Background: Wilms tumor tends to grow into vena cava, even invade atrium, which increased operating difficulty and frequency of surgical complications.

Methods: Forty-two patients of Wilms tumor with intravenous thrombus were retrospective studied. The diagnosis and therapy were discussed according to the medical records and interrelated literatures.

Results: Forty-two children with thrombus were diagnosed by computed tomography and 41 cases by ultrasound simultaneously. 36 children had received preoperative chemotherapy. Surgical resection was performed in all patients. Cardiopulmonary bypass was used for the removal of the intra-atrial thrombus in 5 patients. There were no surgical complications occurred. The patients received chemotherapy and radiotherapy according to clinical staging by National Wilms’ Tumor Study (NWTS)-4 or NWTS-5. 34 patients were successfully followed up, 32 patients survive at present, including one who has been followed up more than 20 years since operation.