An endoscope accessory capable of being removably coupled to the accessory port of an endoscope includes a housing having an introducer port adapted for insertion of an elongated member, a device port adapted for alignment with the accessory port, a fluid port in fluid communication with the device port, and a fluid-tight seal, which forms a seal around the elongated member. The accessory includes a coupling mechanism to couple the accessory to the accessory port to assist in an endoscopic procedure. For example, the elongated member can be inserted through the introducer port, into the accessory port with which the device port is aligned, and into a patient's gastrointestinal tract. The patient's tissue may be irrigated by injecting fluid through the fluid port while the elongated member is manipulated. A locking mechanism, coupled to the housing, can be used to secure the elongated member with respect to the endoscope.