I remember someone saying on one of my gallbladder related threads (there are quite a few!) about sludge causing problems for them when gallstones could not be found. Jack I think.
I had mine out just over 3 weeks ago (yay!). I've had prolonged pain with mine, especially when I got acute cholecystitis (you can get chronic too) and generally as by the time they took it out it was very inflamed, on the way to septic and had split and some stones had escaped.
I had a really bad bout of pain about 6/7 years ago which my GP at the time said was an ulcer. Went on about 2 weeks (and feeling very sick too). I can't help but wonder now if that may also have been gallbladder related.
Before I suggested gallstones to my GP I thought it was recurring ulcer symptoms. When I suggested gallstones my GP said that they can both have very similar symptoms so sent me for tests for both (hpylori and ultrasound).
On a more random note, after not long waking up back on the ward still hazy after the op and a big dose of morphine in recovery my surgeon popped over and was saying about it having split etc... and he had collected the escaped stones. I asked one of the nurses later on (when more with it) if it said how many I'd had. She went to look at the surgery note and came back and said it said "no gallstones". Bit of a twilight zone moment after months of hell with it until she realised she had only read the end of the note, ie no gallstones anymore :)