His first diagnosis doesn't sound correct. Kidney stones cause severe back pain and no vomiting. I think it was his gallbladder the first time he went to the ER, due to where his pain was and the vomiting. It appears that his colon cancer had spread to the liver, which is very common since the liver filters our blood. The gallbladder is just coincidental, but the other two are related. I feel so bad for your father and you, I wish you both all the best and take care.