(A) T2 weighted magnetic resonance imaging of a 13-year-old boy (case 1) with pain in the right hip was normal. (B) T2 weighted magnetic resonance imaging, taken when the symptoms relapsed, shows an abscess pocket (arrow) at the acetabulum near the triradiate cartilage. Fluid collection is shown in the hip joint. (C) The middle two images are of the initial magnetic resonance images. At the pubic portion of the acetabulum (arrow), the signal intensity of the right side was low in T1 weighted image, and high in T2-weighted image compared to that of the left side. (D) The bottom two images were taken when the symptoms relapsed. The difference on T1 weighted image and T2 weighted image are definite. There was fluid collection in the right hip joint.

A boy (case 2) age 11-year-old presented with a left hip joint pain and a recent minor trauma history. The abscess pocket with well-enhanced margins and cortical bone defect were shown on the T1 weighted axial (A) and coronal (B) magnetic resonance imaging taken from another hospital. The abscess had extended to the surrounding soft tissues (black arrow). On T2 weighted fat suppression axial (C) and coronal (D) magnetic resonance imaging, there was no fluid collection in the left hip joint and no specific findings were shown. On T2 weighted fat suppression axial (E) and coronal (F) magnetic resonance imaging taken after relapse, the abscess pocket with well-enhanced margins (white arrow) was still shown in the posterosuperior portion of the acetabulum.