Abstract: A leakpoint wetness sensor for urological investigations including an instrument having a passage therethrough to pass a catheter intended for insertion into the bladder through the urethra. A temperature sensitive reference sensor mounted to the body and exposed to and responsive to ambient temperature. A receptacle in the body so disposed and arranged to receive liquid which leaks from the urethra past the catheter. A temperature sensitive detector sensor mounted to the body where it will be contacted by the leaked liquid and detector sensor being responsive to the temperature of the liquid. A circuit device is responsive to outputs from the sensors to provide a response reflective of a difference between the temperatures when the detector sensor is wetted by leaked liquid.