The invention relates to a device (1) which consists of a urethral catheter (3) and the pressure measuring unit (2). The urethral catheter (3} has a balloon lumen (4) connected to a distal balloon and a urine discharge lumen (7) connected to a distal opening (6). The pressure measuring unit (2} has two lumen connections (8a and 8b). The lumen connection (8b) connected to the urine discharge lumen (7) via a discharge conduit (16) can be alternately connected to the urine discharge (20b) to discharge the urine and to the pressure line (10b) to carry out a calibration measurement of the pressure sensor (2a) via the three-way valve device (13b). The lumen connection {8a} connected to the balloon lumen (4} via a pressure conduit (15)" can be alternately connected to the gas connection (20a) to fill/evacuate the balloon (5) and to the pressure line (10a) to carry out a (semi)-continuous measurement of the balloon"s internal pressure via the three-way valve device (13a).
