Agnes J Wang

Duke University Medical Center, Durham, North Carolina, United States

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Publications (24)58.31 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Different factors can determine the outcomes of percutaneous nephrolithotomy (PNL). We analyzed the effect of tract length (TL) on outcomes after PNL.
    International Urology and Nephrology 08/2014; · 1.33 Impact Factor
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    ABSTRACT: Objective: To compare the risks of fever from different lithotrites after percutaneous nephrolithotomy (PNL). Materials and Methods: The Clinical Research Office of the Endourological Society (CROES) PNL database is a prospective, multi-institutional, international PNL registry. Of 5,803 total patients, 4,968 received preoperative antibiotics, were supplied with complete information and included in this analysis. The lithotrites assessed included no fragmentation, ultrasonic, laser, pneumatic and combination ultrasonic/pneumatic. Risk of fever was estimated using multivariate logistic regression with adjustment for diabetes, steroid use, a history of positive urine culture, the presence of staghorn calculi or preoperative nephrostomy, stone burden and lithotrite. Results: The overall fever rate was 10%. Pneumatic lithotrites were used in 43% of the cohort, followed by ultrasonic (24%), combination ultrasonic/pneumatic (17.3%), no fragmentation (8.4%) and laser (7.3%). Fever rates were no different between patients who underwent no or any fragmentation (p = 0.117), nor among patients when stratified by lithotrite (p = 0.429). On multivariate analysis, fragmentation was not significantly associated with fever [Odds Ratio (OR) 1.17, p = 0.413], while diabetes (OR 1.32, p = 0.048), positive urine culture (OR 2.08, p < 0.001), staghorn calculi (OR 1.80, p < 0.001) and nephrostomy (OR 1.65, p < 0.001) increased fever risk. Fever risk among lithotrites did not differ (p ≥ 0.128). Conclusions: Risk of post-PNL fever was not significantly different among the various lithotrites used in the CROES PNL study.
    Urologia Internationalis 08/2013; · 1.07 Impact Factor
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    ABSTRACT: PURPOSE: Computed tomography (CT) utilization over the last three decades has increased exponentially. CT is commonly used to evaluate many urologic conditions. Ionizing radiation exposure from medical imaging has been linked to the risk of developing malignancy. We measured the organ doses (OD) and calculated effective doses (ED) of different studies and determined if the dose length product (DLP) method is an accurate estimation of radiation exposure. MATERIAL AND METHODS: An anthropomorphic male phantom that has been validated for human organ dosimetry measurements was used to determine radiation doses. High sensitivity MOSFET dosimeters were placed at 20 organ locations to measure specific OD. For each study, the phantom was scanned three times using our institutional protocols. ODs were measured and the ED was calculated (EDMOSFET). The EDMOSFET were compared to calculated EDs (EDcal) derived from the DLP. RESULTS: The EDMOSFET for stone protocol CT, chest CT, CT abdomen and pelvis, CT urogram and renal cell carcinoma (RCC) protocol CT were 3.04 ± 0.34, 4.34 ± 0.27, 5.19 ± 0.64, 9.73 ± 0.71 and 11.42 ± 0.24 milliSievert (mSv), respectively. The EDcal for these studies were 3.33, 2.92, 5.84, 9.64 and 10.06 mSv, p=0.8478. CONCLUSIONS: Effective doses in different urologic CT studies vary considerably. Renal stone protocol CT is accompanied by the lowest dose while CT urogram and RCC protocol accumulate the highest EDs. EDcal derived from the DLP is a reasonable estimate of patient radiation exposure.
    The Journal of urology 06/2013; · 3.75 Impact Factor
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    ABSTRACT: Objective: To compare the effective doses (ED) associated with imaging modalities for follow-up of patients with urolithiasis, including stone protocol NCCT, KUB, IVP and digital tomosynthesis (DT). Methods: A validated Monte Carlo simulation-based software PCXMC 2.0 (STUK, Finland) designed for estimation of patient dose from medical x-ray exposures was used to determine the ED for KUB, IVP (KUB scout plus 3 tomographic images) and DT (2 scouts and 1 tomographic sweep). Simulations were performed using a 2D stationary field onto the corresponding body area of the built-in digital phantom, with actual kVp, mAs, and geometrical parameters of the protocols. The ED for NCCT was determined using an anthropomorphic male phantom which was placed prone on a 64-slice GE Healthcare VCT scanner. High sensitivity metal oxide semiconductor field effect transistors (MOSFET) dosimeters were placed at 20 organ locations and used to measure organ radiation doses. Results: The ED for a stone protocol NCCT was 3.04±0.34 mSv. The ED for a KUB was 0.63 mSv and 1.1 mSv for the additional tomographic film. The total ED for IVP was 3.93 mSv. The ED for digital tomosynthesis performed with two scouts and one sweep (60.0°) was 0.83 mSv. Conclusions: Among the different imaging modalities for follow-up of patients with urolithiasis, DT was associated with the least radiation exposure (0.83 mSv). This effective dose corresponds to a fifth of NCCT or IVP studies. Further studies are needed to demonstrate the sensitivity and specificity of DT for the follow-up of nephrolithiasis patients.
    Journal of endourology / Endourological Society 06/2013; · 1.75 Impact Factor
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    ABSTRACT: INTRODUCTION AND OBJECTIVE: Patients with recurrent nephrolithiasis are often evaluated and followed with computerized tomography (CT). Obesity is a risk factor for the development of nephrolithiasis. We evaluated the radiation dose from CT for obese and non-obese adults. MATERIALS AND METHODS: A validated, anthropomorphic male phantom was scanned according to our institutional protocol for evaluation of renal stones. The obese model consisted of the phantom wrapped in two Custom Fat Layers, which have been verified to have the same radiographic tissue density as fat. High sensitivity metal oxide semiconductor field effect transistor dosimeters were placed at 20 organ locations in the phantoms to measure organ specific radiation doses. The non-obese and obese model have an approximate BMI of 24 kg/m2 and 30 kg/m2, respectively. Three runs of the renal stone protocol CT were performed on each phantom under automatic tube current modulation. Organ-specific absorbed doses were measured and the effective doses were calculated. RESULTS: For both models, the bone marrow received the highest dose, with the skin receiving the second highest dose. The mean effective dose for the non-obese model was 3.04 ± 0.34 milli- Sieverts (mSv), while the effective dose for the obese model was 10.22 ± 0.50 mSv, p<0.0001. CONCLUSIONS: The effective dose of stone protocol CT for obese patients is more than three-fold higher than the dose for a non-obese patient using automatic tube current modulation. The implication of this finding extends beyond the urologic stone population and adds to our understanding of radiation exposure from medical imaging.
    The Journal of urology 12/2012; · 3.75 Impact Factor
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    ABSTRACT: Abstract Background and Purpose: The EMS Swiss LithoBreaker is a new, portable, electrokinetic lithotripter. We compared its tip velocity and displacement characteristics with a handheld, pneumatic lithotripter LMA StoneBreaker.™ We also evaluated fragmentation efficiency using in vitro models of percutaneous and ureteroscopic stone fragmentation. Materials and Methods: Displacement and velocity profiles were measured for 1-mm and 2-mm probes using a laser beam aimed at a photo detector. For the percutaneous model, 2-mm probes fragmented 10-mm spherical BegoStone phantoms until the fragments passed through a 4-mm mesh sieve. The ureteroscopic model used 1-mm probes and compared the pneumatic and electrokinetic devices to a 200-μm holmium laser fiber. Cylindrical (4-mm diameter, 4-mm length) BegoStone phantoms were placed into silicone tubing to simulate the ureter; fragmented stones passed through a narrowing in the tubing. Results: For both 1-mm and 2-mm probes, the electrokinetic device had significantly higher tip displacement and slower tip velocity, P<0.01. In the percutaneous model, the electrokinetic device needed an average of 484 impulses over 430 seconds to fragment one BegoStone, while the pneumatic device needed 29 impulses over 122 seconds to fragment one stone. Both clearance times and number of impulses needed for percutaneous stone clearance were significantly different at P<0.01. Ureteroscopically, the mean clearance time was 97 seconds for the electrokinetic lithotripter, 145 seconds for the pneumatic lithotripter, and 304 seconds for the laser. Comparing the pneumatic device with the electrokinetic device ureteroscopically, there was no significant difference in clearance time, P=0.55. Both the pneumatic and electrokinetic lithotripters, however, demonstrated decreased clearance times compared with the laser, P=0.027. Conclusions: The portable electrokinetic lithotripter may be better suited for ureteroscopy instead of percutaneous nephrolithotomy. It appears to be comparable to the portable pneumatic device in the ureter. Further clinical studies are needed to confirm these findings in vivo.
    Journal of endourology / Endourological Society 08/2012; · 1.75 Impact Factor
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    ABSTRACT: Malignant ureteral obstruction often necessitates chronic urinary diversion and is associated with high rates of failure with traditional ureteral stents. We evaluated the outcomes of a metallic stent placed for malignant ureteral obstruction and determined the impact of risk factors previously associated with increased failure rates of traditional stents. Patients undergoing placement of the metallic Resonance® stent for malignant ureteral obstruction at an academic referral center were identified retrospectively. Stent failure was defined as unplanned stent exchange or nephrostomy tube placement for signs or symptoms of recurrent ureteral obstruction (recurrent hydroureteronephrosis or increasing creatinine). Predictors of time to stent failure were assessed using Cox regression. A total of 37 stents were placed in 25 patients with malignant ureteral obstruction. Of these stents 12 (35%) were identified to fail. Progressive hydroureteronephrosis and increasing creatinine were the most common signs of stent failure. Three failed stents had migrated distally and no stents required removal for recurrent infection. Patients with evidence of prostate cancer invading the bladder at stent placement were found to have a significantly increased risk of failure (HR 6.50, 95% CI 1.45-29.20, p = 0.015). Notably symptomatic subcapsular hematomas were identified in 3 patients after metallic stent placement. Failure rates with a metallic stent are similar to those historically observed with traditional polyurethane based stents in malignant ureteral obstruction. The invasion of prostate cancer in the bladder significantly increases the risk of failure. Patients should be counseled and observed for subcapsular hematoma formation with this device.
    The Journal of urology 07/2012; 188(3):851-5. · 3.75 Impact Factor
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    ABSTRACT: Abstract Background and Purpose: Flexible working angles and fine optical visualization are major requisite factors in performing laparoendoscopic single-site (LESS) urologic procedures. Multiple mechanical design approaches have been used to develop deflectable laparoscopes for LESS procedures. We compared the optical characteristics of three such devices using a bench top approach to simulate LESS in straight and deflected positions. Materials and Methods: A 10-mm fixed-rod rotating lens device (Storz EndoCameleon) and two 5-mm articulating devices (Olympus EndoEye and Stryker IdealEye) were compared using standard industry testing protocols for image resolution (United States Air Force-1951 test target), distortion (multifrequency grid distortion target), and color reproducibility (Gretag Macbeth color checker). Results: The 10-mm fixed-rod rotating lens system demonstrated the highest image resolution (5.04 line pairs/mm), but also the highest distortion (22.8%). Among the 5-mm flexible articulating laparoscopes, resolution was superior with the Olympus EndoEye (4.00 line pairs/mm) compared with the Stryker IdealEye (3.17 line pairs/mm). Distortion (7.0%) and color reproduction (1.18) were superior with the IdealEye vs the EndoEye (18.8 %, 1.27). Laparoscope deflection resulted in attenuation of resolution by 11% with both articulating models, but not with the fixed rod system. Conclusions: Definition of these optical characteristics may inform further development and selection of laparoscopic systems optimized for LESS surgery. A narrow but flexible camera can be crucial in the limited working space available during these procedures. Further investigation is warranted to determine if these objective findings translate into improved surgeon performance.
    Journal of endourology / Endourological Society 05/2012; 26(10):1340-5. · 1.75 Impact Factor
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    ABSTRACT: We measured organ specific radiation dose rates and determined effective dose rates during simulated ureteroscopy using a validated model. To calculate the effective dose, patients were exposed to ureteroscopic management of stones at our institution. A validated anthropomorphic male phantom was placed on a fluoroscopy table and underwent simulated ureteroscopy. High sensitivity metal oxide semiconductor field effect transistor dosimeters were placed at 20 organ sites in the phantom and used to measure organ specific radiation doses. These dose rates were multiplied by the appropriate tissue weighting factor and summed to calculate effective dose rates. Also, we retrospectively reviewed the charts of patients who underwent ureteroscopy at our institution. A total of 30 nonobese males with data on fluoroscopy time were included in analysis. The median effective dose was determined by multiplying median fluoroscopy time by the effective dose rate. The skin entrance was exposed to the highest absorbed dose rate, followed by the small intestine (mean ± SD 0.3286 ± 0.0054 and 0.1882 ± 0.0194 mGy per second, respectively). The mean effective dose rate was 0.024 ± 0.0019 mSv per second. Median fluoroscopy time was 46.95 seconds (range 12.9 to 298.8). The median effective dose was 1.13 mSv (range 0.31 to 7.17). The fluoroscopy used during ureteroscopy contributes to overall radiation exposure in patients with nephrolithiasis. Nonobese males are exposed to a median of 1.13 mSv during ureteroscopy, similar to that of abdominopelvic x-ray. More data are needed to determine clinical implications but urologists must be aware and decrease patient radiation during ureteroscopy.
    The Journal of urology 03/2012; 187(3):920-4. · 3.75 Impact Factor
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    ABSTRACT: Radiation exposure during medical procedures continues to be an increasing concern for physicians and patients. We determined organ-specific dose rates and calculated effective dose rates during right and left percutaneous nephrolithotomy (PCNL) using a validated phantom model. A validated anthropomorphic adult male phantom was placed prone on an operating room table. Metal oxide semiconductor field effect transistor dosimeters were placed at 20 organ locations in the model and were used to measure the organ dosages. A portable C-arm was used to provide continuous fluoroscopy for three 10 minute runs each to simulate a left and right PCNL. Organ dose rate (mGy/s) was determined by dividing organ dose by fluoroscopy time. The organ dose rates were multiplied by their tissue weighting factor and summed to determine effective dose rate (EDR) (mSv/s). Two-dimensional radiation distribution in the abdomen during a left-sided PCNL was visually determined using radiochromic film. The EDR for a left PCNL was 0.021 mSv/s ± 0.0008. The EDR for a right PCNL was 0.014 mSv/s ± 0.0004. The skin entrance was exposed to the greatest amount of radiation during left and right PCNL, 0.24 mGy/s and 0.26 mGy/s, respectively. Radiochromic film demonstrates visually the nonuniform dose distribution as the x-ray beam enters through the skin from the radiation source. The effective dose rate is higher for a left-sided PCNL compared with a right-sided PCNL. The distribution of radiation exposure during PCNL is not uniform. Further studies are needed to determine the long-term implications of these radiation doses during percutaneous stone removal.
    Journal of endourology / Endourological Society 09/2011; 26(5):439-43. · 1.75 Impact Factor
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    ABSTRACT: Hemostatic agents have been suggested as an adjunct for tubeless percutaneous nephrolithotomy (PCNL). We pathologically evaluated the percutaneous tracts injected with the fibrin sealant (FS) Evicel and hemostatic gelatin matrix (HGM) Surgiflo at various time intervals to determine their absorption and tract closure rates. We also evaluated whether these agents reduced urine leak rates in a porcine model. Percutaneous access was obtained in 19 kidneys in 10 domestic swine. The tracts were dilated to 30F using a balloon dilating catheter. Ten kidneys served as controls. Surgiflo was injected into the tract of four kidneys, and Evicel was injected into the tract of five kidneys. Intravenous urography (IVU) was performed on postoperative days (POD) 1 and 10 to 14. IVU was performed on two pigs at POD 30. The pigs were sacrificed and kidneys were harvested for pathologic evaluation. Two (20%) control kidneys had a urine leak on IVU on POD 1. None of the kidneys treated with HGM or FS had a urine leak on POD 1. None of the kidneys had a leak on POD 10 to 14 or POD 30. On pathologic inspection, the tracts of all the control kidneys and HGM kidneys had closed completely at POD 14. Two kidneys treated with FS had fistula at POD 6 and POD 14. At POD 30, the tracts in the control kidneys and kidney treated with HGM had completely healed. Fibrin sealant remained in the tract at POD 30. Fibrin sealant should be used with caution because it can persist in the tract for up to 30 days and may inhibit wound healing. Hemostatic gelatin matrix is the preferable agent because the tract closed by POD 10 to 14, similar to the findings in the control animals. The use of hemostatic agents in a nephroscopy tract may reduce the risk of early urine leak after tubeless PCNL.
    Journal of endourology / Endourological Society 08/2011; 25(8):1353-7. · 1.75 Impact Factor
  • Agnes J Wang, Glenn M Preminger
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    ABSTRACT: Ureteroscopy continues to improve as a method for management of intrarenal stone disease. The development of new technologies and enhanced application of existing therapies is expanding the indications of ureteroscopy for the management of renal calculi. Improvements in image quality have been achieved with the adoption of digital ureteroscopes. Modifications of standard ureteroscopic techniques and improvements in surgical skill training are also being made. Ureteroscopy is demonstrated to be well tolerated and efficacious for the management of intrarenal calculi in multiple-patient populations and is also cost-efficient. The indications for ureteroscopic management of renal calculi are expanding, and this technique is quickly being adopted as a routine option for the management of intrarenal stone disease.
    Current opinion in urology 03/2011; 21(2):141-4. · 2.50 Impact Factor
  • Journal of Urology - J UROL. 01/2011; 185(4).
  • Journal of Urology - J UROL. 01/2011; 185(4).
  • Journal of Urology - J UROL. 01/2011; 185(4).
  • Journal of Urology - J UROL. 01/2011; 185(4).
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    ABSTRACT: Robot assisted partial nephrectomy is rapidly emerging as an alternative to laparoscopic partial nephrectomy for the treatment of renal malignancy. We present the largest multi-institution comparison of the 2 approaches to date, describing outcomes from 3 experienced minimally invasive surgeons. We performed a retrospective chart review, evaluating 118 consecutive laparoscopic partial nephrectomies and 129 consecutive robot assisted partial nephrectomies performed between 2004 and 2008 by 3 experienced minimally invasive surgeons at 3 academic centers. Perioperative data were recorded along with clinical and pathological outcomes. The robot assisted and laparoscopic partial nephrectomy groups were equivalent in terms of age, gender, body mass index, American Society of Anesthesiologists classification (2.3 vs 2.4) and radiographic tumor size (2.9 vs 2.6 cm), respectively. Comparison of operative data revealed no significant differences in terms of overall operative time (189 vs 174 minutes), collecting system entry (47% vs 54%), pathological tumor size (2.8 vs 2.5 cm) and positive margin rate (3.9% vs 1%) for robot assisted and laparoscopic partial nephrectomy, respectively. Intraoperative blood loss was less for robot assisted vs laparoscopic partial nephrectomy (155 vs 196 ml, p = 0.03) as was length of hospital stay (2.4 vs 2.7 days, p <0.0001). Warm ischemia times were significantly shorter in the robot assisted partial nephrectomy series (19.7 vs 28.4 minutes, p <0.0001). Subset analysis based on complexity revealed that tumor complexity had no effect on operative time or estimated blood loss for robot assisted partial nephrectomy, although complexity did affect these factors for laparoscopic partial nephrectomy. In addition, for simple and complex tumors robot assisted partial nephrectomy provided significantly shorter warm ischemic time than laparoscopic partial nephrectomy (15.3 vs 25.2 minutes for simple, p <0.0001; 25.9 vs 36.7 minutes for complex, p = 0.0002). There were no intraoperative complications during robot assisted partial nephrectomy vs 1 complication during laparoscopic partial nephrectomy. Postoperative complication rates were similar for robot assisted and laparoscopic partial nephrectomy (8.6% vs 10.2%). Robot assisted partial nephrectomy is a safe and viable alternative to laparoscopic partial nephrectomy, providing equivalent early oncological outcomes and comparable morbidity to a traditional laparoscopic approach. Moreover robot assisted partial nephrectomy appears to offer the advantages of decreased hospital stay as well as significantly less intraoperative blood loss and shorter warm ischemia time, the latter of which may help to provide maximal preservation of renal reserve. In addition, operative parameters for robot assisted partial nephrectomy appear to be less affected by tumor complexity compared to laparoscopic partial nephrectomy. Interestingly while the advantages of robotic surgery have historically been believed to aid laparoscopic naïve surgeons, these data indicate that robot assisted partial nephrectomy may also benefit experienced laparoscopic surgeons.
    The Journal of urology 08/2009; 182(3):866-72. · 3.75 Impact Factor
  • European Urology 08/2009; · 10.48 Impact Factor
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    ABSTRACT: Robotic-assisted partial nephrectomy is an emerging technique for the treatment of renal malignancy. Our aim is to review the initial reported experience with robotic partial nephrectomy, evaluating techniques, early outcomes, and potential advantages of the robotic approach over the traditional laparoscopic approach. Early experience with robotic partial nephrectomy demonstrates good oncologic outcomes. Other parameters, such as operative time, blood loss, postoperative renal function, and hospital stay, appear to be at least equivalent to laparoscopic partial nephrectomy. New techniques, including refined methods for renorrhaphy, have also been introduced which aim to simplify critical portions of the procedure, although vascular clamping still remains a challenging aspect of the procedure. The learning curve appears to be slight, even for surgeons without extensive laparoscopic experience. Although long-term outcome data is presently lacking, the early experience with robotic partial nephrectomy shows promise. The technique should continue to evolve as it gains acceptance as an alternative to the traditional laparoscopic approach.
    Current opinion in urology 02/2009; 19(1):76-80. · 2.50 Impact Factor
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    ABSTRACT: Robotic partial nephrectomy (RPN) is emerging as an alternative to traditional laparoscopic partial nephrectomy (LPN). Despite the potential advantages of the robotic approach, renorrhaphy remains a challenging portion of the procedure. To present our technique and outcomes for RPN, including sliding-clip renorrhaphy. Between 2007 and 2008, 50 patients underwent RPN performed by a single attending surgeon. In this paper, we describe our technique for RPN, including a sliding-clip renorrhaphy, which is distinguished by the use of Weck Hem-O-Lock clips that are slid into place under complete control of the surgeon seated at the console and secured with a LapraTy clip. For the first 13 procedures, traditional tied-suture or assistant-placed clip closures were performed; sliding-clip renorrhaphy was performed in the remaining 37 cases. Mean tumor size was 2.5 cm. Mean operative time was 145.3 min, and mean overall warm ischemia time was 17.8 min. Mean estimated blood loss was 140.3 ml. The learning curve for overall operative time was 19 cases; the learning curve for portions of the case performed under warm ischemia (including tumor resection and renorrhaphy) was 26 cases. The introduction of a sliding-clip renorrhaphy produced significant reductions in overall operative time and warm ischemia time, while blood loss and hospital stay remained stable over our experience. Limitations of RPN include cost and increased reliance on the bedside assistant. Sliding-clip renorrhaphy provides an efficient and effective repair that is under nearly complete control of the surgeon. This technique appears to contribute to significantly shorter overall operative times and, perhaps most critically, to shorter warm ischemia times. The learning curve for RPN using this technique appears to be foreshortened compared with LPN.
    European Urology 02/2009; 55(3):592-9. · 10.48 Impact Factor

Publication Stats

466 Citations
58.31 Total Impact Points

Institutions

  • 2011–2013
    • Duke University Medical Center
      • Division of Urology
      Durham, North Carolina, United States
  • 2009
    • Albert Einstein College of Medicine
      New York City, New York, United States
  • 2008–2009
    • Washington University in St. Louis
      • Division of Urologic Surgery
      Saint Louis, MO, United States
    • University of Washington Seattle
      • Department of Urology
      Seattle, WA, United States