What is the diagnosis and treatment for a psoas (musculus psoas) abscess?

From the Guidelines

Psoas abscess treatment should prioritize percutaneous drainage combined with antibiotic therapy, but if drainage is not feasible, antibiotic therapy alone can be considered in immunocompetent patients, as recommended by the most recent guidelines 1. When managing a psoas abscess, it's crucial to consider the patient's overall clinical condition and immune status.

• Initial empiric antibiotic therapy should cover Staphylococcus aureus, Streptococcus species, and gram-negative organisms, with regimens such as vancomycin 15-20 mg/kg IV every 8-12 hours plus piperacillin-tazobactam 4.5g IV every 6-8 hours, or meropenem 1g IV every 8 hours for resistant organisms.
• Antibiotics should be adjusted based on culture results and continued for 4-6 weeks.
• Drainage is essential and can be performed percutaneously under CT or ultrasound guidance, or surgically if percutaneous drainage fails or if there's extensive necrotic tissue, as supported by guidelines from 2024 1.
• The 2017 WSES guidelines for management of intra-abdominal infections also suggest that antibiotic therapy alone can be considered in patients with large abscesses when percutaneous drainage is not feasible or available, with careful clinical monitoring 1.
• However, the most recent guidelines from 2024 provide more specific recommendations, including the use of antibiotic therapy alone for 7 days in patients with small diverticular abscesses, and percutaneous drainage combined with antibiotic therapy for 4 days in large diverticular abscesses 1.
• In critically ill patients and immunocompromised patients, surgical intervention could be considered the primary treatment if percutaneous drainage is not feasible or available, as recommended by the 2024 guidelines 1.

From the Research

Diagnosis and Treatment of Psoas Abscess

• Psoas abscess is a severe condition characterized by diagnostic and therapeutic challenges due to its varied etiology and nonspecific symptoms 2.
• The diagnosis of psoas abscess can be made using various imaging techniques, including computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound (US) 2, 3, 4.
• CT-guided percutaneous drainage is a common treatment approach for psoas abscess, with high success rates reported in several studies 2, 3.
• Retroperitoneoscopic drainage is a minimally invasive and potentially definitive therapeutic option for psoas abscess, with low complication rates and no reported mortality 4.
• Antibiotic therapy alone may be sufficient for small abscesses, while larger abscesses may require percutaneous or open drainage 3, 5.

Causes and Characteristics of Psoas Abscess

• Psoas abscess can be primary or secondary, with primary abscesses often caused by intravenous drug abuse and secondary abscesses developing after abdominal surgery 3.
• Mycobacterium tuberculosis is a common causative agent of psoas abscess, particularly in certain regions such as North India 4, 5.
• Clinical features of psoas abscess include back pain, fever, and abdominal discomfort, with laboratory parameters often showing elevated inflammatory markers 3, 5.
• Radiological investigations, such as ultrasonography and CT, are essential for diagnosing and managing psoas abscess 2, 3, 5.

Management and Outcomes of Psoas Abscess

• A multimodal approach using MRI for diagnosis and CT for drainage guidance is recommended for managing psoas abscess 2.
• Percutaneous drainage and antibiotic therapy are effective treatment approaches for psoas abscess, with low complication rates and high success rates reported in several studies 3, 5.
• Open drainage may be required in some cases, particularly for larger or more complex abscesses 3, 5.
• The prognosis for psoas abscess is generally good, with low mortality rates and high rates of symptomatic and radiological improvement reported in several studies 3, 4, 5.