Makindo Medical Notes

The diagnosis of an iliopsoas abscess may be obvious if the patient is noted to favor the position of greatest comfort, which is the supine position with the knee moderately flexed and the hip mildly externally rotated.

About

• Early management of an Iliopsoas Abscess significantly reduces morbidity and mortality.
• The condition affects the psoas and iliacus muscles.
• More common in younger individuals than the elderly.
• More common in males than females.

Anatomy

• The psoas muscle originates from the lateral borders of T12 to L5 vertebrae in the retroperitoneal space and inserts at the lesser trochanter of the femur.
• In 70% of individuals, it is a single structure known as the psoas muscle, but 30% have the psoas minor, which lies anterior to the major muscle.
• The fibres of the psoas muscle blend with those of the iliacus muscle to form the iliopsoas, which serves as the primary flexor of the hip.
• Innervation is provided by the lumbar plexus through branches of the L2–L4 nerves.
• The psoas muscle is surrounded by a rich venous plexus, making it prone to infections spreading hematogenously.

Aetiology

• Infection of the lumbar spine (e.g., spinal TB).
• IV drug use.
• Diabetes mellitus.
• AIDS or renal failure.
• Immunosuppression.
• Crohn’s disease is the most common cause of secondary iliopsoas abscess.

Types

• Primary Iliopsoas Abscess: Caused by blood spread of an infectious process from an occult source (e.g., tuberculosis).
• Secondary Iliopsoas Abscess: Often seen in patients with Crohn's disease or following instrumentations or procedures in the groin, lumbar, or hip regions.

Microbiology

• Staphylococcus aureus: Responsible for 88% of primary iliopsoas abscesses.
• Streptococcus species: 4.9% of cases.
• Escherichia coli (E. coli): 2.8% of cases.
• Mycobacterium tuberculosis: Common in developing countries.
• Other organisms include Proteus, Pasteurella multocida, Bacteroides, Clostridium, Yersinia enterocolitica, Klebsiella, Methicillin-resistant Staphylococcus aureus (MRSA), Salmonella, Mycobacterium kansasii, and Mycobacterium xenopi.

Clinical Presentation

• Pyrexia, fever, weight loss, and pain radiating from the loin to the groin.
• Flank, back, or abdominal pain, limp, and malaise.
• Patient may present with a lump in the groin.
• The typical posture is with the knee moderately flexed and the hip mildly externally rotated to minimize pain.
• Tests for Iliopsoas Inflammation:
  • Examiner places a hand just proximal to the patient’s ipsilateral knee and asks the patient to lift the thigh against resistance, causing contraction of the psoas muscle and resulting in pain.
  • With the patient lying on their unaffected side, hyperextension of the affected hip stretches the psoas muscle, causing pain.
  • These tests may also be positive in cases of appendicitis where there is inflammation of the iliopsoas but no abscess formation.

Investigations

• Full Blood Count (FBC): Elevated white cell count (WCC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) levels.
• Urea & Electrolytes (U&E): May show acute kidney injury (AKI). Lactate levels may also be elevated.
• CT Scan: Computed tomography of the abdomen and pelvis is crucial for diagnosis.
• Fluid Culture and Sensitivity: Obtain culture from the abscess fluid for microbiological analysis.

Complications

• Deep Vein Thrombosis (DVT): A large iliopsoas abscess may compress the iliac vein, leading to DVT.
• Ureteric Involvement: Compression of the ureters may lead to urinary complications.
• Hemorrhage: Risk of bleeding within the retroperitoneal space.
• Generalised Sepsis: Untreated abscesses can lead to systemic infection and sepsis.

Management

• ABC Protocol: Initial management includes airway, breathing, circulation, oxygen administration, analgesia, and addressing sepsis.
• Antibiotics: Broad-spectrum antibiotics should be initiated, covering Staphylococcus and Streptococcus, and adjusted according to culture results.
• Abscess Drainage: Early drainage significantly reduces morbidity and mortality. Computed tomography-guided percutaneous drainage (PCD) is preferred over open surgical drainage.
• Comorbidities Management: Address underlying conditions such as diabetes to optimize recovery.

References

• Iliopsoas abscesses review