This is a set of medical devices, known as fibre optic manometry catheters, used to measure pressure changes in the human gut. This set includes two prototypes and a commercially available product that show the development of this technology. These devices gather information from sensors and use this information to create maps that show how and when the gut muscles are moving. This knowledge is transforming our understanding of gastroenterology and will take the guesswork out of the investigation, diagnosis and treatment of disorders such as constipation and incontinence.