gallbladder attacks can cause nausea, right-sided abdominal pain that radiates to the back around the shoulder blades.
despite your ultrasound scan is normal and so your endoscopy ,there might be dysfunction of the gallbladder or biliary dyskinesia or what is known as gallbladder Diseases Without Stones (Acalculous Gallbladder Disease)
Gallbladder disease without stones, a condition called acalculous gallbladder disease. This refers to a condition in which a person has symptoms of gallbladder stones, yet there is no evidence of stones in the gallbladder or biliary tract. It can be acute (arising suddenly) or chronic (persistent)..which causes lower GB ejection fraction. take a HIDA scan with CCk stimulation .
A HIDA scan with CCK stimulation can be considered if this is suspected. it can be suggested removing the gallbladder can be considered if this is the case. Probably as important is whether the injection of cck recreated the symptoms that you are having. If it does, then gallbladder is the likely cause.If not, look elsewhere. normal gallbladder ejection fraction is usually over 35-75%
in this this condition you may find normal ultrasound with low ejection fraction + symptoms of biliary problem .(and it is associated with slight elevated liver enzymes
other causes might be depending on other symptoms
fatty liver ,hepatitis may cause your symptoms and elevation in liver enzymes +other symptoms
pleurisy, peptic ulcer, severe constipation, severe acid reflux or gastritis may also be a cause if there are associated symptoms
Clay colored stools can be indicative of bile duct obstruction. An MRCP can be considered to evaluate for this.
Cardiac disease can also atypically present this way. A stress test can be considered if the GI evaluation continues the be non-revealing.
If all the testing continues to be negative, you can consider more benign causes, like musculoskeltal pain.
So you need a test after test to finally figure the cause and treat it ,try to watch for every symptom associated with the pain you described this will help directing towards diagnose .