Porcine Kidney Model Research Articles

New ex vivo organ model for percutaneous renal surgery using a laparoendoscopic training box: the sandwich model

Percutaneous renal surgery (PRS) is a challenging procedure for urologic surgeons and requires a large variety of different skills. Our objective was to improve the preexisting porcine kidney-training model for percutaneous renal access and PRS. For our biologic training model, we use porcine kidneys with preserved ureter. The ureter was dissected, stones were placed into the collecting system using a 16, 5F Amplatz sheath, and a 12Ch indwelling catheter was placed in the ureter for further irrigation with blue-dyed saline. The kidney was placed between two porcine full-thickness skin lobes in an existing laparoscopy trainer (SITUS Box). The kidney was punctured with ultrasound guidance, and minimally invasive percutaneous nephrolithotomy (MIP) was then performed as previously described. The model was evaluated in MIP training courses, which are regularly held at the Hannover Medical School. All trainees were urologists with experience in endourologic surgery. Eleven participants were trained in this model. Percutaneous puncture under ultrasonographic guidance and following intrarenal surgery was successful in all 11 (100 %) cases. Therefore, all participants rated the model useful for simulating percutaneous renal surgery. Compared to recently published models, this new porcine kidney model is easy to prepare and is cost-effective by using standard material. Moreover, it provides realistic and reproducible practice for PRS in the laboratory. Unfavorably, the described organ model requires an existing laparoscopy training system. Comprehensively, the presented organ model approximates the natural retroperitoneal circumstances precisely by using the two full-thickness skin flaps with the fatty subcutaneous tissue.

Targeting and Recanalization after Embolization with Calibrated Resorbable Microspheres versus Hand-cut Gelatin Sponge Particles in a Porcine Kidney Model

PurposeTo report on polyethylene glycol hydrogel-based resorbable embolization microspheres (REM) that were synthesized to resorb in < 24 hours, before inflammation and vascular remodeling, to achieve a complete arterial recanalization and to compare targeting and recanalization of REM of 300–500 µm, 500–700 µm, and 700–900 µm with hand-cut gelatin sponge particles (GSP). Materials and MethodsEight pigs underwent polar renal artery embolization with REM or GSP. Angiograms were obtained before embolization and 10 minutes and 7 days after embolization before pigs were sacrificed to determine the occlusion level, the percentage of occlusion, and the recanalization rate for each product. The distribution of embolic material was assessed in pathology, and infarction rate of the kidneys was measured. ResultsREM of 300–500 µm occluded more distal vessels than REM of 500–700 µm and 700–900 µm. At day 7, the recanalization rate was complete for the larger REM, whereas it was about 60% for the two smaller sizes. REM were completely degraded, with no residual material or inflammation. GSP occluded more proximal arteries than REM of 700–900 µm, were partly degraded at day 7, and were accompanied by a foreign body reaction in proximal and distal arteries. GSP recanalized at 79%. The infarction rate was higher with the two smaller sizes of REM and with GSP than with the largest REM. ConclusionsREM of different sizes targeted different occlusion levels in kidney arteries. GSP provided an extended occlusion level without actual targeting. Regardless of embolic material used, angiographic recanalization of renal arteries depended on the extent of necrosis. REM of 700–900 µm demonstrated the lowest infarction rate and the best recanalization rate.

Determination of tissue injury thresholds from ultrasound in a porcine kidney model

Therapeutic ultrasound has an increasing number of applications in urology, including shockwave lithotripsy, stone propulsion, tissue ablation, and hemostasis. However, the threshold of renal injury using ultrasound is unknown. The goal of this study was to determine kidney injury thresholds for a range of intensities between diagnostic and ablative therapeutic ultrasound. A 2 MHz annular array generating spatial peak pulse average intensities (ISPPA) up to 30,000 W/cm2 in water was placed on the surface of in vivo porcine kidneys and focused on the adjacent parenchyma. Treatments consisted of pulses of 100 μs duration triggered every 3 ms for 10 min at various intensities. The perfusion-fixed tissue was scored by three blinded independent experts. Above a threshold of 20,000 W/cm2, the majority of injury observed included emulsification, necrosis, and hemorrhage. Below this threshold, almost all injury presented as focal cell and tubular swelling and/or degeneration. These findings provide evidence for a wide range of potentially therapeutic ultrasound intensities that has a low probability of causing injury. While this study did not examine all combinations of treatment parameters of therapeutic ultrasound, tissue injury appears dose-dependent. [Work supported by NIH DK43881, DK092197, and NSBRI through NASA NCC 9-58.]

A Prospective Analysis of Robotic Tip Cover Accessory Failure

The robotic monopolar scissors tip cover accessory (TCA) is an insulation device that prevents current leak from surfaces on the instrument other than the scissors tip. Reports of insulation failure and patient injury have been made but not systematically studied. We investigate the incidence of TCA failure and potential mechanisms that lead to malfunction. Eighty TCAs (40 first and 40 second generation) were collected after a single urologic or gynecologic surgery at a single academic institution. Each TCA was inspected for damage under a microscope. Current leak was measured in an electrolysis solution, and electrical arcing was tested in a porcine kidney model. Log-rank and Friedman two-way analysis of variance by ranks compared failure at different angulations and power settings. Chi-square analysis compared failure between first and second generation TCAs (f-TCAs and s-TCAs). Visible insulation defects were detected in 39% of f-TCAs (size range <0.5-2.75 mm). Electrical arcing was observed in 33% of f-TCAs. Arcing increased with greater wrist angulation (P=0.014) and higher power settings (P=0.048). Minor damage was observed in 25% of s-TCAs. No electrical arcing was observed in any of the s-TCAs despite angulation and power strain. s-TCAs demonstrated significantly less failure than f-TCAs (P<0.001). In this study, 33% of f-TCAs demonstrated insulation failure after a single surgical use. f-TCA failure increased with greater wrist angulation and electrical power. The improved design of s-TCAs demonstrated no current leak or arcing on ex-vivo testing and appears to have significantly decreased failure potential. Centers still using the f-TCA should transition to the s-TCA and be vigilant in reporting device failures to prevent unnecessary patient morbidity.

Radiofrequency ablation in a porcine kidney model: effect of occlusion of the arterial blood supply on ablation temperature, coagulation diameter, and histology

Radiofrequency ablation (RFA) is susceptible to the cooling effect of flowing blood. The reduced efficacy of RFA in large tumors reflects the in vivo biophysiological limitations imposed by perfusion-mediated vascular cooling. To compare the effects of RFA alone and of RFA combined with occlusion of the arterial blood supply on the tissue temperature, coagulation diameter, and histological changes in the acute phase. The temperature at roll-off, the coagulated tissue diameter, and histologic tissue changes were compared in normal porcine kidneys subjected in situ to two pigs each were subjected to RFA alone (four kidneys) or to RFA plus balloon occlusion of the renal artery (four kidneys). The tissue temperature was measured at three sites: area I, the center of the RFA field; area II, the ischemic field 1 cm distant from the edge of the RFA field; and area III, the normal kidney. Tissue samples were stained with hematoxylin and eosin (H&E). Cell viability in the ablated zone was determined by nicotinamide adenine dinucleotide (NADH) staining of frozen sections. The tissue temperatures achieved by RFA in areas I, II, and III were 101°C, 58°C, and 40°C with and 92°C, 44°C, and 38°C without balloon occlusion, respectively. The maximal coagulation diameter was 31 mm with and 23 mm without occlusion. The coagulation diameter was significantly larger and the temperature in area II was significantly higher in kidneys subjected to RFA with renal artery occlusion. H&E staining showed preservation of the normal renal parenchymal structure outside the thermal lesion and an increase in eosinophilic cells with indistinct cell borders and nuclei within the thermal lesion. H&E and NADH staining demonstrated a sharp demarcation between the ablation and normal tissue area and showed that in area II the addition of balloon occlusion did not produce histologic changes different from those in kidneys subjected to RFA alone. A technique that combines RFA and partial renal artery occlusion may be useful in treatment of the non-resectable renal tumors with sizes appropriate for RF ablation.

Use of an ex-vivo porcine kidney model to compare the blood loss of different size of nephrostomy tracts

Objective To compare the blood loss of different size of nephrostomy tracts in percutaneous nephrolithotomy (PCNL).Methods The model of isolated normal saline ( NS)-perfused porcine kidney was used to determine the blood loss of different size of nephrostomy tracts.By applying the technique of percutaneous nephrostomy,five groups of different size of nephrostomy tracts ( 16,18,22,24,30 F) were established on the porcine kidney gradually,with 10 tracts in every group,then the blood loss of each group was measured respectively.Results The blood loss of the five tracts ( 16,18,22,24,30 F)was (5.84±0.98),(5.99±0.85),(9.76±1.05),(11.90±1.49),(14.48±1.30) g/min,respectively.The blood loss was increased with the size of the tract diameter ( P ＜ 0.05 ).There was no significant difference between 16 F and 18 F groups ( P ＞ 0.05 ).Conclusion The blood loss of PCNL was increased with the size of the nephrostomy tracts.Mini-PCNL could cause less bleeding than standard-PCNL. Key words: Percutaneous nephrolithotomy; Bleeding; Renal access

Pilot Study Evaluation of Standard Laparoscopic Suturing and a Novel Parenchymal Apposition Mechanism for Minimally Invasive Renal Reconstruction

The most technically demanding portion of a laparoscopic partial nephrectomy is the renorrhaphy. The purpose of this study was to determine whether a parenchymal apposition mechanism (PAM) device would be as effective as standard laparoscopic technique (SLT) with respect to efficiency, capability, and safety of renal defect closure. In this pilot study, participants were recruited to perform surgical reconstruction of a standardized renal parenchymal defect with both SLT and the PAM. The PAM prototype was engineered using two salmon egg hooks connected by absorbable suture and placed within a V-shaped foam delivery mechanism. After hook placement, tensioning of the connecting suture using a Weck clip apposed the defect edges. Each participant performed a single closure with SLT and with the PAM device of a standardized defect in ex vivo porcine kidneys. Closure time, tissue trauma/damage during closure, and the intraparenchymal pressure were recorded. A total of 13 subjects, 7 medical students, 3 residents, 2 fellows, and 1 attending were enrolled. There was no statistical difference between the two methods of closure in average time for closure. In a subgroup analysis of subjects who had performed laparoscopic reconstructive procedures as the primary surgeon, SLT was significantly faster than PAM (P=.036). Mean pressures achieved in attempted closure using SLT and PAM were not significantly different (0.38 N for both groups; P=.99). The mean parenchymal trauma rating was not significantly different between the groups; however, the upper limit of the range of trauma ratings was greater in the standard closures. This pilot study demonstrated the feasibility of PAM use in an ex vivo porcine kidney model. Additional testing and continued design modifications are necessary to explore its use in laparoscopic reconstruction of the kidney and other organs.

New ex-vivo organ model for percutaneous renal surgery

Percutaneous Renal Surgery (PRS) is a demanding procedure and success is mostly hampered by the lacking of training facilities. Thus, the purpose of the study was to evaluate a significantly improved pre-existing porcine kidney-training model for percutaneous renal access and PRS. A biologic training model using porcine kidneys coated by a full-thickness porcine skin flap was prepared. The ureter was dissected, stones were placed into the collecting system using an 18F amplatz sheath, and a catheter was placed in the ureter for further irrigation with saline or contrast medium. For initial training with an easy access, a standard guide-wire was inserted in the ureter through the renal parenchyma. The kidney was punctured with radiographic or ultrasound guidance. Minimally invasive percutaneous nephrolithotomy (MIP) was then tested using the model under radiographic or ultrasound guidance. The model was then evaluated in MIP training courses, which are regularly held at The Hannover Medical School. All trainees were urologists with experience in endourologic surgery but lacked practice in PRS. In conclusion, all 36 participants attained access to the collecting system using models with readily placed guide-wires. Subsequently, PRS was successful in all cases. Percutaneous puncture under ultrasound guidance and following intrarenal surgery was successful in 30 (83.3%) cases. Therefore, all participants rated the model useful for simulating percutaneous renal surgery. This new porcine kidney model is easy to build and is made cost effective by using readily available material. Moreover, it provides realistic and reproducible training model for PRS. The "organ" model mimics the retroperitoneum by having a full-thickness skin flap with a layer of subcutaneous fatty tissue.

A novel ex vivo model For percutaneous renal surgery

Objective To lessen the learning curve of percutaneous renal lithotripsy(PCNL),we introduced a novel ex-vivo learning and training model for PCNL under fluoroscopy and ultrasonography-guided access. Methods The model was set up nailing an adult porcine kidney with＞3 cm ureter (freshly removed from the slaughtering factory),with a full thickness flap of the thoracic wall or abdomen wall with two ribs,to a board.The porcine kidney was placed within the flap with the catheterized ureter outside.The kidney was enclosed by the flap so as to create a roodel for percutaneous renal surgery;with the ribs overlying the upper portion of the kidney.The model was fixed to the board by two nails.Artificial stone material was implanted in the renal pelvis.Fluoroscopy guidance access:Retrograde pyelography via injection of contrast medium into the ureteral catheter images the collecting system. After the long axis of the target calyx is identified,the C-arm is rotated 30 degrees toward the surgeon,placing the C-arm axis in the same posterior plane of the kidney.The needle is advanced in the plane of the fluoroscopic beam,and the appropriate needle placement is determined by obtaining a bull's-eye sign on the fluoroscope screen. Rotating the C-arm to a vertical position monitors the depth of the needle penetration. Ultrasonography guidance access:The renal pelvis can he filled with normal saline through a catheter to simulate hydronephrosis and the target calyx is identified under ultrasonography guidance.The tract dilation and stone disintegration were followed.After training,the kidney can be opened to examine the target calyx and the complication of dilation. Results Altogether,126 urologists attended a urologic endoscopic technique training course.Of the 126 trainees,104 (82.5%) successfully performed the whole percutaneous procedure.At the end of training,114 (90.5 %) of the 126 attendees rated the porcine kidney model for simulation of percutaneous renal surgery as very helpful or helpful.Conclusions This biological training model simulates realistically the clinical procedure of PCNL with respect to trainee experience in a low stress environment that provides an opportunity for repetitive performances in order to learn basic technical skills for the clinical procedure of PCNL in the future. Key words: Percutaneous nephrolithotomy; Models,anatomic; Training programs

Hypothermic machine perfusion after static cold storage does not improve the preservation condition in an experimental porcine kidney model

Combining hypothermic techniques, as a more practical approach to preservation, may enhance the condition of kidneys donated after cardiac death. Porcine kidneys were retrieved after 10 min in situ warm ischaemia, then preserved by either 18 h static cold storage (CS), hypothermic machine perfusion for 18 h (HMP) or 14 h static CS followed by 4 h HMP (4HMP). Kidneys were reperfused for 3 h with oxygenated autologous blood on an isolated organ perfusion system to assess renal function and injury. Intrarenal resistance was significantly higher in the 4HMP group than in the CS and HMP groups: mean(s.d.) area under the curve (AUC) 8·48(2·97), 3·41(1·80) and 3·78(1·68) mmHg/min.h respectively (P = 0·011). Creatinine clearance was lower after 4HMP and CS: AUC 2·3(0·6) and 2·2(1·7) ml per min per 100g.h respectively versus 9·8(7·3) ml per min per 100g.h in the HMP group (P = 0·022). Levels of endothelin 1 were higher in the 4HMP and CS groups: mean(s.d.) 21·6(4·0) and 24·2(2·3) pg/ml respectively versus 11·4(4·6) pg/ml in the HMP group (P = 0·002). Morphological damage was increased in the 4HMP group. This porcine kidney study demonstrated no advantage to the addition of 4 h of HMP after CS.

Efficiency Analysis of Bipolar and Multipolar Radiofrequency Ablation in an In Vivo Porcine Kidney Model Using Three-Dimensional Reconstruction of Histologic Section Series

Radiofrequency ablation (RFA) was established for minimally invasive treatment of small kidney tumors in multimorbid patients. Bipolar and multipolar RFA may allow the treatment of larger tumors. Safe tumor coagulation depends on total energy supplied and proper electrode placing. To investigate the influence of energy on ablation size and shape in intact kidneys, we used cooled bipolar and multipolar RFA in an in vivo pig model. Twenty-five male pigs were treated with percutaneous bipolar (one electrode) or multipolar (two electrodes) RFA with various energy transfer under laparoscopic visual control. The animals were sacrificed 4 to 5 hours after RFA. Volume and shape of the coagulation zone was analyzed by three-dimensional reconstruction of hematoxylin and eosin and diaminobenzidine stained paraffin serial sections. Heat-induced cellular activation was addressed by immunohistologic detection of apoptosis marker proteins heat shock protein 70 (Hsp70) and caspase-3 (Casp3). Multipolar RFA led to significant larger tissue ablation than bipolar RFA. Increasing energy, however, did not result in significant enlargement of the coagulation volume. Shape control was better in bipolar RFA. Hsp70 and activated Casp3 immunoreactivity were increased close to the central coagulation zone and occasionally in the caliceal system. RFA causes minimal tissue damage beyond the primary coagulation zone, indicating that RFA is a safe, minimally invasive method for treatment of renal tumors. The ablation of larger volumes necessitates further improvement of multipolar RFA. These findings may be of general interest, because treatment failure correlates with mass size in monopolar RFA and cryoablative techniques as well.

Normothermic kidney preservation

Kidneys from marginal or donation after cardiac death (DCD) donors are particularly susceptible to injury during hypothermic preservation and may benefit from alternative methods of preservation. Normothermic preservation can be adapted to improve the quality of kidneys for transplantation by a variety of techniques. Extracorporeal membrane support to maintain circulation before cooling and organ retrieval has been used to improve the condition of DCD donor kidneys, with lower rates of delayed graft function (DGF) compared with standard retrieval conditions. Experimentally, normothermic perfusion has been used in conjunction with hypothermic techniques as a resuscitation technique to improve graft outcome. An ex-vivo porcine kidney model showed that energy levels could be replenished to improve tissue perfusion during reperfusion. This technique was translated into a porcine transplant model demonstrating that it was a feasible and safe method of preservation. Normothermic preservation techniques have the potential to be adapted into an improved method of retaining tissue viability compared with hypothermic techniques. Furthermore, they may be used as a device to enhance and assess the condition of the kidney which would be particularly beneficial for kidneys from DCD donors.

Perfusion Storage Reduces Apoptosis in a Porcine Kidney Model of Donation After Cardiac Death

Donation after cardiac death (DCD) kidneys suffer a high incidence of delayed graft function attributable to warm ischemia and cold ischemia (CI). Neither the mechanism of injury nor type of cell death has been described. Clinical studies suggest that perfusion storage (PS) of DCD kidneys may reduce injury although the mechanism of protection is unknown. In a porcine model of DCD, we hypothesized that DCD kidneys have increased caspase-1 due to warm ischemia (WI) and increased caspase-3 and apoptosis due to CI. Male Yorkshire pigs subjected to cardiac death were perfused with cold University of Wisconsin solution. The perfused kidneys were removed and stored in cold University of Wisconsin solution for 24 hr. Kidney biopsies were obtained before cardiac death and at 0 and 24 hr of CI. There was an increase in caspase-1 activity due to WI before cold preservation. CI was associated with a massive increase in apoptosis, caspase-3/7 activity, and caspase-3 protein expression. Next, we hypothesized that PS would protect against apoptosis. We compared DCD kidneys subjected to static versus PS for 24 hr. PS significantly reduced proximal tubular apoptosis and was associated with increased B-cell lymphoma-extra large, and hypoxia-inducible transcription factor-1α. These findings suggest that in DCD kidneys, WI preferentially activates caspase-1, whereas CI activates caspase-3 and causes apoptosis. PS may protect DCD kidneys through activation of antiapoptotic pathways involving B-cell lymphoma-extra large and hypoxia-inducible transcription factor-1α.

Diffusing-wave spectroscopy with dynamic contrast variation: disentangling the effects of blood flow and extravascular tissue shearing on signals from deep tissue

We investigate the effects of blood flow and extravascular tissue shearing on diffusing-wave spectroscopy (DWS) signals from deep tissue, using an ex vivo porcine kidney model perfused artificially at controlled arterial pressure and flow. Temporal autocorrelation functions g(1)(τ) of the multiply scattered light field show a decay which is described by diffusion for constant flow, with a diffusion coefficient scaling linearly with volume flow rate. Replacing blood by a non-scattering fluid reveals a flow-independent background dynamics of the extravascular tissue. For a sinusoidally driven perfusion, field autocorrelation functions g(1)(τ, t′) depend on the phase t′ within the pulsation cycle and are approximately described by diffusion. The effective diffusion coefficient Deff(t′) is modulated at the driving frequency in the presence of blood, showing coupling with flow rate; in the absence of blood, Deff(t′) is modulated at twice the driving frequency, indicating shearing of extravascular tissue as the origin of the DWS signal. For both constant and pulsatile flow the contribution of extravascular tissue shearing to the DWS signal is small.

Renal Artery Embolization Combined With Radiofrequency Ablation in a Porcine Kidney Model: Effect of Small and Narrowly Calibrated Microparticles as Embolization Material on Coagulation Diameter, Volume, and Shape

The purpose of this study was to evaluate the effect of renal artery embolization with small and narrowly calibrated microparticles on the coagulation diameter, volume, and shape of radiofrequency ablations (RFAs) in porcine kidneys. Forty-eight RFAs were performed in 24 kidneys of 12 pigs. In 6 animals, bilateral renal artery embolization was performed with small and narrowly calibrated microparticles. Upper and lower kidney poles were ablated with identical system parameters. Applying three-dimensional segmentation software, RFAs were segmented on registered 2mm-thin macroscopic slices. Length, depth, width, volume_segmented, and volume_calculated were determined to describe the size of the RFAs. To evaluate the shape of the RFAs, depth-to-width ratio (perfect symmetry-to-lesion length was indicated by a ratio of 1), sphericity ratio (perfect sphere was indicated by a sphericity ratio of 1), eccentricity (perfect sphere was indicated by an eccentricity of 0), and circularity (perfect circle was indicated by a circularity of 1) were determined. Embolized compared with nonembolized RFAs showed significantly greater depth (23.4±3.6 vs. 17.2±1.8mm; p<0.001) and width (20.1±2.9 vs. 12.6±3.7mm; p<0.001); significantly larger volume_segmented (8.6±3.2 vs. 3.0±0.7ml; p<0.001) and volume_calculated (8.4±3.0ml vs. 3.3±1.1ml; p<0.001); significantly lower depth-to-width (1.17±0.10 vs. 1.48±0.44; p<0.05), sphericity (1.55±0.44 vs. 1.96±0.43; p<0.01), and eccentricity (0.84±0.61 vs. 1.73±0.91; p<0.01) ratios; and significantly greater circularity (0.62±0.14 vs. 0.45±0.16; p<0.01). Renal artery embolization with small and narrowly calibrated microparticles affected the coagulation diameter, volume, and shape of RFAs in porcine kidneys. Embolized RFAs were significantly larger and more spherical compared with nonembolized RFAs.

A Comparison of Running Suture Versus Figure-8 Sutures as the Initial Step in Achieving Hemostasis During Laparoscopic Partial Nephrectomy

During laparoscopic partial nephrectomy, the importance of the initial suture placed under warm ischemic conditions cannot be underestimated. Inadequate hemostasis may lead to further surgical complications. Our goal was to determine which method of suture ligation (running vs figure-8 interrupted) provides better initial hemostasis when performing partial nephrectomy in an ex-vivo porcine model. Deep partial nephrectomy defects were cut in the lateral aspect of six porcine kidneys. The renal artery was cannulated, and the kidneys were perfused from a water reservoir. The level (cm H(2)O) at which parenchymal leakage occurred was measured and recorded in three situations: No parenchymal suture; running suture along the base of the defect; and interrupted figure-8 sutures placed in parallel along the base of the defect. Six kidneys were studied. Using interrupted figure-8 sutures, the mean leak pressure was 56.7 cm H(2)O (over baseline). Using a running suture, the mean leak pressure was 147.5 cm H(2)O (over baseline). Mean values were compared using two-tailed t test and found to be statistically significant (P = 0.05). In an ex-vivo porcine kidney model, use of a running suture along the base of a renal tumor defect (simulating that which is seen during partial nephrectomy) appears to allow for better initial hemostatic control, as compared with interrupted figure-8 sutures placed in parallel.

Microwave Ablation versus Radiofrequency Ablation in the Kidney: High-power Triaxial Antennas Create Larger Ablation Zones than Similarly Sized Internally Cooled Electrodes

To determine whether microwave ablation with high-power triaxial antennas creates significantly larger ablation zones than radiofrequency (RF) ablation with similarly sized internally cooled electrodes. Twenty-eight 12-minute ablations were performed in an in vivo porcine kidney model. RF ablations were performed with a 200-W pulsed generator and either a single 17-gauge cooled electrode (n = 9) or three switched electrodes spaced 1.5 cm apart (n = 7). Microwave ablations were performed with one (n = 7), two (n = 3), or three (n = 2) 17-gauge triaxial antennas to deliver 90 W continuous power per antenna. Multiple antennas were powered simultaneously. Temperatures 1 cm from the applicator were measured during two RF and microwave ablations each. Animals were euthanized after ablation and ablation zone diameter, cross-sectional area, and circularity were measured. Comparisons between groups were performed with use of a mixed-effects model with P values less than .05 indicating statistical significance. No adverse events occurred during the procedures. Three-electrode RF (mean area, 14.7 cm(2)) and single-antenna microwave (mean area, 10.9 cm(2)) ablation zones were significantly larger than single-electrode RF zones (mean area, 5.6 cm(2); P = .001 and P = .0355, respectively). No significant differences were detected between single-antenna microwave and multiple-electrode RF. Ablation zone circularity was similar across groups (P > .05). Tissue temperatures were higher during microwave ablation (maximum temperature of 123 degrees C vs 100 degrees C for RF). Microwave ablation with high-power triaxial antennas created larger ablation zones in normal porcine kidneys than RF ablation with similarly sized applicators.

Preliminary evaluation of a novel side‐fire diode laser emitting light at 940 nm, for the potential treatment of benign prostatic hyperplasia: ex‐vivo and in‐vivo investigations

To evaluate, ex vivo and in vivo, the tissue-removal capacity and coagulation properties of a diode laser emitting light at 940 nm, as in the search for potential therapeutic strategies for benign prostatic hyperplasia that cause less morbidity than transurethral resection of the prostate (TURP), various types of lasers have been tested. A diode laser system (prototype; wavelength 940 nm, Dornier MedTech, Wessling, Germany) was evaluated in an isolated, blood-perfused ex-vivo porcine kidney model at 10-60 W (five kidneys). An in-vivo beagle model was used to investigate the effects on six prostate lobes at a generator output power level of 200 W. After the laser treatment tissue were examined histologically to compare the depth of coagulation and vaporization. With increasing generator output power levels there was an increasing vaporization and coagulation ability for the diode laser at 940 nm in the ex-vivo model. At 60 W the mean (sd) vaporization depth was 1.72 (0.47) mm with a coagulation zone of 9.56 (0.26) mm. In vivo, the diode laser caused rapid ablation with no intraoperative haemorrhage. Histologically, the zone of coagulation had a mean (sd) depth of 4.25 (0.15) mm at 200 W. The tissue removal capacity was estimated at 0.874-1.583 g/min in vivo. Our findings indicate that diode-laser vaporization at 940 nm is feasible and might be effective for acutely relieving bladder outlet obstruction in an in-vivo setting. Due to its mean coagulation zone of 4.25 mm the diode laser seems to have effective haemostatic properties.

High Intensity Focused Ultrasound Renal Tissue Ablation: A Laparoscopic Porcine Model

High intensity focused ultrasound for renal lesions is still experimental. In a porcine model we evaluated the safety and efficacy of a newly designed laparoscopic high intensity focused ultrasound probe and software that allows real-time ultrasound guidance during renal tissue ablation. A Sonatherm 600 high intensity focused ultrasound system with a newly designed laparoscopic high intensity focused ultrasound probe was used through a standard Endopath 18 mm port. A total of 16 lesions were created in 15 kidneys in a total of 8 animals and randomized into 2 groups, including acute with sacrifice 4 days postoperatively and subacute with sacrifice 14 days postoperatively. Lesion size and location varied for each surgical procedure to simulate various treatment scenarios. Mean +/- SD planned ablation volume was 7.1 +/- 5.1 cc and mean treatment time was 7.2 +/- 06.88 minutes. For all lesions an injury volume was observed with a central zone of complete necrosis and no viable tissue. Mean total injury volume was 6.5 + 3.5 cc (range 1.1 to 13.7), comparable to preoperative mean planned ablation volume (p = 0.84). Mean necrosis volume was 4.89 +/- 2.9 cc (range 0.8 to 10.5), appreciably lower than preoperative mean planned ablation volume (p = 0.33). Presence of the collecting system interposed with the treatment region did not impact the injury volume-to-planned ablation volume ratio or the necrosis volume-to-planned ablation volume ratio. No animals died before study completion. Two intraoperative complications occurred, including a back wall musculature burn and a ureteral burn. Laparoscopic high intensity focused ultrasound for renal tissue using the newly developed probe was feasible and efficacious. The ability to perform renal high intensity focused ultrasound through an 18 mm laparoscopic port offers a new alternative for renal tumor ablation.

Ex vivo and in vivo investigations of the novel 1,470 nm diode laser for potential treatment of benign prostatic enlargement

Perioperative haemorrhage is still the major complication of transurethral resection of the prostate (TURP) for benign enlargement of the prostate. Photoselective vaporisation of the prostate (PVP) with the potassium-titanyl-phosphate (KTP) laser has been shown to achieve instant tissue ablation with excellent haemostatic properties. Our aim was to determine the tissue removal capacity, coagulation and haemostatic property of the novel 1,470 nm diode laser, ex vivo and in vivo. We evaluated two prototype diode laser systems at 1,470 nm in an ex vivo, isolated, blood-perfused, porcine kidney model (n = 5; 10 W-50 W) and in an in vivo investigation of beagle prostate (n = 4; 100 W) to assess vaporisation capacities and coagulation properties at different generator settings. The diode laser evaluation was compared with an 80 W KTP laser in the porcine model. After the laser treatment we performed a histological examination to compare the depth of coagulation and vaporisation. The diode laser system (50 W) showed significantly lower (P < 0.0001) capacities for tissue removal than the 80 W KTP laser (0.96 mm +/- 0.17 mm and 5.93 mm +/- 0.25 mm, respectively, P < 0.0001), while coagulation zones were significantly (P < 0.001) larger in diode laser-treated kidneys (3,39 mm +/- 0.93 mm and 1.27 mm +/- 0.13 mm, respectively). In vivo, the diode laser displayed rapid ablation of prostatic tissue with no intraoperative haemorrhage. Histological examination revealed coagulation zones of 2.30 mm (+/-0.26) at 100 W in the diode laser-treated prostates.