Abdominal USG — Acute Cholecystitis (Murphy + Wall Thickening)

A 58-year-old woman presents to the emergency department with severe right upper quadrant pain of 8 hours' duration, fever (38.5°C), and nausea. On clinical examination, she has a positive Murphy sign. Abdominal ultrasound is performed. The structure marked **D** in the diagram (sonographic Murphy sign) is demonstrated as focal tenderness elicited by probe pressure over the visualized gallbladder during inspiration. Which of the following best describes the clinical significance of this finding in acute cholecystitis?