Presentation
Right lower abdominal pain with tenderness, fever and leukocytosis. Had appendectomy 15 years prior.
Patient Data
Multiloculated fluid collection of the right iliacus muscle (volume ~ 90 mL). It displays an iso- to high signal to the normal muscles on T1, high signal on T2 and STIR with peripheral enhancement, fat stranding and thickening with enhancement of the adjacent peritoneal reflections. Edematous infiltration of the right erector spinae and quadratus lumborum muscles as well as the internal oblique and transversus abdominis muscles (myositis).
Case Discussion
MRI features most consistent with iliacus muscle abscess.
Ultrasound-guided percutaneous drainage was performed with aspiration of 80 cc of frank pus and sent for microbiological analysis.
Psoas muscle abscess may be classified as primary or secondary depending on the presence or absence of underlying disease:
primary psoas muscle abscess: can occur in patients with diabetes mellitus, intravenous drug use, AIDS, renal failure or immunosuppression
secondary psoas muscle abscess: from appendicitis, diverticulitis, Crohn's disease, perforated colon carcinoma, or neighboring spondylodiscitis
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