Psoas Abscess

INTRODUCTION Iliopsoas abscess is an uncommon but important and potentially life-threatening infection that is typically difficult to recognize. Even today, most of the literature on psoas abscess includes case reports and small case series with few institutions seeing more than one case of iliopsoas abscess in a year. Large review series have been published by Ricci et al. and more recently by De and Pal. Originally described by Abeille in 1854 as an abscess of the psoas muscle, the etiology of the disease has changed substantially in the Western world since Mycobacterium tuberculosis has decreased in frequency. The incidence of iliopsoas abscess has increased from 3.9 cases per year to more than 12 per year in 1995. At our institution, 1 to 4 cases of iliopsoas abscess are currently seen each year. ANATOMY An iliopsoas abscess occurs in the retroperitoneal space that contains both the iliopsoas and iliacus muscle. The psoas major muscle is a long broad muscle that originates in the retroperitoneum from the lateral borders of T12 to L5 vertebrae. The muscle courses along the vertebral and lumbar regions to the pelvic brim, passing beneath the inguinal ligament and in front of the capsule of the hip joint, ending in a tendon that inserts into the lesser trochanter of the femur. The iliacus contributes fully to the tendinous insertion at the femur, which is often why the muscles are referred to as a single muscle, the iliopsoas.