Abscess pulsatility: a sonographic sign of osteomyelitis.

Introduction: Early diagnosis and aggressive treatment of acute osteomyelitis may improve prognosis and prevent further complications. Sonography is useful in the evaluation of osteomyelitis. It can demonstrate early signs of inflammation, such as soft tissue changes near the affected bone, periosteal thickening, periosteal elevation, and subperiosteal abscess.

Case presentation: A 68-year-old female presented to the emergency department with 3 weeks of worsening left lower extremity pain. She was initially seen by urgent care for left shin erythema and swelling and treated for cellulitis with intramuscular ceftriaxone without improvement. On presentation, she was afebrile and hemodynamically stable with erythema, swelling, and tenderness of the left pretibial soft tissues. Her labs revealed leukocytosis and elevated inflammatory markers. Point-of-care ultrasound demonstrated a bidirectional flow of fluid through a disruption in the bone cortex visualized on greyscale imaging and confirmed with color and spectral Doppler. The patient was diagnosed with osteomyelitis and treated with antibiotics and incision and drainage by orthopedic surgery.

Discussion: The unique sonographic finding of pulsatile flow of fluid within an abscess near bone has not been previously described in the literature. The presence of Doppler signal in any fluid other than blood is known as pseudoflow. The presence of pulsatility in this case, which could represent either blood or pseudoflow, drew the ultrasound operator's eye to the cortical defect and lead to the diagnosis of osteomyelitis.

Conclusions: The sonographic finding of pulsatility in an abscess near bone should raise the concern for communication with the medullary cavity.