3477: Primary pyomyositis in children: Sonographic appearance

Abstract

Objectives: Primary pyomyositis is rare, subacute, deep bacterial infection of skeletal muscle not associated with contiguous infection of the skin, bone or soft tissues. Most common in first to second decades of life, male predominance. Methods: Fourteen children (mean age 8.2y) diagnosed and successfully treated for primary pyomyositis are presented with emphasis on imaging, especially sonographic evaluation. Sites of infection were iliopsoas, obturator, hip adductors, levator scapula, thoracolumbar paraspinal and gastrocnemius muscles. The imaging modalities involved were plain radiographs, isotope scans, ultrasonography, CT and MRI. The follow up studies were mainly ultrasound. Results: Sonographic findings included thickening and hypoechogenicity along affected muscles, fluid collections between muscle fibers c/w abscess formation and required drainage. Iliopsoas and hip muscles when involved were associated with hip effusion. The infection resolved completely in 11 patients; one patient developed acute compartment syndrome of the calf and later osteonecrosis of the tibial shaft. Conclusions: US was helpful for detection of pyomyositis, for percutaneous drainage, for ruling out bony involvement and for routine monitoring until full recovery.