Methylene blue-guided parenchyma-sparing ex vivo resection and autotransplantation for a type III renal arteriovenous fistula with large renal vein aneurysm: A technical case report.

High-flow renal arteriovenous malformations (AVMs), type III with vein aneurysms, are rare and often require nephrectomy. A 54-year-old man presented with lumbar pain and hematuria. Computed tomography angiography revealed an 8- × 12-cm right renal vein aneurysm and a type III arteriovenous fistula occupying >30% of the kidney. After ex vivo nephrectomy with cold perfusion, selective methylene blue injection delineated the AVM nidus and parenchyma, guiding resection and excision. The procedure was performed by a multidisciplinary team including a vascular surgeon, transplant surgeon, and urologist. The kidney was reconstructed and reimplanted. Postoperative creatinine levels stabilized at 1.10 mg/dL, and computed tomography angiography confirmed AVM exclusion and preserved perfusion. Methylene blue mapping can enable parenchyma-sparing repair in selected cases.