Acute Pancreatitis - Hypoechoic Edematous Pancreas

A 45-year-old obese woman presents with severe epigastric pain radiating to the back, nausea, and vomiting 8 hours after a fatty meal. Serum lipase is 8× the upper limit of normal. Trans-abdominal ultrasound shows the structure marked **A** to be diffusely enlarged and hypoechoic compared with the adjacent liver, with indistinct margins and a small rim of peripancreatic fluid. The gallbladder contains multiple echogenic stones with posterior acoustic shadowing. Based on the Revised Atlanta Classification 2012, what is the PRIMARY role of ultrasound in confirming the diagnosis of acute pancreatitis in this patient?