Pubic Osteomyelitis Identified on Follow-Up MRI Following Adductor Myositis in a Patient With Escherichia coli Bacteremia.

A previously healthy 54-year-old man presented with a high-grade fever and bilateral groin pain. Initial non-contrast imaging failed to identify an infectious focus, while blood cultures revealed the presence of Escherichia coli. Pelvic MRI on hospital day 5 demonstrated bilateral adductor brevis myositis without osseous involvement. Despite antimicrobial therapy, symptoms persisted. Follow-up MRI on hospital day 13 revealed new pubic bone marrow edema, confirming a diagnosis of pubic osteomyelitis. The patient was successfully treated with a 12-week course of antimicrobial therapy, resulting in clinical resolution. This case illustrates a key diagnostic challenge in gram-negative bacteremia: musculoskeletal infections can evolve dynamically, and early imaging may underestimate the extent of the disease. The anatomical continuity between muscle and bone enables the contiguous spread of infection. In this case, symptom-guided follow-up MRI was instrumental in detecting delayed bone involvement and optimizing treatment decisions. Clinicians should consider interval imaging when initial studies are inconclusive and symptoms persist.