Endoscopic cannulas and methods of their use are disclosed. In some embodiments, an endoscopic cannula may include an elongated body having a proximal end and a distal end. A viewing channel and a working channel may extend through the elongated body. The viewing channel can be configured for passing therethrough an endoscope to the distal end of the elongated body for viewing outside the elongated body, while the working channel can be configured for passing therethrough an injection needle distally of the elongated body. The cannula may also include a suction pod disposed on a bottom surface of the elongated member, the suction pod being in communication with a suction channel extending through the elongated body to create suction between the suction pod and a tissue surface to temporary attach the elongated body to the tissue surface.