[Psoas abscess in pyogenic sacroiliitis].

A 47-year-old man was admitted with septic fever over a few days. A CT-scan showed a psoas abscess, which was drained by surgery. In the meantime antibiotics were started. In spite of this treatment, he continued to have septic fever. Bone scintigraphy and MR-scan showed activity in the right sacroiliac joint compatible with sacroiliitis. The joint was opened surgically and revised. The patient was treated with antibiotics for nine weeks and was fully restituted. It must be concluded that the psoas abscess was secondary to the sacroiliitis, a rare event.