Effect of multisite radiofrequency ablation on porcine renal function.

BACKGROUND AND PURPOSE: The acute and long-term effects of radiofrequency ablation (RFA) on kidney function have not been well studied. The functional change when RFA is used in combination with renal ischemia is likewise unknown. Our goal was to determine the change in renal function caused by various volumes of RFA on a porcine kidney model and the effect cold ischemia had on the results. MATERIALS AND METHODS: Twenty-two female pigs with solitary kidneys underwent various volumes of RFA both with and without cold ischemia. Animals were divided into control, 10%, 15%, and 20% ablation of the total kidney volume. Measurements of creatinine were obtained for 2 weeks. RESULTS: In the nonischemic group, the mean acute (day 1-3) creatinine changes in control, 10%, 15%, and 20% ablations were 0.6, 2.4, 1.7, and 2.6 mg/dL, respectively. In the cold-ischemia group, the mean acute creatinine changes were 0.85, 2.33, 3.3, and 3.75 mg/dL, respectively. Regression line analysis demonstrated a positive linear relationship in both groups. Fourteen-day mean creatinine changes for the nonischemic group were similar to those in the control animals and did not show a correlation with ablation volume. The mean creatinine changes at 14 days in the cold-ischemia group showed a positive linear correlation with ablation volume. CONCLUSIONS: The volume of RFA correlates with an acute change in renal function in the porcine model for both nonischemic and cold-ischemia groups. This study may help predict the extent of acute renal dysfunction in patients undergoing RFA for large or multiple renal masses. These results also suggest renal function may recover after nonischemic RFA.

Assessment of basic human performance resources predicts performance of ureteroscopy.

BACKGROUND: Our objective was to predict endoscopic performance in a cadaver model using basic performance resources (BPRs) measurements. METHODS: Medical students (n = 16) underwent intense ureteroscopic training on a virtual reality ureteroscopy trainer and were rated on performing ureteroscopy on a cadaver. The medical students also underwent 13 validated BPR measurements. Urology residents also performed cadaveric ureteroscopy and BPRs. A predictive model built from urology residents' (n = 16) BPRs and performance assessment was used to predict medical student cadaveric ureteroscopy performance based on their BPRs alone. RESULTS: The predictive model built with urology residents predicted the ureteroscopic performance of 10 of 16 medical students within 15% of their rated ureteroscopic performance on the cadaver. CONCLUSIONS: A predictive model built with urology residents can moderately predict the ureteroscopic performance of medical students from BPRs. Additional in vivo evaluation is required.

Ureteral replacement using small-intestinal submucosa and a collagen inhibitor in a porcine model.

PURPOSE: Small-intestinal submucosa (SIS) has been successful as an onlay graft in ureteral repair, but tubularized segment interposition of SIS has been unsuccessful. Our objective was to evaluate whether a type I collagen inhibitor, halofuginone, would prevent stricture formation in tubularized SIS interposition. MATERIALS AND METHODS: We performed either laparoscopic partial ureteral excision followed by an SIS onlay graft (N = 5) or complete laparoscopic ureteral excision followed by an SIS interposition graft (N = 7) in domestic pigs. Animals received either no (N = 3), low-dose (N = 5), or high-dose (N = 4) halofuginone. Animals had ureteral stenting for 2 weeks after surgery and were permitted to survive for 6 or 9 weeks. An intravenous urogram (IVU) was performed prior to sacrifice. Kidneys were examined grossly and histologically. RESULTS: One animal that received an onlay graft died of an unrelated illness. The remaining four ureteral onlay animals, including one control and two low-dose and one high-dose pig, had grossly normal kidneys at harvest. The IVU was normal in the control and high-dose animal but showed delayed excretion with mild hydroureteronephrosis in the low-dose animals. Pathologic examination of the SIS site revealed circumferential reepithelialization with inflammation and mild fibrosis. All seven tubularized interposition graft kidneys demonstrated either severe hydroureteronephrosis (N = 5) or renal atrophy (N = 2), and all had complete obstruction on IVU. Pathologic examination revealed a stenotic ureteral lumen with extensive surrounding inflammation and fibrosis. CONCLUSIONS: An SIS onlay graft was successful in the porcine model of ureteral injury. Halofuginone, a type I collagen inhibitor, did not demonstrate a significant beneficial effect in this technique. Ureteral tubularized interpositions with SIS are unsuccessful and not improved by halofuginone.

Virtual ureteroscopy predicts ureteroscopic proficiency of medical students on a cadaver.

PURPOSE: Training on a virtual reality (VR) simulator has been shown to improve the performance of VR endoscopic tasks by novice endoscopists. However, to our knowledge the translation of VR skills into clinical endoscopic proficiency has not been demonstrated. We established criterion validity for a VR ureteroscopy simulator by evaluating VR trained subjects in a cadaver model. MATERIALS AND METHODS: A total of 32 participants, including 16 medical students and 16 urology residents, were evaluated at baseline on a VR ureteroscopy simulator (Uromentor, Simbionix, Lod, Israel), performing simple diagnostic ureteroscopy. The students then underwent 5 hours of supervised training on the simulator. Two weeks later all participants were reevaluated (VR2) on the simulator when repeating the initial task. Each participant was then assessed on the performance of a similar diagnostic ureteroscopy in a male cadaver. RESULTS: In medical students VR2 and cadaver performances correlated closely for several measured parameters (total time for task completion and overall global ratings score). In contrast, there was little correlation between the 2 performances in residents. Indeed, performance on the cadaver correlated more closely with the training level than VR2 scores. Despite VR training medical students were unable to perform cadaver ureteroscopy comparably to residents. CONCLUSIONS: For novice endoscopists performance on the simulator after training predicted operative (cadaver) performance and, thus, it may be useful for the education and assessment of physicians in training. However, VR training is unable to override the impact of clinical training, although it may help shorten the learning curve early in training.

Assessment of basic human performance resources predicts the performance of virtual ureterorenoscopy.

PURPOSE: Regardless of training, innate ability may influence the acquisition of endoscopic skills. Until recently objective methods to assess innate ability have not been available. We compared objective measures of human basic performance resources (BPRs) using nonlinear causal resource analysis (NCRA) and expert rated endoscopic performance of medical students on a virtual reality (VR) simulator. MATERIALS AND METHODS: BPRs were measured in 18 medical students (group 1) using 13 validated tests. BPR results were compared to the results of ureteroscopic skills assessment on the VR simulator. An NCRA model was devised to predict performance based on BPRs and the limiting performance resource (LPR). The same BPRs were measured in a second group of 14 medical students (group 2). Using the model created from group 1 performance of VR ureterorenoscopy was predicted based on LPR for each student in group 2. Predicted performance was compared to rated performance. RESULTS: The average difference in score between 2 expert raters was 7.2%. The average difference in predicted score based on the NCRA model and rated score was only 8.0%. In 9 of the 14 group 2 subjects (63%) the performance prediction by NCRA was in excellent agreement (+/-10%) with the expert rating on the VR simulation. NCRA over predicted performance in 2 subjects (14%) and under predicted performance in 3 (21%). CONCLUSIONS: Objective prediction of ureteroscopic performance in the VR environment using LPRs (measures of innate ability) for each subject is possible and practical using new measurement and modeling methods. The selection of surgical candidates, training and the educational curriculum could be impacted.

Use of a virtual reality simulator for ureteroscopy training.

PURPOSE: Virtual reality surgical simulators may shorten operative time and reduce the potential for iatrogenic injury by providing training outside the operating room. We hypothesized that training on a virtual ureteroscopy (VU) simulator would allow novice endoscopists to overcome the initial learning curve before entering the operating room. MATERIALS AND METHODS: We evaluated 16 medical students on their ability to perform specific ureteroscopic tasks on a VU simulator. The students trained on the simulator for a total of 5 hours over multiple sessions using different training modules and then were retested on the initial module. Likewise, 16 urology residents with varying degrees of endoscopic experience were assessed on the same test module twice, without additional simulator training. RESULTS: The students improved task completion time from 17.4 to 8.7 minutes (p <0.05), while the residents performed the task in 7.6 minutes at baseline and 6.7 minutes at the second trial. Stratification of residents by years of urology training revealed that the mean completion time for the students after training did not differ statistically from that of first year residents who had performed a median of 14 clinical ureteroscopies. Furthermore, the subjective performance scores of the students were comparable to those of the first year residents. CONCLUSIONS: Novice medical students trained on a VU simulator improved task completion time by 50% after training, and performed comparably to residents who had completed nearly 1 year of urology training. VR training may allow beginning urology residents to shorten the initial learning curve associated with ureteroscopy training, although this hypothesis requires further validation.

Sutureless laparoscopic heminephrectomy using laser tissue soldering.

BACKGROUND AND PURPOSE: Widespread application of laparoscopic partial nephrectomy has been limited by the lack of a reliable means of attaining hemostasis. We describe laser tissue welding using human albumin as a solder to control bleeding and seal the collecting system during laparoscopic heminephrectomy in a porcine model. MATERIALS AND METHODS: Laparoscopic left lower-pole heminephrectomy was performed in five female domestic pigs after occluding the hilar vessels. Using an 810-nm pulsed diode laser (20 W), a 50% liquid albumin-indocyanine green solder was welded to the cut edge of the renal parenchyma to seal the collecting system and achieve hemostasis. Two weeks later, an identical procedure was performed on the right kidney, after which, the animals were sacrificed and both kidneys were harvested for ex vivo retrograde pyelograms and histopathologic analysis. RESULTS: All 10 heminephrectomies were performed without complication. The mean operative time was 82 minutes, with an average blood loss of 43.5 mL per procedure. The mean warm ischemia time was 11.7 minutes. For each heminephrectomy, a mean of 4.2 mL of solder was welded to the cut parenchymal surface. In three of the five acute kidneys and all five 2-week kidneys, ex vivo retrograde pyelograms demonstrated no extravasation. In addition, no animal had clinical evidence of urinoma or delayed hemorrhage. Histopathologic analysis showed preservation of the renal parenchyma immediately beneath the solder. DISCUSSION: Laser tissue welding provided reliable hemostasis and closure of the collecting system while protecting the underlying parenchyma from the deleterious effect of the laser during porcine laparoscopic heminephrectomy.

Laparoscopic application of radio frequency energy enables in situ renal tumor ablation and partial nephrectomy.

PURPOSE: To our knowledge we present the initial series of renal mass in situ laparoscopic radio frequency ablation. We also discuss the indications for and results of subsequent laparoscopic partial nephrectomy. MATERIALS AND METHODS: Laparoscopic radio frequency ablation was performed in 13 patients with a mean age of 59 years (range 18 to 81) and a total of 17 small enhancing renal masses. In 5 patients the tumor was subsequently excised completely, whereas in 7 it was left in situ after treatment. In 1 patient with 5 lesions only the largest lesion was excised, while the other 4 were left in situ. RESULTS: Mean tumor size was 1.96 cm. (range 0.9 to 3.6). Tumors that remained in situ tended to be endophytic and located in the mid pole. Pathological analysis revealed renal cell carcinoma in 10 patients, angiomyolipoma in 2 and oncocytoma in the patient with multiple lesions. None of the 8 patients with renal cell carcinoma who had at least 6 weeks of followup (mean 9.8 months, range 1.5 to 22) had any evidence of persistent tumor enhancement on surveillance computerized tomography or any other evidence of disease progression. There was 1 focal positive margin in a patient who underwent radio frequency ablation and excision of renal cell carcinoma but the patient remained disease-free 1 year after treatment. CONCLUSIONS: Early experience with laparoscopic radio frequency ablation in situ or combined with partial nephrectomy shows that it appears to be a safe method of managing small enhancing renal masses. Radio frequency assisted laparoscopic partial nephrectomy is reserved for easily accessible exophytic tumors, while strict surveillance is required for lesions remaining in situ after ablation. Additional followup is required to assess long-term effectiveness.

Percutaneous radiofrequency ablation of renal tumors: technique, limitations, and morbidity.

OBJECTIVES: To evaluate our evolving experience with percutaneous radiofrequency (RF) renal tumor ablation and focus on our technique to ensure maximal treatment efficacy and reduce the possibility of complications. METHODS: Fifteen patients with small (less than 4 cm) posterior or lateral contrast-enhancing (more than 10 Hounsfield units) renal tumors were candidates for RF treatment. Of these patients, 12 (13 tumors) received computed tomography-guided percutaneous RF ablation. General anesthesia was administered in all but our first 2 patients, who received intravenous sedation. After treatment, patients were closely followed up with computed tomography scans at 6 weeks and 3, 6, and 12 months, and every 6 months thereafter. Successful ablation was defined as a lesion along with a margin of normal parenchyma that no longer enhanced (less than 10 Hounsfield units) on follow-up contrast imaging. RESULTS: The mean tumor size was 2.4 +/- 0.6 cm. The average procedure time was 95 minutes (range 60 to 150) and length of stay 0.9 days. All patients underwent the procedure without any major complications. At a mean follow-up of 4.9 months, 12 (93%) of 13 tumors were successfully ablated. In 3 patients, the procedure was not performed because of intervening bowel or lung parenchyma when positioned in the prone position before the procedure. Computed tomography-guided percutaneous RF ablation of small renal tumors is a viable minimally invasive treatment option with a high short-term success rate and low morbidity. This new technology must be uniformly applied to assess its long-term efficacy.