A measurement device (11) is disclosed for measurement of a flow of urine (7) in a flexible tube (4), the device (11) comprising jaws (12, 13) arranged for receiving a section of the tube (4), the device (11) further comprises an arrangement (14, 15, 6) for directing light through the tube (4) in said first direction so as to perform said measurement. A measurement tube (20) is also disclosed having a measurement area (22) within substantially parallel inner walls (23) with a distance in the range of to 4 millimetres as well as the use of the measurement tube (20) with the device (11).
