Figure 9. Progression of inflammatory mass to an abscess collection. 17-year-old man with 2 days of vomiting and mild lower abdominal pain. (a) CT with intravenous (iv) contrast medium on admission shows a 4 cm phlegmonous soft tissue mass with surrounding fat stranding (arrow). Initial management plan was for antibiotic therapy to be followed by interval appendicectomy. (b) CT with iv contrast medium 9 days later, obtained because of clinical deterioration, shows a liquefied right iliac fossa abscess (arrow) with a locule of gas.