title: Bipolar radiofrequency ablation of the kidney: comparison with monopolar radiofrequency ablation.
abstract: OBJECTIVE
  We report initial ex vivo and in vivo studies using bipolar radiofrequency (RF) ablation of porcine kidneys. An internal ground electrode is positioned in the kidney opposite the RF electrode, resulting in ablation of all the intervening renal tissue.
  
  
  METHODS
  Ex vivo preparations of 10 porcine kidneys were perfused continuously with Ringer's solution and treated with either standard external grounded RF (N = 3) or bipolar RF ablation with 1 (N = 2), 2 (N = 3), or 3 (N = 2) cm of separation between the ground probe and the RF probe using a Model 30 RITA generator (RITA, Mountain View, CA). Target temperatures were 90 degrees C for 8 minutes. Gross and histologic assessments were made acutely. Four domestic pigs were treated with monopolar RF ablation of the lower pole of one kidney and bipolar RF with a 12-mm separation between the probes of the contralateral lower pole. Animals were harvested 48 hours later to maximize tissue damage for gross measurements and histologic evaluation.
  
  
  RESULTS
  Ex vivo studies revealed grossly monopolar lesions 1.5 cm in maximum diameter and 1.75 cm(3) in volume. In comparison, bipolar lesions were 2.8 cm in maximum diameter and 10.3 cm(3) in volume using 3 cm of electrode separation. There was histologic evidence of cell death in all specimens. In vivo studies showed two distinct gross lesions with RF: one blanched and one hemorrhagic. Using bipolar RF, larger blanched lesions were achievable than with monopolar RF (2.80 cm(3) v 1.63 cm(3)). Overall, the combinations of blanched and hemorrhagic lesions were similar with monopolar and bipolar RF (5.01 v 5.31 cm(3)). Histologic evaluation verified cell death in the blanched lesions and rare areas of normal tissue in the hemorrhagic lesions.
  
  
  CONCLUSIONS
  As shown by ex vivo data, bipolar RF can create larger lesions than does monopolar RF. In vivo, at 48 hours, both blanched and hemorrhagic gross lesions were seen using RF. In this model, blanched lesions predominated when performing bipolar RF.
authors.affiliation: Department of Surgery, Division of Urology, University of Wisconsin Medical School, G5/339 Clinical Science Center, 600 Highland Avenue, Madison, WI 53792-3236, USA. nakada@surgery.wisc.edu
authors.forename: Stephen Y
authors.initials: SY
authors.lastname: Nakada
authors.forename: Travis J
authors.initials: TJ
authors.lastname: Jerde
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Warner
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Wright
authors.forename: Dieter
authors.initials: D
authors.lastname: Haemmerich
authors.forename: David M
authors.initials: DM
authors.lastname: Mahvi
authors.forename: Fred T
authors.initials: FT
authors.lastname: Lee
mesh_terms: D000818:Animals; D017115:Catheter Ablation / Q000009:adverse effects / Q000379:methods*; D046508:Culture Techniques; D004566:Electrodes; D005260:Female; D007150:Immunohistochemistry; D007668:Kidney / Q000473:pathology* / Q000601:surgery*; D008297:Male; D023421:Models, Animal; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D034421:Sus scrofa