HighlightsA rapid imaging protocol with defined clinical criteria for acute cholecystitis (AC) resulted in significant improvements in perioperative and quality measures.Acute on chronic cholecystitis (ACC) may present with typical and/or atypical clinical features of AC, and was the most common pathology found in our specimens for the RIP.HIDA and CT scan had similar performance for de novo AC. However, diagnostic performance for both studies was reduced in the setting of ACC.Delayed filling of the gallbladder on HIDA in a patient with high risk features is ACC until proven otherwise, and urgent cholecystectomy should be considered.