ACUTE PANCREATITIS ASSOCIATED TO PANCREATIC HYDATID CYST. UNDERSTANDING THE MECHANISM BY ENDOSCOPIC ULTRASOUND.

MPD, main pancreatic duct. The liver and lungs are the most frequent localizations of hydatid disease, whereas pancreatic hydatid cysts are rare, accounting for less than 1% of cases.1 Acute pancreatitis is associated with hydatid parasitosis in 2% of cases in endemic areas.2 Like liver cysts, [3] and [4] pancreatic hydatid cysts may cause acute pancreatitis. [5], [6], [7], [8] and [9] Whereas parasite migration into the common bile duct is advocated as the etiological mechanism to explain acute pancreatitis caused by liver hydatidosis, [3] and [4] it is unclear why some patients affected by pancreatic cysts develop this complication. Two hypotheses are advocated: main pancreatic duct (MPD) compression caused by the cyst itself [6], [10] and [11] and MPD obstruction by hydatid scolices' migration from the hydatid cyst. [5], [9] and [12] Unfortunately, neither of these hypotheses has been confirmed at imaging/surgery. Preoperative diagnosis of a pancreatic hydatid cyst may be difficult. Symptoms are often aspecific: pain, [7], [12], [13] and [14] an epigastric mass, [12] and [15] or weight loss.7 At imaging, hydatid cysts may be mistaken for cystic pancreatic tumors or intraductal papillary mucinous neoplasia, especially when single.11 The onset of acute pancreatitis may prompt urgent pancreas imaging, although, in these cases, a hydatid cyst may be misdiagnosed as a pseudocyst, [6] and [7] which is a common complication of acute/recurrent pancreatitis.