Background: A 26-year-old woman presented at the emergency department with a painful abdomen and fever up to 39°C, despite antibiotics. She had given prematurely birth by caesarian section to a twin 8 days earlier. On clinical examination she had a diffuse painful and tender abdomen, especially on the right side and suprapubic region. Laboratory findings showed an increased c-reactive protein of 24 mg/dL (normal < 0,3) and increased white blood cell count of 13 × 10E9/L (normal 4,3-10 × 10E9/L). There was also a decreased hemoglobin level of 8,4 g/dL (normal 12- 15 g/dL). An ultrasonography was performed by the gynecologist and revealed a large heterogeneous fluid collection anteriorly of the uterus.