An artificial sphincter containing, in use, a pressurizing fluid, said artificial sphincter comprising: an inflatable occlusion means for occluding a body passage, a stretchable fluid reservoir, a pump means having a first port in fluid communication with said occlusion means via a first tube and a second port in fluid communication with said fluid reservoir via a second tube for selectively transferring pressurizing fluid from said occlusion means to said reservoir to deflate said occlusion means so that a blocked body passage may be opened; a balloon holder having a lumen which establishes fluid communication in between said fluid reservoir and said second tube, a pressure compensation balloon which is in fluid communication with the lumen of said balloon holder and which, in use, is to be implanted in the abdomen of a patient, wherein the artificial sphincter further comprises; a semipermeable check valve which is located in the lumen of said balloon holder, wherein said semipermeable check valve always allows fluid flow coming from the second tube to pass towards said stretchable fluid reservoir and wherein said semipermeable check valve only allows a restricted fluid flow from the stretchable fluid reservoir towards the second tube, characterized in a pressure sensitive check valve in between the pressure compensation balloon and the lumen of said balloon holder, wherein said pressure sensitive check valve always allows fluid flow from the pressure compensation balloon towards the lumen so that the fluid contained in the pressure compensation balloon is freely flowable towards the inflatable occlusion means and, in use, a sudden pressure increase which occurs in the abdomen of a patient is instantly conveyed to the inflatable occlusion means and wherein said pressure sensitive check valve blocks fluid flow towards the pressure compensation balloon only when the fluid pressure in pressure compensation balloon is substantially less than the fluid pressure in the lumen of the balloon holder. an inflatable occlusion means for occluding a body passage, a stretchable fluid reservoir, a pump means having a first port in fluid communication with said occlusion means via a first tube and a second port in fluid communication with said fluid reservoir via a second tube for selectively transferring pressurizing fluid from said occlusion means to said reservoir to deflate said occlusion means so that a blocked body passage may be opened; a balloon holder having a lumen which establishes fluid communication in between said fluid reservoir and said second tube, a pressure compensation balloon which is in fluid communication with the lumen of said balloon holder and which, in use, is to be implanted in the abdomen of a patient, wherein the artificial sphincter further comprises; a semipermeable check valve which is located in the lumen of said balloon holder, wherein said semipermeable check valve always allows fluid flow coming from the second tube to pass towards said stretchable fluid reservoir and wherein said semipermeable check valve only allows a restricted fluid flow from the stretchable fluid reservoir towards the second tube, characterized in a pressure sensitive check valve in between the pressure compensation balloon and the lumen of said balloon holder, wherein said pressure sensitive check valve always allows fluid flow from the pressure compensation balloon towards the lumen so that the fluid contained in the pressure compensation balloon is freely flowable towards the inflatable occlusion means and, in use, a sudden pressure increase which occurs in the abdomen of a patient is instantly conveyed to the inflatable occlusion means and wherein said pressure sensitive check valve blocks fluid flow towards the pressure compensation balloon only when the fluid pressure in pressure compensation balloon is substantially less than the fluid pressure in the lumen of the balloon holder.