The primary indicator that I've had in my bloods was a raised amylase level in my blood. This came out at 3-9x the normal when in hospital but had reduced back to regular levels in between attacks.
Gallbladder has no stones as shown by an ultra-sound. Have also had an endoscopic ultrasound to check for any physical abnormalities or any missed stones in finer detail. Nothing there either.
Recently have had an MRI to check for a spamming sphincter that could be causing a blockage. That all came up clear too.
Symptoms during an attack begin with a pain centrally just below my rib cage. Starts off mild and then becomes unbearable within a couple of hours. The pain has occurred upon waking all three times. After the pain, I'll start vomiting. It lasts intensely for a day and then slowly cools off over the next day or two before I leave the hospital.
The only other possible test that I've been told I could have that I haven't had already is a genetics test. Fortunately the NHS would be the ones paying for it, but seeing as this information is useless in determining treatment, I've decided it's not worth it for the time being.
All very strange.