An implantable device and method for adjustably restricting a selected body lumen such as the urethra of a patient to treat urinary incontinence. The device includes an expandable element or membrane such as a balloon attached pressure-tightly to a flexible conduit at its forward end and includes a rear port portion containing an elastic septum and flow connected to the expandable element by a first passageway. The conduit contains a second passageway which allows it to be slid along an elongated guide probe initially inserted surgically into a patient's body adjacent the body lumen which is to be adjustably restricted. A suitable flowable material is injected from a syringe source into the device rear port sufficient to expand the membrane element and restrict the body lumen to the desired degree. The syringe and guide probe are removed and the skin incision is closed over the rear port end of the implanted device. The rear port septum is located under but near the patient's skin so that if it becomes necessary to post-operatively increase or decrease the degree of body lumen restriction it may be easily accessed with the needle of the syringe.