EUS as an Adjunct to ERCP for the Diagnosis of Malignant Pancreaticobiliary Duct Stricture

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Background. The sensitivity of EUS is comparable to ERCP for establishing the etiology of bile duct or pancreatic duct strictures. As ERCP is more widely available, patients with duct strictures generally get an ERCP as the initial diagnostic test. Patients with inconclusive ERCP are usually referred for EUS. Aim. To determine the diagnostic impact of EUS as an adjunct to ERCP in bile duct or pancreatic duct strictures. Method: All EUS cases performed at a tertiary referral health care center between 1993 to 2002 were retrospectively reviewed. Subjects with bile duct or pancreatic duct strictures who had undergone ERCP prior to EUS were identified. Patients with established diagnosis of pancreatic cancer prior to performance of EUS were excluded. The primary outcome was to differentiate malignant from benign strictures. Diagnosis of malignancy was established by obtaining tissue using EUS-FNA or laproscopic exploration/surgery. Benign stricture was defined by inconclusive ERCP and EUS and either diagnostic laparoscopy /surgery or a minimal clinical follow up of one year. The outcome was defined by contacting patients and by reviewing medical records. Results. 81 subjects with a bile duct/ pancreatic duct stricture, of which 25 were subsequently proven malignant, were identified. EUS imaged a mass lesion in 18 (72%) of the 25 malignancies and EUS-FNA identified malignant or atypical cells in 12/16 (75%) cases in which it was performed. Of the 56 cases with benign ductal strictures, EUS corroborated the ERCP findings of chronic pancreatitis (CP) in 18 and diagnosed 12 additional cases of CP. EUS misdiagnosed 1 pancreatic cancer as CP. EUS imaged a mass in 12 benign cases and EUS FNA, performed in 7, showed normal cells in 6 and atypical cells in 1 case. Sensitivity, specificity, positive predictive value and negative predictive value of EUS to detect malignant stricture in subjects with inconclusive ERCP is 76%, 78%, 61% and 88% respectively. Conclusion. EUS is useful as an adjunctive test to ERCP in diagnosing the etiology of ductal strictures when the imaging is suggestive of malignancy or EUS FNA is positive or atypical. EUS may also be useful in corroborating ERCP diagnosis of chronic pancreatitis. However, since malignancy may still be present in a subset of patients with pancreaticobiliary ductal strictures who have a normal EUS or CP on EUS, these patients should be closely followed and explored when clinically warranted.