonography. Mucosal hyperplasia was observed in 10 of 11 undilated type APBD cases (91%) in which cholecystectomy was performed. In addition, the presence of anomalous union was shown by endoscopic ultrasonography in 9 of 11 patients with undilated type APBD (82%) and all 7 of those with dilated type. The characteristic ultrasonographic pattern of diffuse thickened inner hypoechoic layer was observed exclusively in patients with mucosal hyperplasia of the gallbladder associated with APBD among 2085 endoscopic ultrasonography examinations performed during the study period.

Diffuse thickened inner hypoechoic layer of the gallbladder wall was frequently observed in APBD patients, especially those with the undilated type, on ultrasonography and/or endoscopic ultrasonography. This finding corresponded histologically to mucosal hyperplasia of the gallbladder mucosa. Thickened inner hypoechoic layer is a useful ultrasonographic sign that indicates mucosal hyperplasia of the gallbladder and, particularly, the possible coexistence of undilated type APBD before the appearance of overt malignancy.