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Endoscopic ultrasonography to evaluate pancreatitis

Cleveland Clinic Journal of Medicine. 2012 March;79(3):202-206 | 10.3949/ccjm.79a.11092
March 1, 2012|Cleveland Clinic Journal of Medicine
Siwar Albashir, MD;Tyler Stevens, MD
Author and Disclosure Information

Siwar Albashir, MD
Department of Internal Medicine, Cleveland Clinic

Tyler Stevens, MD
Department of Gastroenterology and Hepatology, Digestive Disease Institute, Cleveland Clinic

Address: Tyler Stevens, MD, Digestive Disease Institute, A31, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195; e-mail stevent@ccf.org

ABSTRACTEndoscopic ultrasonography (EUS) has become a well-accepted test in the workup of acute and chronic pancreatitis. However, further studies are needed to define its diagnostic role in patients with recurrent acute pancreatitis and minimal-change chronic pancreatitis.

KEY POINTS

  • EUS can identify the cause of acute pancreatitis when other imaging tests (computed tomography, transabdominal ultrasonography) are unrevealing.
  • EUS can safely and accurately detect bile duct stones and other causes of recurrent acute pancreatitis. It can also detect mild and severe structural features of chronic pancreatitis.
  • An endoscopic pancreatic function test may be a useful adjunct to EUS to detect mild exocrine insufficiency in early chronic pancreatitis.

ENDOSCOPIC ULTRASONOGRAPHY IN CHRONIC PANCREATITIS

Chronic pancreatitis, a relatively common and sometimes debilitating cause of chronic upper abdominal pain, may be difficult to diagnose using noninvasive imaging tests. Minimal-change chronic pancreatitis is defined as a syndrome of pancreatic abdominal pain with no or slight structural changes detected on imaging but with histologic inflammation and fibrosis diagnostic of chronic pancreatitis.9

A clinical rationale for trying to detect chronic pancreatitis early in its course is that interventions can be started earlier. These include abstinence from alcohol, giving exogenous pancreatic enzymes, and advanced interventions such as celiac plexus blocks for pain control. Some patients may even benefit from resection of the pancreas if pain is severe and resistant to conservative measures.

EUS can detect both parenchymal and ductal changes that correlate with histologic fibrosis.10 Parenchymal changes include hyperechoic foci, hyperechoic strands, lobularity, cysts, and shadowing calcifications. Ductal changes include dilation of the main pancreatic duct, irregularity, hyperechoic duct margins, and visible side branches.

Several studies have evaluated the ability of EUS to diagnose early chronic pancreatitis.9,11–15 Reference standards used to determine the accuracy of EUS have included histology,10,16–18 pancreatic function testing,19–22 and ERCP.11,15,23,24

The best diagnostic test may be pancreatic histology. However, biopsy of the pancreas is impractical and exposes patients to high risk. In addition, the patchy and focal distribution of histologic changes may decrease its reliability. Fortunately, the histologic findings of fibrosis have been shown to correlate with EUS criteria in patients undergoing EUS before surgical resection in three recent studies.16–18 A threshold of four or more criteria out of a possible nine was found to provide the optimal sensitivity and specificity for histologic pancreatic fibrosis.16,17 The criteria used were four parenchymal features (hyperechoic foci, strands, hypoechoic lobules, cysts) and five ductal features (irregularity of the main pancreatic duct, dilation, hyperechoic duct walls, visible side branches, and calcifications or stones).

EUS is sensitive for chronic pancreatitis, but ‘true’ accuracy is impossible to know

Figure 1. Example images of a patient with minimal-change chronic pancreatitis. This 40-year-old woman presented with upper abdominal pain that worsened with fatty foods. Computed tomography (top) showed a relatively normal pancreas. (Arrows delineate the borders of the body of the pancreas.) Endoscopic ultrasonography (bottom) showed several criteria for chronic pancreatitis, including an ectatic main pancreatic duct (black arrows), visible side branches (red arrow), and nonshadowing echogenic foci (white arrow head).
It is impossible to know the “true” accuracy of EUS because of the heterogeneity of design and inherent limitations of these studies. However, we can reasonably deduce that EUS is sensitive for mild chronic pancreatitis, even early in its course before computed tomography can reveal calcifications or atrophy (Figure 1).

Unfortunately, greater sensitivity may come at the expense of worse specificity. Certain demographic variables may alter the EUS appearance of the pancreas. A multivariate analysis25 found several variables that predicted abnormalities on EUS even in the absence of clinically evident pancreatitis; the strongest were heavy ethanol use (odds ratio [OR] 5.1, 95% confidence interval [CI] 3.1–8.5), male sex (OR 1.8, 95% CI 1.3–2.55), clinical suspicion of pancreatic disease (OR 1.7, 95% CI 1.2–2.3), and heavy smoking (OR 1.7, 95% CI 1.2–2.4). More prospective studies are needed to further differentiate true disease from false-positive findings of chronic pancreatitis.

Also, traditional EUS scoring symptoms have counted features in an unweighted fashion and assigned an arbitrary cut point (eg, four or more features) for diagnosis. This approach fails to account for the greater importance of some features (eg, calcifications) compared with others.

Interobserver variability is another important limitation of EUS in diagnosing chronic pancreatitis.26,27 In one multicenter study of EUS interpretation, the overall kappa (agreement beyond chance) was only 0.45 for overall chronic pancreatitis diagnosis and worse for many individual criteria for chronic pancreatitis. The endosonographers disagreed most about hyperechoic strands and foci, main pancreatic duct irregularity, and visible side branches (kappa < 0.4).

The Rosemont classification

These limitations led a group of experts to meet in Chicago, IL, to develop a consensus-based and weighted EUS scoring system for the diagnosis of chronic pancreatitis, termed the Rosemont classification.

In this system, the previous parenchymal and ductal features are assigned stricter definitions and reclassified as major and minor criteria. Based on the presence of major and minor features, EUS results are stratified as “normal,” “indeterminate for chronic pancreatitis,” “suggestive of chronic pancreatitis,” or “most consistent with chronic pancreatitis.”15,28

Further validation of this scoring system is needed before it can be used widely.

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