Cholangiography and Pancreatography

Introduction

Endoscopic cannulation of the major papilla with imaging of the biliary tree and the pancreatic ductal system (endoscopic retrograde cholangiopancreatography [ERCP]) was first successfully accomplished with an end-viewing duodenoscope and reported in 1968. Subsequent development of side-viewing endoscopes with a catheter-deflecting elevator greatly advanced the technique. Diagnostic studies were supplemented by the first endoscopic sphincterotomies in the early 1970s. Overall, these developments expanded the field of endoscopy and permitted the performance of less invasive diagnostic and therapeutic maneuvers in the pancreaticobiliary ductal system(s), which were previously limited to open surgical and percutaneous techniques.

In recent years, the refinement and proliferation of magnetic resonance imaging (MRI) and endoscopic ultrasound (EUS) techniques have changed the practice of ERCP. Now that quality diagnostic studies are readily available to the pancreaticobiliary endoscopist, ERCP has evolved from a stand-alone diagnostic procedure into an almost exclusively therapeutic endeavor. Although diagnostic indications for ERCP have now been displaced by the aforementioned less invasive, lower risk imaging modalities, the need for mastery of the radiographic findings of ERCP remains. Expert level execution and interpretation of diagnostic ERCP is a crucial component for skillful, efficient deployment of therapeutic interventions. Diagnostic ERCP findings also complement (and, in a few scenarios, are superior to) noninvasive imaging modalities for establishing or excluding pathology (e.g., pancreatic ductal leaks and fistulae).

This chapter reviews the indications for ERCP, techniques involved in its performance, and frequently encountered normal and pathologic diagnostic findings.

Indications and Contraindications for ERCP

Imaging of the pancreaticobiliary ductal system without anticipated therapy is appropriate in a narrow set of clinical circumstances. Patients requiring ductal imaging who are unable to undergo MRI/magnetic resonance cholangiopancreatography (MRCP) (e.g., those with implantable devices and/or a large body habitus) may require diagnostic ERCP as a first diagnostic test for ductography. However, conditions that indicate ERCP as purely a diagnostic modality are usually exceptional (e.g., cholestasis without dilated ducts, suspicion of early sclerosing cholangitis, confirmation of pancreatic fistula after nondiagnostic imaging if clinical suspicion persists), and it should only be performed in a setting of at least moderate pretest suspicion. In certain settings, such as clinical diagnosis of acute cholangitis with shock or sepsis, therapeutic ERCP is considered lifesaving, and need not be preceded by cross-sectional imaging. Overall, ERCP is indicated in clinical settings in which there is significant suspicion of pathology and a clear intention for therapeutics. A general list of indications is shown in Table 49.1 .

Most contraindications to ERCP are relative, and the degree of risk must be balanced against the potential benefit. In patients with necrotizing pancreatitis and low clinical suspicion for ductal stones, ERCP is relatively contraindicated, as pancreatography may result in bacterial contamination of the pancreatic bed and undrained fluid collections. Other relative contraindications include unstable cardiopulmonary disease or severe coagulopathy. Patients with comorbid life-threatening conditions can have endoscopic retrograde cholangiography (ERC) performed in the intensive care unit (with or without fluoroscopy) if deemed medically necessary. ERCP with manometry and/or sphincterotomy is now generally not indicated in patients with type III sphincter of Oddi dysfunction, given the negative results of a 2014 high-quality, randomized study.

Endoscopic Equipment

ERCP is performed using side-viewing instruments with video chip processors that provide high-quality images. Digital video systems (over fiberoptic) are now the standard, as they offer the advantage of television monitor viewing by all persons in the endoscopy suite, real-time teaching capabilities, and seamless coordination between the endoscopist and the ERCP team. Endoscopes have a working length of 120 cm and are generally categorized as diagnostic (11-mm distal diameter) or therapeutic (13.7-mm distal diameter). Some newer-generation endoscopes combine a large working channel diameter (up to 4.2 mm) with a standard 11-mm insertion tube diameter ( Fig. 49.1 ). A pediatric duodenoscope with an outer diameter of less than 7.5 mm is available (Olympus America Inc., Center Valley, PA). Most ERCP examinations should now be performed with CO ₂ insufflation. Data suggest that CO ₂ insufflation reduces postprocedure abdominal distention and pain, and likely expedites recovery.

Current-generation endoscopes are capable of undergoing submersion disinfection. After cleaning, endoscopes should be hung in vertical position to facilitate drying. However, in the setting of growing concern over carbapenem-resistant Enterobacteriaceae infections linked to contaminated duodenoscopes even after “standard” reprocessing procedures, enhanced techniques for disinfection and surveillance are now recommended. Special attention should be given to the elevator mechanism during disinfection. Surveillance cultures of the duodenoscope instrument channel and its distal components are also recommended, with reprocessing of duodenoscopes if cultures are positive.

Digital Imaging and Radiation Safety

Endoscopists at high-volume centers often have dedicated suites for ERCP. However, many physicians in the community and/or at lower-volume centers must coordinate procedures with a radiology department and use general purpose or angiographic units. Manufacturers now market dedicated fluoroscopy units for ERCP. Flat tables with a fixed overhead carriage have limited versatility. Consequently, the preferred x-ray table configuration includes the ability to tilt the patient's head up and down 30 degrees and has a C-arm carriage, which allows axial, cranial, caudal, vertical, and horizontal movements, to create image vectors from multiple angles ( Fig. 49.2 ). Because the patient is usually positioned prone with the head at the foot of the table, having the ability to reverse the viewing image in both the vertical and the horizontal axes is helpful. In the past, endoscopists used older-generation x-ray units, including portable C-arm units with limited image resolution. This practice is no longer acceptable because high-quality fluoroscopy and quality images are key to accurate diagnosis and management. High-quality ERCP imaging requires resolution equivalent to that for neuroradiology (brain blood vessels). Resolution of greater than 2.5 line pairs per millimeter is strongly recommended for both fluoroscopy and final images ( Fig. 49.3 ). This resolution is best accomplished with image intensifiers that have smaller diameters (6–9 inches).

Radiation safety standards should be followed. Monitoring levels of personal exposure, selecting the highest-quality equipment, using radiation shielding, and undergoing formal training in techniques to limit exposure are recommended to limit cumulative radiation dosage to the patient and the ERCP team ( Box 49.1 ). Collimating to the area of interest rather than magnifying is good practice. Use of newer-generation pulse fluoroscopy gives intermittent viewing, which, although slightly jerky, is often adequate for the majority of maneuvers during a case and with a fraction of the radiation exposure. Appropriate lead aprons, lead glasses, and thyroid shields are recommended ( Fig. 49.4 ).

Box 49.1

Strategies to Limit Personal Radiation Exposure During ERCP

Personal Shielding Protection

• Full (wrap) coverage body aprons

• Leaded glasses

• Thyroid shield

• Regular, systematic inspection of personal shielding for defects

Fluoroscopy Equipment

• Under-couch x-ray tube preferred to over-couch and mobile C-arms

• Leaded drapes, shielding between operator and collector

• High-quality, digital systems

Operator Behavior

• Use of collimation rather than magnification for enhanced images

• Pulsed rather than continuous fluoroscopy

• Use of “last image hold” over radiograph for reference

• Use of endoscopic rather than fluoroscopic cues for appropriate ERCP maneuvers (e.g., exchange of endoscopic accessories within the duodenoscope channel)

Staff Monitoring and Education

• Dual dosimeter monitoring with regular operator feedback

• Displays with cumulative fluoroscopy time and radiation exposure

• Structured training on fluoroscopy equipment and radiation safety

ERCP, endoscopic retrograde cholangiopancreatography.

Endoscopic Technique