Pancreatic-Hydatid-Masquerading-as-Cystic-Neoplasm

Hydatid cyst is a zoonotic disease which affects predominantly liver followed by lungs in more than 90% cases. Involvement of pancreas is very rare, accounting for less than 1% cases. Establishing diagnosis preoperatively is difficult due to rarity of hydatid involving pancreas and also the image findings mimic more commonly encountered cystic neoplasm of pancreas. Less aggressive treatment approach is preferred in hydatid disease while cystic neoplasms demand pancreatic resections. We present a case of pancreatic hydatid cyst which was misdiagnosed as mucinous cystic neoplasm. Abstract


Introduction
Hydatid cyst is a zoonotic disease which affects predominantly liver followed by lungs in more than 90% cases. Involvement of pancreas is very rare, accounting for less than 1% cases. Establishing diagnosis preoperatively is difficult due to rarity of hydatid involving pancreas and also the image findings mimic more commonly encountered cystic neoplasm of pancreas. Less aggressive treatment approach is preferred in hydatid disease while cystic neoplasms demand pancreatic resections. We present a case of pancreatic hydatid cyst which was misdiagnosed as mucinous cystic neoplasm.
Hydatid disease of pancreas is a rare condition, with an incidence of less than 1%. Establishing diagnosis may be difficult because clinical and imaging findings are similar to other more commonly encountered cystic lesions of pancreas. We present a case of isolated Hydatid cyst in the tail of pancreas which masquerading as mucinous cystic neoplasm of pancreas.
A 33year gentleman presented with pain in left lumbar region of 10 days duration. There was no associated vomiting, fever, GI bleed, Bowel/Bladder disturbances. No associated loss of appetite or loss of weight. No addictions or comorbidities were present. On examination abdomen was soft and there was no organomegaly. Investigations revealed a normal blood picture, liver and renal function tests. Ultrasound abdomen demonstrated a cystic lesion measuring 4x3cm in body and tail of pancreas. Contrast enhanced CT done ( Figure 1). It revealed a 5x4 cms well defined multiseptate cystic lesion with peripheral rim calcification in tail of pancreas. Splenic vein was abruptly cut off with evidence of infiltration. Ectopic and malrotated left kidney was present. A provisional diagnosis of Mucinous cystic neoplasm of pancreas was made based on imaging findings. Surgical resection was planned. In view of lesion located in distal pancreas with infiltration of splenic vein, distal pancreatectomy with splenectomy was planned. Pneumococcal vaccine was given preoperatively. Hydatid disease is a zoonotic disease caused by echinococcus granulosus. The most commonly involved organ is liver followed by lung. Pancreatic hydatid cyst (PHC) disease is rare, even in regions where hydatidosis is endemic,with the reported incidence rates consistently below 1% [1].
On laparotomy, there was a well encapsulated cystic lesion measuring 5x4cms in the tail of pancreas. Lesion was abutting splenic vein, transverse mesocolon and duodenum. No regional lymphadenopathy or free fluid noted. Distal pancreatectomy with splenectomy was done ( Figure 2). Postoperative recovery was uneventful. Postoperative histopathology revealed the lesion as Hydatid cyst of pancreas ( Figure 3). Patient was given 3 weeks of albendazole therapy.  PHC may be a primary (involving the pancreas only) or a secondary (with multiple organ involvement) disease [2]. Pancreatic cysts are solitary in 90%, and their distribution is heterogeneous. Approximately 50%-58% are found in the pancreatic head, 24%-34% in the body, and 16%-19% in the pancreatic tail [3]. Majority are asymptomatic and incidentally detected. In symptomatic patients, clinical presentation depend on the location of the cyst within the pancreas. Cysts located in the pancreatic head may cause obstructive jaundice by either exerting external compression on or fistulizing into the common bile duct. It can also cause acute pancreatitis due to compression on main pancreatic duct. Hydatid cysts in the pancreatic body and tail usually remain asymptomatic until they grow large enough to compress adjacent organs or anatomical structures. Early satiety due to gastric compression, splenic vein compression which may lead to splenic vein thrombosis with severe complications such as left-sided portal hypertension.

Discussion
The most important step in the diagnosis of PHC is clinical suspicion. Contrast CT delineates nature of cyst, cyst size, location, relation with pancreato-biliary system, and presence of cysts in other organs. CT imaging features are similar to mucinous cystic neoplasm. Mucinous cystic neoplasms are well encapsulated, multiloculated with enhancing sepate on contrast. Eventhough peripheral curvilinear calcifications of the cyst wall are more suggestive of hydatid, they are also reported in 10-25% of mucinous cystic neoplasms [4]. It is also useful in treatment monitoring and postoperative recurrence detection [5]. ERCP is indicated in patients with cholangitis or pancreatitis secondary to biliary or pancreatic duct obstruction. The differential diagnosis of PHC include neoplastic (cystadenoma, cystadenocarcinoma, neuroendocrine tumors, vascular, metastatic cystic lesions) or nonneoplastic (congenital pancreatic cysts, pseudocysts) cystic lesions [6]. Hydatid serology is diagnostic if positive.