- Psoas abscess is a suppurative collection in the psoas muscle
- It is commonly missed or diagnosed late, with potential for severe morbidity
- The psoas muscle extends through the retroperitoneal space from the lateral borders of T12 to L5 and inserts on the lesser trochanter of the femur (30% have an additional psoas minor muscle anterior to the psoas major).
Psoas abscess may be primary in origin (see risk factors) or secondary, due to local spread from:
- Vertebral osteomyelitis
- Inflammatory bowel disease (especially Crohn’s disease)
- Septicaemia and septic shock
- Epidural abscess
Causative organisms include:
- staphylococcus spp (most common)
- Gram negative enteric bacteria
- Tuberculosis (immunosuppressed, or in endemic areas)
Risk factors for primary psoas abscess include:
- Underlying immunosuppression (e.g DM, HIV, malignancy)
- Local recent surgery or trauma
- Infected psoas hematoma
- Psoas haematoma may occur in haemophiliac patients
- may be non-specific initially
- increasing pain, usually over several days, affecting the back, buttock, groin or hip
- pain may radiate to the hip and thigh (L-2,3,4 dermatome)
- risk factors may be present
- suspect if no clear history of any trauma or other musculoskeletal injury
- fever may be present
- point tenderness of the back (may be absent or diffuse early in the presentation)
- evidence of psoas irritation
- position of comfort is the supine position, with the knee moderately flexed and the hip mildly externally rotated
- hip pain with movement (especially resisted hip flexion) or weight bearing
- glucose (diabetes mellitus)
- FBC (leukocytosis)
- Septic screen including blood cultures and urine MCS (exclude UTI)
- CT abdomen may diagnose psoas abscess, and may exclude alternate diagnoses
- MRI is the gold standard, it is more sensitive than CT abdomen and can also diagnoses/ exclude epidural abscess
- ultrasound and radiographs are not useful (a scoliosis due to muscle spasm, concave to the affected side, may be present)
- rarely required
- empiric antibiotics: flucloxacillin or vancomycin
- treat tuberculosis if required
- consider CT-guided drainage
- surgical drainage if CT-guided drainage is not possible or fails (~10% of cases)
Supportive care and monitoring
References and links
- van den Berge M, de Marie S, Kuipers T, Jansz AR, Bravenboer B. Psoas abscess: report of a series and review of the literature. Neth J Med. 2005 Nov;63(10):413-6 PMID: 16301764.
- Wong OF, Ho PL, Lam SK. Retrospective review of clinical presentations, microbiology, and outcomes of patients with psoas abscess. Hong Kong Med J. 2013 Oct;19(5):416-23. PMID: 23603777.
- Yacoub WN, Sohn HJ, Chan S, Petrosyan M, Vermaire HM, Kelso RL, Towfigh S, Mason RJ. Psoas abscess rarely requires surgical intervention. Am J Surg. 2008 Aug;196(2):223-7. PMID: 18466865.
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.