Case Discussion <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. 繼續教育考題 1. (A) Which of the following pathogens are most often found in patients with primary psoas abscess? A Staphylococcus aureus B Streptococci group C Escherichia coli D Klebsiella pneumonia 2. (C) Which of the following symptoms are the most frequently presented in patients with psoas abscess? A Abdominal tenderness B Tender palpable mass C Pain with flexion and external rotation of the affected hip D Fever 3. (E) Which of the following factors are risks for developing psoas abscess? A Diabetes mellitus B Previous trauma C HIV virus infection D Drug abusers E All of the above 4. (B) Which of the image diagnostic modality is the most accurate in detecting psoas abscess? A Ultrasonography B CT or MRI C Gallium-67 scanning D Plan abdominal radiographs 5. (A) Which of the following is the most frequent etiology of secondary psoas abscess in western countries? A Crohn's disease B Appendicitis C Colonic inflammation or neoplasm D Retroperitoneal infections 6. (B) Which of the following treatment strategy is the most effective for primary psoas abscess? A Surgical drainage only B Percutaneous drainage combined with systemic antibiotic administration C Systemic antibiotic administration D None of above 7. (D) Which of the following statement regarding to diagnosis of psoas abscess is NOT TRUE? A Plain abdominal radiographs occasionally define an outline of the inflammatory mass B Gallium-67 scanning may be useful in the diagnosis of psoas abscess and detection of concomitant infectious foci C Definitive diagnosis is made by fine needle aspiration under imaging guidance, and microbial culture of the causative organism D None of above 8. (A) Which of the following statement regarding to treatment of psoas abscess is NOT TRUE? A Surgical drainage is not preferred for the patients in whom the psoas abscess is associated with underlying bowel disease B With appropriate treatment, psoas abscess rarely results in death C Death from psoas abscess is associated more commonly with inadequate or delayed drainage, or both D None of above 9. (E) Which of the following statement should be taken as differential diagnosis of psoas abscess? A Epidural abscess B Septic arthritis of hip joint C Diverticulitis D Focal myocitis E All of above 10. (D) Which of the following statement regarding laboratory examinations of psoas abscess is FALSE? A Leucocytosis with raised erythrocyte sedimentation rate is often detected B Anaemia may be noted C Urine analysis usually is normal D Elevated CK/CKMB is frequently noted

答案解說 (A) (C) (E) (B) (A) (B) (D) (A) Surgical drainage is preferred for the patients in whom the psoas abscess is associated with underlying bowel disease (E) (D) CK/CKMB usually is not elevated