MR imaging of septic sacroiliitis

Area of Science:

• Radiology
• Infectious Diseases
• Orthopedics

Background:

• Septic sacroiliitis presents diagnostic challenges, leading to treatment delays and increased patient morbidity.
• Conventional imaging modalities like CT and nuclear medicine have limitations in detecting septic sacroiliitis.
• Early and accurate diagnosis is crucial for effective management and improved patient outcomes.

Purpose of the Study:

• To assess the diagnostic capability of MR imaging for septic sacroiliitis.
• To characterize the specific MR imaging features of septic sacroiliitis.
• To compare the detection rates of MR imaging against CT and nuclear medicine.

Main Methods:

• Retrospective evaluation of patients diagnosed with septic sacroiliitis who underwent pelvic MR imaging.
• Inclusion of five patients with six affected sacroiliac joints, all assessed with MR, CT, 99mTc-methylene diphosphonate bone scans, and 67Ga-citrate scans.
• Prospective and retrospective analysis of MR imaging findings, correlated with other imaging results.

Main Results:

• MR imaging detected abnormalities consistent with sacroiliitis in all six affected joints, both prospectively and retrospectively.
• Nonspecific findings included inflammation/fluid in the joint space, bone marrow, and iliopsoas muscle.
• Unique to septic sacroiliitis on MR was fluid/inflammation tracking posterior to the iliopsoas muscle.
• Conventional imaging showed lower detection rates: 67Ga-citrate (5/6 joints), CT (3/6 joints), and 99mTc-MDP (1/6 joints).

Conclusions:

• MR imaging demonstrates high sensitivity for detecting septic sacroiliitis.
• The identification of fluid/inflammation posterior to the iliopsoas muscle is a key distinguishing feature on MR.
• MR imaging may be a superior modality for the early diagnosis of septic sacroiliitis compared to CT and nuclear medicine.