Introduction

An iliopsoas abscess describes a collection of pus in iliopsoas compartment (iliopsoas and iliacus).

Epidemiology

  • Incidence: 0.40 cases per 100,000 person-years
  • Peak incidence: 40-50 years
  • Sex ratio: 1:1
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+

Aetiology

Primary
  • Haematogenous spread of bacteria
  • Staphylococcus aureus: most common

Secondary
  • Crohn's (commonest cause in this category)
  • Diverticulitis, colorectal cancer
  • UTI, GU cancers
  • Vertebral osteomyelitis
  • Femoral catheter, lithotripsy
  • Endocarditis

Clinical features

Clinical features

Clinical examination
  • Patient in the supine position with the knee flexed and the hip mildly externally rotated
  • Specific tests to diagnose iliopsoas inflammation:
    • Place hand proximal to the patient's ipsilateral knee and ask patient to lift thigh against your hand. This will cause pain due to contraction of the psoas muscle.
    • Lie the patient on the normal side and hyperextend the affected hip. In inflammation this should elicit pain as the psoas muscle is stretched.

Investigations

CT is the gold standard.

Prognosis

Note the mortality rate can be up to 19-20% in secondary iliopsoas abscesses compared with 2.4% in primary abscesses.