Abstract: Apparatus for diagnosing urinary stress incontinence of a subject, including a substantially rigid, disposable probe insertable into the urethra of the subject, generally along a longitudinal axis of the urethra. A reusable sensor unit, is removably coupled to the probe, for sensing physiological parameters of the subject. The apparatus preferably includes a fluid pressure sensor, contained in the sensor unit, in pressure communication with a distal end of the probe. The probe includes a flexible diaphragm in fluid communication with the distal end. The diaphragm provides the pressure communication between the pressure sensor and the distal end while substantially preventing fluid communication between the distal end and the pressure sensor.