Stephan Hollerbach, PhD
Abbreviations: MRI, magnetic resonance imaging, PBD, pancreatico-biliary disease
Today there is a great need for minimally invasive procedures that permit the rapid tissue-based diagnosis in all patients with unclear pancreatobiliary disease, particularly those with suspected precancerous or clearly malignant lesions.
With the advent of minimally invasive endoscopic procedures during the 1970s, ERCP has become the primary method of diagnosing and treating many patients with pancreatobiliary disease (PBD). However, this role was later challenged by the introduction of less-invasive procedures such as high-end US, helical CT scanning, EUS, and finally magnetic resonance imaging (MRI) in clinical gastroenterology during the past 2 decades. These techniques have added a new dimension in the diagnosis of pancreatic and biliary diseases, leaving the more invasive ERCP procedures as primary “therapeutic” instruments for the treatment of biliary and pancreatic obstruction. This development was rather logical and expected because purely diagnostic ERCP still carries a significant risk of acute pancreatitis in up to 1.5% to 5.0% of cases and a small, albeit distinct, potential for procedure-related death.1, 2, 3
Fortunately, the contemporary clinical gastroenterologist is “armed” with several complementary imaging and endoscopic techniques to detect PBD with high resolution. Hence, the primary diagnosis of PBD is much easier to establish today than it was 30 years ago, particularly in patients with small stones in the common bile duct (EUS or MRCP) and those with advanced pancreatic/biliary cancer (US, CT, MRI) that unfortunately comprise up to 40% to 50% of cases seen in a GI department. These patients will only benefit from ERCP interventions when the goal of this procedure has been previously clearly defined before introduction of contrast and catheters. However, the optimal sequence of how to best use available imaging techniques in individual patient cases remains to be a puzzling decision in some cases because the specificity of most indirect procedures can still be unsatisfactory. This is the case, for instance, with patients with small pancreatic lesions and those with chronic pancreatitis in whom the development of cancer must be ruled out. Today there is a great need for minimally invasive procedures that permit rapid tissue-based diagnosis in all patients with unclear PBD, particularly those with suspected precancerous or clearly malignant lesions. No systemic chemotherapy or radiotherapy should be performed without cytohistologic evidence of cancer and its subtype. However, brush cytology specimens obtained during ERCP have a notoriously low sensitivity (approximately 30%), whereas biliary forceps biopsy specimens are usually only available after endoscopic sphincterotomy with a diagnostic yield of 40% to 50% and they put the patient at some additional risk of bleeding. Currently, EUS with simultaneous US-guided FNA biopsy appears to be the best-suited method for this task.4, 5, 6 Since its introduction in the early 1980s, EUS has progressed from a relatively crude and merely diagnostic modality to a “multitasking” instrument that can provide diagnosis and local staging of PBD. Since then, EUS has emerged as a clinically useful tool with a major impact on patient management in many instances, particularly in patients with obscure common bile duct stones, submucosal GI tumors, biliary pancreatitis, chronic pancreatitis, pancreatic and biliary malignancies, including cystic lesions of the pancreas oradrenals, other retroperitoneal tumors, and a multitude of mediastinal diseases.7, 8, 9, 10, 11, 12 The risk of serious side effects has been consistently shown throughout the studies to be rather low, between 1% to 2%, even with interventional FNA procedures.13 This explains why a rising number GI centers set out to take advantage of EUS-FNA and obtain a cytohistologic diagnosis before further endoscopic interventions.
The retrospective study by Ross et al14 suggests a relatively novel diagnostic “tandem” approach. This technique involves performing EUS with FNA first for the tissue-based cytohistologic diagnosis, followed by therapeutic ERCP for local treatment in patients with suspected malignant obstruction at the level of the distal bile ducts and pancreatic head at the same setting. This approach offers several hypothetic and some evidence-based advantages. First, EUS imaging is carried out under “untouched” or naive conditions, which minimizes any artifacts that could be potentially induced by EUS, ERCP-induced pancreatic necrosis, ERCP brushing, or previous duct stenting. Second, conscious sedation has to be used only once for the same patient to undergo both interventions simultaneously. Third, the clinician performing both interventions gets an impression beyond the bowel wall about what anatomic and pathophysiologic changes she or he has to be aware of before the introduction of the ERCP catheters. Although not specifically investigated, the latter approach may—at least theoretically—be very useful in endoscopic practice to guide the therapeutic endoscopist, particularly in situations when a difficult access to the ducts is to be expected and decisions, such as the timing and size of precut sphincterotomy, must be considered. Finally, performing EUS-FNA and ERCP in tandem is presumably cost-effective and may reduce procedure time and the time until the final tissue-based diagnosis is available. In this study, the diagnostic yield of EUS-FNA in this highly selected study population was rather high (overall accuracy 88%) and the rate of endoscopic sphincterotomy or stenting was high (51 and 96 of 114 patients). The safety profile looks acceptable with side effects about 10.5% (mostly pancreatitis) and was in the range of the reported complications after biliary EUS and stent insertion in other studies that focused on therapeutic ERCP. The mean procedure time for both (74 minutes) looks somewhat long at first sight; however, at second look it becomes clear that the range was substantial because it was probably difficult to access the tumor or papilla in this group of rather ill patients with advanced disease. Compared with a 2-step, 2-procedure approach, the data are clearly in favor of the 1-step approach.
作者:admin@医学,生命科学 2011-01-13 12:40