An Endoscopic Retrograde Cholangiopanchreatography is a procedure in which an endoscope is introduced by the mouth until the second section of the small intestine is reached. The ERCP is useful for the extraction of stones found inside the duct that begins in the liver and ends in the small intestine, commonly called the bile duct. The opening that connects the bile duct with the intestine is called the papilla, and is approximately 2 to 3 mm (0.07 to 0.10 in) large in diameter. In this procedure, an incision is made to the papilla to extract the stones found within the bile duct, allowing the bile to drain freely from the liver to the intestine. Generally, this procedure is done in an outpatient clinical setting depending on the conditions of the patient.