Acute calculous cholecystitis (ACC) is the second most frequent surgical condition in emergency departments. The recommended treatment is surgical treatment (ST) and the accepted mortality is <1%, but in severe and/or fragile patients is higher. Despite the Tokyo Guidelines, there no consensus on who is the unfit patient for ST. A recent study has identified 4 risk factors that predicts the mortality in a 92% of patients (ACME) and could help to develop new guidelines in ACC. The aim of this study is this validation of the new simplified scoring system for mortality in ACC.

This is a retrospective single-center observational study of 387 adults with ACC during 2 non-consecutive years (2017/2021), including baseline demographic characteristics, comorbidity severity defined as Charlson Comorbidity Index (CCI), ASA Score, Tokyo Guidelines' severity classification and the new ACME Score. The primary outcome is to study the prediction of mortality of ACME score. Secondary outcomes include complications following Clavien-Dindo's classification, C-statistic, and ROC Curves.

Inclusion Criteria:

• The selected patients were among those who had acute cholecystitis according to the TG18 or received a diagnosis of ACC in the histopathological report.

Exclusion Criteria:

• The study case definition was a "Pure ACC", therefore, patients with any other concomitant diagnosis potentially influencing outcome such as acute pancreatitis, acalculous cholecystitis, chronic cholecystitis, acute cholangitis, postoperative cholecystitis, gallbladder adenocarcinoma and those who had undergone cholecystectomy as a prophylactic measure in another intervention were excluded from the study.

All the admisions with the inclusion criteria during 2017 and 2021.