Iliopsoas Abscess
🦴 The diagnosis of an iliopsoas abscess may be suspected if a patient prefers lying supine with the knee flexed and hip mildly externally rotated – the position of greatest comfort.
📖 About
- ⚡ Early recognition and drainage reduce morbidity and mortality.
- 🫀 Involves the psoas and iliacus muscles (iliopsoas).
- 👨 More common in younger patients and males.
🧩 Anatomy
- 📍 Psoas originates T12–L5 → inserts at lesser trochanter of femur.
- 🧬 70% have only psoas major, 30% also have psoas minor (anterior).
- 💪 Fibres blend with iliacus → main hip flexor.
- ⚡ Innervated by L2–L4 (lumbar plexus).
- 🩸 Surrounded by venous plexus → prone to haematogenous spread.
🦠 Aetiology
- Spinal TB (esp. developing countries).
- IV drug use, diabetes, AIDS, renal failure, immunosuppression.
- Inflammatory bowel disease – Crohn’s is the most common secondary cause.
📌 Types
- Primary: Haematogenous spread (e.g. Staph aureus, TB).
- Secondary: Spread from Crohn’s, diverticulitis, appendicitis, or post-procedural infections.
🧫 Microbiology
- 🟡 Staphylococcus aureus → ~88% of primary cases.
- 🟢 Streptococcus → ~5%.
- 🔵 E. coli → ~3%.
- 🧬 Mycobacterium tuberculosis (common worldwide in TB endemic regions).
- Other: Proteus, Klebsiella, Bacteroides, Clostridium, MRSA, Salmonella, atypical mycobacteria.
🩺 Clinical Presentation
- Fever, weight loss, malaise.
- Flank, back, or abdominal pain radiating to groin.
- Limp or groin lump may be present.
- 🛏️ Classic posture: supine, hip flexed & externally rotated, knee flexed.
- Psoas signs:
- Resisted hip flexion → pain.
- Passive hip extension (patient on side) → pain.
- May also be positive in appendicitis with psoas irritation but no abscess.
🔬 Investigations
- 🩸 FBC: ↑ WCC, ↑ ESR, ↑ CRP.
- 🧪 U&E: may show AKI; lactate if septic.
- 🖼️ CT abdomen/pelvis = gold standard for diagnosis.
- 💉 Fluid aspiration → culture & sensitivity.
⚠️ Complications
- 🩸 Compression of iliac vein → DVT.
- 🟡 Ureteric compression → hydronephrosis/renal impairment.
- 💥 Retroperitoneal haemorrhage.
- 🌡️ Sepsis, multi-organ failure.
💊 Management
- 🫁 ABC resuscitation → oxygen, IV fluids, analgesia, sepsis protocol.
- 💉 Broad-spectrum antibiotics (cover Staph/Strep/Gram negatives) → adjust after culture.
- 💉 Drainage: CT-guided percutaneous drainage (preferred) or surgical drainage if large/complex.
- ⚖️ Optimise comorbidities (e.g. diabetes control).
📌 UK Exam Pearls
- 👨 Young male with fever + back pain + limp → think psoas abscess.
- 🛏️ Classic posture (hip flexion + external rotation) is a diagnostic clue.
- 🧪 Staph aureus = most common cause (esp. primary abscess).
- 🌍 TB is an important cause worldwide (spinal spread).
- 📸 CT scan is the diagnostic gold standard.
- 💉 Early drainage + antibiotics = key to reducing mortality.
- 🇬🇧 In UK practice, consider Crohn’s disease when secondary psoas abscess is suspected.
🔗 References
