A catheter (200) for insertion into a hollow viscus of a subject, comprising: a drainage opening (204) and an instillation opening at a distal end an inlet port (209) at a proximal end for instilling a fluid; an outlet port (205) at the proximal end for draining fluid from the viscus; a drainage channel (201) connecting the drainage opening to the outlet port; an instillation channel (211) connecting the inlet port to the instillation opening; a valve (223) proximate the drainage channel at the distal end for closing it against the entry of fluid from the viscus; a valve control port (220) at the proximal end for receiving a control fluid under pressure; and a control channel (222) connecting the valve control port to the valve such that the valve is responsive to admitted control fluid under pressure to close itself.