Endoscopic ultrasound as a predictor and guide to successful endotherapy in chronic pancreatitis

BACKGROUND AND OBJECTIVES: Pancreatic calculi (PCs) are sequelae of chronic pancreatitis (CP) and may obstruct and produce ductal hypertension leading to pain, the cardinal feature of CP. Indications for endotherapy include stones <5 mm size, stones in the head of pancreas which are not impacted and absence of downstream strictures. The assessment before the procedure is done by magnetic resonance cholangiopancreatography (MRCP) or computed tomography (CT). However, problems are encountered during endoscopic retrograde cholangiopancreatography (ERCP) clearance which are not anticipated despite MRCP/CT. The problems are possible impacted stones, hard stones, indeterminate stricture, and change of finding during ERCP. Hence, controversy exists. Endoscopic ultrasound (EUS) can help by providing concordance or discordance with MRCP images and may help in further clarification. The aim of this study is to evaluate the role, feasibility, and management changes of EUS before ERCP in patients planned for endotherapy in CP. Another objective was to evaluate whether EUS features of pancreatic duct (PD) stones can serve as a predictor of successful removal during ERCP. METHODS: The data of 412 patients during the study period (2009–2016) with CP were retrospectively analyzed. A total of 143 were associated with stones in head/papillary region of pancreas. Out of these, 75 were excluded and remaining 68 were evaluated by EUS using a linear/radial echoendoscope before ERCP. RESULTS: Out of 68 cases, 48 were associated with hard stones with acoustic shadowing while 20 were associated with soft stones without acoustic shadowing. In 20 soft stones cases, ERCP was successful in 18 patients. In 48 with hard stones, there was failure of endotherapy in 40 which required extracorporeal shock wave lithotripsy (ESWL)/surgery. The presence of large (≥5mm), hard, immobile stones were negative predictors of successful endotherapy. Small, ampullary/papillary stones were positive predictors. CONCLUSION: The present study suggests that EUS can differentiate “soft PD stones” (without an acoustic shadow) from “hard PD stones”(with acoustic shadow). “Hard PD stones” are better managed by ESWL. An EUS can influence important therapeutic decisions before endotherapy and can prevent unsuccessful attempts at ERCP and thus improve overall success/prognosis. An EUS has an additional advantage of making a diagnosis of ampullary/papillary stones and biliary obstruction which can be treated endoscopically. It can guide whether endotherapy needs to be performed through major or minor papilla. EUS by diagnosing pancreatic tumor/strictures missed on other imaging modalities allows early surgical reference and hence improves long term prognosis.