Devices, methods, and systems for measuring the size of gastric pouches. At least some embodiments include a catheter comprising an outer elongate tube, an inner elongate tube disposed within the outer elongate tube, a proximal balloon attached to the outer elongate tube, a distal balloon having a first end attached to the outer elongate tube and a second end attached to the inner elongate tube, at least two detection electrodes positioned on the outer elongate tube relative to at least two excitation electrodes, and a pressure transducer positioned on the outer elongate tube.