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What is Mirizzis syndrome and explain in detail?
Mirizzis syndrome is a rare complication in which a gallstone becomes impacted in the cystic duct or neck of the gallbladder causing compression of the common hepatic duct, resulting in obstruction and jaundice. The obstructive jaundice can be caused by direct extrinsic compression by the stone or from fibrosis caused by chronic cholecystitis (inflammation). A cholecystocholedochal fistula can occur.

Presentation
Mirizzis syndrome has no consistent or unique clinical features that distinguish it from other more common forms of obstructive jaundice. Symptoms of recurrent cholangitis, jaundice, right upper quadrant pain, and elevated bilirubin and alkaline phosphatase may or may not be present. Acute presentations of the syndrome include symptoms consistent with cholecystitis.
Surgery is extremely difficult as Calots triangle is often obliterated and the risks of causing injury to the CBD are high.

Pathophysiology
Multiple and large gallstones can become impacted in the Hartmanns pouch of the gallbladder, leading to chronic inflammation—which leads to compression of the common bile duct (CBD), necrosis, fibrosis, and ultimately fistula formation into the adjacent common hepatic duct (CHD) or common bile duct (CBD)