Psoas Abscess: A Primer for the Internist

, Department of Internal Medicine, Lincoln Health Center and Durham Regional Hospital, Durham, NC

South Med J. 2001;94(1) 

In This Article

Psoas Muscle Anatomy

The psoas muscle is a retroperitoneal organ that originates from the lateral borders of the 12th thoracic to fifth lumbar vertebrae and inserts on the lesser trochanter of the femur. In 70% of people, it is a single structure (psoas major), but 30% also have a smaller psoas minor muscle, which lies anterior to the psoas major along the same course. It is innervated by branches of L2, L3, and L4, before formation of the femoral nerve. The psoas muscle lies in close proximity to many other organs, including the sigmoid colon, jejunum, appendix, ureters, aorta, renal pelvis, pancreas, iliac lymph nodes, and spine. Thus, infections in these organs can contiguously spread to the psoas muscle. The psoas muscle has a rich vascular supply that is believed to predispose it to hematogenous spread from sites of occult infection.


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