Motility study, antro-duodenal: A study for detecting and recording the contractions of the muscles of the stomach and the first part of the small intestine (the duodenum). An antro-duodenal motility study is performed to diagnose problems in the way the muscles of the stomach and small intestine are working. To conduct the study, a tube is passed through the nose, throat, esophagus, and stomach until the tip of the tube lies in the small intestine. The tube senses when the muscles of the stomach and small intestine contract and squeeze the tube tightly. The contractions are recorded for analysis by a computer. Also known as antroduodenal manometry.