I'm happy that your father is going to be better. You are right about kidney cancer - it can be deadly, and for some reason it is not screened for as rigorously as other cancers since many people know very little about it. My father was unfortunately diagnosed too late for anything to be done, and we wondered how he could have gotten it. [public service announcement follows]: Most causes of kidney cancer are environmental, in that what you do and where you go can cause it. The top four are the typical; asbestos, heavy metal, etc, and SMOKING is the fifth main reason. Kidneys are filters, and whatever carcinogens that get past the lungs end up in the blood which is filtered through the kidneys.

As a sort of similar story, my mother was preparing for a walkathon for diabetes a few years ago and because of her age ('over 21'), her doctor insisted that she undergo a stress test which she promptly failed. She then needed to have an angiogram since the stress test results confounded the doctor. I will never forget the conversation with the doctor afterwards, who asked me how many heart attacks my mom has had. When I replied that she had no heart issues at all, just the diabetes (like all Puerto Ricans, it seems), he responded that 4 of her 5 main coronary arteries were severely clogged and she needed a quadruple ASAP.

Like your dad, my mom went into medical treatment for something completely unrelated to what eventually needed to be done ASAP.