A user-controllable urinary catheter prosthesis (20) is provided for minimally-invasive insertion into a subject. The prosthesis (20) includes a proximal intra-urethral assembly (22), configured to be inserted entirely within a urethra (102) via a meatus (104). A user-activatable hydraulic activator (50) is disposed along a flexible intra-urethral catheter (30, 430), which is shaped so as to define a urinary outlet (40, 440) at a proximal end (41, 441) thereof. A distal bladder assembly (32, 132, 232, 332) is configured to be disposed in a bladder of the subject, and includes a bladder anchor (48). A hydraulic valve (60, 160, 260, 360) is configured to assume an open state, in which urine flow is allowed between the distal bladder assembly (32, 132, 232, 332) and the urinary outlet (40, 440); and a closed resting state, in which urine is entirely blocked from entering the distal bladder assembly (32, 132, 232, 332) and exiting the urinary outlet (40, 440). Application of pressure to the hydraulic activator (50) transitions the hydraulic valve (60, 160, 260, 360) from the closed resting state to the open state. Other embodiments are also described.