The patient proceeded to theater and subsequent appendectomy. 

Pathology confirmed the pre-operative imaging diagnosis:

MACROSCOPIC DESCRIPTION: "Appendix": Appendix 40x10x10mm with brown ragged mesoappendix showing full thickness perforation.

MICROSCOPIC DESCRIPTION: Sections of the appendix show mucosal ulceration, associated with transmural acute inflammatory cell infiltrate. Part of the wall is disrupted, consistent with a perforation. The serosa is covered by heavy inflammatory exudate. There is no evidence of malignancy. 

DIAGNOSIS: Acute appendicitis with perforation