The cystic duct connects the top of the gallbladder’s neck to the common hepatic duct. It then joins the common bile duct, which meets pancreatic duct before it empties into the duodenum. In the average adult, the cystic duct measures four centimeters in length.
The gallbladder stores bile produced in the liver. In order to enter into the duodenum, bile must travel out of the gallbladder, through the cystic duct's spiral valve, and into the common bile duct. Along with fluid from the pancreas, the bile enters the duodenum through the ampulla of vater.
While there is no other use for the cystic duct, health problems can result when it develops obstructions. If gallstones become lodged in the spiral valve or other parts of the duct, the movement of bile becomes impeded or blocked completely. Should this happen, bile will become trapped within the gallbladder. The bile will build up to the point where the gallbladder will swell. In the worst case scenario, the gallbladder will rupture, leading to a surgical emergency.