Psoas abscess

Section: Critical care Curriculum: Curriculum, page 47

General

• M>F
• Age 50
• Bilateral uncommon
• Anatomy of Psoas Major
  • Origin: Disc of T12-L5 vertebrae
  • Inserts: Lesser Trochanter of Femur
  • Crossed pelvic brim and deep to inguinal lig
  • Anterior to hip joint capsule (separated by iliopsoas bursa)
  • Nearby structure where infection can spread
    • AA
    • Vertebral Body
    • Sigmoid and appx
    • Hip joint
    • Iliac LN

Classification

• Primary (haematogenous/lymphatic) vs secondary (direct)
  • Primary (haematogenous/lymphatic seeding from distant site)
    • Risk Factors
      • Immunosuppression
      • DM
      • IVDU
      • HIV
      • Renal failure
      • Septic emboli
      • Cardiac origin infective endocarditis
  • Secondary (direct)
    • Risk Factors
      • Trauma
      • Local instrumentation
      • Local structures
        • Vertebral Body
          • Osteomyelitis
        • Hip joint capsule
          • Post arthroplasty
        • GIT
          • All cause colitis
          • Appendicitis
          • Diverticulitis
        • Mycotic aortic aneurysm
        • Complication from renal surgery
        • GUT
          • PID, TOA, UTI, pyelo
        • MSK
          • Septic joint hip, osteomyelitis, discitis, potts disease (TB)

Pathology/Micro

• Primary
  • Single organism
  • Most common = staph aureus (including MRSA)
  • In countries where TB is common, mycobacterium tuberculosis
• Secondary (dependent on pathology)
  • Likely enteric organisms
  • Monomicrobial
  • Polymicrobial
  • Tuberculosis of the spine is an important cause of retroperitoneal abscesses in immunocompromised individuals and in those immigrating from underdeveloped countries.

Clinical

• Symptoms - weeks to months
• Could present shocked
• Local
  • Back/flank pain +/- radiation to hip
  • Inguinal mass
    • If not tender and below inguinal lig - cold mass could be TB
  • Limping
• Systemic
  • Fever
  • Anorexia
  • Weight loss
• Signs
  • Psoas sign positive - hip extension
  • POSITION OF COMFORT - HIP FLEXED, LUMBAR LORDOSIS

Complications

• Local
  • Hydronephrosis
  • Ileus
  • Septic arthritis of hip
  • DVT
• Systemic
  • Shock

Investigations

• Bloods
  • WBC, CRP
  • Culture Blood culture for haematogenous spread
  • Quantiferon gold
• Aspirate
  • TB - AFB gram staining
• Biopsy
  • ?suspicion for malignancy
• Imaging
  • CT abdo pelvis - ID hypodense ?loculated area in psoas muscle and concurrent abdominal pathology
  • MRI if suspicious for joint or spinal involvement

Differential diagnosis

• Haematoma
• Retrocaecal appendicitis
• Bursitis
• Septic hip arthritis

Management

• Principles
  • Source control - drainage, abx
  • If secondary, treat underlying cause
• Antibiotics
  • Emperic
    • Suggest cover for
      • Staph Aureus (+/- to cover MRSA
        • Cefazolin or Cefalexin
        • Or for MRSA - Vancomycin, co-trimoxazole, Clindamycin
      • Cover enteric bugs
        • Cefuroxime and Metronidazole, Tazocin, Meropenum
  • Then guided by cultures
  • Duration dependent on situation but likely prolonged course e.g. 4 weeks
• Radiological
  • Percutaneous drain placement - CT guided
  • Failed abx management (most won’t settle alone), large abscess
• Surgical
  • Laparoscopic vs open
  • Indications complex abscess failed drainage and abx
    • Multiloculated
    • Significant local involvement needing surgical intervention
      • E.g bowel pathology IBD
  • Open drainage • McBurney incision • Muscle splitting • Extraperitoneal plane developed • Peritoneum pushed medially • Identify psoas muscle: medial posterior abdominal wall • Aspirate muscle with 18G needle. • Incise to drain pus • Place large closed suction drain, through separate skin incision • Close wound in layers

Prognosis

• 20% - septic shock
• Recurrence or poor prognosis related to
  • Disease Factors
    • E.coli
    • Bacteraemia
    • Inadequate drainage
  • Patient Factors
    • Advanced age
    • CV disease
    • Immunosuppression