A young woman with fever and low back pain

A previously healthy, 20-year-old woman taking oral contraceptives presented to the Emergency Department (ED) with fever (body temperature, 39.2°C) and low back pain. Physical examination showed right costovertebral angle tenderness. Laboratory tests revealed elevated white blood cell count (13.2×109/L) and C-reactive protein level (9.75 mg/dL). Coagulation test results were unremarkable except for D-dimer level (1.5 μg/mL). Urinalysis results were normal. Abdominal CT with contrast was performed (figure 1). Figure 1 CT scan with contrast. What is the most likely diagnosis? 1. Renal infarction 2. Acute focal bacterial nephritis 3. Renal Abscess 4. Antiphospholipid syndrome Acute focal bacterial nephritis …