Currently, there is limited scientific evidence regarding the effectiveness of fluorescent cholangiography in emergency cholecystectomy for acute cholecystitis. The primary aim of this study was to assess the efficacy of near-infrared fluorescent cholangiography to detect extrahepatic biliary anatomy in different severity degrees of acute cholecystitis.

The study aims to to evaluate the efficacy of near-infrared fluorescent cholangiography for real-time visualization of the extrahepatic biliary tree (cystic duct, common hepatic duct, cystic duct-common hepatic duct junction, common bile duct and any accessory or aberrant ducts) in emergency laparoscopic cholecystectomy before and after hepatocystic triangle dissection and in different degrees of severity of acute cholecystitis according to the American Association of Surgery for Trauma (AAST) classification, specifically distinguishing between non-gangrenous (grade I) and gangrenous or complicated (grades II-V) forms. For intra-operative fluorescent cholangiography, 2.5 mg indocyanine green (ICG) was administered intravenously 45-60 min prior to surgery, according to the recent guidelines from the International Society for Fluorescence Guided Surgery. All the operations were performed by the same team of surgeons. Near-infrared fluorescent cholangiography was performed by using Stryker's fluorescence imaging system (Stryker, Portage, Miami, USA). Near-infrared fluorescent cholangiography was performed at three defined time point during laparoscopic cholecystectomy: (i) following exposure of Calot's triangle, prior to any dissection; (ii) after partial dissection of Calot's triangle; (iii) after complete dissection of Calot's triangle, according to the "Critical View of Safety" method.

Inclusion Criteria:

• patients with a clinical and radiological (abdominal ultrasound and/or computed tomography) diagnosis of acute cholecystitis based on the revised TG18 who underwent laparoscopic cholecystectomy within 24-72 hours from the onset of symptoms;
• patients with ASA score of 1-3;

Exclusion Criteria:

• patients with a known allergy to indocyanine green;
• ASA score 4-5;
• patients deemed non-operable via laparoscopic approach due to high cardio-respiratory risk;
• previous surgical interventions on the biliary tract;
• history of liver cirrhosis or severe liver disease;
• ongoing pregnancy or breastfeeding.

All patients aged >18 years-old with a clinical and radiological (abdominal ultrasound and/or computed tomography) diagnosis of acute cholecystitis based on the revised Tokyo guidelines 2018 who underwent laparoscopic cholecystectomy within 24-72 hours from the onset of symptoms and patients fit for surgery with ASA score of 0-3.