A medical instrument for injecting an agent is disclosed. In one embodiment, a main elongated cylindrical body has a multiple channels therethrough that house a balloon inflation tube and two syringe push tubes having injection needles. Each of the syringe push tubes exit at respective lateral exit ports positioned on opposite sides of the main elongated cylindrical body. A secondary elongated cylindrical body is coupled to the main cylindrical body and includes a retention balloon positioned in fluid communication with the balloon inflation tube. During operation, the retention balloon is filled with liquid through to act as a retainer for the medical instrument inside a bladder of a patient to position and immobilize the medical instrument inserted into a sphincter of a urethra of the patient. During this process, the injection needles are deployed and the agent, such as a bulking agent, is injected.
