Postpartum intramuscular abscess of the biceps femoris in a patient with a history of intravenous drug use

Postpartum soft-tissue infections are uncommon and rarely involve deep intramuscular sites. We present a case of a 28-year-old postpartum woman, a woman with a history of intravenous drug use, who developed a swollen, painful, and warm right thigh two weeks after giving birth. Noncontrast CT and US demonstrated a large intramuscular fluid collection within the biceps femoris, with thick walls and surrounding inflammatory changes. Contrast-enhanced MRI confirmed a liquefactive intramuscular abscess showing high signal on DWI and low signal on ADC without bone marrow edema or signs of necrotizing fasciitis. Femoral and popliteal veins were patent, excluding deep vein thrombosis. Prompt surgical drainage and antibiotic therapy led to full recovery. This case underscores the clinical relevance of considering intramuscular abscesses in postpartum women with sepsis or localized thigh pain and highlights the diagnostic value of MRI, particularly DWI/ADC sequences, for accurate characterization and exclusion of osteomyelitis or necrotizing fasciitis.