I had similar painful "attacks" over the last 16 months which, towards the end, were lasting up to 10 hours each time. I would only get the attacks every few months or so. I ended up having an ultrasound as the GP was concerned at the intensity of the pain, and the ultrasound revealed a large gallstone. I survived on fruit and salad for a month before surgery could be scheduled, had a very fast recovery time and am now pain free.