A gallbladder can absolutely be diseased, and if you're having attacks... well then, it's up to you if you'd like to forego surgery and live with the excruciating pain.
I had people (spiritual/psychic/natural healer-type) telling me, "you created the gallstones, you can get rid of them...with diet...you don't need surgery." Ummm...yeahhh.
I'd like to tell you right now, that is a crock of BS. I was terrified that something would go wrong in the surgery & it might end up causing me more problems, but I managed the fear and went through with the surgery.
To illustrate my claim of "b.s." above, I decided to experiment after the "stones" were removed. (Took me about 2 months before I could bring myself to look at them but eventually I did --5 of them in all, all exactly the same size, each a round ball just a touch smaller than a dime) What did I see? They were essentially large balls of wax. (Cholesterol I assume) I decided to see if what all the "healers" were telling me (drink lemon juice to dissolve them, cut down on fat, etc. etc.) might have actually worked.
I put one stone into pure lemon juice, and left it there for 2 weeks. NOT ONE BIT OF DISSOLVING occurred, and clearly you could never create an acidic environment in your gallbladder equavalent to pure lemon juice. You cannot disolve wax, and your gallbladder is not equipped to do so either. (by the way, my cholesterol levels have always been low, with excellent good cholesterol ratios)
It is possible that other's Gallstones have a different composition than mine. So, I broke the stone in half - inside the wax was a crystaline structure radiating out from a center point. I put the opened stone back into pure lemon juice to see if IT would disolve now... and guess what... Not one bit. So, there you have it.
There was also NO PHYSICAL POSSIBILITY of me ever passing stones that size... the ducts are simply not large enough.
Lastly, no amount of Malic Acid contained in apples and ingested would EVER affect such stones. I cannot say that it wouldn't help with the tiny junk clogging anyone's liver, but it certainly isn't going to affect a fully formed gall stone.