Psoas abscess

Background

Psoas major and nearby muscles.

Horizontal disposition of the peritoneum in the lower part of the abdomen, showing psoas major.

Primary infection
- Psoas muscle is susceptible to infection from distant sites due to rich blood supply, proximity to overlying retroperitoneal lymphatic channels
Secondary infection
- Direct spread/extension via adjacent infection
- S. aureus is most common pathogen (80%)

Clinical Features

Late finding of a large psoas abscess progressing to visible left buttock mass with erythematous skin eruption.

Abdominal pain radiating to hip, flank
Pain with thigh flexion (esp against resistance)
Limp
Fever
Nausea
Back pain^[1]

Differential Diagnosis

Hip pain

Acute Trauma

Femur fracture
- Proximal
  - Intracapsular
    - Femoral head fracture
    - Femoral neck fracture
  - Extracapsular
    - Intertrochanteric femur fracture
    - Trochanteric femur fracture
- Shaft
  - Mid-shaft femur fracture (all subtrochanteric)
Hip dislocation
Pelvic fractures

Chronic/Atraumatic

RLQ Pain

GI
- Appendicitis
  - Perforated appendicitis
- Peritonitis
- Crohn's disease (terminal ileitis)
- Diverticulitis (cecal, Asian patients)
- Inguinal hernia
- Mesenteric ischemia
- Ischemic colitis
- Meckel's diverticulum
- Neutropenic enterocolitis (typhlitis)
GU
Other

Evaluation

Psoas muscle abscess on CT.

(A) Abdominal computed tomography, revealing abscess formation on the left psoas muscle, which was depicted as a localized low density area. (B) Magnetic resonance imaging shows multiseptated psoas abscess and gluteal abscess.

Work Up^[2]

Lab Studies

CBC
Chem-10
Lactic
Blood cultures

CT abdomen/pelvis with contrast (imaging study of choice)^[3]
MRI has higher sensitivity (if available)^[4]
Lower accuracy with US
MRI or US preferred in pregnant patients

Diagnosis

Typically on imaging

Management

Antibiotics
- Vancomycin plus
- Piperacillin/tazobactam 3.375g, OR
- Ceftriaxone + Metronidazole
Ultimate treatment is surgical drainage: Surgery or IR consultation

References

↑ Dietrich A, Vaccarezza H, and Vaccaro CA. “Iliopsoas abscess: presentation, management, and outcomes,” Surgical Laparoscopy, Endoscopy & Percutaneous Techniques, vol. 23, no. 1, pp. 45–48, 2013.
↑ Shields D, Robinson P, Crowley TP. “Iliopsoas abscess—a review and update on the literature,” International Journal of Surgery. 2012; 10(9): 466–469.
↑ Hosn S. Psoas muscle abscess. Radiology Reference Article. Radiopaedia.org. Radiopaediaorg. 2015. Available at: http://radiopaedia.org/articles/psoas-muscle-abscess. Accessed May 21, 2015.
↑ Hosn S. Psoas muscle abscess. Radiology Reference Article. Radiopaedia.org. Radiopaediaorg. 2015. Available at: http://radiopaedia.org/articles/psoas-muscle-abscess. Accessed May 21, 2015.

Authors:

[1] Dietrich A, Vaccarezza H, and Vaccaro CA. “Iliopsoas abscess: presentation, management, and outcomes,” Surgical Laparoscopy, Endoscopy & Percutaneous Techniques, vol. 23, no. 1, pp. 45–48, 2013.

[2] Shields D, Robinson P, Crowley TP. “Iliopsoas abscess—a review and update on the literature,” International Journal of Surgery. 2012; 10(9): 466–469.

[3] Hosn S. Psoas muscle abscess. Radiology Reference Article. Radiopaedia.org. Radiopaediaorg. 2015. Available at: http://radiopaedia.org/articles/psoas-muscle-abscess. Accessed May 21, 2015.

[4] Hosn S. Psoas muscle abscess. Radiology Reference Article. Radiopaedia.org. Radiopaediaorg. 2015. Available at: http://radiopaedia.org/articles/psoas-muscle-abscess. Accessed May 21, 2015.

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Psoas abscess

Contents

Background

Clinical Features