A kit comprising: a urinary catheter comprising a first and a second longitudinal lumens; at least one ultrasonic transducer disposed about a distal portion of said urinary catheter; a balloon mounted on said urinary catheter at the distal portion, and enclosing said at least one ultrasonic transducer, a reservoir containing a therapeutic fluid; and a reservoir containing an acoustic coupling medium, wherein: said urinary catheter further comprises a first opening in said first longitudinal lumen, said first opening disposed inside said balloon and configured to inflate said balloon with at least some of said acoustic coupling medium, said urinary catheter further comprises a second opening in said second longitudinal lumen, said second opening disposed outside said balloon and configured to deliver therapeutic fluid into the urinary bladder, between the balloon and the bladder internal surface, and activation of said at least one ultrasonic transducer in said urinary bladder causes cavitation bubbles to form in said therapeutic fluid adjacent an internal surface of the urinary bladder, and little or no cavitation bubbles are formed in said acoustic coupling medium in said balloon, characterised in that said balloon comprises a shape of an elongated cylinder, said balloon comprises two lateral sides which are larger in diameter than the diameter of a middle portion of said elongated cylinder, said two lateral sides are adapted to contact said bladder internal surface allowing therapeutic fluid flow or reside therebetween, in a space formed between the middle portion of the balloon and the bladder internal surface. a urinary catheter comprising a first and a second longitudinal lumens; at least one ultrasonic transducer disposed about a distal portion of said urinary catheter; a balloon mounted on said urinary catheter at the distal portion, and enclosing said at least one ultrasonic transducer, a reservoir containing a therapeutic fluid; and a reservoir containing an acoustic coupling medium, wherein: said urinary catheter further comprises a first opening in said first longitudinal lumen, said first opening disposed inside said balloon and configured to inflate said balloon with at least some of said acoustic coupling medium, said urinary catheter further comprises a second opening in said second longitudinal lumen, said second opening disposed outside said balloon and configured to deliver therapeutic fluid into the urinary bladder, between the balloon and the bladder internal surface, and activation of said at least one ultrasonic transducer in said urinary bladder causes cavitation bubbles to form in said therapeutic fluid adjacent an internal surface of the urinary bladder, and little or no cavitation bubbles are formed in said acoustic coupling medium in said balloon, characterised in that said balloon comprises a shape of an elongated cylinder, said balloon comprises two lateral sides which are larger in diameter than the diameter of a middle portion of said elongated cylinder, said two lateral sides are adapted to contact said bladder internal surface allowing therapeutic fluid flow or reside therebetween, in a space formed between the middle portion of the balloon and the bladder internal surface.