In some cases, laparoscopic cholecystectomy (LC) may be difficult to perform in patients with acute cholecystitis (AC) with severe inflammation and fibrosis. The Tokyo Guidelines 2018 (TG18) expand the indications for LC under difficult conditions for each level of severity of AC. It is absolutely necessary to avoid any increase in bile duct injury (BDI), particularly vasculo-biliary injury (VBI). Based on expert consensus on these difficulty indicators, bail-out procedures (including cholecystostomy to evacuating galbladder, patial cholecystectomy, even conversion to open cholecystectomy) have been indicated for cases in which LC for AC is difficult to perform. A bail-out procedure should be chosen if, when the Calot's triangle is appropriately retracted and used as a landmark, a critical view of safety (CVS) cannot be achieved because of the presence of nondissectable scarring or severe fibrosis.

To achieve a CVS, it is vital to dissect at a location above (on the ventral side of) the imaginary line connecting the base of the left medial section (Segment 4) and the roof of Rouvière's sulcus and to fulfill the three criteria of CVS before dividing any structures. Achieving a CVS prevents the misidentification of the cystic duct and the common bile duct, which are most commonly confused.