An apparatus (11) for measuring pressure of fluid in a shunt comprises a distensible member (12) arranged adjacent to a graduated scale (14). The shunt comprises a shunt valve and the apparatus is attachable to, or incorporated into the shunt at a location either at the shunt valve or upstream of the shunt valve. Both the distensible member and the scale comprise radiopaque markers (15). The fluid in the shunt acts directly on the distensible member and the distensible member is distensible in the direction of the scale.
