Morning Report

Morning Report: Psoas Abscess

Presenter: Emily Sze PGY-1

Summary: 47-year-old male presents to the ED complaining of 2 weeks of worsening of his chronic lower back and abdominal pain, along with nausea, vomiting, diarrhea, and dysuria. He is a current IVDU, most recently injected heroin 1 week ago, and was previously in a methadone program. He also smoked crack a few days ago. He had his appendix removed as a teenager. He was seen at outside hospital a few days ago for the same complaint and sent home with oxycodone and Valium.

On exam: 37.3C (99.1F), intoxicated, +ttp abdomen, –ttp spinal/paraspinal region, neuro exam normal.

Work-up: wbc count 19.9, mild anemia hgb 10.9, wet abd CT showed a psoas abscess of size 1.8x2cm.

Learning points:

  • Always consider psoas abscess in differential for lower back pain, particularly in a patient with risk factors
  • Psoas abscess has high mortality rate (2.4% for primary, 18.9% for secondary), usually due to sepsis from delayed diagnosis/treatment
    • Look for +psoas sign, position of comfort (hip flexion/lumbar lordosis)
  • Primary psoas abscess – caused by hematogenous/lymphatic spread (20-60% of psoas abscesses in USA
    • Risk factors:
      • IVDU
      • Immunosuppression (diabetes, renal failure, HIV, etc)
    • Epidemiology: males, childhood to young adulthood, tropical/developing countries
    • Bugs: Staph aureus (#1), including MRSA; Mycobacterium tuberculosis in endemic areas -> vancomycin, clindamycin, linezolid
  • Secondary psoas abscess – caused by direct spread
    • Risk factors:
      • Trauma
      • Vertebral osteomyelitis, especially from Pott’s disease
      • Crohn’s ileocolitis (0.4-4.3% incidence)
      • Infected aortic aneurysm (20% incidence)
      • Ruptured renal or pancreatic abscess
      • Septic hip arthritis (hip bursa communicates with iliopsoas bursa in 15% of people
      • Iatrogenic: instrumentation, epidural catheter, total hip arthroplasty (12%), shock wave lithotripsy, nephrectomy
    • Bugs: usually enteric, often polymicrobial ? Zosyn, fluoroquinolone, cephalosporin, Flagyl
  • Imaging: dry CT, wet CT, MRI are options
    • Sensitivity for all 3 modalities is 100% after 6 days of symptoms
    • Earlier than 6 days, sensitivity is 33%, 50%, and 50%

 

EBM article: 

  1. Eric B. Tomich, DO and David Della-Giustina, MD. Bilateral Psoas Abscess in the Emergency Department. West J Emerg Med. 2009 Nov; 10(4): 288–291.
  2. Takada T, Terada K, Kajiwara H, Ohira Y. Limitations of Using Imaging Diagnosis for Psoas Abscess in Its Early Stage. Intern Med. 2015;54(20):2589-93.
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