[Lemmel's Syndrome: A Rare Cause of Acute Cholangitis].

Lemmel syndrome is a rare entity that causes biliary obstruction due to compression of the common bile duct by a periampullary diverticulum. It can manifest as acute cholangitis and is often underdiagnosed. However, once identified, it can be successfully treated with endoscopic retrograde cholangiopancreatography, being one of the most used methods. Lemmel syndrome should be considered in elderly patients with a diagnosis of periampullary duodenal diverticulum, once the presence of choledocholithiasis and pancreatobiliary neoplasms have been ruled out.