An in vivo evaluation of a novel spiral cut flexible ureteral stent.

OBJECTIVE: The flow characteristics, ureteral conformance, and histopathologic changes of a novel spiral cut flexible ureteral stent (Percuflex Helical, Boston Scientific, Boston, MA) were evaluated in vivo in an acute and chronic porcine model. MATERIALS AND METHODS: Flow characteristics and ureteral conformance of the novel stent were determined in 6 acute and 6 chronic swine models and compared with a control ureteral stent (Percuflex Plus, Boston Scientific). The flow characteristics were determined in vivo after ligating the renal vessels and via a nephrostomy tube delivering a standard rate of 0.9% saline at 35 cm H(2)O. Flows in the unobstructed ureter, normal stent, intraluminally obstructed stent, extraluminal obstructed stent, and both intraluminally and extraluminally obstructed conditions were determined. In the chronic animals, flow was determined at day 10, with the stent in place and immediately after stent removal. Conformance and hydronephrosis was assessed on pyelograms. Histopathologic changes were also evaluated in the chronic animals. RESULTS: The acute and chronic flow characteristics in the novel stent were equivalent to the control stent. Size and weight of the kidney, degree of hydronephrosis, stent migration, and presence of urinary tract infection were also similar between the test and control stents. There were no differences seen in histopathologic grading or degree of encrustation in either stent. The novel stent appeared to conform better to the shape of the ureter in both acute and chronic animals. CONCLUSION: The novel helical stent appears to drain as well as a standard stent and causes no increased degree of histopathologic changes in the ureter.

Are multiple cryoprobes additive or synergistic in renal cryotherapy?

OBJECTIVE: To investigate the relationship between multiple cryoprobes was investigated to determine whether they work in an additive or synergistic fashion in an in vivo animal model because 1.47 mm (17-gauge) cryoprobes have been introduced to the armamentarium for renal cryotherapy. METHODS: Laparoscopic-guided percutaneous cryoablation was performed in both renal poles of 3 pigs using 3 IceRod cryoprobes. These 12 cryolesions were compared with 12 cryolesions using a single IceRod cryoprobe. Each cycle consisted of two 10-minute freeze cycles separated by a 5-minute thaw. The iceball volume was measured using intraoperative ultrasonography. The kidneys were harvested, and cryolesion surface area was calculated. The lesions were fixed and excised to obtain a volume measurement. Statistical analysis was used to compare the single probe results multiplied by 3 to the multiple probe group for iceball volume, cryolesion surface area, and cryolesion volume. RESULTS: The iceball volume for the first freeze cycle for the single cryoprobe multiplied by 3 was 8.55 cm3 compared with 9.79 cm3 for the multiple cryoprobe group (P=.44) and 10.01 cm3 versus 16.58 cm3 for the second freeze (P=.03). The cryolesion volume for the single cryoprobe multiplied by 3 was 11.29 cm3 versus 14.75 cm3 for the multiple cyroprobe group (P=.06). The gross cryolesion surface area for the single cryoprobe multiplied by 3 was 13.14 cm2 versus 13.89 cm2 for the multiple probe group (P=.52). CONCLUSION: The cryolesion created by 3 simultaneously activated 1.47-mm probes appears to be larger than that of an additive effect. The lesions were significantly larger as measured by ultrasonography and nearly so (P=.06) as measured by the gross cryolesion volume.

Optimal freeze cycle length for renal cryotherapy.

PURPOSE: To our knowledge the optimal freeze cycle length in renal cryotherapy is unknown. Ten-minute time based freeze cycles were compared to temperature based freeze cycles to -20C. MATERIALS AND METHODS: Laparoscopic renal cryotherapy was performed on 16 swine. Time based trials consisted of a double 10-minute freeze separated by a 5-minute thaw. Temperature based trials were double cycles of 1, 5 or 10-minute freeze initiated after 1 of 4 sensors indicated -20C. A 5-minute active thaw was used between freeze cycles. Control trials consisted of cryoneedle placement for 25 minutes without freeze or thaw. Viability staining and histological analysis were done. RESULTS: There was no difference in cellular necrosis between any of the temperature based freeze cycles (p = 0.1). Time based freeze cycles showed more nuclear pyknosis, indicative of necrosis, than the 3 experimental freeze cycles for the renal cortex (p = 0.05) but not for the renal medulla (p = 0.61). Mean time to -20C for freeze cycle 1 was 19 minutes 10 seconds (range 9 to 46 minutes). In 4 of 21 trials (19%) -20C was never attained despite freezing for 25 to 63 minutes. CONCLUSIONS: There was no difference in immediate cellular necrosis among double 1, 5 or 10-minute freeze cycles. Cellular necrosis was evident on histological analysis for trials in which -20C was attained and in freeze cycles based on time alone. With a standard 10-minute cryoablation period most treated parenchyma 1 cm from the probe never attained -20C. Cell death appeared to occur at temperatures warmer than -20C during renal cryotherapy.

Robotic pyeloplasty: the University of California-Irvine experience.

PURPOSE: For the treatment of ureteropelvic junction obstruction laparoscopic dismembered pyeloplasty and open pyeloplasty have similar outcomes. We present our experience with robot assisted laparoscopic dismembered pyeloplasty. MATERIALS AND METHODS: We retrospectively reviewed all adult robot assisted laparoscopic dismembered pyeloplasties performed at our institution between November 2002 and July 2009. Preoperative evaluation included abdominal computerized tomography angiogram to assess for crossing vessels and diuretic renal scan to quantify the degree of obstruction. Followup with diuretic renal scan and a patient pain analog scale was performed 3, 6 and 12 months after surgery. If the study was normal at 12 months, the patient was followed with ultrasound of the kidneys and bladder to look for ureteral jets. Absent ureteral jets, worsening hydronephrosis or patient complaint of pain necessitated repeat diuretic renogram. RESULTS: A total of 61 robot assisted laparoscopic dismembered pyeloplasties were performed in 21 men and 40 women. Followup was available for 57 patients with an average ± SD age of 35 ± 16 years and average followup of 18 ± 15 months. Mean operative time was 335 ± 88 minutes and estimated blood loss was 61 ± 48 ml. Average hospitalization time was 2 ± 0.9 days and the average postoperative analgesia requirement was 13 ± 9.6 mg morphine sulfate equivalents. The overall success rate was 81% based on a normal diuretic renogram and lack of pain using a validated pain scale. There were 3 grade III Clavien complications for a 4.9% major complication rate. CONCLUSIONS: Robot assisted laparoscopic dismembered pyeloplasty is a feasible technique for ureteropelvic junction reconstruction. When measured by the more stringent application of diuretic renography and analog pain scales, the success rate for ureteropelvic junction obstruction management appears similar to that of open or standard laparoscopic approaches.

A novel ex-vivo ureteral apparatus for assessing the impact of intraluminal pharmaceutical agents on ureteral physiology.

BACKGROUND AND PURPOSE: Safe intraluminal access to the ureter and kidney is essential for endourologic procedures. Pharmacologic manipulation of ureteral smooth muscle could conceivably ease access and decrease morbidity. To minimize systemic effects, local intraluminal administration would be optimal, but the urothelium presents a barrier to the passage of medications. We present a novel ex-vivo apparatus and technique to measure ureteral peristalsis and assess drug diffusion. MATERIALS AND METHODS: Excised 3-cm pieces of porcine or human ureters were placed inside a specially designed apparatus that allows separate manipulation of the intra- and extraluminal environments while measuring peristalsis. Intraluminal antegrade perfusion was maintained by a reservoir. A pressure transducer was placed at the inflow end of each ureter segment. After equilibration, phenylephrine (10 µM) was then added extraluminally to induce peristalsis. Nifedipine was then added to the intraluminal reservoir or the external organ bath. The concentration of nifedipine needed to cause aperistalsis was measured. RESULTS: In 12 trials, extraluminal nifedipine caused aperistalsis at a concentration of 1 ± 0.1 µM, while intraluminal nifedipine needed 10.2 ± 1.1 µM. Significantly higher concentrations of nifedipine were needed intraluminally to cause aperistalsis, (P < 0.0001). CONCLUSIONS: With our apparatus, we can control the intraluminal and extraluminal ureteral environments, and measure peristalsis before and after drug administration. This apparatus should help investigators who are interested in studying both the diffusion of a wide range of drugs, as well as the effects of those medications on ureteral physiology. In this study, the urothelium acted as a significant barrier to the diffusion of nifedipine.

Differences in grip forces among various robotic instruments and da Vinci surgical platforms.

INTRODUCTION: The da Vinci surgical platform is becoming increasingly available and utilized. Due to the lack of haptic feedback, visual cues are necessary to estimate grip forces and tissue tensions during surgery. We directly measured the grip forces of robotic EndoWrist instruments using the three available da Vinci robotic surgical platforms. METHODS: Robotic instruments were tested in the da Vinci S, Si, and Standard systems. A load cell was placed in a housing unit that allowed for measurement of the grip forces applied by the tip of each robotic instrument. Each instrument was tested six times, and all data were analyzed using Student's t-tests or analysis of variance when appropriate. RESULTS: Slight differences in grip force were seen when the instrument was tested through 2 degrees of freedom at the tip (p = 0.02, analysis of variance) and when comparing a new instrument to an older instrument (p = 0.001 at the neutral position). There was no statistical difference in grip force between the left and right robotic arms. There was a broad range of grip forces between the various robotic instruments. The lowest grip force was registered in the double fenestrated grasper (2.26 ± 0.15 N), whereas the highest was seen in the Hem-o-lok clip applier (39.92 ± 0.89 N). In comparison to the S and Si, the Standard platform appeared to have significantly higher grip forces. CONCLUSION: Different grip forces were observed among the various robotic instruments commonly used during urologic surgery and between the Standard and the S and Si platforms.

The impact of cavernosal nerve preservation on continence after robotic radical prostatectomy.

OBJECTIVE: • To evaluate associations between baseline characteristics, nerve-sparing (NS) status and return of continence, as a relationship may exist between return to continence and preservation of the neurovascular bundles for potency during radical prostatectomy (RP). PATIENTS AND METHODS: • The study included 592 consecutive robotic RPs completed between 2002 and 2007. • All data were entered prospectively into an electronic database. • Continence data (defined as zero pads) was collected using self-administered validated questionnaires. • Baseline characteristics (age, International Index of Erectile Function [IIEF-5] score, American Urological Association symptom score, body mass index [BMI], clinical T-stage, Gleason score, and prostate-specific antigen level), NS status and learning curve were retrospectively evaluated for association with overall continence at 1, 3 and 12 months after RP using univariate and multivariable methods. • Any patient taking preoperative phosphodiesterase inhibitors was excluded from the postoperative analysis. RESULTS: • Complete data were available for 537 of 592 patients (91%). • Continence rates at 12 months after RP were 89.2%, 88.9% and 84.8% for bilateral NS, unilateral NS and non-NS respectively (P= 0.56). • In multivariable analysis age, IIEF-5 score and BMI were significant independent predictors of continence. • CavernosalNS status did not significantly affect continence after adjusting for other co-variables. CONCLUSION: • After careful multivariable analysis of baseline characteristics age, IIEF-5 score and BMI affected continence in a statistically significant fashion. This suggests that baseline factors and not the physical preservation of the cavernosal nerves predict overall return to continence.

Prospective randomized trial of three different methods of nephrostomy tract closure after percutaneous nephrolithotripsy.

OBJECTIVE: • To evaluate the safety and efficacy of 'tubeless' nephrostomy tract closure in reducing postoperative morbidity after percutaneous nephrolithotomy (PCNL). MATERIALS AND METHODS: • In all, 31 patients undergoing PCNL were randomized into three groups, each with a different method of nephrostomy tract closure: using either a gelatin matrix haemostatic sealant (FloSeal), fascial stitch or Cope loop nephrostomy tube. • We compared operative time, estimated blood loss (EBL), postoperative stay, analgaesics use, changes in creatinine and haemoglobin levels, and stone clearance rate, as well as postoperative short-form (SF)-36 quality-of-life and pain analogue scores at five different time points after surgery. • All data were analysed using a one-way anova test. • A repeated measures anova test was used selectively to assess the progression of SF-36 and pain analogue scores. RESULTS: • The preoperative variables operative time, EBL, postoperative stay (P = 0.45), analgaesia use (P = 0.79), changes in creatinine (P = 0.28) and haemoglobin (P = 0.09) levels, and postoperative SF-36 scores were not significantly different. • In contrast, the differences in analogue pain scales at 1 week after surgery (P = 0.02) and the trends of analogue pain score progression (P = 0.03) were statistically significant. • Three patients underwent second-look procedures for residual stones and there was one case of postoperative pyelonephritis in a multiple sclerosis patient. CONCLUSIONS: • The Cope loop closure patients recovered fastest, while FloSeal closure patients experienced initial increase in pain followed by resolution at 1 month. • As a result of the small study group sizes, it is difficult to show any significant difference in postoperative pain, especially in long-term follow-up; further clinical evaluation is necessary.

Sprayed fibrin sealant as the sole hemostatic agent for porcine laparoscopic partial nephrectomy.

PURPOSE: Tisseel® is used to control minor bleeding during laparoscopic procedures. The DuploSpray MIS™ spray system allows thin, even application over a larger surface area. We use sprayed Tisseel as the sole agent to control hemorrhage and seal the renal collecting system after severe porcine laparoscopic partial nephrectomy. METHODS AND MATERIALS: We performed staged bilateral severe laparoscopic partial nephrectomy in 12 Yucatan pigs using a longitudinal cut from upper to lower pole through the entire collecting system. In each pig 1 kidney was harvested immediately while the other was harvested after 4 weeks. After hilar clamping laparoscopic partial nephrectomy was done with cold scissors in 6 pigs while LigaSure™ was used in the other 6. Sprayed Tisseel was applied, and bleeding and urinary leakage were evaluated. Additional Tisseel was applied for repeat bleeding. We performed retrograde pyelogram (chronic) and burst pressure testing of the arterial and collecting systems. RESULTS: All animals survived 4 weeks. One urinoma was seen on retrograde pyelogram in the cold cut group. Average hilar clamp time was similar in the acute and chronic study arms. Average estimated blood loss was significantly less in the LigaSure group (p = 0.0045). Average arterial burst pressure was significantly different in the chronic and acute groups (605.8 vs 350.4 mm Hg, p = 0.008) but average collecting system burst pressure was similar (186.3 and 149.5 mm Hg, respectively). CONCLUSIONS: Sprayed Tisseel without suturing effectively sealed the arterial and collecting system after severe laparoscopic partial nephrectomy in the porcine model.

First prize: Chitosan and the urothelial barrier: effects on ureteral intraluminal drug penetration and peristalsis.

INTRODUCTION: Relaxing the ureter prior to endourologic procedures could ease instrument access. In an ex-vivo model, intraluminal nifedipine has been shown to relax the ureter. Chitosan is the deacetylation product of chitin and can alter bladder urothelium. This study examines the effect of nifedipine on peristalsis before and after pretreating the ureter with chitosan. METHODS: Intact 4-cm tubular porcine ureteral segments were placed in a novel organ bath. To induce peristalsis, phenylephrine (10 µM) was added. Chitosan (0.5% [w/v], 30 minutes) or Krebs (control) was then used to treat the urothelium. The rate and amplitude of ureteral peristalsis was then measured. Intraluminal nifedipine (1 µM) was then added to the intraluminal reservoir. Peristaltic rate and amplitude and the time to aperistalsis were measured. Methylene blue was then added after treatment with chitosan or control to measure diffusion. RESULTS: After Krebs pretreatment, intraluminal nifedipine (1 µM) significantly reduced peristaltic frequency (p = 0.0184) but did not stop peristalsis after 60 minutes of exposure in six trials. After chitosan, nifedipine (1 µM) stopped ureteral peristalsis within an average of 12.30 ± 4.72 minutes. Chitosan alone did not cause aperistalsis. Intraluminal methylene blue did not diffuse into the extraluminal bath after saline or chitosan pretreatment. Histological analysis of the ureter before and after pretreatment with chitosan showed no urothelial disruption. CONCLUSIONS: By pretreating the intraluminal surface of the ureter with chitosan, nifedipine blocks ureteral peristalsis at low concentrations. Chitosan changes ureteral urothelial permeability without barrier disruption and has no observed effect on ureteral contraction.

Ice burn: protecting the flank during renal cryotherapy.

INTRODUCTION AND OBJECTIVES: Cryoablation is a viable minimally invasive strategy for the treatment of small renal masses. One of the most common postoperative complaints is pain or paresthesia at the cryoprobe insertion site. The use of a 14-gauge angiocatheter to insulate the flank during renal cryotherapy was investigated. MATERIALS AND METHODS: Six Yorkshire swine underwent laparoscopy-guided percutaneous cryoablation of the upper and lower poles of both kidneys with a 1.47 mm (17 gauge) cryoneedle. Treatment consisted of a double 10-minute freeze separated by a 5-minute active thaw. Trials were randomized to placement of the cryoneedle directly through the flank or through a 14-gauge angiocatheter as an insulating sheath. Temperatures were recorded adjacent to the cryoneedle at two depths in the flank with a Multi-Point Thermal Sensor. RESULTS: Twelve trials were completed each with a bare and sheathed cryoneedle. The coldest temperature observed was -26 degrees C for the bare cryoneedle and -21 degrees C for the sheathed cryoneedle. At the outer sensor, there was a 4.1 degrees C increase in mean temperature for freeze 1, and 6.2 degrees C increase in mean temperature for freeze 2 with sheath use. At the inner sensor, there was a 3.0 degrees C increase in mean temperature for freeze 1, and 9.4 degrees C increase in mean temperature for freeze 2 with sheath use. There was a trend toward statistical significance of sheath insulation at the outer (p = 0.07) and inner (p = 0.08) temperature sensors. CONCLUSIONS: A 14-gauge angiocatheter may provide some insulation and thereby might help protect against "ice burn" during renal cryotherapy.

In vitro, ex vivo and in vivo isotherms for renal cryotherapy.

PURPOSE: Preoperative planning for renal cryotherapy is based on isotherms established in gel. We replicated gel isotherms and correlated them with ex vivo and in vivo isotherms in a porcine model. MATERIALS AND METHODS: PERC-17 CryoProbes (1.7 mm) and IceRods (1.47 mm) underwent trials in gel, ex vivo and in vivo porcine kidneys. Temperatures were recorded at 13 predetermined locations with multipoint thermal sensors. RESULTS: At the cryoprobe temperatures were not significantly different along the probe in any medium for either system (p = 0.0947 to 0.9609). However, away from the probe ex vivo and in vivo trials showed warmer temperatures toward the cryoprobe tip for each system (p = 0.0003 to 0.2141). Mean +/- SE temperature 5 mm distal to the cryoprobe tip in vivo was 19.2C +/- 16.1C for CryoProbes and 27.3C +/- 11.2C for IceRods. Temperatures were consistently colder with CryoProbes than with IceRods in gel (p <0.00005), ex vivo (p <0.00005) and in vivo (p = 0.0014). At almost all sites temperatures were significantly colder in gel and in ex vivo kidney than in in vivo kidney for CryoProbes (p = 0.0107 and 0.0008, respectively) and for IceRods (each p <0.00005). CONCLUSIONS: Gel and ex vivo isotherms do not predict the in vivo pattern of freezing. Thus, they should not be used for preoperative planning. The cryoprobe should be passed 5 mm beyond the tumor border to achieve suitably cold temperatures. Multipoint thermal sensor probes are recommended to record actual temperature during renal cryotherapy.

Impact of pneumoperitoneum on renal cryotherapy.

PURPOSE: Pneumoperitoneum is known to decrease blood flow to the kidney during laparoscopy. We investigated if this change in blood flow would increase the size of the cryolesion. MATERIALS AND METHODS: Twelve Yorkshire swine underwent laparoscopy-guided percutaneous cryoablation of the upper and lower pole of each kidney at four randomized pneumoperitoneum pressures (10, 15, 20, and 25 mm Hg). Cryolesions were made with a 1.47-mm IceRod (Galil Medical, Plymouth Meeting, PA). Each site underwent two 10-minute freeze cycles separated by a 5-minute active thaw with pressurized helium gas. At the conclusion of each freeze cycle, the iceball volume was measured with intraoperative ultrasound. After completion of the four cryolesions, the kidneys were harvested, and the cryolesion surface area was calculated. The lesions were fixed in 10% buffered formalin and then excised with a 1-mm margin to obtain a volume measurement using fluid displacement. RESULTS: Iceball volume was 3.41, 2.85, 3.44, and 2.36 cm(3) for freeze cycle 1 (p = 0.16) and 3.67, 3.34, 4.88, 3.95 cm(3) for freeze cycle 2 (p = 0.20) at 10, 15, 20, and 25 mm Hg, respectively. Cryolesion volume by fluid displacement was 4.06, 3.77, 3.97, and 3.93 cm(3) (p = 0.86) and cryolesion surface area was 4.55, 4.38, 4.39, and 4.20 cm(2) (p = 0.71) at 10, 15, 20, and 25 mm Hg, respectively. CONCLUSIONS: In this study, pneumoperitoneum pressure between 10 and 25 mm Hg did not affect iceball size as measured by intraoperative ultrasound, cryolesion volume by fluid displacement, or cryolesion surface.

Case report: omental splenosis discovered during robotic prostatectomy.

Splenosis describes ectopic splenic implants that usually occur after trauma and splenectomy. We present a case of omental splenosis discovered during robot-assisted prostatectomy.

Anatomic guide for port placement for daVinci robotic radical prostatectomy.

BACKGROUND AND PURPOSE: At present, robotic arm port placement for daVinci trade mark robot-assisted laparoscopic radical prostatectomy is based on the umbilicus. However, the robotic arm has a maximum manufactured required working distance of 25 cm. Accordingly, normal variability of patient height, weight, and umbilical location can leave the working arms too short to reach the membranous urethra. We present data to support port placement using the pubis, rather than the umbilicus, as the landmark. MATERIALS AND METHODS: If we assume the 25-cm working distance of the robot arm (Z) equals the hypotenuse of a triangle and the Y axis is the sum of the distance from the membranous urethra to the skin (Y1) plus the displacement of the skin secondary to CO(2) insufflation (Y2), then the horizontal distance X is from the robot port site to the pubis. To ascertain Y1, we randomly selected the CT scans of 25 men and measured the depth from the skin over the pubis to the membranous urethra. To determine Y2, we measured the change in height from the table of the port site after CO(2) insufflation in 11 robotic laparoscopic prostatectomies. RESULTS: The average distance of Y1 was 11 cm; Y2 was 6 cm. Using the formula (Z(2) - (Y1 + Y2)(2))(1/2), the maximum distance X from the port site to the pubis, for an average man, should not exceed 18 cm. CONCLUSION: The optimal landmark for calculating the placement of ports for the daVinci robotic arm placement should be the pubis and not the umbilicus. Tall men (>72 inches) are at risk for exceeding functional robot arm length, and in these men, port sites should not be more than 18 cm from the pubis.