Primary psoas abscess is a rare infection with an often vague and non-specific clinical presentation, especially in children. In Asia and Africa 99.5% of all psoas abscesses are primary, compared with 61% in the United States and Canada and 18.7% in Europe.1 2 Approximately 70% of psoas abscesses occur in patients younger than 20 years of age, with a male preponderance of 3:1.1 Fifty seven per cent of psoas abscesses occur on the right side, 40% on the left side, and 3% bilaterally.3We present the following case and show the magnetic resonance imaging to emphasise the presenting signs, symptoms, and findings of this unusual infection. A 13 year old white girl was in excellent health until she developed a dull ache in the superior posterior thigh without radiation. She denied any direct trauma or excessive strenuous activity. Over five days she developed progressively severe, dull pain, localised to the posterior hip in association with fever to 38.9°C, nausea, vomiting, and diarrhoea. She walked with a limp. Her past medical history was non-contributory; she denied smoking, alcohol, drug use, or sexual activity. The girl was 1.52 m tall and weighed 70 kg. Vital signs were normal; temperature rose to 38.9°C within 24 hours of admission. A detailed general physical examination was normal. Abdominal …