Updated: 6/13/2021

Psoas Abscess - Pediatric

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  • summary
    • Psoas Abscess is an infection of the psoas muscle that may present in the pediatric population and must be considered when evaluating hip pain in children.
    • Diagnosis generally requires MRI studies to evaluate for a psoas abscess.
    • Treatment is percutaneous image-guided drainage and antibiotics in most cases.
  • Epidemiology
    • Demographics
      • more common in tropics
  • Etiology
    • Pathophysiology
      • may spread to hip joint causing septic arthritis because of
        • indirect passage via psoas bursa
          • lies between hip joint and psoas
          • connects psoas directly to hip joint in 15% of cadavers
      • direct passage between the iliofemoral and iliopubic ligaments
    • Microbiology
      • Staph aureus
        • most common organism
    • Associated conditions
      • septic hip - pediatric
      • tuberculous spondylitis
  • Presentation
    • Symptoms
      • presents like hip septic arthritis
        • fever
        • hip pain
        • limp or refusal to bear weight
    • Physical exam
      • inspection
        • hip rests in a position of flexion
      • palpation
        • may have tender mass in iliac fossa
      • provovative tests
        • psoas sign
          • pain caused by extension and internal rotation of the limb
  • Imaging
    • Radiographs
      • recommended views
        • AP and frog-leg lateral pelvic x-rays to rule out septic hip
      • findings
        • may show loss of definition or enlargment of psoas muscle shadow
    • Ultrasound
      • diagnostic imaging study of choice
    • Bone scan
      • helpful in diagnosis
    • CT scan with contrast
      • indications
        • can confirm diagnosis when ultrasound or MRI not available
        • avoid if possible due to radiation exposure
      • findings
        • include the presence of a mass and local attenuation within the involved musclee, with ring enhancement
        • may be negative in early stages
    • MRI
      • indications
        • can confirm diagnosis if ultrasound not available
        • difficult to obtain expeditiously
      • findings
        • will show changes early in the disease process
  • Treatment
    • Nonoperative
      • percutaneous ultrasound or CT-guided drainage
        • indications
          • treatment of choice in most cases
    • Operative
      • open drainage
        • indications
          • useful for secondary psoas abscess e.g. spread from the bowel
            • can simultaneously address intraabdominal source
  • Complications
    • Septic arthritis
      • psoas abscess can spread to hip joint
    • Sepsis
Questions (1)

(OBQ13.94) A 17-month-old girl presents with intermittent fever, hip pain and irritability for 2 weeks. She walks with a limp. On examination, temperature is 38°C, and her hip is held in flexion. Passive hip extension, internal rotation, and abduction causes severe pain. WBC is 29,300 cells/microliter. ESR is 66 mm/h. Radiograph, bone scan and CT scan are shown in Figures A through C. What is the diagnosis?

QID: 4729
FIGURES:
1

Septic arthritis

21%

(775/3709)

2

Psoas abscess

73%

(2698/3709)

3

Sacroiliitis

1%

(37/3709)

4

Transient synovitis

4%

(131/3709)

5

Osteomyelitis

1%

(44/3709)

L 2 C

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EXPERT COMMENTS (1)
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