Grade	AAST disease grade	Corres- ponding Tokyo grade	Management	Ref- erences
I	Local disease; confined to the organ; minimal abnormality	I	Operative (laparoscopic if possible) if within 10 days of onset of symptoms; consider antibiotics±percutaneous cholecystostomy tube if beyond 10 days	7 9 10 11
II	Local disease; confined to the organ; severe abnormality	II	Operative (laparoscopic if possible; consideration of conversion to open/subtotal cholecystectomy as dictated by intraoperative findings); antibiotics and percutaneous cholecystostomy tube may be considered, but evidentiary support for populations who may benefit from this approach is sparse	7 9 10–12
III	Beyond the organ; locally advanced only	II	Operative (laparoscopic if possible; consideration of conversion to open/subtotal cholecystectomy as dictated by intraoperative findings); antibiotics and percutaneous cholecystostomy tube may be considered, but evidentiary support for populations who may benefit from this approach is sparse	7 9 10–12
IV	Beyond the organ; regional extension	II	Operative (laparoscopic if possible; consideration of conversion to open/subtotal cholecystectomy as dictated by intraoperative findings)	7 9 10–12
V	Beyond the organ; widespread involvement	III	Operative (laparoscopic if possible; consideration of open approach in the setting of septic shock; strong consideration of conversion to open/subtotal cholecystectomy as dictated by intraoperative findings)	7 9 10–12