A gastrointestinal device including a casing including fixation elements adapted for intraluminal fixation of the device in a gastrointestinal tract (e.g., the anorectal wall), a valve disposed in the casing and controllable to move from a closed position, which significantly restricts passage of gastrointestinal (e.g., fecal) matter therepast, and an open position, which permits passage of gastrointestinal matter therepast, and a controller operatively connected to the valve for externally controlling the position of the valve between the closed and open positions.