A 14-week-old boy who is known to have a single right kidney presented to our emergency department with history of fever for 1 day. A sepsis work up was performed (complete blood count, blood culture, urine culture and lumbar puncture) in the emergency room. On the second day of admission he developed swelling in the parieto-occipital area. Head CT showed crescent-shaped extra cranial area of homogeneous low attenuation. He remained asymptomatic with a stable haemoglobin and haematocrit. Swelling subsequently resolved within 5 weeks.