We report a rare case of an isolated and unsuspected thrombosis in the right internal iliac vein. The presentation was atypical with regard to the clinical manifestations and the thrombus location. The patient was admitted for an acute abdominal pain in the right iliac fossa. The thrombosis was suspected on the basis of a portal-phase contrast-enhanced abdominal CT but the lack of a delayed phase did not allow confirmation. Contrast-enhanced ultrasound confirmed the diagnosis, by displaying a well-defined filling defect.