Tin C Ngo

Stanford Medicine, Stanford, California, United States

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Publications (14)33.51 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: To identify factors associated with the development of chronic kidney disease (CKD) after nephrectomy and to create a clinical model to predict CKD after nephrectomy for kidney cancer for clinical use. We identified 144 patients who had normal renal function (eGFR > 60) prior to undergoing nephrectomy for kidney cancer. Selected cases occurred between 2007 and 2010 and had at least 30 days follow up. Sixty-six percent (n = 95) underwent radical nephrectomy and 62.5% (n = 90) developed CKD (stage 3 or higher) postoperatively. We used univariable analysis to screen for predictors of CKD and multivariable logistic regression to identify independent predictors of CKD and their corresponding odds ratios. Interaction terms were introduced to test for effect modification. To protect against over-fitting, we used 10-fold cross-validation technique to evaluate model performance in multiple training and testing datasets. Validation against an independent external cohort was also performed. Of the variables associated with CKD in univariable analysis, the only independent predictors in multivariable logistic regression were patient age (OR = 1.27 per 5 years, 95% CI: 1.07-1.51), preoperative glomerular filtration rate (GFR), (OR = 0.70 per 10 mL/min, 95% CI: 0.56-0.89), and receipt of radical nephrectomy (OR = 4.78, 95% CI: 2.08-10.99). There were no significant interaction terms. The resulting model had an area under the curve (AUC) of 0.798. A 10-fold cross-validation slightly attenuated the AUC to 0.774 and external validation yielded an AUC of 0.930, confirming excellent model discrimination. Patient age, preoperative GFR, and receipt of a radical nephrectomy independently predicted the development of CKD in patients undergoing nephrectomy for kidney cancer in a validated predictive model.
    The Canadian Journal of Urology 12/2013; 20(6):7035-7041. · 0.74 Impact Factor
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    ABSTRACT: Abstract Purpose: The Accordion is a novel endoscopic device that prevents retropulsion of ureteral stones and their fragments during ureteroscopic laser lithotripsy. We describe our experience with its use focusing on three main endpoints: operating time, fluoroscopy time, and stone-free rates. Methods: Of 308 consecutive cases of unilateral ureteroscopic laser lithotripsy from 2006-2010, we analyzed 235 cases of ureteral stones. Chart review was performed to document patient demographics (age, sex, and race), stone characteristics (stone size, density, laterality, location, and multiplicity), operative characteristics (use of preoperative and/or postoperative stents, ureteral balloon dilators, ureteral access sheaths, the Holmium laser, and the Accordion device), and surgical outcomes (operative time, fluoroscopy time, stone-free status, and complications). Results: The baseline characteristics between the Accordion and non-Accordion group were statistically similar. In univariate nonparametric tests of medians, Accordion device usage was not associated with a significant reduction in fluoroscopy time (median 1.68 vs. 1.95 minutes, p=0.28) or operating time (median 52.5 vs. 61 minutes, p=0.19). However, the stone-free rate for the Accordion group was significantly higher compared to the non-Accordion group (84.2% vs. 53.6%, p=0.001). In multivariate generalized linear models, Accordion usage was not associated with decreased operating or fluoroscopy times. Accordion use was associated with statistically significant greater odds of stone-free status (odds ratio 4.35, 95% confidence interval 2.36-8.00). Complication severity and rates were comparable between the two groups. Conclusions: The Accordion antiretropulsive device improves stone-free rates during ureteroscopic laser lithotripsy. Prospective studies are needed to validate these results.
    Journal of endourology / Endourological Society 02/2013; · 1.75 Impact Factor
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    ABSTRACT: Purpose. Minimal data exists comparing dextranomer/hyaluronic acid (Dx/HA) and calcium hydroxyapatite (CaHA) for the endoscopic treatment of VUR in the hands of a single user. Materials and Methods. We reviewed our consecutive single-user case series of 27 children (42 ureters) receiving endoscopic treatment with CaHA and 21 children (33 ureters) who received Dx/HA injection. Children receiving CaHA injections were divided into two groups of 13 and 14 patients (Coaptite I and II) to assess the learning curve effects. Postoperatively, RBUS and VCUG were performed. Multiple regression analysis was performed to assess statistical significance of success rates. Results. The total CaHA group had a per-ureter success rate (Grade 0) of 52% after one injection. When separated into two cohorts, the single injection per-ureter success rates were 43% for Coaptite I and 62% for Coaptite II. In contrast, the Dx/HA series had a single injection per-ureter success rate (Grade 0) of 78%. Conclusions. Our consecutive case experience shows improved results for Dx/HA compared to CaHA, though the learning curve effects and evolution of injection technique likely played a role in the improved outcomes in the Dx/HA cohort. A randomized controlled multicenter trial would provide the most accurate data comparing these two agents.
    Advances in Urology 01/2013; 2013:263602.
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    ABSTRACT: Several radical prostatectomy series have linked small prostates with high grade cancer based on the hypothesis that a small prostate results from a low androgen milieu that selects for less hormone dependent, more aggressive tumors. We previously reported that this association resulted from ascertainment bias from the performance characteristics of prostate specific antigen rather than from tumor biology in our radical prostatectomy cohort. In this study we analyzed this association in a more generalized population of men who underwent prostate needle biopsy. The prostate needle biopsy database at our institution was queried for all initial biopsies. Included patient characteristics were age, race, family history of prostate cancer, prostate specific antigen, abnormal digital rectal examination and prostate volume in ml on transrectal ultrasound. Multivariate logistic regression was used to determine the influence of prostate volume on the odds of high grade cancer. The study population included 1,295 patients during 2000 to 2010, of whom 582 (44.9%) had prostate cancer and 398 (30.7%) had high grade cancer. When all patients were pooled, the OR for high grade cancer was 0.85 (95% CI 0.78-0.92) for each 10 ml increase in prostate volume. When patients were divided by clinical T stage, the corresponding ORs for those with T1c disease was 0.83 (95% CI 0.74-0.93) and for those with T2 or greater disease it was 0.99 (0.98-1.00). The association between small prostates and high grade cancer exists only in men with clinical T1c (normal digital rectal examination) prostate cancer. It likely resulted from ascertainment bias due to the performance characteristics of prostate specific antigen rather than tumor biology.
    The Journal of urology 12/2011; 187(2):477-80. · 4.02 Impact Factor
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    ABSTRACT: Videourodynamics is useful for evaluating and treating neurological disorders in children. Traditional urodynamic parameters can be obtained while simultaneous visualization of the urinary system can reveal anatomical anomalies. This additional information comes at the cost of radiation exposure to the child. We characterized radiation exposure from videourodynamics. We reviewed all recent videourodynamic studies and recorded patient demographics, urological diagnoses, physical attributes, total fluoroscopy time, total radiation exposure in mGy, bladder capacity and the number of filling cycles performed. Multivariate linear regression was used to identify patient factors that independently influenced total radiation exposure. A total of 64 videourodynamic studies were performed in 34 female and 28 male patients with a mean age of 8.6 years (95% CI 7.2-10.0). The most common diagnosis was neurogenic bladder in 40 patients, although 49 had multiple diagnoses. Mean total fluoroscopy time was 1.8 minutes (95% CI 1.4-2.1) and mean total radiation exposure was 10 mGy (95% CI 7.5-13.3). On multivariate linear regression patient weight and bladder capacity were the only independent predictors of total radiation exposure. Videourodynamics entail significant radiation exposure. Patient weight and bladder capacity were independent predictors of total radiation exposure. Physician awareness of radiation exposure may result in the judicious use of fluoroscopy and aid in counseling parents on the risk of videourodynamics. Further research is needed to quantify organ specific doses of radiation due to medical imaging in children and the associated cancer risks.
    The Journal of urology 08/2011; 186(4 Suppl):1672-6. · 4.02 Impact Factor
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    ABSTRACT: Sacral nerve modulation is a Food and Drug Administration approved treatment for refractory urgency, frequency, urge incontinence and nonobstructive urinary retention in adults. The sparse literature on sacral nerve modulation in children focuses on its initial efficacy in patients with neurogenic bladder and dysfunctional elimination. We describe our initial experience with sacral nerve modulation and the phenomenon of growth spurts associated with lead malfunction that necessitates revision. After receiving institutional review board approval we retrospectively reviewed the charts of pediatric patients who underwent sacral nerve modulation surgery at our institution. Charts were examined for patient demographics, subjective success, the need for further surgery and success after revision. Four patients underwent sacral nerve modulation at an average age of 12.1 years. All patients reported initial success, defined as greater than 50% symptom improvement. Subsequently 3 patients required a total of 5 revisions due to lead malfunction with an average of 1.5 years between surgeries. In those requiring revision the average somatic growth between revisions was 8.1 cm. Return of efficacy was reported after each revision. All patients had functioning nerve stimulators in place and continued to have a positive subjective response. The sparse data on sacral nerve modulation in children shows efficacy and safety similar to those in adults. Somatic growth may be associated with lead malfunction and require surgical revision. We report a small series showing that revision can be done successfully and safely. Informed consent for sacral nerve modulation in pediatric patients should include a discussion of somatic growth as a possible cause of lead malfunction necessitating revision.
    The Journal of urology 08/2011; 186(4 Suppl):1576-80. · 4.02 Impact Factor
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    ABSTRACT: BACKGROUND: Multiple large epidemiologic studies have examined the relationship between smoking and prostate cancer incidence and mortality only to arrive at contradictory results. In this series, we studied the effect of smoking on pathologic outcomes and biochemical recurrence in a cohort of men undergoing radical prostatectomy. METHODS: We identified 630 men who underwent radical prostatectomy between 1989 and 2005 who had detailed smoking histories. There were 321 smokers and 309 nonsmokers. Pathologic outcomes included prostate weight, volume of cancer, volume of high grade cancer, margin status, seminal vesicle involvement, extraprostatic extension, perineural invasion, angiolymphatic invasion, and the presence of nodal metastasis. Biochemical recurrence was defined as a postoperative PSA ≥ 0.1 ng/ml. Univariate analysis and multivariate linear and Cox regression were used to study the impact of smoking on these outcomes. RESULTS: The volume of cancer (2.54 vs. 2.16 ml, P = 0.016) and the volume of high grade cancer (0.58 vs. 0.28 ml, P = 0.004) were greater in smokers compared with nonsmokers. Smoking independently predicted greater volumes of cancer and high grade cancer in multivariate analysis. Heavy smokers (≥20 pack-year history) had a greater risk of biochemical recurrence on univariate survival analysis. Smoking also predicted a greater risk of biochemical recurrence on Cox regression, the magnitude of which was approximately 1% per pack-year smoked. CONCLUSIONS: Smoking is associated with adverse pathologic features and a higher risk of biochemical recurrence in men undergoing radical prostatectomy. If confirmed by additional studies, smoking history may need to be included into risk assessment models.
    Urologic Oncology 08/2011; · 3.65 Impact Factor
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    ABSTRACT: Recent studies have demonstrated deleterious effects of ionizing radiation from diagnostic and therapeutic imaging procedures. One of the barriers to minimizing patient exposure is physician awareness. We prospectively studied whether providing surgeons with feedback on their fluoroscopy utilization would affect intraoperative fluoroscopy times. In 2007, we prospectively began to track fluoroscopy usage for all urology cases. Nine months later, surgeons started to receive periodic reports with their mean fluoroscopy time compared with their peers. We reviewed all ureteroscopic cases for nephrolithiasis from the date tracking began (2006-2010, n = 311). Using the initial 9-month period as a control, we studied the effect of providing feedback on mean fluoroscopy times in subsequent periods and analyzed patient factors that may affect radiation exposure. Mean fluoroscopy times for unilateral ureteroscopy decreased by 24% after surgeons received feedback (2.74-2.08 minutes, p = 0.002). On multivariate analysis, factors that independently predicted decreased fluoroscopy times included female sex (p = 0.02), stones in the distal ureter (p = 0.04), and if the surgeon had received feedback (p = 0.0004). Factors that increased fluoroscopy times included the presence of hydronephrosis (p = 0.001), use of a ureteral access sheath (p = 0.04), ureteral balloon dilation (p = 0.0001), and placement of a postoperative stent (p = 0.002). Providing surgeons with feedback on their fluoroscopy usage reduces patient and surgeon radiation exposure. Implementing such a tracking system requires minimal changes to existing operating room staff workflow. Further study is warranted to study the impact of this program on other procedures that utilize fluoroscopy in urology and other specialties.
    Journal of endourology / Endourological Society 03/2011; 25(5):763-7. · 1.75 Impact Factor
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    ABSTRACT: The prostate cancer risk calculator from the Prostate Cancer Prevention Trial estimates the risk of positive biopsy and 1 containing high grade disease (Gleason score 7 or greater) based on prostate specific antigen, digital rectal examination, family history, race and prior negative biopsy. Since data used to create the calculator came from an unreferred population that underwent mainly sextant biopsy, to our knowledge its usefulness in the contemporary urology practice is unknown. We performed the same multivariate logistic regression used to derive the prostate cancer risk calculator in a cohort of men from the Stanford Prostate Needle Biopsy Database who underwent initial prostate needle biopsy using an extended 12-core scheme. Our predictions of overall prostate cancer risk did not differ significantly from those of the calculator. Prostate specific antigen, abnormal digital rectal examination and family history were independent risk factors. However, our model predicted a much greater risk of high grade disease than the prostate cancer risk calculator. Prostate specific antigen, abnormal digital rectal examination and age were independent risk factors for high grade disease. The difference between our estimated risk of high grade prostate cancer and that of the prostate cancer risk calculator can be potentially explained by 1) differences between the cohorts (referred vs unreferred) or 2) the difference in grading, ie grading accuracy due to the difference in biopsy schemes or to temporally related grade shifts. Caution should be used when applying the prostate cancer risk calculator to counsel patients referred for suspicion of prostate cancer since it underestimates the risk of high grade disease.
    The Journal of urology 02/2011; 185(2):483-7. · 4.02 Impact Factor
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    ABSTRACT: Although Wilms tumor is the most common primary renal malignancy in children, it is exceedingly rare in adults and has an estimated incidence of less than 0.2 cases per million. Little is known about the biology of this tumor in adults and clinicians have had to rely on pediatric treatment protocols. Overall, prognosis is worse in adults, though like in children, unfavorable histology and higher stage at presentation confer a worse prognosis.
    The Canadian Journal of Urology 02/2011; 18(1):5568-9. · 0.74 Impact Factor
  • Journal of Urology - J UROL. 01/2011; 185(4).
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    ABSTRACT: Renal pseudoaneurysm is a rare vascular lesion that arises when an arterial injury within the kidney leads to contained hemorrhage. The associated hematoma forms outside the arterial wall and is typically surrounded by a layer of fibrous inflammatory tissue and blood clot. These lesions are unstable and their rupture can lead to life-threatening hemorrhage. Renal pseudoaneurysm has been reported to occur in various clinical scenarios, including after renal trauma, surgery and percutaneous procedures, as well as inflammatory and neoplastic processes within the kidney. Endovascular selective angioembolization is the mainstay of treatment, although surgery might be indicated when hemostasis and repair of the arterial wall defect are required. Percutaneous ultrasound-guided embolization is an additional option for patients with unfavorable vascular anatomy, or who cannot tolerate or have contraindications to the use of intravenous contrast agents. Some evidence suggests that these lesions can regress without intervention, although observation alone is not recommended as a management strategy in the vast majority of patients owing to the high risk of rupture. Evaluation and management of patients with renal pseudoaneurysm must take into account each individual's circumstances, due to the difficulty of accurately predicting the probability of spontaneous resolution or rupture.
    Nature Reviews Urology 10/2010; 7(11):619-25. · 4.79 Impact Factor
  • Tin C Ngo, Mark L Gonzalgo
    The Journal of urology 03/2010; 183(5):1750. · 4.02 Impact Factor
  • Source
    Journal of Urology - J UROL. 01/2010; 183(4).

Publication Stats

24 Citations
6 Downloads
709 Views
33.51 Total Impact Points

Institutions

  • 2011
    • Stanford Medicine
      • Stanford Emergency Department (Hospitals and Clinics)
      Stanford, California, United States
  • 2010–2011
    • Stanford University
      • Department of Urology
      Stanford, CA, United States