Centerline..Stomach, small intestine, colon, Upper GI symptoms probably stomach or small intestine.Lower GI symptoms I'd go with the transverse colon.There really isn't much else. Pancreas can be center but usually isn't "tender to touch" is usually more "take me to the ER now" and comes with other symptoms. Gall bladder is usually on the right and usually is 6-10 hours of severe pain with nausea/vomiting and mostly after fatty meals with pain radiating to the shoulder blade on the right side.I get pain there all the time. I assume it is my colon, it is right there, goes right by the center line, and other parts of it hurt.