<Brief
History>
A 82 year-old man was admitted due to left lower quadrant
abdominal pain for two weeks.
This man was healthy until two weeks ago, he began to
suffer from left lower quadrant abdominal pain. Two days
later, he began to notice that the pain became severe when
walking. Meanwhile, low grade fever was found by his family.
He visited local medical doctor and osteoarthritis with
radiculopahty was told. NSAIDs were given to relieve his pain
at that time. After days of medical treatment, his condition
deteriorated and he became bed-redden and was sent to a
medical center. Physical examination showed left lower
quadrant tenderness. The pain became more severe especially
when his left leg was elevated. Initial laboratory revealed
leukocytosis with neutrophilia (WBC: 19.2x103
, neutrophil: 90%). Other
laboratory examinations including urine analysis, serum biochemistry study did not
reveal specific abnormality. Under the impression of
septic arthritis and/or diverticulitis, antibiotics were given. Series of
X ray study including KUB, hip joint, abdominal echo
did not revealed any abnormalities.
However, after two days
of treatment, his condition became worse, spiking fever developed
and his blood pressure became unstable. He received emergent
abdominal MRI examination and the result showed left psoas
abscess. (fig. 1
)
Emergent operation to drain the abscess was performed. Areas
of wild-extended necrotic muscle and an intramuscular abscess
were found on surgical exploration. Purulent material was
drained and the culture yielded Staphylococcus aureus.
Appropriate antibiotic therapy was started, and the patient
recovered rapidly.
Fig. 1 Cross sectional magnetic resonance imaging of the
pelvis showing abnormal signal intensity of the psoas muscle.
<Discussion>
The cause of primary psoas abscess remains uncertain.
Proposed mechanisms of psoas abscess formation include
haematogenous spread from primary infectious foci or local
trauma with intramuscular haematoma formation predisposing to
abscess development. In secondary psoas abscess the most
commonly associated disorder is Crohn's disease; other
disorders include appendicitis, colonic inflammation or
neoplasm, disc infections, and a variety of intra-abdominal or
retroperitoneal infections. Primary psoas abscesses are caused
by Staphylococcus aureus (88.4%), streptococci (4.9%), and
Escherichia coli (2.8%). In the past decade the majority of
patients with a primary psoas abscess were intravenous drug
users or infected with the human immunodeficiency virus.
Pain with flexion and external rotation of the affected hip
is the most common physical finding. A tender palpable mass
may be found in the iliac fossa and inguinal area. Fifty per
cent of patients have abdominal tenderness, but guarding and
rebound tenderness are uncommon. Because of the non-specific
pain location, the diagnosis of psoas abscess may be delayed
or missed. Differentiation between psoas abscess and hip
pathology can be difficult; however, prudent physical
examination of the hip can be useful. Laboratory studies are
non-specific and typically show leucocytosis, anaemia, a
raised erythrocyte sedimentation rate, and, usually, normal
urine analysis.
Plain abdominal radiographs occasionally define an outline
of the inflammatory mass. Chest radiographs may disclose
minimal pleural effusion or raised hemidiaphragm. An
intravenous pyelogram may show deviation of the kidney and
ureter. However, the most accurate diagnostic imaging is CT or
MRI, which typically show a low density lesion of the psoas
muscle and gas within the muscle itself. Definitive diagnosis
is made by fine needle aspiration under imaging guidance, and
microbial culture of the causative organism. Gallium-67
scanning may be useful in the diagnosis of psoas abscesses and
detection of concomitant infectious foci.
Treatment for primary psoas abscess includes percutaneous
drainage combined with systemic antibiotic administration.
Surgical drainage is preferred for the patients in whom the
psoas abscess is associated with underlying bowel disease.
With appropriate treatment, psoas abscess rarely results in
death (2.5%). Death from psoas abscess is associated more
commonly with inadequate or delayed drainage, or both.
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