title: Ruptured mycotic aortic aneurysm.
abstract: A right flank mass, in a patient with fever of unknown origin, pain, and superiorly displaced right kidney on excretory urogram, was explored through a subcostal incision. Finding of a retroperitoneal abscess was anticipated; instead of a ruptured mycotic aortic aneurysm was encountered. An awareness that entities such as this may exist is imperative in the differential diagnosis of flank  masses. Treatment through a flank incision presents an elusive if not impossible feat. Because of the gravity of the underlying disease, misdiagnosis almost always results in death.
mesh_terms: D000038:Abscess / Q000175:diagnosis; D000785:Aneurysm, Infected / Q000150:complications* / Q000175:diagnosis; D001012:Aorta, Abdominal; D001019:Aortic Rupture / Q000175:diagnosis / Q000209:etiology*; D003937:Diagnosis, Differential; D006406:Hematoma / Q000209:etiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010532:Peritoneal Diseases / Q000175:diagnosis