Declining HIDA Scan Ejection Fraction

I have been experiencing typical gallbladder symptoms for about two+ years; mild to moderate pain in upper right quandrant of chest and back; indigestion; occasional stabbing pains behind breast bone and a frequent feeling like a balloon about to burst under my lower right rib cage. I also wake up frequently with a very sore back and side in the same area. The symptoms began two years ago but were infrequent at first. I had an ultrasound and HIDA scan at the time. The ultrasound showed no stones and the HIDA Scan ejection fraction was 87%. The symptoms have become more frequent over the past two years and pain now often lasts for several days (although not a continuous pain, but rather off and on throughout the day). The latest bout lasted for six days. After this latest occurrence, I went to my family doctor. The ultrasound was repeated and again, showed no stones. The HIDA Scan, also repeated now showed an ejection fraction of 42. Therefore, I assume this means my gallbladder function is only about half what it was two years ago when symptoms first appeared. I was given a diagnosis of Chronic Acalculous Cholecytitis and referred to a surgeon to discuss my options. My family doctor believes my gallbladder function will continue to decrease so recommends removing it. I understand that gallbladders without gallstones are not generally removed unless the ejection refration is 35 and no stones? I would appreciate any input on this condition.