Intraductal ultrasonography (IDUS) of the pancreato-biliary duct system. Personal experience and review of literature

Focal intrahepatic strictures: a review of diagnosis and management

INTRODUCTION

Focal intrahepatic strictures are becoming more common owing to more prevalent and accurate cross-sectional imaging. However, data relating to their management are lacking. The purpose of the present review was to synthesize the current evidence regarding these lesions and to formulate a strategy for diagnosis and management.

METHODS

A literature search of relevant terms was performed using Medline. References of papers were subsequently searched to obtain older literature.

RESULTS

Focal intrahepatic strictures involve segmental hepatic ducts and/or left and right main hepatic ducts during their intrahepatic course. Most patients are asymptomatic while the minority present with vague abdominal pain or recurrent sepsis and only rarely with jaundice. Investigations used to distinguish benign from malignant aetiologies include blood tests (CEA, Ca19.9), imaging studies [ultrasonography (US), computed tomography (CT), magnetic resonance cholangiopancreatography (MRCP) and fluorodeoxyglucose-positron emission tomography (FDG-PET)], endoscopic modalities [endoscopic retrograde cholangiopancreatography (ERCP)/endoscopic ultrasound (EUS)/cholangioscopy] and tissue sampling (brush cytology/biopsy).

CONCLUSIONS

A focal intrahepatic stricture requires thorough investigation to exclude malignancy even in patients with a history of biliary surgery, hepatolithiasis or parasitic infection. If during the investigative process a diagnosis or suspicion of malignancy is demonstrated then surgical resection should be performed. If all diagnostic modalities suggest a benign aetiology, then cholangioscopy with targeted biopsies should be performed.

Preoperative evaluation of the longitudinal extent of borderline resectable hilar cholangiocarcinoma by intraductal ultrasonography

BACKGROUND AND AIM

In patients with hilar cholangiocarcinoma (HC), longitudinal tumor extent is important for curative resection. The purpose of this study was to evaluate the longitudinal extents of HC using transpapillary intraductal ultrasonography (IDUS) for optimal surgical planning.

METHODS

From July 2006 to April 2010, a total of 42 patients with borderline resectable HC were enrolled at Samsung Medical Center, a tertiary referral hospital in Seoul, Korea. All patients were evaluated using multi-detector computed tomography (MDCT), endoscopic retrograde cholangiopancreatography (ERCP) and IDUS. The new modified Bismuth Type (MBT) classification, in which the traditional Bismuth type IV stage is divided into stages IVa and IVb, was used to determine whether the tumor invaded the left lateral section. Among the subtypes of HC, the periductal infiltrative type (PDI) and intraductal papillary neoplasm of the bile duct (IPN-B) were compared. The accuracies of CT, ERCP, and IDUS were assessed through comparison with the postoperative histology findings.

RESULTS

A total of 42 patients were prospectively enrolled, and the tumor extent could be assessed histologically in 30 patients. The accuracies of CT, ERCP, and IDUS were 66.6%, 60%, and 90%, respectively. The accuracy of IDUS was 85.7% in 21 patients with PDI and 100% in nine patients with IPN-B.

CONCLUSIONS

Hilar cholangiocarcinoma staging based on IDUS findings was highly accurate. We therefore highly recommend using IDUS for optimal surgical planning in patients with borderline resectable HC.

Intraductal ultrasonography combined with percutaneous transhepatic cholangioscopy for the preoperative evaluation of longitudinal tumor extent in hilar cholangiocarcinoma

BACKGROUND AND AIM

In hilar cholangiocarcinoma, an accurate assessment of preoperative resectability is important to optimize surgical resection. We investigated the accuracy of the combination of intraductal ultrasonography (IDUS) and percutaneous transhepatic cholangioscopy (PTCS) for evaluating longitudinal extent in hilar cholangiocarcinoma.

METHODS

Patients diagnosed with hilar cholangiocarcinoma underwent multidetector computed tomography (MDCT) and magnetic resonance cholangiography (MRC) for tumor staging and Bismuth type. Percutaneous transhepatic biliary drainage was performed at the left or right bile duct of the liver section that was anticipated to be preserved in the surgical treatment. After tract dilation, PTCS with cholangioscope-directed biopsy and IDUS were sequentially performed to evaluate Bismuth type. Surgical treatment was executed according to tumor staging and longitudinal tumor extent. Postoperative histological Bismuth types were compared to preoperative Bismuth types based on MDCT, MRC, PTCS with biopsy, and IDUS.

RESULTS

From June 2006 to November 2008, 25 patients with hilar cholangiocarcinoma were enrolled, with 20 of these patients evaluable. The accuracy of MDCT, MRC, PTCS with biopsy, and IDUS for the evaluation of Bismuth type was 80%, 84.2%, 90%, and 85.0%, respectively, in 20 patients, and 82.4%, 82.4%, 94.1%, and 88.2%, respectively, in 18 patients with Bismuth type IIIa, IIIb, or IV cancer. The accuracy of the combination of IDUS and PTCS with biopsy was 95% in 20 patients, and 100% in 18 with Bismuth type IIIa, IIIb, or IV cancer.

CONCLUSIONS

The combination of IDUS and PTCS with biopsy was highly accurate for assessing Bismuth type and may help in the identification of an optimal surgical plan for the treatment of hilar cholangiocarcinoma, especially in Bismuth type IIIa, IIIb, or IV.

Clinical application of intraductal ultrasound during endoscopic retrograde cholangiopancreatography

Intraductal ultrasound (IDUS) used during endoscopic retrograde cholangiopancreatography (ERCP) can facilitate reliable evaluation of biliary and pancreatic disorders. The smaller diameter, flexibility, and the image quality offered by IDUS devices makes them ideal for evaluating a variety of difficult biliary and pancreatic diseases, especially in undefined strictures, luminal filling defects, and ampullary neoplasms. This article examines the numerous possible roles for IDUS in the evaluation of biliary and pancreatic conditions, as well as in ampullary neoplasms. IDUS is a simple, easy to learn, and safe technique that should be considered an integral tool in the therapeutic endoscopist's armamentarium.

Prospective evaluation of indeterminate ERCP findings by intraductal ultrasound

BACKGROUND AND AIM

Although the role of intraductal ultrasound (IDUS) in the evaluation of specific disease entities is well known, its utility in evaluating indeterminate findings in a heterogeneous group of patients undergoing endoscopic retrograde cholangiopancreatography (ERCP) is unknown. This study evaluates the diagnostic accuracy of IDUS in patients with indeterminate findings at ERCP.

METHODS

This was a prospective study of all patients who underwent IDUS for evaluation of an indeterminate biliary stricture or main pancreatic duct (MPD) dilation noted at ERCP over an 8-month period. The accuracy of IDUS was established based on long-term follow-up, surgery, or further investigations.

RESULTS

Twenty-nine (5%) of 600 patients who underwent ERCP had an indeterminate finding that warranted further evaluation by IDUS: this was biliary stricture in 19 patients and MPD dilation in 10. Technical success was 100%. Mean duration of follow-up was 435 days (range 192-614 days). In patients with biliary stricture, IDUS diagnosed 11 as benign and eight as malignant. In patients with MPD dilation, IDUS diagnosed intraductal papillary mucinous tumor in six patients and chronic pancreatitis in four. Findings on IDUS supported the correct diagnosis in 27 of 29 patients (93%). In two patients with dominant hilar stricture in the setting of primary sclerosing cholangitis, IDUS was false positive in one and false negative in the other. One patient died of multiorgan failure due to post-ERCP pancreatitis.

CONCLUSIONS

A technically easy procedure, IDUS offers unique advantages in the evaluation of patients with indeterminate findings at ERCP.

Biliary tract candidiasis: diagnostic and therapeutic approaches in a case series

BACKGROUND

Biliary obstruction with its wide range of potential causes is a common disorder in gastroenterology. Infections of the biliary tract with Candida and other fungal species leading to obstructive jaundice have increasingly been recognized in the last few years. Besides a few case reports, there are few data in the literature giving us an idea how to diagnose and treat these patients.

METHODS

We report on a series of seven patients suffering from biliary tract candidiasis who were diagnosed and treated at our institution. Predisposition factors, reliability of various diagnostic modalities, and treatment options based on our own experience are presented and discussed.

RESULTS

Besides the general diagnostic modalities such as laboratory findings or ultrasonography, we often observed mycelia in the bile duct system endoscopically. Typical morphological changes in peripheral bile ducts could be detected during endoscopic retrograde cholangiopancreatography (ERCP). Aspiration of bile and subsequent microbiological analysis in combination with ERCP findings revealed diagnosis of bile duct candidiasis in all cases. Treatment included both antiinfectious drugs and endoscopic therapy such as bile duct drainage, lavage, or débridement. With respect to fungal eradication, therapy was successful in 71% of cases as proven by microbiological analysis of bile aspirates. Since many of these patients suffer not only from biliary mycosis but also from disease necessitating immunosuppression, the prognosis was poor in some cases.

CONCLUSION

Biliary tract candidiasis because of immunosuppression is an increasingly recognized disease and remains a major clinical challenge. Besides laboratory analysis and ultrasonography, diagnostic modalities should include aspiration of bile during ERCP and microbiological analysis. Antiinfectious drug treatment as the main therapeutic column for biliary candidiasis should be complemented by endoscopic intervention.

Pancreatic imaging: current and emerging technologies

This review discusses the current imaging modalities for the diagnosis and staging of solid and cystic pancreatic lesions and for the assessment of acute and chronic pancreatitis, and the future role of emerging technologies in the management of pancreatic diseases. Multidetector row spiral computed tomography is superior to conventional single-detector row spiral computed tomography in the detection and staging of pancreatic adenocarcinoma. Positron emission tomography is a sensitive but relatively nonspecific diagnostic modality. Positron emission tomography-computed tomography fusion may improve the staging accuracy for pancreatic cancer. Echo-enhanced ultrasound may have an emerging role in evaluating pancreatic masses. Endoscopic ultrasound with fine needle aspiration for cytology is the single best method for diagnosis and staging of nonmetastatic pancreatic cancer with a high accuracy for determining tumor resectability. In acute pancreatitis, a modification of the standard computed tomography severity index, which places greater emphasis on extrapancreatic complications, has shown superior correlation with various patient outcome measures. Endoscopic retrograde cholangiopancreatography is still the test of choice for morphological evaluation of chronic pancreatitis, whereas magnetic resonance cholangiopancreatography offers a noninvasive alternative in selected patients. Endoscopic ultrasound can be useful for detecting early chronic pancreatitis. Secretin-stimulated imaging techniques may eventually provide a noninvasive method of reliably assessing pancreatic exocrine function.

Duodenal EUS to identify thickening of the extrahepatic biliary tree wall in primary sclerosing cholangitis

BACKGROUND

Diagnosing primary sclerosing cholangitis (PSC) is problematic and requires meeting a burden of proof through clinical, biochemical, radiologic, and histological features. Endoscopic ultrasound yields detailed images of the extrahepatic biliary tree, but its value in contributing to the diagnosis of this condition is unknown.

OBJECTIVES

To determine the potential for transduodenal EUS to detect common bile duct wall thickening in PSC.

DESIGN

A prospective, controlled study with retrospective, blinded data analysis.

SETTING

Single tertiary referral center for inflammatory bowel disease and EUS.

PATIENTS

Four groups of patients were assessed with radial endosonography: PSC (n = 9); inflammatory bowel disease (IBD) with abnormal liver blood tests (n = 21); choledocholithiasis (n = 15); and normal controls (n = 50). Measurements were made of the common bile duct diameter and wall thickness.

INTERVENTIONS

Transduodenal radial EUS of the biliary tree.

MAIN OUTCOME MEASUREMENTS

Common bile duct diameter and wall thickness.

RESULTS

The mean diameter (SD) of the common bile duct for the PSC, IBD, choledocholithiasis, and normal control groups measured 8.9 mm (2.8), 5.4 mm (1.7), 7.2 mm (2.2), and 5.0 mm (1.9), respectively (PSC and choledocholithiasis groups compared to the IBD group, P < .05 for a single test of hypothesis, but correction for the multiple testing of data removed this significance; normal control group P < .005). Mean ductal wall thickness (SD) was 2.5 mm (0.8) for the PSC group, 0.7 mm (0.4) for the IBD group, 0.8 mm (0.4) for the choledocholithiasis group, and 0.8 mm (0.4) for the normal control group, respectively (PSC group compared to the other 3 groups, P < .005).

LIMITATIONS

Assessment of intrahepatic PSC is problematic.

CONCLUSION

Thickening (>1.5 mm) of the common bile duct wall is seen in patients with PSC but not in those with apparently uncomplicated IBD or choledocholithiasis. The results of this study suggest that standard endosonography contributes to the imaging and potentially to the diagnosis of PSC.

Nonoperative imaging techniques in suspected biliary tract obstruction

Evaluation of suspected biliary tract obstruction is a common clinical problem. Clinical data such as history, physical examination, and laboratory tests can accurately identify up to 90% of patients whose jaundice is caused by extrahepatic obstruction. However, complete assessment of extrahepatic obstruction often requires the use of various imaging modalities to confirm the presence, level, and cause of obstruction, and to aid in treatment plan. In the present summary, the literature on competing technologies including endoscopic retrograde cholangiopancreatography (ERCP), percutaneous transhepatic cholangiopancreatography (PTC), endoscopic ultrasound (EUS), intraductal ultrasonography (IDUS), magnetic resonance cholangiopancreatography (MRCP), helical CT (hCT) and helical CT cholangiography (hCTC) with regards to diagnostic performance characteristics, technical success, safety, and cost-effectiveness is reviewed. Patients with obstructive jaundice secondary to choledocholithiasis or pancreaticobiliary malignancies are the primary focus of this review. Algorithms for the management of suspected obstructive jaundice are put forward based on current evidence. Published data suggest an increasing role for EUS and other noninvasive imaging techniques such as MRCP, and hCT following an initial transabdominal ultrasound in the assessment of patients with suspected biliary obstruction to select candidates for surgery or therapeutic ERCP. The management of patients with a suspected pancreaticobiliary condition ultimately is dependent on local expertise, availability, cost, and the multidisciplinary collaboration between radiologists, surgeons, and gastroenterologists.

Endosonographic and histopathological staging of extrahepatic bile duct cancer: time to leave the present TNM-classification?

OBJECTIVES

The discrepancy between high rates of sensitivity, specificity, and accuracy for intraductal ultrasonography (IDUS) in extrahepatic bile duct carcinoma and the failure to depict different wall layers as defined by the TNM classification have not yet been elucidated sufficiently.

METHODS

In a prospective study, endosonographic images were correlated with histomorphology including immunohistochemistry. Using IDUS, we examined fresh resection specimens of patients who had undergone pancreato-duodenectomy. For histological analysis, the formalin-fixed and paraffin-embedded specimens were stained by hematoxylin-eosin, elastica-van-Gieson, and immunohistochemically by smooth muscle-actin. To confirm our hypothesis, further cases from the archives were analyzed histopathologically and immunohistochemically.

RESULTS

The various wall layers of the extrahepatic bile duct as described by the International Union Against Cancer are neither histomorphologically nor immunohistochemically consistently demonstrable. Especially, a clear differentiation between tumor invasion beyond the wall of the bile duct (T2) and invasion of the pancreas (T3) by histopathological means is often not possible. Endosonographic images using high-resolution miniprobes similarly confirm the difficulty in imaging various layers in the bile duct wall.

CONCLUSIONS

Most adaptations made by the sixth edition of the TNM classification accommodate to the endosonographic and most of the histopathological findings as demonstrated in our study. In contrast to the new edition, however, our findings suggest to combine T2- and T3-staged tumors into one single class leading to clarification, and improved reproducibility of histopathological staging.

Cholangiocarcinoma and intraductal sonography

The instruments and processing systems of intraductal ultrasonography (IDUS) and 3D-IDUS are developing. IDUS is a reliable method for the evaluation of cholangiocarcinoma, and accurate staging is the most significant role of IDUS. DPR images produced by 3D-IDUS are useful to assess the tumor extension and the relationship with surrounding organs. 3D-IDUS is more useful for the precise diagnosis of cancer extension in cholangiocarcinoma, especially in invasion into the portal vein and pancreas, than CT scan and angiography. Tumor volume calculated with 3D-IDUS should determine the prognosis for the patients and facilitate the evaluation of efficacy of laser therapy.

Endoscopic retrograde cholangiopancreatography, intraductal ultrasonography, and magnetic resonance cholangiopancreatography in bile duct strictures: a prospective comparison of imaging diagnostics with histopathological correlation

OBJECTIVES

A variety of imaging techniques are available to diagnose bile duct strictures; the most effective imaging technique, however, has not been established yet. In the present study, we compared the impact of endoscopic retrograde cholangiopancreatography (ERCP), intraductal ultrasonography (IDUS), and magnetic resonance cholangiopancreatography (MRCP) with regard to diagnosing bile duct strictures.

METHODS

We prospectively examined 33 patients with jaundice due to bile duct strictures by ERCP plus IDUS and MRCP. The objectives were to assess diagnostic quality of imaging, complete presentation of the bile duct, and differentiation of malignant from benign lesions. Surgical and histopathological correlations, which were used as the gold standard, were available in all cases since all included patients underwent laparotomy.

RESULTS

Diagnostic image quality for ERCP was 88% and 76% for MRCP (p > 0.05). Comparing ERCP and MRCP, complete presentation of the biliary tract was achieved in 94% and 82%, respectively (p > 0.05). ERCP and MRCP allowed correct differentiation of malignant from benign lesions in 76% and 58% (p= 0.057), respectively. By supplementing ERCP with IDUS, the accuracy of correct differentiation of malignant from benign lesions increased significantly to 88% (p= 0.0047).

CONCLUSIONS

Comparing ERCP with MRCP, we found adequate presentation of bile duct strictures in high imaging quality for both techniques. ERCP supplemented by IDUS gives more reliable and precise information about differentiation of malignant and benign lesions than MRCP alone without additional imaging sequences.

Innovative methods of biliary tract diagnosis: intraductal ultrasound and tissue acquisition

Tissue can be acquired from the bile and pancreatic duct with either brush cytology or biopsy forceps, often without the need for sphincterotomy. Although the diagnosis of malignancy with these sampling techniques is often specific, the sensitivity is limited, and a wide range of diagnostic accuracies has been reported. A combination of biopsy and brush cytology along with some newer techniques in the development stage may increase the sensitivity. Intraductal ultrasound is a newer technique offers the endoscopist the ability to image the bile and pancreatic duct wall, adjacent organs, and vascular structures with a high degree of detail. This visualization can be accomplished during the course of an ERCP or percutaneously under fluoroscopic guidance. Indications for the procedure include detection of choledocholithiasis, differentiation of benign and malignant ductal strictures, pancreaticobiliary tumor staging, and detection of various pancreatic tumors. Continued research into the design of the probes, which could improve durability and extend the depth of penetration, may promote more widespread use of this novel technology.

Clinical utility of intraductal US for evaluation of choledocholithiasis

BACKGROUND

Intraductal US can improve the diagnostic accuracy of cholangiography performed under C-arm fluoroscopy in patients with suspected choledocholithiasis. This study aimed to determine the clinical utility of intraductal US for patient management.

METHODS

Patients with suspected choledocholithiasis undergoing ERCP with a C-arm fluoroscope at two tertiary academic medical centers were enrolled. After initial cholangiography, findings and decisions concerning the need for further interventions were recorded. Intraductal US (20 MHz) was then selectively performed in patients with equivocal cholangiography or those without cholangiographic evidence of bile duct stones. Intraductal US was also performed after endoscopic sphincterotomy and stone extraction to confirm bile duct clearance.

RESULTS

Fifty-two patients (28 men, 24 women) were enrolled and intraductal US was selectively performed in 35 (64%). Of the 21 patients with normal cholangiography, 8 (38%) had stones or sludge by intraductal US. Endoscopic sphincterotomy was performed as a direct result of intraductal US in these 8 and the findings were confirmed in 7. In the 14 patients in whom cholangiography demonstrated small (<5 mm) or round filling defects, intraductal US concurred in 9 and found air bubble/no stone in 5. Sphincterotomy was avoided in these 5 patients. Overall, intraductal US led to a change in clinical management in 13 of 35 patients (37%) in whom it was performed.

CONCLUSIONS

Selective use of intraductal US affects the clinical management of a large proportion of patients who undergo C-arm fluoroscopy-guided ERCP for suspected bile duct stones.

Endoscopically inserted endoluminal receiver coil for high-resolution magnetic resonance imaging of the pancreas: Initial results in an animal model

BACKGROUND

This study assessed the feasibility of high-resolution magnetic resonance imaging of the pancreas by means of an endoscopically inserted endoluminal magnetic resonance receiver coil.

METHOD

A 0.032-inch diameter internal magnetic resonance imaging receiver coil was endoscopically inserted into the pancreatic duct in 4 pigs through the accessory channel of a standard duodenoscope to obtain high-resolution magnetic resonance images by using T1- and T2-weighted sequences.

RESULTS

The pig anatomy precluded the usual transoral approach; however, transgastric access allowed endoscopic transpapillary insertion of a receiver coil into the pancreatic duct in all animals without the need for sphincterotomy. The small swine pancreas could then be visualized by magnetic resonance imaging with a 0.3 x 0.3-mm in-plane resolution.

CONCLUSION

High-resolution pancreas magnetic resonance imaging is feasible by using an endoscopically inserted endoluminal receiver coil. The smaller stomach and larger pancreatic duct diameter in humans will facilitate clinical application of the imaging procedure.

Endoscopic ultrasonography and endoscopic retrograde cholangiopancreatography imaging for pancreaticobiliary pathology: the gastroenterologist's perspective

With advances in noninvasive radiologic technology, additional adjunctive techniques are developing, and the roles for ERCP and EUS are continuously changing. In a diagnostic setting, ERCP is currently best reserved for patients with a high likelihood of needing endoscopic therapy, and EUS is especially useful for cases in which other imaging techniques have been inconclusive or are of inferior diagnostic capability. In a therapeutic setting, ERCP and EUS retain important roles in the management of both benign and malignant pancreatic and biliary disease. Certainly, technological advances also directly affect these modalities and expanded applications for ERCP and EUS for the pancreas and biliary tract are anticipated.

Diagnosis and fine needle aspiration of intraductal papillary mucinous tumor by endoscopic ultrasound

A recently established clinical entity, intraductal papillary mucinous tumor (IPMT) of the pancreas embraces a spectrum of pathology ranging from benign to malignant disease. IPMT must be differentiated from other cystic neoplasms of the pancreas, as well as inflammatory cystic lesions. As the pancreas lies in close proximity to the gastric and duodenal walls, endoscopic ultrasonography (EUS) is ideally suited for imaging the pancreas. Additionally, EUS facilitates fine needle aspiration of pancreatic cysts and/or a dilated pancreatic duct for cytologic and tumor marker analysis. This article presents a brief history of IPMT, differential diagnosis, current imaging modalities, findings of cytologic and tumor marker analysis, prognosis, and treatment strategy. Special emphasis is dedicated to the role of EUS, as well as EUS with fine needle aspiration.

Is endosonography an effective method for detection and local staging of the ampullary carcinoma? A prospective study

BACKGROUND

The relatively rare carcinoma of the ampulla of Vater is a neoplasia with a good prognosis compared to pancreatic cancer. Preoperative staging is important in planning the most suitable surgical intervention.

AIM

To prospectively evaluate the diagnostic accuracy of Endoscopic Ultrasonography (EUS) in comparison with conventional US and CT scan, in staging of patients with ampullary carcinoma.

PATIENTS AND METHODS

20 patients (7 women and 13 men) with histologically proven carcinoma of the ampulla of Vater were assessed by EUS, CT scan and US. Results were compared to surgical findings.

RESULTS

Endoscopic biopsies were diagnostic in 76% of the patients. Detection of ampullary cancer with US and CT scan was 15% and 20% respectively. Only indirect signs of the disease were identified in the majority of cases using these methods. Overall accuracy of EUS in detection of ampullary tumours was 100%. The EUS was significantly (p < 0.001) superior than US and CT scan in ampullary carcinoma detection. Tumour size, tumour extension and the existence of metastatic lymph nodes were also identified and EUS proved to be very useful for the preoperative classification both for the T and the N components of the TNM staging of this neoplasia. The diagnostic accuracy for tumour extension (T) was 82% and for detection of metastatic lymph nodes (N) was 71%.

CONCLUSION

EUS is more accurate in detecting ampullary cancer than US and CT scan. Tumor extension and locally metastatic lymph nodes are more accurately assessed by means of EUS than with other imaging methods.

Gastrointestinal miniprobe sonography: the current status

Endoscopic ultrasonography (EUS) represents a major advance in endoscopic imaging. The usefulness and effectiveness of EUS have been established during the past few years. However, endosonography using dedicated echoendoscopes (7.5/12 MHz) has some serious drawbacks, as follows: 1) Combining endoscopy and ultrasonography in one instrument increases the diameter of such echoendoscopes (12-13 mm); 2) Because of the large diameter, complete passage of severe strictures is often not possible and, for examination of the pancreatobiliary duct system, is not feasible at all; 3) Image quality and resolution for small lesions is not always satisfactory; and 4) Conventional endosonography requires a second examination separate from the previous routine endoscopy. Recently developed ultrasonographic miniprobes (diameters about 2 mm; frequencies 12-20 MHz) can be passed through the working channel of standard endoscopes to provide high frequency ultrasound images. These miniprobes might overcome some of the above-mentioned drawbacks and contribute to patients' security and convenience. Moreover, in various diseases of the GI tract and the pancreatobiliary duct system, diagnostic accuracy of miniprobe ultrasonography has been shown to be even superior to that of EUS. In summary, miniprobe ultrasonography seems to be a promising tool in the armamentarium of gastroenterological diagnostics.