Ovarian vein thrombosis
While this case is certainly not mind-blowing, it is a very nice example of thrombosis of the right gonadal/ovarian vein: a dilated vein with a central low-attenuation filling defect. This likely accounted for the patient's presentation with dull abdominal pain. It would have been possible to miss this finding if the radiologists had not seen a few such cases in the past. Much of being a successful radiologist is knowing the imaging appearance of the basic anatomy you learned in medical school: the right gonadal vein goes to the IVC and the left gonadal vein to the renal vein.
Gonadal vein thrombosis is frequently managed with anticoagulation like deep vein thrombosis of the limbs, as the patient is at risk for pulmonary embolism if left untreated.