Idiopathic and spontaneously regressing thrombus in right renal vein and inferior vena cava.

We present the case of a 57-year-old woman with a thrombus in the right renal vein and the inferior vena cava that disappeared spontaneously during 6 months of observation. She had no thrombus-related disease such as kidney cancer, dehydration, multiple myeloma, nephrotic syndrome, or abnormal coagulability. While various examinations were being performed over a 2 month period the thrombus regressed spontaneously. After 6 months of follow-up the thrombus could not be seen on abdominal computerized tomography scan. Twenty months after disappearance of the thrombus the patient is doing well and has no recurrence of thrombus.