Pancreatic echinococcosis.

Echinococcosis (hydatid disease) is caused by the larval stage of . It most frequently involves the liver, followed by the lung. Pancreatic echinococcosis is very rare, even in endemic areas, with an incidence of 0.14% to 0.2%. We describe a case of a 34-year-old woman who presented with epigastric pain for 1 month. Contrast-enhanced computed tomography demonstrated a 4.0-cm hypodense mass in the pancreatic head and an uncinate process with suggestion of hyperdense/enhancing curvilinear densities. Magnetic resonance imaging with and without intravenous contrast showed a nonenhancing cystic mass. Endoscopic ultrasound demonstrated a cystic structure with curvilinear floating membranes consistent with the water lily sign, pathognomonic of hydatid disease. Enzyme-linked immunosorbent assay for echinococcal antigen was positive.