Various embodiments of bulking or cushioning agents or material and related medical devices and methods are disclosed. For example, a method of performing a medical procedure in a tract of a body may include injecting a material in a liquid phase proximate a target site between a first tissue layer and a second tissue layer, allowing the material to transition from the liquid phase to the gel phase in response to a raise in temperature of the material to approximately at or above the predetermined temperature, and performing a surgical procedure on the target site. The material may have the liquid phase at temperatures below a predetermined temperature and a gel phase at temperatures approximately at or above the predetermined temperature.