A 33-year-old female presented with acute colicky left loin-to-groin pain and microscopic haematuria, with a background of 6 months of muscle and joint pains and diplopia. A CT kidneys/ureters/bladder demonstrated fat stranding surrounding the left ureter, as it passed over the left common iliac vessels. Arterial and delayed phase imaging revealed an obstructed ureter secondary to a left common iliac artery aneurysm, later found to be mycotic. No previous descriptions of a mycotic aneurysm presenting as renal colic have been found in the literature. The diagnosis and management of infective endocarditis and mycotic aneurysm are discussed, with a review of the literature. This serves as a good example of a common presenting complaint occurring secondary to a rare and serious pathology.