Sphincter of Oddi in health and disease.

Sphincter of Oddi (SO) is a dynamic structure located strategically at the confluence of the bile duct, the pancreatic duct and the duodenum. The advent of lateral viewing endoscope along with a minimally compliant pneumocapillary manometry system has greatly enhanced our ability to evaluate the SO in health and disease. These studies have shown that the SO motor function is a complex phenomenon controlled by a variety of neurohumoral agents. The sphincter also actively participates in the Migratory Motor Complex (MMC). The major function of the SO seems to be in regulating the flow of bile and pancreatic juice into the duodenum. By maintaining a basal tone, the sphincter diverts bile into the gallbladder under fasting conditions. On the other hand it functions as "a pump" as well to milk bile into the duodenum. Recent manometric studies also have unravelled a number of abnormalities involving the SO motor function often referred to as SO dysfunction. Most such patients respond favorably to sphincter ablation. Studies are underway to better define patients with SO dysfunction as well as to identify them using noninvasive investigations.