What is the management of psoas signs?

Management of Psoas Signs

When a patient presents with a positive psoas sign (pain with passive hip extension or active hip flexion against resistance), immediately obtain CT scan with contrast or MRI to rule out psoas abscess, as this represents a potentially life-threatening infection requiring urgent drainage and antibiotics. 1, 2

Initial Clinical Assessment

Physical Examination Findings to Elicit

• Perform passive hip extension - pain indicates psoas muscle irritation 2
• Test active hip flexion against resistance - pain suggests psoas involvement 2
• Deep palpation in the lower quadrant - assess for tenderness or firm, wooden feel over the psoas region 2
• Assess for fever and localized tenderness over the psoas muscle region, as the classic triad of fever, flank pain, and limitation of hip movement occurs in only a minority of cases 3

Key Clinical Context

• Leukocytosis is the most common laboratory finding in psoas abscess 3
• Hemocultivres are positive in only 5-30% of patients, so negative blood cultures do not exclude the diagnosis 4
• High-risk populations include immunocompromised patients (HIV, diabetes mellitus, hematologic malignancies, neutropenia) and those with gastrointestinal or genitourinary malignancies causing obstruction 4

Diagnostic Imaging Algorithm

First-Line Imaging

• CT scan with contrast is highly effective, revealing enlargement of the psoas muscle with bacterial foci 1
• CT accurately confirms clinical diagnosis in approximately 82% of patients (9 of 11 cases in one series) 3
• Ultrasound has poor sensitivity - negative findings occurred initially in 36% of patients (4 of 11 cases) 3

When to Use MRI

• MRI without and with IV contrast is the preferred modality for suspected spine infection with sensitivity of 97% and specificity of 93% 1
• MRI is the imaging modality of choice for definitive diagnosis, showing abnormal enhancement of vertebral bodies and psoas muscle 1
• MRI demonstrates pyomyositis most effectively 4

Radiograph Limitations

• Plain radiographs have low sensitivity in early disease, as 30-40% of bone destruction is needed before radiographic changes become apparent 1

Treatment Strategy

Immediate Management

• All patients require drainage plus antibiotics - this is non-negotiable for psoas abscess 3
• Surgical drainage was required in 82% of cases (9 of 11 patients), while percutaneous CT-guided drainage succeeded in 18% 3

Antibiotic Selection Based on Etiology

Primary Psoas Abscess:

• Staphylococcus aureus causes approximately 90% of primary cases 4
• Cover for Staphylococcus aureus, Streptococcus group A, Streptococcus pneumoniae, and gram-negative enteric bacilli 4

Secondary Psoas Abscess:

• Gram-negative enteric bacilli (E. coli, Klebsiella, Enterobacter) predominate in secondary abscesses 4, 5
• Consider intraabdominal or retroperitoneal sources, urological problems (pyelonephritis, obstructive uropathy), or direct invasion through colonic mucosa 4

Surgical Consultation Criteria

• Vertebral involvement with spinal instability requires immediate surgical consultation 1
• Surgical intervention is indicated for bony lesions producing spinal instability, spinal cord or nerve root compression, or significant sequestered paraspinal abscess 1
• Multiple surgical approaches (anterior, lateral, posterior, or posterolateral) may be considered depending on infection location and extent 1

Prognosis and Pitfalls

Expected Outcomes

• Prognosis is generally good with appropriate antibiotic treatment and complete drainage 3
• Mortality occurred in 18% of cases (2 of 11 patients), with septic shock presenting in another 18% 3

Common Diagnostic Pitfalls

• Only 9% of patients present with the classic triad, so absence of typical findings should not delay imaging 3
• Initial diagnosis of psoas abscess was made in only 18% of cases (2 of 11 patients) at hospital admission, highlighting the difficulty of clinical diagnosis 3
• High degree of suspicion is essential for early diagnosis given nonspecific clinical presentations 3