Potency of real-time virtual sonography for the preoperative evaluation of invasion in nephroblastoma.

Fusion with a real-time virtual sonography system is an ultrasonography fusion technology with magnetic position navigation. We present a case of a left nephroblastoma successfully resected using real-time virtual sonography for tumor margin assessment and excision boundary determination. A 2-year-old girl presented with fever and abdominal distension. Contrast-enhanced computed tomography revealed a large heterogeneous mass (90 × 75 × 125 mm3) in the left kidney. Needle biopsy confirmed nephroblastoma. Chemotherapy with vincristine and actinomycin was initiated according to the International Society of Pediatric Oncology Wilms Tumor 2001 guidelines. Subsequent computed tomography revealed that the tumor size decreased to 45 × 25 × 63 mm3; however, margins with adjacent muscles remained unclear, indicating potential invasion beyond Gerota's fascia. Real-time virtual sonography evaluation revealed a single fat layer separating the tumor from the muscle groups, showing tumor regression to the medial side of Gerota's fascia, with visible respiratory movements on ultrasonography. Left nephrectomy, including Gerota's fascia, was performed, preserving the abdominal wall muscles. Pathology confirmed that the tumor had penetrated the renal capsule but was completely resected with clear margins. The postoperative diagnosis was high-risk stage II blastemal type nephroblastoma, prompting chemotherapy on postoperative day 12. During the 5-year follow-up, no recurrence was observed. Real-time virtual sonography is a valuable adjunct for detailed preoperative evaluation when computed tomography alone is inadequate, facilitating precise tumor margin assessment and successful surgical outcomes.