A 50 year old male presents to the ED with severe right hip pain. He has had mild pain for a few weeks walking with a limp but now worsening over 3 days. He denies any trauma. He reports he has a history of an “infection in spine” but he completed treatment a few months prior. Vitals are remarkable for temperature of 100.4, heart rate 110. On exam, patient has no abdominal tenderness, no midline spinal tenderness, no pelvic tenderness, but refuses to move his right leg and has severe pain with passive flexion and extension of right hip. A CT abdomen/pelvis is obtained and shown below. What’s the diagnosis?   Scroll down for answer.

ANSWER:  PSOAS ABSCESS

•Risk factors: HIV, TB, IV drug use, muscle trauma

•May occur via hematogeneous/lymphatic spread (primary) or as direction extension of nearby infectious processes (secondary)

     - Crohn’s disease, diverticulitis, appendicitis, vertebral osteomyelitis, septic arthritis, intra-abdominal malignancy are all potential sources 

•Organisms

     - Staph aureus is most common cause for non-intra-abdominal associated causes (ex: hematogeneous or spinal)

     - E. coli is the most common when etiology is intra-abdominal 

•Classic triad = back pain + limp + fever (only in 30%)

•Other symptoms

     - Poorly localized abdominal or flank pain

     - Fever, malaise

     - Pain with passive hip movements

•Diagnosis

     - MRI more sensitive, but CT is appropriate first-line, particularly to look for other etiologies (ex: appendicitis) 

•Management

     - Broad spectrum antibiotics covering both Staph aureus and intra-abdominal organisms - Antibiotics alone may be sufficient for small abscesses

     - Open drainage of abscess vs percutaneous drainage

References

Shields, D., et al. “Iliopsoas Abscess – A Review and Update on the Literature.” International Journal of Surgery, vol. 10, no. 9, 2012, pp. 466–469., doi:10.1016/j.ijsu.2012.08.016.