PMC6727460_01
X-ray pelvis: No obvious abnormality is seen.
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F1
Pelvic X-ray and a left knee X-ray were performed to rule out any bony abnormality, and both were normal (Fig. 1).
US left hip demonstrates no obvious effusion.
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F2
An ultrasound scan of the hips suggested a very small left-sided effusion (Fig. 2). The decision was made to proceed with an ultrasound scan first before possible aspiration (Fig. 2).
Axial T1 (a) and T2 (b) magnetic resonance imaging demonstrates a rounded abscess (see arrow) as low signal on T1 and high signal on T2  . There is surrounding muscle edema in keeping with reactive myositis.
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F3
Inflammatory changes also tracked inferiorly into the groin (Fig. 3a-c). With the MRI findings to hand and following discussion with the pediatric surgeons, it was felt that the collection did not require surgical intervention (Fig. 3a-c).