The device (1) has a pressure transducer (3) for detecting positive pressure in an inner area of a hollow body, and a measuring head (5) staying in an effective connection with the transducer. The head is designed as a retaining unit, and has a sealing unit (9) at a lower side, and a pressure source introduces a medium into the body through the head. A control device detects a pressure difference between a pressure lying at the transducer when a stopper is inserted into the body and a pressure lying at the transducer when the stopper is not inserted into the body.
