Disclosed herein are methods and devices for treating diverticular disease. The method can include injecting a sterile fluid between a mucosal layer of the diverticulum and a serosal layer of the diverticulum to form an expanded cavity in the diverticulum comprising the sterile fluid; injecting a filler material in the expanded cavity; and removing at least a portion of the sterile fluid from the expanded cavity. The device can include a flexible overtube having a lumen; a flexible shaft at least partially disposed within the lumen of the flexible overtube; a cutting tip at a distal end of the flexible shaft; an input port fluidly coupled to the lumen of the flexible shaft; and an output port fluidly coupled to a proximal end of the lumen of the overtube. Also disclosed herein are systems and kits for treating diverticular disease.