Acute Appendicitis

A 24-year-old male presents to the emergency department with a 36-hour history of periumbilical pain that migrated to the right lower quadrant, accompanied by anorexia, nausea, and low-grade fever (38.2°C). On examination, he has marked tenderness and guarding at McBurney's point with a positive Rovsing's sign. Ultrasound with graded compression shows the structure marked **B** — a non-compressible, blind-ending tubular structure measuring 8 mm in outer diameter with surrounding echogenic fat stranding and increased color Doppler flow. Which of the following is the most appropriate next step in management?

A 22-year-old female presents to the emergency department with 18 hours of periumbilical pain that has now localised to the right iliac fossa. She has fever (38.1°C), anorexia, and vomiting. On examination, she has tenderness at McBurney's point with positive Rovsing's sign. Laboratory investigations show leucocytosis (14,200/μL, 86% neutrophils) and elevated CRP (64 mg/L). Graded-compression ultrasound of the right lower quadrant is performed. The structure marked **B** in the diagram shows an outer-to-outer diameter of 9 mm. Which of the following best describes the diagnostic significance of this measurement in acute appendicitis?