David Teh Chung Tzou

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Journals/Publications

• Tzou, D. T., Tailly, T. O., & Stern, K. L. (2023). Ultrasound-Guided PCNL - Why Are We Still Performing Exclusively Fluoroscopic Access?. Current urology reports, 24(7), 335-343.
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  While urologists are traditionally taught to perform percutaneous nephrolithotomy (PCNL) utilizing exclusively fluoroscopy, ultrasound has emerged as a safe alternative. This article showcases the major reasons why ultrasound-guided access should be considered the first-line approach for performing access for PCNL.
• Raskolnikov, D., Tzou, D. T., Ahn, J. S., Bechis, S. K., Chi, T. L., Sorensen, M. D., Stoller, M. L., & Harper, J. D. (2022). Multi-Institutional Variation in Performance of Low-Dose Computed Tomography for the Evaluation of Suspected Nephrolithiasis. Journal of Endourology, 36(10), 1377-1381.
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  Guidelines from the American Urological Association (AUA) and American College of Radiology (ACR) recommend that patients with suspected nephrolithiasis undergo low-dose CT of the kidney, ureter, and bladder (LD CT KUB) as opposed to higher dose conventional imaging. We hypothesized that even at institutions with established LD protocols, higher dose imaging is common. We identified four academic medical centers where LD CT KUB protocols were implemented to yield an effective dose (EDose) consistent with national guidelines. Fifty consecutive adult patients who underwent CT KUB specifically for the evaluation of nephrolithiasis were retrospectively reviewed at each site. Patient age, sex, body mass index (BMI), imaging location, and EDose (millisieverts [mSv]) were recorded. Two hundred patients with a mean age of 54 years were identified. Forty-six patients (23%) underwent CT KUB with an EDose 4 mSv, accounting for 10% to 48% of each institution's cohort. One hundred sixteen patients had a BMI
• Tzou, D. T., Stern, K. L., Duty, B. D., Hsi, R. S., Canvasser, N. E., De, S., Wong, A. C., Royal, C. R., Sloss, M. L., Ziemba, J. B., Harper, J. D., Bechis, S. K., Zampini, A. M., Borofsky, M. S., Bell, J. R., Friedlander, J. I., Leavitt, D. A., Nevo, A., Patel, N. D., , Patel, R. M., et al. (2022). Heterogeneity in stone culture protocols and endourologist practice patterns: a multi-institutional survey. Urolithiasis, 51(1), 15.
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  Kidney stone cultures can be beneficial in identifying bacteria not detected in urine, yet how stone cultures are performed among endourologists, under what conditions, and by what laboratory methods remain largely unknown. Stone cultures are not addressed by current clinical guidelines. A comprehensive REDCap electronic survey sought responses from directed (n = 20) and listserv elicited (n = 108) endourologists specializing in kidney stone disease. Questions included which clinical scenarios prompt a stone culture order, how results influence post-operative antibiotics, and what microbiology lab protocols exist at each institution with respect to processing and resulting stone cultures. Logistic regression statistical analysis determined what factors were associated with performing stone cultures. Of 128 unique responses, 11% identified as female and the mean years of practicing was 16 (range 1-46). A specific 'stone culture' order was available to only 50% (64/128) of those surveyed, while 32% (41/128) reported culturing stone by placing a urine culture order. The duration of antibiotics given for a positive stone culture varied, with 4-7 days (46%) and 8-14 days (21%) the most reported. More years in practice was associated with fewer stone cultures ordered, while higher annual volume of percutaneous nephrolithotomy was associated with ordering more stone cultures (p 
• Bergersen, A. M., Khan, I., Wong, A. C., Chipollini, J. J., Weiss, B. D., & Tzou, D. T. (2021). Online Kidney Stone Educational Materials Do Not Meet Recommended Readability Standards. Urology practice, 8(2), 246-252.
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  The prevalence of kidney stones is rising and there is an increasing demand for reliable, easy to understand information for patients. To evaluate the readability of common Internet-based resources for kidney stones, we examined whether the most popular online educational materials may be contributing to decreased health literacy for this chronic condition.
• Bergersen, A. M., Khan, I., Wong, A. C., Chipollini, J. J., Weiss, B. D., & Tzou, D. T. (2021). Reply by Authors. Urology practice, 8(2), 252.
• Tzou, D. T., Weiss, B. D., Chipollini, J. J., Bergersen, A. M., Khan, I., & Wong, A. C. (2021). Reply by Authors. Urology Practice, 8(2), 252-252. doi:10.1097/upj.0000000000000183.04
• Lwin, A. A., Zeng, J., Evans, P., Phung, M. C., Hynes, K. A., Price, E. T., Twiss, C. O., Tzou, D. T., & Funk, J. T. (2020). Holmium Laser Enucleation of the Prostate Is Safe and Feasible as a Same Day Surgery. Urology, 138, 119-124.
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  To assess the safety, feasibility and treatment outcomes of holmium laser enucleation of the prostate (HoLEP) as a same day surgery (SDS).
• Taguchi, K., Chen, L., Usawachintachit, M., Hamamoto, S., Kang, M., Sugino, T., Unno, R., Tzou, D. T., Sherer, B. A., Okada, A., Yasui, T., Ho, S. P., Stoller, M. L., & Chi, T. (2020). Fatty acid-binding protein 4 downregulation drives calcification in the development of kidney stone disease. Kidney international, 97(5), 1042-1056.
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  Nephrolithiasis is a significant source of morbidity, and its incidence has increased significantly over the last decades. This rise has been attributed to concurrent increasing rates of obesity, associated with a 3-time risk of developing NL. To date, the mechanism by which obesity is linked to stone formation has not been elucidated. We aimed to utilize a transcriptomics approach to discover the missing link between these two epidemic diseases. We investigated gene expression profiling of nephrolithiasis patients by two RNA-sequencing approaches: comparison between renal papilla tissue with and without the presence of calcified Randall's plaques (RP), and comparison between the papilla, medulla, and cortex regions from within a single recurrent stone forming kidney. Results were overlaid between differently expressed genes found in the patient cohort and in the severely lithogenic kidney to identify common genes. Overlay of these two RNA-sequencing datasets demonstrated there is impairment of lipid metabolism in renal papilla tissue containing RP linked to downregulation of fatty acid binding protein (FABP) 4. Immunohistochemistry of human kidney specimens and microarray analysis of renal tissue from a nephrolithiasis mouse model confirmed that FABP4 downregulation is associated with renal stone formation. In a FABP4 knockout mouse model, FABP4 deficiency resulted in development of both renal and urinary crystals. Our study revealed that FABP4 plays an important, previously unrecognized role in kidney stone formation, providing a feasible mechanism to explain the link between nephrolithiasis and metabolic syndrome.
• Ahmad, T. R., Tzou, D. T., Usawachintachit, M., Reliford-Titus, S., Wu, C., Goodman, J., Antonelli, J. A., Viprakasit, D. P., Averch, T. D., Sivalingam, S., Chew, B. H., Bird, V. G., Pais, V. M., Streeper, N. M., Sur, R. L., Nakada, S. Y., Penniston, K. L., & Chi, T. (2019). Low Income and Nonwhite Race are Strongly Associated with Worse Quality of Life in Patients with Nephrolithiasis. The Journal of urology, 202(1), 119-124.
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  Kidney stones are a source of significant morbidity which have been shown to negatively impact health related quality of life. We sought to understand the association between health related quality of life, socioeconomic status and race among patients with kidney stones.
• Armas-Phan, M., Tzou, D. T., Bayne, D. B., Wiener, S. V., Stoller, M. L., & Chi, T. (2019). Ultrasound guidance can be used safely for renal tract dilatation during percutaneous nephrolithotomy. BJU international.
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  To compare clinical outcomes in patients who underwent percutaneous nephrolithotomy (PCNL) with renal tract dilatation performed under fluoroscopic guidance vs renal tract dilatation with ultrasound guidance.
• Bayne, D. B., Usawachintachit, M., Armas-Phan, M., Tzou, D. T., Wiener, S., Brown, T. T., Stoller, M., & Chi, T. L. (2019). Influence of Socioeconomic Factors on Stone Burden at Presentation to Tertiary Referral Center: Data From the Registry for Stones of the Kidney and Ureter. Urology, 131, 57-63.
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  To determine social factors associated with advanced stone disease (defined as unilateral stone burden >2 cm) at time of presentation to a regional stone referral center. Little is known about social determinants of urolithiasis. We hypothesize that socioeconomic factors impact kidney stone severity at intake to referral centers.
• Beiko, D., Razvi, H., Bhojani, N., Bjazevic, J., Bayne, D. B., Tzou, D. T., Stoller, M. L., & Chi, T. (2019). Techniques ‒ Ultrasound-guided percutaneous nephrolithotomy: How we do it. Canadian Urological Association journal = Journal de l'Association des urologues du Canada.
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  Ultrasonography has emerged as an alternative to fluoroscopy for image-guided guided PCNL (F-PCNL), ultrasound-guided PCNL (US-PCNL) is easier to learn and reduces radiation exposure to patients and providers. Despite these advantages, uptake of ultrasound-guided PCNL (US-PCNL) in Canada has been almost nonexistent, largely because it is not incorporated into urologists' training. In this article, we seek to familiarize Canadian urologists with this approach by describing our step-by-step technique for US-PCNL. Additionally, we provide keys to successful implementation of percutaneous nephrolithotomy (PCNL) in many countries. Compared to fluoroscopy-this technique.
• Sorensen, M., Harper, J. D., Tzou, D. T., Zetumer, S., Usawachintachit, M., Taguchi, K., Bechis, S. K., Duty, B. D., Hsi, R. S., Sur, R. L., Reliford-Titus, S., Chang, H. C., Isaacson, D., Bayne, D. B., Wang, Z. J., Stoller, M. L., & Chi, T. (2019). Computed Tomography Radiation Exposure Among Referred Kidney Stone Patients: Results from the Registry for Stones of the Kidney and Ureter. Journal of Endourology, 33(7), 619-624. doi:10.1089/end.2019.0091
• Tzou, D. T., Armas-Phan, M., Bayne, D. B., Wiener, S. V., Stoller, M. L., & Chi, T. (2019). Ultrasound guidance can be used safely for renal tract dilatation during percutaneous nephrolithotomy. BJU International, 125(2), 284-291. doi:10.1111/bju.14737
• Tzou, D. T., Metzler, I. S., Tsai, C., Goodman, J., Bayne, D. B., & Chi, T. (2019). Ultrasound-guided Morcellation During Difficult Holmium Laser Enucleation of the Prostate. Urology.
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  To demonstrate how bladder ultrasound can be useful in completing morcellation during difficult Holmium Laser Enucleation of the Prostate (HoLEP). As HoLEP has emerged as a standard of care for the treatment of benign prostatic hyperplasia, multiple studies have reported the potentially catastrophic complication of bladder injury during morcellation. This video aims to assist any urologist performing HoLEP by providing step-by-step instruction for using ultrasound to complete morcellation safely.
• Tzou, D. T., Metzler, I. S., Usawachintachit, M., Stoller, M. L., & Chi, T. (2019). Ultrasound-guided Access and Dilation for Percutaneous Nephrolithotomy in the Supine Position: A Step-by-Step Approach. Urology, 133, 245-246.
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  Ultrasound guidance for percutaneous nephrolithotomy (PCNL) has gained acceptance amongst urologists given its numerous advantages over fluoroscopy. While traditionally performed in the prone position, this video demonstrates a step-by-step approach to performing PCNL in the supine position, solely under ultrasound guidance.
• Tzou, D. T., Zetumer, S., Usawachintachit, M., Taguchi, K., Bechis, S. K., Duty, B. D., Harper, J. D., Hsi, R. S., Sorensen, M., Sur, R. L., Reliford-Titus, S., Chang, H. C., Isaacson, D., Bayne, D. B., Wang, Z. J., Stoller, M. L., & Chi, T. (2019). Computed Tomography Radiation Exposure Among Referred Kidney Stone Patients: Results from the Registry for Stones of the Kidney and Ureter. Journal of endourology, 33(7), 619-624.
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  Kidney stone patients routinely have CT scans during diagnostic work-up before being referred to a tertiary center. How often these patients exceed the recommended dose limits for occupational radiation exposure of >100 mSv for 5 years and >50 mSv in a single year from CT alone remains unknown. This study aimed to quantify radiation doses from CTs received by stone patients before their evaluation at a tertiary care stone clinic. From November 2015 to March 2017, consecutive new patients enrolled into the Registry for Stones of the Kidney and Ureter (ReSKU™) had the dose-length product of every available CT abdomen/pelvis within 5 years of their initial visit recorded, allowing for an effective dose (EDose) calculation. Multivariate logistic regression analysis identified factors associated with exceeding recommended dose limits. Models were created to test radiation reducing effects of low-dose and phase-reduction CT protocols. Of 343 noncontrast CTs performed, only 29 (8%) were low-dose CTs (calculated EDose 20 mSv and >50 mSv/year, respectively. Increased body mass index, number of scans, and multiphase scans were associated with exceeding exposure thresholds ( 50%. Stone patients referred to a tertiary stone center may receive excessive radiation from CT scans alone. Unnecessary phases and underutilization of low-dose CT protocols continue to take place. Enacting new approaches to CT protocols may spare stone patients from exceeding recommended dose limits.
• Zetumer, S., Wiener, S., Bayne, D. B., Armas-Phan, M., Washington, S. L., Tzou, D. T., Stoller, M., & Chi, T. (2019). The Impact of Stone Multiplicity on Surgical Decisions for Patients with Large Stone Burden: Results from ReSKU. Journal of endourology, 33(9), 742-749.
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  American Urological Association (AUA) guidelines recommend percutaneous nephrolithotomy (PCNL) for total stone burden greater than 20 mm, yet it is unclear if the number of stones affects adherence to this guideline. We aim to assess the impact of stone multiplicity on the choice of ureteroscopy (URS) PCNL as a first-line therapy for patients with high burden (>20 mm), and examine whether the AUA guideline-discordant care impacts patient outcomes. Data were collected from the Registry for Stones of the Kidney and Ureter (ReSKU) database, a prospectively collected registry of patients with stone disease. Multivariate logistic regression (MLR) was used to estimate the association between stone multiplicity and the decision to perform URS for high stone burden (>20 mm) patients. MLR was further used to estimate the association between performing URS and the following outcomes: stone-free rate, need for a second operation, and complications. Postoperative hospital stay was compared between patients receiving URS PCNL using Student's -test. One hundred twenty-five patients were included in this analysis. For patients with total stone burden exceeding 20 mm, those with more than three stones had roughly nine times the likelihood of undergoing URS over PCNL compared with patients with a single stone (adjusted odds ratio 9.21, confidence interval [95% CI] 2.55-40.58,  = 0.001). Stone-free rates, Clavien-Dindo scores, and frequency of second-look operations did not differ significantly between URS and PCNL patients. URS patients were discharged an average of 1.26 days earlier than patients who received PCNL (95% CI 0.72-1.81,  20 mm will undergo URS and who will undergo PCNL. These deviations from AUA guidelines do not appear to worsen patient outcomes. These results suggest that careful consideration of each patient may warrant deviation from guidelines.
• Bayne, D. B., Usawachintachit, M., Tzou, D., Taguchi, K., Shindel, A., & Chi, T. (2018). Increasing Body Mass Index Steepens the Learning Curve for Ultrasound-guided Percutaneous Nephrolithotomy.. Urology, 68-73. doi:10.1016/j.urology.2018.07.033
• Funk, J., & Tzou, D. (2018). Response to Stutz et al. re: "Management of Suspected Bladder Injury and Capsular Perforation After Holmium Laser Enucleation of the Prostate".. Journal of Endourology Case Reports, 4(1), N/A-Epublication.
• Lwin, A., Hynes, K., Tzou, D., & Funk, J. (2018). Management of Suspected Bladder Injury and Capsular Perforation After Holmium Laser Enucleation of the Prostate. Journal of Endourology Case Reports, 4(1), 87-90. doi:https://doi.org/10.1089/cren.2018.0021
• Taguchi, K., Harper, J. D., Stoller, M. L., Duty, B. D., Sorensen, M. D., Sur, R. L., Usawachintachit, M., Tzou, D. T., Wenzler, D. L., Isaacson, D., Xu, A., Chu, C., Zaid, U. B., Taylor, E. R., Ramaswamy, K., & Chi, T. (2018). Identifying factors associated with need for flexible ureteroscope repair: a Western Endourology STone (WEST) research consortium prospective cohort study. Urolithiasis, 46(6), 559-566.
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  Maintenance of flexible ureteroscopes can involve high costs and administrative burden. Instrument fragility necessitates eventual repair, rendering scopes inaccessible during refurbishment. We conducted a multi-institutional prospective cohort study to identify perioperative factors influencing flexible ureteroscope durability. Patients undergoing flexible ureteroscopy (URS) at six United States endourology centers were enrolled between August 2014 and June 2015. Surgeon self-reported concern and satisfaction with scope performance as well as upward and downward angles of deflection for each scope tip were measured before and after each procedure. The need for scope repair was determined by the operating surgeon at the time of the procedure and recorded. 424 URS cases using 74 flexible ureteroscopes were identified. Scope repair was required in 28 cases (6.6%) involving 26 scopes (35.1%). Upon univariate analysis, shorter patient height, absence of guidewire use, presence of a ureteral access sheath (UAS), longer procedure time, larger stone size, lithotrite type, surgeon training level, and self-reported concern were associated with scope repair. Upon multivariate analysis, UAS use (OR = 2.53, p = 0.005) and degree loss of scope upward flexion during a case (OR = 1.02, p = 0.03) increased the odds of a scope needing repair while the use of safety guidewire decreased the odds of a scope repair (OR = 0.50, p = 0.045). Lithotrite use and surgeon concern were associated with degree loss of scope upward flexion. The use of a UAS, absence of a safety guidewire, and the loss of upward ureteroscope flexion should be considered when evaluating means of optimizing reusable ureteroscope durability.
• Taguchi, K., Usawachintachit, M., Tzou, D. T., Sherer, B. A., Metzler, I., Isaacson, D., Stoller, M. L., & Chi, T. (2018). Micro-Costing Analysis Demonstrates Comparable Costs for LithoVue Compared to Reusable Flexible Fiberoptic Ureteroscopes. Journal of endourology, 32(4), 267-273.
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  Reusable ureteroscope durability and need for repair are significant sources of expense and inefficiency for patients and urologists. Utilization of LithoVue™, a disposable flexible digital ureteroscope, may address some of these concerns. To identify its economic impact on clinical care, we performed a micro-cost comparison between flexible reusable fiberoptic ureteroscopes (URF-P6™) and LithoVue.
• Tzou, D. T., & Chi, T. (2018). Editorial Comment. The Journal of urology, 200(5), 972.
• Tzou, D. T., Cadwell, C., Simko, J. P., Chi, T., & Stoller, M. L. (2018). Management of Inverted Papilloma During Holmium Laser Enucleation of the Prostate. Urology, 116, e5-e6.
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  Inverted papilloma of the prostatic urethra is an especially rare finding. A 75-year-old man with urinary retention wished to proceed with a holmium laser enucleation of the prostate (HoLEP) and was found to have a mass arising from his prostate vs bladder on preoperative imaging. Cystourethroscopy revealed the mass arising from the median lobe of the prostate. After transurethral resection and frozen analysis confirmed the benign pathology of an inverted papilloma, the patient subsequently underwent a successful HoLEP during the same surgical setting. Images of this rare prostatic mass are presented to increase urologist recognition and to assist management during HoLEP.
• Tzou, D. T., Isaacson, D., Usawachintachit, M., Wang, Z. J., Taguchi, K., Hills, N. K., Hsi, R. S., Sherer, B. A., Reliford-Titus, S., Duty, B., Harper, J. D., Sorensen, M., Sur, R. L., Stoller, M. L., & Chi, T. (2018). Variation in Radiologic and Urologic Computed Tomography Interpretation of Urinary Tract Stone Burden: Results From the Registry for Stones of the Kidney and Ureter. Urology, 111, 59-64.
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  To compare the measured stone burden recorded between urologists and radiologists, and examine how these differences could potentially impact stone management. As current urologic stone surgery guideline recommendations are based on stone size, accurate stone measurements are crucial to direct appropriate treatment. This study investigated the discrepant interpretation that often exists between urologic surgeons and radiologists' estimation of patient urinary stone burden.
• Tzou, D. T., Metzler, I. S., Stoller, M. L., & Chi, T. (2018). Ultrasound-Guided Morcellation During Holmium Laser Enucleation of the Prostate. Journal of Endourology Case Reports, 4(1), 133-135. doi:10.1089/cren.2018.0057
• Tzou, D. T., Metzler, I. S., Stoller, M. L., & Chi, T. (2018). Ultrasound-Guided Morcellation During Holmium Laser Enucleation of the Prostate. Journal of endourology case reports, 4(1), 133-135.
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  Holmium laser enucleation of the prostate (HoLEP) has emerged as an accepted standard of care for the treatment of benign prostatic hyperplasia. This surgery relies on morcellation of the prostate adenoma once enucleation of the transition zone has been completed. Caution is required during this portion of the operation, as engaging bladder mucosa within the morcellator can result in bladder injury, a rare but potentially catastrophic complication of HoLEP. Morcellation of the prostatic tissue can be additionally challenging if visualization is poor from either equipment failure or increased bleeding from a highly vascularized prostate. We report the case of a 66-year-old Caucasian man with an estimated 158 g prostate who underwent HoLEP at our institution. Enucleation was uneventful; however, upon placement of the nephroscope to begin morcellation, it was immediately evident that the lens of the nephroscope was damaged as there was extremely poor visualization. Without a replacement nephroscope available, this would have normally resulted in aborting the case and returning another day to complete the morcellation. Concurrent bladder ultrasonography was performed and allowed for additional visual feedback to the operator, helping guide the morcellator to safely engage the enucleated adenoma and complete the operation. This case report demonstrates the ability of performing the morcellation portion of HoLEP mainly with the visualization provided by concurrent bladder ultrasonography. By providing additional imaging feedback to the operator, ultrasound can be a complementary tool to assist in safely performing morcellation in situations of suboptimal cystoscopic visualization during HoLEP.
• Tzou, D., & Chi, T. (2018). Editorial Comment. The Journal of Urology, 200(5). doi:https://doi.org/10.1016/j.juro.2018.05.161
• Tzou, D., Cadwell, C., Simko, J. P., Chi, T., & Stoller, M. L. (2018). Management of Inverted Papilloma During Holmium Laser Enucleation of the Prostate.. Urology. doi:10.1016/j.urology.2018.01.009
• Tzou, D., Isaacson, D., Usawachintachit, M., Wang, Z. J., Taguchi, K., Hills, N. K., Hsi, R. S., Sherer, B. A., Reliford-Titus, S., Duty, B., Harper, J. D., Sorensen, M., Sur, R. L., Stoller, M. L., & Chi, T. (2018). Variation in Radiologic and Urologic Computed Tomography Interpretation of Urinary Tract Stone Burden: Results From the Registry for Stones of the Kidney and Ureter.. Urology, 59-64. doi:10.1016/j.urology.2017.10.002
• Tzou, D., Lwin, A., & Funk, J. (2018). Response to Stutz et al. re: “Management of Suspected Bladder Injury and Capsular Perforation After Holmium Laser Enucleation of the Prostate”. Journal of Endourology Case Reports, 4(1), 205-205. doi:10.1089/cren.2018.0089
• Usawachintachit, M., Sherer, B., Hudnall, M., Tzou, D. T., Taguchi, K., Hsi, R. S., Stoller, M., & Chi, T. (2018). Clinical Outcomes for Cystinuria Patients with Unilateral Versus Bilateral Cystine Stone Disease. Journal of endourology, 32(2), 148-153.
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  Cystinuria is a genetic disorder marked by elevated urinary cystine excretion and recurrent cystine nephrolithiasis. Interestingly, despite seemingly similar contralateral renal anatomy, a subset of cystinuric patients consistently form stones in only one kidney. The aim of this study is to evaluate clinical outcomes in unilateral vs bilateral cystine stone formers.
• Chi, T., Usawachintachit, M., Weinstein, S., Kohi, M. P., Taylor, A., Tzou, D. T., Chang, H. C., Stoller, M., & Mongan, J. (2017). Contrast Enhanced Ultrasound as a Radiation-Free Alternative to Fluoroscopic Nephrostogram for Evaluating Ureteral Patency. The Journal of urology, 198(6), 1367-1373.
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  We compared contrast enhanced ultrasound and fluoroscopic nephrostography in the evaluation of ureteral patency following percutaneous nephrolithotomy.
• Hudnall, M., Usawachintachit, M., Metzler, I. S., Tzou, D. T., Harrison, B., Lobo, E., & Chi, T. (2017). Ultrasound guidance reduces percutaneous nephrolithotomy cost compared to fluoroscopy. Urology, 103, 52-58.
• Isaacson, D., Ahmad, T., Metzler, I., Tzou, D. T., Taguchi, K., Usawachintachit, M., Zetumer, S., Sherer, B., Stoller, M., & Chi, T. (2017). Defining the Costs of Reusable Flexible Ureteroscope Reprocessing Using Time-Driven Activity-Based Costing. Journal of endourology, 31(10), 1026-1031.
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  Careful decontamination and sterilization of reusable flexible ureteroscopes used in ureterorenoscopy cases prevent the spread of infectious pathogens to patients and technicians. However, inefficient reprocessing and unavailability of ureteroscopes sent out for repair can contribute to expensive operating room (OR) delays. Time-driven activity-based costing (TDABC) was applied to describe the time and costs involved in reprocessing.
• Taguchi, K., Usawachintachit, M., Hamamoto, S., Unno, R., Tzou, D. T., Sherer, B. A., Wang, Y., Okada, A., Stoller, M. L., Yasui, T., & Chi, T. (2017). Optimizing RNA Extraction of Renal Papilla Biopsy Tissue in Kidney Stone Formers: A New Methodology for Genomic Study. Journal of endourology, 31(9), 922-929.
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  Endoscopic tools have provided versatile examination and treatment for kidney stone procedures. Despite endourologists researching urinary stone disease using endoscopes to collect tissue, this tissue collection method is limited. Endoscopically removed tissues are small in size, restricting the types of genome-based examination possible. We investigated a new method of renal papilla biopsy and RNA extraction to establish a genomic research methodology for kidney stone disease.
• Tzou, D. T., Usawachintachit, M., Taguchi, K., & Chi, T. (2017). Ultrasound use in urinary stones: adapting old technology for a modern-day disease. Journal of Endourology, 31(S1), S89-S94.
• Tzou, D. T., Weinstein, S., Usawachintachit, M., Mongan, J., Greene, K. L., & Chi, T. (2017). Contrast Enhanced Ultrasound Detects Recurrent Renal Cell Carcinoma in the Setting of Chronic Renal Insufficiency. Clinical genitourinary cancer, 15(4), e735-e737.
• Usawachintachit, M., Isaacson, D. S., Taguchi, K., Tzou, D. T., Hsi, R. S., Sherer, B. A., Stoller, M. L., & Chi, T. (2017). A Prospective Case-Control Study Comparing LithoVue, a Single-Use, Flexible Disposable Ureteroscope, with Flexible, Reusable Fiber-Optic Ureteroscopes. Journal of endourology, 31(5), 468-475.
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  LithoVue™ is a novel, single-use, digital flexible ureteroscope that was released to the US market in January 2016. There are scant data regarding its performance in humans. Procedural outcomes comparing LithoVue with reusable ureteroscopes are presented in patients undergoing ureteroscopy for upper urinary tract pathology.
• Usawachintachit, M., Tzou, D. T., Hu, W., Li, J., & Chi, T. (2017). X-ray-free ultrasound-guided percutaneous nephrolithitomy: how to select the right patient?. Urology, 100, 38-44.
• Usawachintachit, M., Tzou, D. T., Mongan, J., Taguchi, K., Weinstein, S., & Chi, T. (2017). Feasibility of retrograde ureteral contrast injection to guide ultrasonographic percutaneous renal access in the non-dilated collecting system. Journal of Endourology, 31(2), 129-134.
• Usawachintachit, M., Tzou, D. T., Mongan, J., Weinstein, S., & Chi, T. (2017). Antegrade ultrasound contrast injection facilitates accurate nephrostomy tube positioning during percutaneous nephrolithotomy. International Journal of Urology, 24(3), 239-240.
• Usawachintachit, M., Tzou, D. T., Washington, S. L., Hu, W., Li, J., & Chi, T. (2017). Ultrasound-Guided Renal Access and Tract Dilation. Videourology (New Rochelle, N.Y.), 31(1).
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  Ultrasound guidance is a unique alternative to fluoroscopy for percutaneous renal access. Besides being free of ionizing radiation exposure to the patient and intraoperative personnel, it offers several advantages including easier identification of the posterior renal calix and surrounding visceral structures. In this video, we demonstrate how ultrasound can be used to guide percutaneous nephrolithotomy (PCNL) in a step-by-step manner. From March to June 2016, 16 consecutive patients of age 18 and more with kidney or proximal ureteral stones underwent completely X-ray-free ultrasound-guided PCNL. No patients were excluded during the study period. Under general anesthesia, we place an externalized ureteral catheter through a flexible cystoscope with the patient in a frog-leg position. Retrograde saline injection is used to distend the collecting system only when needed. Then the patient is placed in a prone position. An ultrasound machine with a 3.5-MHz convex abdominal probe (Hitachi Aloka Medical America) is used to guide all steps of PCNL. For renal access, a longitudinal approach for needle insertion is usually chosen. An 18-gauge Echotip needle (Cook Medical) is slowly advanced through the skin either in front of or behind the probe. On the ultrasound screen, the entire needle should be fully seen from skin to kidney and into the targeted calix. Entry into the collecting system is confirmed with either aspiration of urine or efflux of urine through the puncture needle. Then, the needle stylet is removed and a J-tip coaxial guidewire (Bard Medical) is inserted into the renal pelvis or down the proximal ureter under ultrasound monitoring. Gently moving the wire back and forth will help identify the location of the wire tip relative to the collecting system. Subsequently, the needle is withdrawn, a 1-cm skin incision is made surrounding the wire, and a 10F fascial dilator and a safety wire introducer are then passed over the wire. Although the wire appears with a bright echogenic signal, the dilator and the safety wire introducer are not echogenic. Their advancement over the wire can be observed ultrasonographically as they obscure the echogenic appearance of the wire. A second wire is subsequently advanced into the collecting system through the safety wire introducer. A high-pressure balloon dilator (BARD X-Force, Bard Medical) is then advanced into the collecting system over one of the wires. Because the deflated balloon tip can be difficult to identify on the ultrasound screen, the wire should be moved back and forth while passing the balloon and the operative surgeon should look for a change in the wire contour to judge where the balloon tip is relative to the wire. The placement of the tip of this balloon dilator is crucial, as ideally, it should be just within the collecting system of the target calix. A working tract is then dilated and the access sheath is carefully advanced until the back end of the balloon is seen. Then the balloon is withdrawn, an offset rigid nephroscope is inserted, and the stone is treated. The mean age of patients was 48.8 ± 19.9 years. Forty-four percent of patients were male with a mean body mass index of 29.9 ± 7.9 kg/m and a mean stone size of 33.7 ± 15.0 mm. All procedures were effectively performed with ultrasound guidance with a mean operative time of 101.3 ± 32.2 minutes. Patients and intraoperative personnel were not exposed to any ionizing radiation during the surgery. No patients experienced any significant immediate postoperative complication. All patients were stone free (no visible stone fragments) based on intraoperative visual inspection using a flexible nephroscope and a renal ultrasound and KUB at 30 days after surgery, and no secondary procedures were required. Ultrasound guidance for renal access and tract dilation in prone PCNL is feasible and efficient. Although some situations such as obese patients or nondilated collecting system may present a challenge, the benefits of adopting this technique-namely eliminating ionizing radiation exposure and live imaging of anatomy surrounding the collecting system-provide value during PCNL. This study was supported by the NIH R21-DK-109433 (TC) and the NIH NIDDK K12-DK-07-006: Multidisciplinary K12 Urologic Research Career Development Program (TC). No competing financial interests exist. Runtime of video: 5 mins 12 secs.
• Washington, S. L., Eslami, A., & Tzou, D. T. (2017). Cystoscopic Evaluation of Bladder Leiomyoma. Urology, 106, e1-e2.
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  We report the case of a 40-year-old woman with a history of uterine polyps and 3 months' worth of gross hematuria who was found to have a bladder mass on cystoscopy. Although this mass appeared benign visually, it demonstrated enhancement on axial imaging, with increased internal vascularity on Doppler ultrasound. A transurethral resection demonstrated bladder leiomyoma. This case increases the urologist's recognition of a well-described but previously underrepresented condition by showcasing its visual appearance on cystoscopy.
• Chang, H. C., Tzou, D. T., Usawachintachit, M., Duty, B. D., Hsi, R. S., Harper, J. D., Sorensen, M. D., Stoller, M. L., Sur, R. L., & Chi, T. (2016). Rationale and design of the registry for stones of the kidney and ureter (ReSKU): a prospective observational registry to study the natural history of urolithiasis patients.. Journal of Endourology, 30(12), 1332-1338.
• Tzou, D. T., Taguchi, K., Chi, T., & Stoller, M. L. (2016). Animal models of urinary stone disease. International Journal of Surgery, 36(Pt D), 596-606.
• Michalak, J., Tzou, D., & Funk, J. (2015). HoLEP: the gold standard for the surgical management of BPH in the 21(st) Century. American Journal of Clinical and Experimental Urology, 3(1), 36-42.
• Tzou, D. T., Dalkin, B. L., Christopher, B. A., & Cui, H. (2009). The failure of a nerve sparing template to improve urinary continence after radical prostatectomy: attention to study design. Urologic Oncology, 27(4), 358-362.
• Tzou, D., Tan, Y., Hwang, J., Florero, M., Ewing, C., Esserman, L., Hwang, S., Morita, E., & Leong, S. (2006). The Number of Lymphatic Channels Does Not Affect Metastasis to the Sentinel Lymph Node in Breast Cancer. Journal of Investigative Medicine, 54(2_suppl), 385-385. doi:10.1177/108155890605402s150

Presentations

• Tzou, D. T. (2024, Jan). Culture Negative Kidney Stones Harbor Diverse Bacteria & Bacterial Endotoxins. Research on Calculus & Kinetics (ROCK) Annual Meeting. Minneapolis, MN.
• Tzou, D. T. (2023, Aug). Program Chairman - Arizona Urological Society (AZUS) Annual Meeting. AZUS. Tucson, AZ.
• Tzou, D. T. (2023, August). Course Director: University of Arizona & Mayo Arizona Urology Resident & Simulation Symposium. University of Arizona & Mayo Arizona Urology Resident & Simulation Symposium. Arizona Simulation Technology & Education Center (ASTEC) - Tucson, AZ.
• Tzou, D. T. (2023, October). 24-Hour Urine Abnormalities Amongst Patients with Infection Renal Calculi. 99th Annual Western Section American Urological Association (WSAUA) Meeting. Lake Tahoe, CA.
• Royal, C. R., Anwar, F., Robishaw-Denton, J. K., Vedantam, G., Lainhart, W. D., & Tzou, D. (2022, Nov). Determining Optimal Kidney Stone Culture Microbiology Protocols. 98th Annual Meeting of the Western Section American Urological Association / Calculi Podium Session. Kauai, HI: Western Section American Urological Association.
• Tzou, D. (2022, Dec). What is Dust?. 3rd Annual Trans-Atlantic Leaders in Endourological Technologies (The TALENTS) Meeting. Rome, Italy.
• Tzou, D. (2022, July). Course Director: University of Arizona & Mayo Arizona Urology Resident & Simulation Symposium. University of Arizona & Mayo Arizona Urology Resident & Simulation Symposium. Arizona Simulation Technology & Education Center (ASTEC) - Tucson, AZ.
• Tzou, D. (2022, May). Course Faculty: Instructional Course 027IC - Adaptive PCNL: Utilizing a Contemporary Toolbox. 117th Annual Meeting of the American Urological Association. New Orleans, LA: American Urological Association.
• Tzou, D. (2022, May). Course Faculty: Instructional Course 102HO - Interventional Ultrasonography: A New Urology Paradigm for Using Renal Ultrasound to Guide Renal Access and Biopsies. 117th Annual Meeting of the American Urological Association. New Orleans, LA: American Urological Association.
• Tzou, D. (2022, Nov). State of the Art Lecture: Ultrasound and Endourology - Reducing Radiation and Increasing Patient Safety. 98th Annual Western Section American Urological Association (WSAUA) Meeting. Kauai, HI: Western Section American Urological Association.
• Tzou, D. (2022, Oct). Course Faculty: Hands-On Ultrasound PCNL Access. 39th World Congress of Endourology and Uro-Technology. San Diego, CA: World Congress of Endourology and Uro-Technology.
• Tzou, D., Anwar, F., Badowski, M., Jernigan, B., Harris, D. T., Chi, T., & Vedantam, G. (2022, May). Kidney Stone Endotoxin Concentration Correlates with Post-Operative Sepsis Following Percutaneous Nephrolithotomy. 117th Annual Meeting of the American Urological Association/Podium Session. New Orleans, LA: American Urological Association.
• Muse, A., Sloss, M., Shah, S., Jauregui, C., Wong, A., & Tzou, D. (2021, November). Feasibility of Performing X-ray Free Percutaneous Nephrolithotomy for Staghorn Stones. 97th Annual Western Section American Urologic Association / Calculi Podium Session. Indian Wells, CA: Western Section AUA.
• Tzou, D., & Vedantam, G. (2021, November). Kidney Stone Endotoxin Concentration Correlates with Post-Operative Sepsis Following Percutaneous Nephrolithotomy. 97th Annual Western Section American Urological Association Meeting / Calculi Podium Session. Indian Wells, CA: Western Section AUA.
• Tzou, D., Hinkel, C., Ahn, J., Tsai, C., & Chi, T. (2020, Fall). Tips And Tricks For Ultrasound-guided Access In Obese Patients During Percutaneous Nephrolithotomy (pcnl) In The Supine Position. Western Section American Urological Assocation.
• Cobb, K., Tzou, D., Sorensen, M., Duty, B., Dibianco, J., Friedlander, D., Bechis, S., & Sur, R. (2019, Nov./Fall). Indications for Stent Omission After Ureteroscopic Lithotripsy – A Multi Center Prospective Study.. 95th Annual Western Section American Urological Association Annual Conference. Monterey, CA: Western Section American Urological Association.
• Lovett, M., Phung, M., Biffar, D. E., Lee, B. R., Hamilton, A. J., & Tzou, D. T. (2019, Nov./Fall). Development of a Low-Cost, High-Fidelity Simulator for Ultrasound- Guided Percutaneous Nephrolithotomy (PCNL) Training.. 95th Annual Western Section American Urological Association Annual Conference. Monterey, CA: Western Section American Urological Association.
• Tzou, D., Badowski, M., Jernigan, B., Chaus, F., Lee, B. R., Harris, D. T., & Ghishan, F. K. (2019, Nov./Fall). Feasibility of Detecting Both Superficial and Intra-renal Stone Endotoxin Concentrations.. 95th Annual Western Section American Urological Association Annual Conference. Monterey, CA: Western Section American Urological Association.
• Tzou, D., Metzler, I. S., Tsai, C., Goodman, J., & Chi, T. (2019, May, Spring). Ultrasound-guided morcellation during difficult holmium laser enucleation of the prostate (HoLEP). 114th Annual Meeting of the American Urological Association. Chicago, IL: American Urological Association.
• Tzou, D. (2018, November/Fall). Ultrasound-guided percutaneous nephrolithotomy (PCNL) in both the prone and supine positions: a step-by-step approach.. 94th Annual Meeting of the Western Section American Urological Association - Moderated Video Session. Maui, HI: Western Section American Urological Association (WSAUA).
• Tzou, D. (2018, October/Fall). Ultrasound-guided morcellation during difficult holmium laser enucleation of the prostate (HoLEP). 94th Annual Meeting of the Western Section American Urological Association - Moderated Video Session. Maui, HI: Western Section American Urological Association (WSAUA).
• Tzou, D. T., Zetumer, S., Usawachintachit, M., Reliford-Titus, S., Taguchi, K., Sherer, B., Stoller, M., & Chi, T. (2018, May). Radiation Exposure from CT scans for Urolithiasis: Results from the Registry for Stones of the Kidney and Ureter (ReSKU). 113th Annual Meeting of the American Urological Association - Podium Presentation. San Francisco, CA: American Urological Association.
• Tzou, D., Armas-Phan, m., Reliford-Titus, S., Zetumer, s., Taguchi, K., Usawachintachit, M., Stoller, M., & Chi, T. (2018, May). Renal Tract Dilation is a significant source of radiation exposure during PCNL: Results from the Registry for Stones of the Kidney and Ureter (ReSKU). 113th Annual Meeting of the American Urological Association. San Francisco, CA: American Urological Association.

Poster Presentations

• Tzou, D., Stern, K. L., Duty, B. D., Hsi, R. S., Canvasser, N. E., De, S., Wong, A. C., Royal, C. R., Sloss, M. L., Ziemba, J. B., Harper, J. D., Bechis, S. K., Zampini, A., Borofsky, M. S., Bell, J. R., Friedlander, J., Leavitt, D. A., Nevo, A., Patel, N., , Patel, R. M., et al. (2022, Nov). Stone Culture Practice Patterns Amongst Fellowship Trained Endourologists - A Multi-Institutional Study. 98th Annual Meeting of Western Section American Urological Association / Moderated Poster Session. Kauai, HI: Western Section American Urological Association.
• Tzou, D., Stern, K. L., Duty, B. D., Hsi, R. S., Canvasser, N. E., De, S., Wong, A. C., Royal, C. R., Sloss, M. L., Ziemba, J. B., Harper, J. D., Bechis, S. K., Zampini, A., Borofsky, M. S., Bell, J. R., Friedlander, J., Leavitt, D. A., Nevo, A., Patel, N., , Patel, R. M., et al. (2022, Oct). Stone Culture Practice Patterns Amongst Fellowship Trained Endourologists - A Multi-Institutional Study. 39th World Congress of Endourology and Uro-Technology / Moderated Poster Session. San Diego, CA: World Congress of Endourology and Uro-Technology.
• Muse, A., Sloss, M., Shah, S., Sandberg, D., Wong, A., Lwin, A., Hinkel, C., Arif, H., & Tzou, D. (2020, Fall). Understanding the Barriers to Implementing and Achieving Low-Dose Computerized Tomography for Patients with Nephrolithiasis. Western Section American Urological Association.
• Tzou, D. (2018, October/Fall). Renal Tract Dilation is a significant source of radiation exposure during PCNL: Results from the Registry for Stones of the Kidney and Ureter (ReSKU). 94th Annual Meeting of the Western Section American Urological Association - Moderated Poster Presentation. Maui, HI: Western Section American Urological Association (WSAUA).
• Tzou, D., Armas-Phan, M., Wiener, S., Bayne, D., Reliford-Titus, S., Stoller, M., & Chi, T. (2018, September). Relationship between Calcium Oxalate Stone Analysis and 24-Hour Urine: Results from the Registry for Stones of the Kidney and Ureter (ReSKU). 36th World Congress of Endourology Meeting - Moderated Poster Presentation. Paris, France: World Congress of Endourology.
• Sherer, B., Frenandez, A., Tzou, D. T., Ho, S., & Stoller, M. (2017, September). Biomineralization in Kidney Stone Formers. 35th World Congress of Endourology Meeting - Moderated Poster Presentation. Vancouver, BC: World Congress of Endourology.
• Sherer, B., Isaacson, D., Kornberg, Z., Usawachintachit, M., Tzou, D., Taguchi, K., Chi, T., & Stoller, M. (2017, September). Pharmaceutical Burden and Medication Compliance in Patients with Cystinuria. 35th World Congress of Endourology Meeting - Moderated Poster Presentation. Vancouver, BC: World Congress of Endourology.
• Tzou, D. T., Isaacson, D., Usawachintachit, M., Wang, Z., Taguchi, T., Sherer, B., Stoller, M., & Chi, T. (2017, May). The Importance of Urologist Estimation of Stone Burden: Results from the Registry for Stones of the Kidney and Ureter (ReSKU). 112th Annual Meeting of the American Urological Association - Moderated Poster Presentation. San Francisco, CA: American Urological Association.
• Tzou, D., Usawachintachit, M., Isaacson, D., Taguchi, K., Sherer, B., Stoller, M., & Chi, T. (2017, September). Radiation Exposure from CT scans for Urolithiasis: Results from the Registry for Stones of the Kidney and Ureter (ReSKU). 35th World Congress of Endourology Meeting - Moderated Poster Presentation. Vancouver, BC: World Congress of Endourology.