Biomedical subjects
Publications and source records attributed to Kenneth Ogan.
Carcinoid tumors are neuroendocrine tumors that typically arise in the gastrointestinal tract. We present the case of a 74-year-old woman with a primary carcinoid tumor in an ileal conduit urinary diversion who presented with gross hematuria. We also provide a brief review of relevant reports. The patient subsequently underwent resection and replacement of her ileal conduit.
BACKGROUND: Our objective was to predict endoscopic performance in a cadaver model using basic performance resources (BPRs) measurements. METHODS: Medical students (n = 16) underwent intense ureteroscopic training on a virtual reality ureteroscopy trainer and were rated on performing ureteroscopy on a cadaver. The medical students also underwent 13 validated BPR measurements. Urology residents also performed cadaveric ureteroscopy and BPRs. A predictive model built from urology residents' (n = 16) BPRs and performance assessment was used to predict medical student cadaveric ureteroscopy performance based on their BPRs alone. RESULTS: The predictive model built with urology residents predicted the ureteroscopic performance of 10 of 16 medical students within 15% of their rated ureteroscopic performance on the cadaver. CONCLUSIONS: A predictive model built with urology residents can moderately predict the ureteroscopic performance of medical students from BPRs. Additional in vivo evaluation is required.
BACKGROUND AND PURPOSE: The acute and long-term effects of radiofrequency ablation (RFA) on kidney function have not been well studied. The functional change when RFA is used in combination with renal ischemia is likewise unknown. Our goal was to determine the change in renal function caused by various volumes of RFA on a porcine kidney model and the effect cold ischemia had on the results. MATERIALS AND METHODS: Twenty-two female pigs with solitary kidneys underwent various volumes of RFA both with and without cold ischemia. Animals were divided into control, 10%, 15%, and 20% ablation of the total kidney volume. Measurements of creatinine were obtained for 2 weeks. RESULTS: In the nonischemic group, the mean acute (day 1-3) creatinine changes in control, 10%, 15%, and 20% ablations were 0.6, 2.4, 1.7, and 2.6 mg/dL, respectively. In the cold-ischemia group, the mean acute creatinine changes were 0.85, 2.33, 3.3, and 3.75 mg/dL, respectively. Regression line analysis demonstrated a positive linear relationship in both groups. Fourteen-day mean creatinine changes for the nonischemic group were similar to those in the control animals and did not show a correlation with ablation volume. The mean creatinine changes at 14 days in the cold-ischemia group showed a positive linear correlation with ablation volume. CONCLUSIONS: The volume of RFA correlates with an acute change in renal function in the porcine model for both nonischemic and cold-ischemia groups. This study may help predict the extent of acute renal dysfunction in patients undergoing RFA for large or multiple renal masses. These results also suggest renal function may recover after nonischemic RFA.
Metastatic renal cell carcinoma is associated with a poor prognosis and a median survival time of only 6-12 months. However, the emergence of immunotherapies has rekindled interest in cytoreductive nephrectomy as a therapeutic option. Phase III randomized trials have demonstrated that cytoreductive nephrectomy significantly improves overall survival in selected patients with metastatic renal cell carcinoma treated with interferon immunotherapy. While cytokine-based immunotherapy may be considered the standard systemic therapy, clinical studies are ongoing to develop molecular biomarkers and new therapies with improved efficacy and tolerability. With further advances in our understanding of the pathogenesis, behavior and molecular biology of renal cell carcinoma, cytoreductive nephrectomy, in combination with molecular targeted therapies, may become the new standard of care for patients with metastatic renal cell carcinoma.
OBJECTIVES: To present our experience using radiofrequency ablation (RFA) for the treatment of small renal tumors. Our objective was to assess the short-term (1 to 3 years) oncologic efficacy of RFA. METHODS: Consecutive renal tumors treated since May 2001 with a minimal follow-up of 6 months were included. Patients were treated with a temperature-based radiofrequency generator and were followed up with serial imaging at 6 weeks, 3 and 6 months, and every 6 months thereafter. RESULTS: A total of 109 small renal tumors (91 patients) were treated with computed tomography-guided percutaneous RFA (n = 63) or laparoscopic RFA (n = 46). The mean tumor size was 2.4 cm (range 0.8 to 4.7). The initial ablation was successful in 107 (98%) of 109 tumors. The two incomplete ablations were successfully re-ablated. Of the 60 patients with at least 1 year of follow-up, 60% had biopsy proven renal cell carcinoma (an additional 24% had no tissue diagnosis). In this group, one local recurrence (1.7%) was detected during a mean follow-up of 19.4 months (range 12 to 33), and in those with known renal cell carcinoma, none had evidence of distant progression (0%). The local recurrence was successfully re-ablated such that all 109 cases had no clinical or radiographic evidence of disease at last follow-up. Three patients died of causes unrelated to cancer. CONCLUSIONS: The results of our study have shown that in the short term, RFA appears to be a reasonable therapeutic nephron-sparing approach for treating select patients with small renal tumors. The cancer control appears adequate to date, but longer follow-up is necessary before widespread application.
OBJECTIVES: To evaluate the utility of a portable, at-home, low-cost, camera-less laparoscopic trainer to provide laparoscopy training inexpensively and outside the constraints of the hospital environment. METHODS: Twenty-two urology residents (postgraduate year 1 to 7) were tested prospectively on four basic laparoscopic tasks on a standard video laparoscopic trainer (pretest). Objective and subjective data were collected for each participant. The subjects were then randomized to 5 hours of training on either a portable, camera-less trainer (group 1) or a standard video laparoscopic trainer (group 2). Each resident was then retested on the initial same four laparoscopic tasks (post-test). Efficiency ratios were calculated for each task, incorporating both time and accuracy. Improvements between the pretest and post-test evaluations were compared between the two groups using the two-group t test. RESULTS: All subjects significantly improved their performance with training. The average improvement in the time required to complete the laparoscopic tasks for all participants was 36%. Efficiency increased by 52%. However, no difference was found between the two groups. In the poststudy self-evaluations, 91% of participants in group 1 either agreed or strongly agreed that the at-home trainer was a helpful teaching modality. CONCLUSIONS: The improvements in laparoscopic skills on our inexpensive, portable, at-home, camera-less trainer were not significantly different from those gained using a traditional video laparoscopic trainer. Participants trained on our portable trainer were able to improve objectively and subjectively by both external and internal evaluations. Thus, our system will allow trainees to develop their laparoscopic skills in an inexpensive manner in the comfort of their own home.
Renal cell carcinoma is relatively common in patients with von Hippel-Lindau disease, yet characteristically follows a less aggressive course compared with sporadic renal cell carcinoma. We report on 2 patients with von Hippel-Lindau disease and atypically aggressive renal tumors. In these patients, more rigorous screening guidelines may help to identify the more aggressive variants.
Renal tumor classification is important because histopathological subtypes are associated with distinct clinical behavior. However, diagnosis is difficult because tumor subtypes have overlapping microscopic characteristics. Therefore, ancillary methods are needed to optimize classification. We used oligonucleotide microarrays to analyze 31 adult renal tumors, including clear cell renal cell carcinoma (RCC), papillary RCC, chromophobe RCC, oncocytoma, and angiomyolipoma. Expression profiles correlated with histopathology; unsupervised algorithms clustered 30 of 31 tumors according to appropriate diagnostic subtypes while supervised analyses identified significant, subtype-specific expression markers. Clear cell RCC overexpressed proximal nephron, angiogenic, and immune response genes, chromophobe RCC oncocytoma overexpressed distal nephron and oxidative phosphorylation genes, papillary RCC overexpressed serine protease inhibitors, and extracellular matrix products, and angiomyolipoma overexpressed muscle developmental, lipid biosynthetic, melanocytic, and distinct angiogenic factors. Quantitative reverse transcriptase-polymerase chain reaction and immunohistochemistry of formalin-fixed renal tumors confirmed overexpression of proximal nephron markers (megalin/low-density lipoprotein-related protein 2, alpha-methylacyl CoA racemase) in clear cell and papillary RCC and distal nephron markers (beta-defensin 1, claudin 7) in chromophobe RCC/oncocytoma. In summary, renal tumor subtypes were classified by distinct gene expression profiles, illustrating tumor pathobiology and translating into novel molecular bioassays using fixed tissue.
BACKGROUND AND PURPOSE: Ablation by cold (cryoablation) or radiofrequency energy (RFA), has been popularized for the treatment of small renal tumors. Regrettably, there currently is no reliable method of radiologically monitoring the propagation of RF lesions in real time. Ultrasonography enhanced by gas-filled microbubble contrast agents allows depiction of regions of tissue perfusion and has been described as a useful adjunct in diagnosing renal pseudotumors, improving prostate biopsy results, and confirming successful ablation of liver tumors. We hypothesized that contrast-enhanced ultrasonography (CEUS) would allow us to define, in real time, areas of cell death secondary to RFA and thus determine successful treatment. MATERIALS AND METHODS: Five female swine underwent initial laparoscopic exploration and creation of ipsilateral upper- and lower-pole renal RFA lesions. Lesion size was measured with standard gray-scale, Doppler, and microbubble CEUS. After 2 weeks, an identical procedure was performed on the contralateral kidney, including repeat sonographic measurements on the first kidney. All swine were then immediately sacrificed, and both kidneys (20 lesions) were harvested for pathologic analysis (hematoxylin-eosin and nicotinamide adenine dinucleotide stains). Radiographic lesion size was then compared with the gross and microscopic findings. RESULTS: The RFA lesions could not be imaged accurately in real time with standard gray-scale or Doppler sonography. However, microbubble CEUS was able to monitor parenchymal blood flow and, thus, the lesions (no blood flow) in real time. Hypoechoic lesions (no bubble enhancement) imaged during contrast sonography corresponded with regions of cell death as demonstrated on pathologic analysis. CONCLUSIONS: Microbubble CEUS is can monitor RFA lesions in real time. This novel imaging modality should allow more effective renal tumor ablation.
PURPOSE: The optimal management of lower pole renal calculi is controversial. We compared shock wave lithotripsy (SWL) and ureteroscopy (URS) for the treatment of patients with small lower pole stones in a prospective, randomized, multicenter trial. MATERIALS AND METHODS: A total of 78 patients with 1 cm or less isolated lower pole stones were randomized to SWL or URS. The primary outcome measure was stone-free rate on noncontrast computerized tomography at 3 months. Secondary outcome parameters were length of stay, complication rates, need for secondary procedures and patient derived quality of life measures. RESULTS: A total of 67 patients randomized to SWL (32) or URS (35) completed treatment. The 2 groups were comparable with respect to age, sex, body mass index, side treated and stone surface area. Operative time was significantly shorter for SWL than URS (66 vs 90 minutes). At 3 months of followup 26 and 32 patients who underwent SWL and URS had radiographic followup that demonstrated a stone-free rate of 35% and 50%, respectively (p not significant). Intraoperative complications occurred in 1 SWL case (unable to target stone) and in 7 URS cases (failed access in 5 and perforation in 2), while postoperative complications occurred in 7 SWL and 7 URS cases. Patient derived quality of life measures favored SWL. CONCLUSIONS: This study failed to demonstrate a statistically significant difference in stone-free rates between SWL and URS for the treatment of small lower pole renal calculi. However, SWL was associated with greater patient acceptance and shorter convalescence.
PURPOSE: We evaluated the effect of cranberry juice on urinary stone risk factors. MATERIALS AND METHODS: A total of 12 normal subjects and 12 calcium oxalate stone formers underwent 2, 7-day phases of study in random order while on a controlled metabolic diet. Subjects ingested 1 l of cranberry juice (CBJ) daily in 1 phase and 1 l of deionized water in the other phase. On the last 2 days of each phase 2, 24-hour urine collections and blood samples were obtained for stone risk factors and serum chemistries. RESULTS: No significant differences were found between normal subjects and stone formers in response to CBJ and, therefore, the groups were combined. CBJ significantly increased urinary calcium (from 154 to 177 mg per day, p =0.0008) and urinary oxalate (from 26.4 to 29.2 mg per day, p =0.04), thereby increasing urinary saturation of calcium oxalate by 18%. Urinary citrate was unchanged and urinary magnesium increased slightly. Urinary pH decreased (from 5.97 to 5.67, p =0.0005), and urinary ammonium, titratable acidity and net acid excretion increased during CBJ ingestion. Urinary uric acid decreased (from 544 to 442 mg per day, p <0.0001) as did serum uric acid. Thus, the urinary saturation of brushite and monosodium urate was reduced by CBJ but the amount of undissociated uric acid increased. CONCLUSIONS: CBJ exerts a mixed effect on urinary stone forming propensity. It reduces urinary pH likely by providing an acid load and decreases urinary uric acid perhaps by retarding urate synthesis. Overall CBJ increases the risk of calcium oxalate and uric acid stone formation but decreases the risk of brushite stones.
PURPOSE: Small-intestinal submucosa (SIS) has been successful as an onlay graft in ureteral repair, but tubularized segment interposition of SIS has been unsuccessful. Our objective was to evaluate whether a type I collagen inhibitor, halofuginone, would prevent stricture formation in tubularized SIS interposition. MATERIALS AND METHODS: We performed either laparoscopic partial ureteral excision followed by an SIS onlay graft (N = 5) or complete laparoscopic ureteral excision followed by an SIS interposition graft (N = 7) in domestic pigs. Animals received either no (N = 3), low-dose (N = 5), or high-dose (N = 4) halofuginone. Animals had ureteral stenting for 2 weeks after surgery and were permitted to survive for 6 or 9 weeks. An intravenous urogram (IVU) was performed prior to sacrifice. Kidneys were examined grossly and histologically. RESULTS: One animal that received an onlay graft died of an unrelated illness. The remaining four ureteral onlay animals, including one control and two low-dose and one high-dose pig, had grossly normal kidneys at harvest. The IVU was normal in the control and high-dose animal but showed delayed excretion with mild hydroureteronephrosis in the low-dose animals. Pathologic examination of the SIS site revealed circumferential reepithelialization with inflammation and mild fibrosis. All seven tubularized interposition graft kidneys demonstrated either severe hydroureteronephrosis (N = 5) or renal atrophy (N = 2), and all had complete obstruction on IVU. Pathologic examination revealed a stenotic ureteral lumen with extensive surrounding inflammation and fibrosis. CONCLUSIONS: An SIS onlay graft was successful in the porcine model of ureteral injury. Halofuginone, a type I collagen inhibitor, did not demonstrate a significant beneficial effect in this technique. Ureteral tubularized interpositions with SIS are unsuccessful and not improved by halofuginone.
PURPOSE: Regardless of training, innate ability may influence the acquisition of endoscopic skills. Until recently objective methods to assess innate ability have not been available. We compared objective measures of human basic performance resources (BPRs) using nonlinear causal resource analysis (NCRA) and expert rated endoscopic performance of medical students on a virtual reality (VR) simulator. MATERIALS AND METHODS: BPRs were measured in 18 medical students (group 1) using 13 validated tests. BPR results were compared to the results of ureteroscopic skills assessment on the VR simulator. An NCRA model was devised to predict performance based on BPRs and the limiting performance resource (LPR). The same BPRs were measured in a second group of 14 medical students (group 2). Using the model created from group 1 performance of VR ureterorenoscopy was predicted based on LPR for each student in group 2. Predicted performance was compared to rated performance. RESULTS: The average difference in score between 2 expert raters was 7.2%. The average difference in predicted score based on the NCRA model and rated score was only 8.0%. In 9 of the 14 group 2 subjects (63%) the performance prediction by NCRA was in excellent agreement (+/-10%) with the expert rating on the VR simulation. NCRA over predicted performance in 2 subjects (14%) and under predicted performance in 3 (21%). CONCLUSIONS: Objective prediction of ureteroscopic performance in the VR environment using LPRs (measures of innate ability) for each subject is possible and practical using new measurement and modeling methods. The selection of surgical candidates, training and the educational curriculum could be impacted.
PURPOSE: Virtual reality surgical simulators may shorten operative time and reduce the potential for iatrogenic injury by providing training outside the operating room. We hypothesized that training on a virtual ureteroscopy (VU) simulator would allow novice endoscopists to overcome the initial learning curve before entering the operating room. MATERIALS AND METHODS: We evaluated 16 medical students on their ability to perform specific ureteroscopic tasks on a VU simulator. The students trained on the simulator for a total of 5 hours over multiple sessions using different training modules and then were retested on the initial module. Likewise, 16 urology residents with varying degrees of endoscopic experience were assessed on the same test module twice, without additional simulator training. RESULTS: The students improved task completion time from 17.4 to 8.7 minutes (p <0.05), while the residents performed the task in 7.6 minutes at baseline and 6.7 minutes at the second trial. Stratification of residents by years of urology training revealed that the mean completion time for the students after training did not differ statistically from that of first year residents who had performed a median of 14 clinical ureteroscopies. Furthermore, the subjective performance scores of the students were comparable to those of the first year residents. CONCLUSIONS: Novice medical students trained on a VU simulator improved task completion time by 50% after training, and performed comparably to residents who had completed nearly 1 year of urology training. VR training may allow beginning urology residents to shorten the initial learning curve associated with ureteroscopy training, although this hypothesis requires further validation.
PURPOSE: Training on a virtual reality (VR) simulator has been shown to improve the performance of VR endoscopic tasks by novice endoscopists. However, to our knowledge the translation of VR skills into clinical endoscopic proficiency has not been demonstrated. We established criterion validity for a VR ureteroscopy simulator by evaluating VR trained subjects in a cadaver model. MATERIALS AND METHODS: A total of 32 participants, including 16 medical students and 16 urology residents, were evaluated at baseline on a VR ureteroscopy simulator (Uromentor, Simbionix, Lod, Israel), performing simple diagnostic ureteroscopy. The students then underwent 5 hours of supervised training on the simulator. Two weeks later all participants were reevaluated (VR2) on the simulator when repeating the initial task. Each participant was then assessed on the performance of a similar diagnostic ureteroscopy in a male cadaver. RESULTS: In medical students VR2 and cadaver performances correlated closely for several measured parameters (total time for task completion and overall global ratings score). In contrast, there was little correlation between the 2 performances in residents. Indeed, performance on the cadaver correlated more closely with the training level than VR2 scores. Despite VR training medical students were unable to perform cadaver ureteroscopy comparably to residents. CONCLUSIONS: For novice endoscopists performance on the simulator after training predicted operative (cadaver) performance and, thus, it may be useful for the education and assessment of physicians in training. However, VR training is unable to override the impact of clinical training, although it may help shorten the learning curve early in training.
PURPOSE: Radio frequency ablation (RFA) of renal tumors is a relatively new technology. Few groups are familiar with the posttreatment appearance of these lesions and how they differ from cryoablated renal masses. We describe the evolution of the appearance of these lesions on followup contrast enhanced (CE) computerized tomography (CT). METHODS AND MATERIALS: A total of 64 consecutive renal tumors treated with RFA from April 2000 to September 2003 for which posttreatment CE-CT was done were included in this study. CE-CT was reviewed at 6 weeks, 3 months, 6 months and every 6 months thereafter to determine the characteristic features and evolution of these lesions. RESULTS: Renal tumors were treated with CT guided percutaneous (34), laparoscopic (28) or open (2) RFA. At a median followup of 13.7 months (range 6 weeks to 29 months) 62 RFA lesions demonstrated an absence of contrast enhancement on CE-CT. Treated endophytic tumors developed a low density, nonenhancing, wedge-shaped defect with fat infiltration seen between the ablated tissue and normal parenchyma. Treated exophytic tumors retained a configuration similar to that of the original with a lack of contrast enhancement and minimal shrinkage. Percutaneous treated lesions developed a peritumor scar or halo that demarcated ablated and nonablated tissue (perirenal fat). Persistent tumor was marked by contrast enhancement within the ablation borders of the original mass in 1 case, whereas tumor recurred after initial successful ablation with an enhancing nodule in 1. CONCLUSIONS: The radiographic features and evolution of radio frequency ablated renal tumors are unique. Successfully treated tumors demonstrated no contrast enhancement, minimal shrinkage and occasional retraction from normal parenchyma by fat infiltration.
OBJECTIVES: Hydropneumothorax (HPTX) is recognized as a potential complication of percutaneous nephrostolithotomy (PCNL), particularly with supracostal access. Postoperative chest radiography (CXR) is routinely used to evaluate the chest after PCNL. We prospectively compared the sensitivity of intraoperative chest fluoroscopy with immediate postoperative portable CXR and postoperative day 1 chest computed tomography (CT) for the detection of pleural fluid. METHODS: A total of 89 consecutive patients (mean age 47.9 +/- 13.3 years; 100 renal units) undergoing PCNL were prospectively evaluated with intraoperative fluoroscopy at the conclusion of the procedure and then with anteroposterior CXR in the postanesthesia care unit and postoperative day 1 noncontrast, thin-cut CT of the kidneys and lung bases. CT imaging of the lung bases comprised the reference standard for detecting pleural fluid. RESULTS: A total of 104 percutaneous renal accesses in 100 renal units, 60 above and 44 below the 12th rib, were used. In 16 cases (16%), a second-stage procedure was performed to clear residual stone fragments detected on post-PCNL CT. HPTX was detected in 1, 8, and 38 cases by initial fluoroscopy, immediate postoperative CXR, and CT scan, respectively. Intervention was necessary in 7 patients. In 2 patients with fluoroscopic evidence of pleural fluid (1 at the initial PCNL and 1 during second-look flexible nephroscopy), intraoperative pleural drainage was performed percutaneously. In the other 5 patients, intervention was determined by the size of the HPTX on chest CT scan (n = 1) or the presence of symptoms (n = 4). In no case was intervention performed on the basis of the immediate postoperative CXR findings when intraoperative chest fluoroscopy was negative. CONCLUSIONS: Intraoperative chest fluoroscopy during PCNL is sufficient to detect clinically significant HPTXs, and, therefore, routine postoperative CXRs are not necessary. However, a high index of suspicion based on clinical symptoms postoperatively should prompt chest imaging.
PURPOSE: To our knowledge we present the initial series of renal mass in situ laparoscopic radio frequency ablation. We also discuss the indications for and results of subsequent laparoscopic partial nephrectomy. MATERIALS AND METHODS: Laparoscopic radio frequency ablation was performed in 13 patients with a mean age of 59 years (range 18 to 81) and a total of 17 small enhancing renal masses. In 5 patients the tumor was subsequently excised completely, whereas in 7 it was left in situ after treatment. In 1 patient with 5 lesions only the largest lesion was excised, while the other 4 were left in situ. RESULTS: Mean tumor size was 1.96 cm. (range 0.9 to 3.6). Tumors that remained in situ tended to be endophytic and located in the mid pole. Pathological analysis revealed renal cell carcinoma in 10 patients, angiomyolipoma in 2 and oncocytoma in the patient with multiple lesions. None of the 8 patients with renal cell carcinoma who had at least 6 weeks of followup (mean 9.8 months, range 1.5 to 22) had any evidence of persistent tumor enhancement on surveillance computerized tomography or any other evidence of disease progression. There was 1 focal positive margin in a patient who underwent radio frequency ablation and excision of renal cell carcinoma but the patient remained disease-free 1 year after treatment. CONCLUSIONS: Early experience with laparoscopic radio frequency ablation in situ or combined with partial nephrectomy shows that it appears to be a safe method of managing small enhancing renal masses. Radio frequency assisted laparoscopic partial nephrectomy is reserved for easily accessible exophytic tumors, while strict surveillance is required for lesions remaining in situ after ablation. Additional followup is required to assess long-term effectiveness.