Acute infectious aortitis presenting as pyelonephritis

A 65-years-old man with poorly controlled type 2 diabetes presented to the emergency department in sepsis with a 2-week history of new-onset fever, abdominal pain and pyuria. A Computed Tomography without contrast ruled out nephrolithiasis and hydronephrosis, but showed infiltration around the infra-renal aorta (5 x 1 cm) and several retroperitoneal lymph nodes. The periaortic infiltration raised suspicion for acute infectious aortitis. Aortic CT angiography confirmed an aortic pseudo-aneurysm in the infra-renal aorta without signs of impending aortic rupture. A Positron Emission Tomography-Computed Tomography confirmed abnormal 18F-FDG uptake adjacent to the right posterolateral aortic wall. The patient underwent abdominal aortic reconstruction with cryopreserved arterial allograft. Infectious aortitis is a rare but lethal cause of sepsis. Males over 50 years old with diabetes mellitus and peripheral vascular atherosclerotic disease are considered at higher risk. The diagnosis should be considered when a septic patient has vascular risk factors, abdominal pain, bacteremia and suggestive imaging. A CT without contrast showing infiltration around the aorta should, in some context, be promptly followed by Aortic CTA to search for acute aortitis among other less urgent differentials. Antibiotic therapy and involvement of vascular surgeons should be initiated in the emergency department.