Iliopsoas Abscess

1. Clinical findings:

· Usually occur more often in younger pts (adolescents, young adults); more common in males

· Back, abdominal or flank pain

· Fever

· Can present with an inguinal mass (if deep extension)

· “psoas sign”= pain with extension of the hip (whereas hip flexion usually exacerbates inflammation within the hip joint)

· Symptoms can be sub-acute, lasting weeks-months before diagnosis

· Can mimic intraperitoneal and retroperitoneal processes

 

 

2.  Location: think about where the muscle is located...

· Iliopsoas muscle is actually 2 muscles: the iliacus and the psoas muscle

· psoas muscle:  arises from the transverse processes and the lateral aspects of the T12 & L5, passes deep to the inguinal ligament and anterior to the hip joint.  Then forms a tendon that inserts into the lesser trochanter of the femur

· iliacus muscle: starts at the iliac crest, joins the psoas to insert via the same tendon. The iliacus and psoas muscles are the main hip flexors.

· The iliopsoas compartment is an extraperitoneal space which contains the iliopsoas muscles.

· The tendon is separated from the hip capsule by the iliopsoas bursa, which communicates with the hip joint in up to 15 percent of people

· Adjacent structures include: vertebral bodies, pelvic bones, GI tract (sigmoid colon, appendix), GU tract, abd aorta, hip joints etc.

 

 

3. Primary vs. Secondary infection:

· Psoas abscesses may arise via hematogenous spread (primary) or contiguous spread (secondary)

· Primary abscesses occur from hematogenous spread: risk factors include immunosuppression (HIV, DM, etc.), trauma/hematoma, IVDU

· Secondary abscesses occur via contiguous spread from a nearby source of infection, including those arising in the vertebral bodies, GI tract, GU tract, abdominal aorta, hip joints, etc.

· Microbiology: Primary: in endemic areas, TB is a common cause; staph is most common bacterial cause. Secondary: polymicrobial, enteric gram negatives

 

 

4. Management:

· Blood cultures (+ in ~50% of cases) & aspiration of abscess fluid for organism identification

· Gram stain and culture, AFB when high risk for TB or if gram stain neg

· Definitive drainage: percutaneous vs. surgical

· If secondary abscess, treatment of adjacent infection is also essential

· Abx: if early aspiration is not possible, empiric tx with coverage for MRSA+ enteric

 

 

5. Outcomes:

· Serious morbidity and mortality (can present as septic shock in 20%, mortality is ~10%); risk factors for poor outcome include: delayed diagnosis, inadequate tx, bacteremia, E. Coli infxn

· Relapse is common (20-30% of cases)

 

(Victoria Kelly MD, 11/8/10)