A 37-year-old female patient with no medical or family history had no particular problems during pregnancy. However, at 36 weeks of pregnancy, a nonreassuring fetal status was found, and her first child was born by cesarean delivery. She had no postoperative abnormalities, and the surgical wound site healed well.However, 7 days after surgery, right buttock pain developed with
no trigger. She visited the hospital because of the gradually worsening
buttock pain, gait disturbance, and fever. Her body temperature
was 38.4C, and severe tenderness was present in the right
buttock. A pelvic compression test was positive for the right
buttock. Blood testing showed a white blood cell level of
13.96 109/L, a left shift on the differential white blood count, and
a remarkably elevated C-reactive protein level of 220 mg/L. A pelvic
radiograph showed no remarkably abnormal findings such as
osteolysis or osteosclerosis (Fig. 1), but contrast-enhanced
computed tomography revealed enlargement of the right iliac
muscle and an abscess accompanied by ring-enhancing lesions
anteroposterior to the right sacroiliac joint (Fig. 2).
Magnetic resonance imaging centered on the right sacroiliac
jointwas performed. The T1-weighted image showed low intensity,
and the T2-weighted image revealed abnormal high intensity of the
bone marrow and a lesion believed to be an abscess 1.5 cm in
diameter in the region anteroposterior to the joint (Fig. 3). Based on
these results, the patient was diagnosed with pyogenic sacroiliitis.
X-ray-guided puncture of the sacroiliac joint and abscess was performed,
and approximately 2 mL of milketea-like puncture fluid
was collected. Culture of the puncture fluid revealed the presence
of MRSA. Blood and urine cultures were negative. After a 3-week
combined administration of vancomycin and rifampicin, a 3-week
administration of arbekacin was performed. Her symptoms subsequently
disappeared, her blood test results became normal, and
she was discharged from the hospital. One year after discharge, no
recurrence was observed, and she has a favorable prognosis.