Diagnosis of early chronic pancreatitis by endoscopic ultrasound. Are we there yet?

The diagnosis of chronic pancreatitis at an early stage is a clinical challenge. A major limitation is the inability of clinicians to obtain a tissue or histological sample to confirm the clinical diagnosis. Currently available imaging modalities have limited sensitivity or specificity for diagnosing early chronic pancreatitis. Endoscopic ultrasonography (EUS), introduced in the early 1980's, was first developed to image the pancreas. It overcame many of the limitations (abdominal gas and fat) of transabdominal ultrasonography when evaluating patients for possible pancreatic diseases. To date, EUS represents the most promising imaging modality for diagnosing chronic pancreatitis. Contrary to endoscopic retrograde pancreatography (ERCP), EUS has a very low risk of complications and can detect abnormalities suggestive of chronic pancreatitis in the pancreatic parenchyma and ductal system which are not visible on any other imaging modality. The minimal changes in echotexture are difficult to interpret because there is no reliable gold standard confirmatory test. There is now some evidence in the literature suggesting that these early changes detected by EUS correlate with the histological changes of chronic pancreatitis and may predict progression to more advanced disease. The EUS diagnosis of chronic pancreatitis relies on quantitative (more than qualitative) parenchymal and ductal criteria found during evaluation of the pancreas. It is generally accepted that, in the absence of any criteria, chronic pancreatitis is unlikely, whereas in the presence of 5 or more criteria (out of 9-11) chronic pancreatitis is likely although ERCP and pancreatic function tests may still be normal. The diagnostic significance of patients with fewer (1-4) criteria found on EUS is currently unclear, particularly when other diagnostic tests such as ERCP and function testing are normal. In these cases, there is a potential for "over-diagnosis" of chronic pancreatitis, since the EUS changes cannot be confirmed by other modalities. How can we better understand the implications of EUS detected changes when other tests are normal?