Endoscopic retrograde cholangiopancreatography (ERCP)
The American College of Radiology (ACR) makes the following imaging recommendations:
Ultrasonography is the preferred initial imaging test for the diagnosis of acute cholecystitis; scintigraphy is the preferred alternative
CT is a secondary imaging test that can identify extrabiliary disorders and complications of acute cholecystitis
CT with intravenous (IV) contrast is useful in diagnosing acute cholecystitis in patients with nonspecific abdominal pain
MRI, often with IV gadolinium-based contrast medium, is also a possible secondary choice for confirming a diagnosis of acute cholecystitis
MRI without contrast is useful for eliminating radiation exposure in pregnant women when ultrasonography has not yielded a clear diagnosis
Contrast agents should not be used in patients on dialysis unless absolutely necessary