Pancreaticobiliary Disorders: What Are the Roles of CT, MRCP, and EUS Relative to ERCP?

Endoscopic retrograde cholangiopancreatography (ERCP) was first described in 1968 (see Chapter 1 ). Despite being technically challenging because of the limited range of available endoscopes and accessories at that time, it became an important modality for diagnostic evaluation of the pancreaticobiliary system in Japan and Europe. The therapeutic role of ERCP was recognized and developed after the introduction of sphincterotomy in 1972 by Classen and Demling from Germany and Kawai et al. from Japan. The therapeutic utility of ERCP expanded from removal of bile duct stones to relief of malignant hepatobiliary obstruction after the development of bile duct and pancreatic stents in the 1980s. Despite initial concerns about its utility and safety, ERCP was subsequently accepted in the United States. The use of ERCP in the United States reached a peak in the mid-1990s. Along with the development of formal ERCP training, the introduction of laparoscopic cholecystectomy in 1989 may have also contributed to the increased use of ERCP in the early 1990s.

Since the initial development of ERCP, imaging of the pancreaticobiliary tract has undergone a remarkable transition with the development of high-resolution computed tomography (CT), endoscopic ultrasonography (EUS), and magnetic resonance imaging with cholangiopancreatography (MRI/MRCP). With the availability of these less invasive, safer imaging modalities, the role of ERCP has now transitioned mainly to a therapeutic tool, especially because of the recognition of the high risk of potential adverse effects associated with diagnostic ERCP (see Chapter 8 ). High-quality prospective studies have also led to the recognition of conditions where ERCP is now not the best management option.

In a study published in 2007 using the National Inpatient Sample (NIS) database, Jamal et al. showed that the use of ERCP in the United States increased from 1988 to 1996, but from 1996 to 2002 showed a steady decline. The age-adjusted ERCP rate declined approximately 20% from 1996 to 2002. The study also concluded that the declining trend was mainly attributable to a decrease in the use of diagnostic ERCP, as the utilization of therapeutic ERCP continued to increase during the study period. The trend of declining ERCP use was also noted in the outpatient ambulatory centers from the Stage Ambulatory Surgery Database (SASD) during the same period. It is our assumption that the use of ERCP has continued to decline since then, and with the recent EPISOD trial showing no benefit of ERCP in patients with suspected type III sphincter of Oddi dysfunction (SOD) (see Chapter 47 ), this trend will likely continue. In the pediatric population, the use of therapeutic ERCP increased from 2000 to 2009 but diagnostic ERCP use showed a significant decrease.

The reason for the declining role of ERCP is twofold. First, the high and, in most cases, unacceptable risk of adverse events, and second, the availability of alternate noninvasive and less risky imaging modalities. The adverse events associated with ERCP and how to minimize these have already been discussed in Chapter 8 and will not be discussed here in detail. We summarize here the literature comparing ERCP with EUS, MRI, and CT imaging for various diagnostic purposes in the major pancreaticobiliary diseases. The therapeutic role of ERCP in obtaining biliary and pancreatic duct drainage and treatment of choledocholithiasis is well established and will not be reviewed here. Cost of care is an important consideration in current-day medicine and should play a role in deciding the choice of diagnostic evaluation. Along with the increased risk of adverse events, studies have shown that ERCP is less cost-effective than less invasive modalities such as EUS and MRCP for evaluation of the biliary tree in patients with suspected biliary disease, especially in a population with low disease prevalence. There are multiple studies comparing the cost and diagnostic yield of MRI/MRCP versus EUS for diagnosing biliary diseases. However, in patient populations with a high prevalence of pancreaticobiliary disease, where the probability of performing therapeutics is greater than 50%, ERCP is more cost-effective than EUS and MRCP. Such patients include those with indeterminate biliary strictures, obstructive jaundice, and high likelihood of choledocholithiasis based on clinical criteria.

Role of Noninvasive Imaging and EUS Compared With ERCP in Benign Hepatobiliary Diseases

Stone Disease

Choledocholithiasis is the most common indication for ERCP. Because laparoscopic cholecystectomy is commonly not associated with bile duct exploration, ERCP is the preferred and first-line therapeutic modality for the management of bile duct stones. Given the risk of adverse events, there is not a diagnostic role for ERCP in all patients in whom bile duct stones are expected. Among those with symptomatic cholelithiasis and suspected choledocholithiasis, it is important to select patients carefully for ERCP. Even though CT imaging is sensitive for detecting the presence and level of bile duct dilation, the sensitivity of CT imaging for choledocholithiasis is relatively low (around 75%) and CT imaging should ideally not be used in patients with suspected choledocholithiasis. MRI/MRCP ( Fig. 34.1 ) has a sensitivity >90% for the diagnosis of choledocholithiasis but is lower for stones <6 mm in diameter, where the sensitivity is approximately 75%; it is also decreased in the presence of dilated bile ducts. Both EUS and MRI/MRCP have very high sensitivity and specificity for diagnosing bile duct stones, with EUS ( Fig. 34.2 ) being slightly superior to MRI/MRCP especially for small distal bile duct stones. The American Society for Gastrointestinal Endoscopy (ASGE) practice guidelines categorize symptomatic cholelithiasis patients with suspected choledocholithiasis into three groups based on the likelihood of the presence of common bile duct stones. This categorization uses clinical presentation, laboratory, and transabdominal ultrasonographic findings. Patients with high likelihood of choledocholithiasis (defined as >50% probability) should undergo preoperative ERCP, whereas those with low likelihood (<30%) should undergo cholecystectomy directly. Those patients with medium likelihood (30% to 50%) should undergo either preoperative MRI or EUS or intraoperative cholangiography ( Fig. 34.3 ) to confirm the presence of choledocholithiasis before undergoing ERCP.

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