One or more medical devices may be provided that may be used, for example, in bariatric surgery including a vertical sleeve gastrectomy. Occlusion devices can be integrated with a catheter or tube to occlude one or more proximal or distal landmarks of a stomach and a stapling guide may be used to occlude a lateral boundary of the stomach to define a cavity. A volume of the potential resultant sleeve may be determined by inserting fluid or gas into the catheter or tube, measuring pressure, and calculating the volume of the cavity.
