The SPRIMACC study is a prospective multicenter observational study with the primary endpoint to prospectively validate the Chole-Risk score in predicting a complicated postoperative course (post-operative major complications (Clavien-Dindo>=3a), length of stay (LOS) > 10 days or need of readmission within 30 days from the discharge) in patients undergoing Early Cholecystectomy (EC) for Acute Calculous Cholecystitis (ACC). The secondary endpoints of the study are to prospectively validate and compare other wellknown risk prediction models (the POSSUM/P-POSSUM score, the Modified Frailty Index (mFI), the Charlson Comorbidity Index (CCI), the American Society of Anesthesiologists (ASA) score and the APACHE II score) in predicting a complicated post-operative course in patients undergoing EC.

Inclusion Criteria:

• have a diagnosis of Acute Calculous Cholecystitis (ACC) as defined by Tokyo Guidelines 2018 criteria

• be candidate to Early Cholecystectomy (EC) during the index admission*

• be ≥ 18 years old

• be stratified for the risk of Common Bile Duct Stones (CBDS) according to the Israelian Score, and, in case of confirmation of CBDS receive pre-operative Endoscopic Retrograde Cholangiopancreatography (ERCP).

• provide signed and dated informed consent form

• willing to comply with all study procedures and be available for the duration of the study.

  • All the patients treated with initial open cholecystectomy, those who undergo Early Laparoscopic Cholecystectomy (ELC), those with conversion from laparoscopic to open cholecystectomy or those who undergo bail out procedures (e.g. subtotal cholecystectomy) will be included.

Exclusion Criteria:

• pregnancy or lactation

• acute cholecystitis not related to a gallstone etiology

• onset of symptoms >10 days before cholecystectomy**

• concomitant cholangitis or pancreatitis

• intraoperative treatment of common bile duct stones

• anything that would place the individual at increased risk or preclude the individual's full compliance with or completion of the study.

  • Patients with ACC associated with common bile duct stones who underwent pre-operative ERCP could be included if they receive EC within 10 days from onset of symptoms

All consecutive patients presenting with ACC as defined according to the Tokyo Guidelines 2018 to one of the participating hospitals will be assessed for eligibility on presentation.