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Biomedical subjects

Kenneth Ogan

Publications and source records attributed to Kenneth Ogan.

At least 19 recordsLinked to original sources
PubMed2004

Ureteral replacement using small-intestinal submucosa and a collagen inhibitor in a porcine model.

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.

Animals↗
PubMed2004

Assessment of basic human performance resources predicts the performance of virtual ureterorenoscopy.

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.

Clinical Competence↗
PubMed2004

Use of a virtual reality simulator for ureteroscopy training.

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.

Adult↗
PubMed2004

Virtual ureteroscopy predicts ureteroscopic proficiency of medical students on a cadaver.

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.

Adult↗
PubMed2004

The radiographic evolution of radio frequency ablated renal tumors.

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.

Adenocarcinoma, Clear Cell↗
PubMed2003

Sensitivity of chest fluoroscopy compared with chest CT and chest radiography for diagnosing hydropneumothorax in association with percutaneous nephrostolithotomy.

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.

Adult↗
PubMed2003

Laparoscopic application of radio frequency energy enables in situ renal tumor ablation and partial nephrectomy.

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.

Adolescent↗
PubMed2003

Infrared thermography and thermocouple mapping of radiofrequency renal ablation to assess treatment adequacy and ablation margins.

OBJECTIVES: The primary disadvantage of renal tumor RF ablation is the inability to monitor the intraoperative propagation of the RF lesion with real-time imaging. We sought to assess whether adequately lethal temperatures are obtained at the margins of the intended ablation zone using laparoscopic thermography to monitor radiofrequency (RF) lesions in real time, thermocouple measurements, and histopathologic evaluation. METHODS: Renal RF lesions were created under direct laparoscopic vision in the upper (1 cm diameter) and lower (2 cm) poles of the right kidney in 5 female pigs. The RF lesions were produced with the RITA generator and probe, set at 105 degrees C for 5-minute ablations. During RF treatment, a laparoscopic infrared (IR) camera measured the surface parenchymal temperatures, as did multiple thermocouples. The pigs were then either immediately killed (n = 3) or allowed to live for 2 weeks (n = 2). The kidneys were removed to correlate the temperature measurements with histologic analysis of the ablated lesion. RESULTS: Using a threshold temperature of greater than 70 degrees C for visual "temperature" color change, the IR camera identified the region of pathologic necrosis of the renal parenchyma during RF ablation. Thermocouple measurements demonstrated that the temperatures at the intended ablation radius reached 77.5 degrees C at the renal surface and 83.7 degrees C centrally, and temperatures 5 mm beyond the set radius reached 52.6 degrees C at the surface and 47.7 degrees C centrally. The average diameter of the gross lesion on the surface of the kidney measured 17.1 mm and 22.4 mm for 1-cm and 2-cm ablations, respectively. These surface measurements correlated with an average diameter of 16.1 mm and 15.9 mm (1-cm and 2-cm ablations, respectively) as measured with the IR camera. All cells within these ablation zones were nonviable by nicotinamide adenine dinucleotide diaphorase analysis. The average depth of the lesions measured 19 mm (1-cm ablation) and 25 mm (2-cm ablation) on gross histologic examination. CONCLUSIONS: The laparoscopic IR camera is able to monitor the surface renal temperatures during RF treatment. Thermocouple measurements during RF ablation confirmed the thermographic findings and demonstrated that lethal temperatures at the margin of the intended treatment zone are routinely obtained and that a rapid decline in temperature occurs beyond the predicted ablation margin.

Animals↗
PubMed2003

Nephrectomy after radiofrequency ablation-induced ureteropelvic junction obstruction: potential complication and long-term assessment of ablation adequacy.

Little information is available concerning the morbidity of radiofrequency ablation (RFA) or the evolution of an RFA lesion over time. We report our findings in a kidney removed 1 year after RFA of a 2.3-cm renal tumor. After RFA, the patient experienced flank pain, followed by hydronephrosis, ureteropelvic junction obstruction, and eventual loss of function in the treated kidney. Nephrectomy revealed no residual renal cell carcinoma. RFA can completely destroy renal cell carcinoma in situ without histologic evidence of persistence or recurrence for up to 1 year after treatment. Care must be taken to avoid concurrent damage to the collecting system.

Catheter Ablation↗
PubMed2003

Laparoscopic radical nephrectomy: oncologic efficacy.

Laparoscopic radical nephrectomy has evolved tremendously over the past decade to the point where it should be considered the standard of care for localized renal tumors not amenable to nephron-sparing surgery. The benefits of decreased postoperative pain, shortened hospital stay, quicker convalescence, and improved cosmesis have been proved in numerous studies. Long-term oncologic results of LRN have demonstrated equivalent outcomes to ORN.

Humans↗
PubMed2003

Sutureless laparoscopic heminephrectomy using laser tissue soldering.

BACKGROUND AND PURPOSE: Widespread application of laparoscopic partial nephrectomy has been limited by the lack of a reliable means of attaining hemostasis. We describe laser tissue welding using human albumin as a solder to control bleeding and seal the collecting system during laparoscopic heminephrectomy in a porcine model. MATERIALS AND METHODS: Laparoscopic left lower-pole heminephrectomy was performed in five female domestic pigs after occluding the hilar vessels. Using an 810-nm pulsed diode laser (20 W), a 50% liquid albumin-indocyanine green solder was welded to the cut edge of the renal parenchyma to seal the collecting system and achieve hemostasis. Two weeks later, an identical procedure was performed on the right kidney, after which, the animals were sacrificed and both kidneys were harvested for ex vivo retrograde pyelograms and histopathologic analysis. RESULTS: All 10 heminephrectomies were performed without complication. The mean operative time was 82 minutes, with an average blood loss of 43.5 mL per procedure. The mean warm ischemia time was 11.7 minutes. For each heminephrectomy, a mean of 4.2 mL of solder was welded to the cut parenchymal surface. In three of the five acute kidneys and all five 2-week kidneys, ex vivo retrograde pyelograms demonstrated no extravasation. In addition, no animal had clinical evidence of urinoma or delayed hemorrhage. Histopathologic analysis showed preservation of the renal parenchyma immediately beneath the solder. DISCUSSION: Laser tissue welding provided reliable hemostasis and closure of the collecting system while protecting the underlying parenchyma from the deleterious effect of the laser during porcine laparoscopic heminephrectomy.

Albumins↗
PubMed2003

Photodynamic therapy for refractory superficial bladder cancer: long-term clinical outcomes of single treatment using intravesical diffusion medium.

BACKGROUND: Diffuse superficial transitional-cell carcinoma (TCC) refractory to standard therapies poses a clinical dilemma. Photodynamic therapy (PDT), which uses an interaction between absorbed light and a retained photosensitizing agent to destroy tissue, has been used to treat diffuse superficial bladder TCC, although there are few reports of long-term outcomes. PATIENTS AND METHODS: A series of 34 patients, 29 with TCC carcinoma in situ (CIS) and 5 with multiple small papillary stage T(a) or T(1) lesions, received porfimer sodium (P) 48 hours before whole-bladder PDT with 630-nm laser light. A 0.02% soybean emulsion diffusion medium was instilled into the bladder, and the laser optical fiber was positioned under triplanar sonography prior to PDT. The mean follow-up was 52 months. RESULTS: At 3 months, a complete response (CR) in 14 (44%) of the 32 evaluable patients, a partial response (PR) in 4 (12%), and no response (NR) in 14 (44%). Four of the five patients with extensive papillary lesions did not respond. The NR rate for patients with CIS with or without resected papillary lesions was 37%. The mean time to recurrence in the CR group was 9.8 months, and five members of this group (36%) underwent cystectomy (mean time 20 months) for persistent/progressive disease (N = 3) or bladder contracture (N = 2). In the NR group, 6 (43%) underwent cystectomy (mean time 14 months) for persistent/progressive disease. Metastatic bladder cancer was the cause of death in only 4 of the 12 patients who have died. Of the remaining 22 patients, 15 are still alive and have an intact bladder, nine with no disease and six with only superficial disease. CONCLUSION: This is the first report of long-term results following whole-bladder PDT using diffusion medium for isotropic light distribution. More than half of the patients with TCC refractory to traditional intravesical therapy received benefit from a single PDT session. Patients with extensive flat papillary lesions do not appear to respond well. Patients who achieve a CR have less likelihood of and longer time interval before needing cystectomy for progressive disease than NR patients. Our PDT protocol is associated with minimal morbidity in these high-risk patients.

Administration, Intravesical↗
PubMed2003

Feasibility of laparoscopic partial nephrectomy using pledgeted compression sutures for hemostasis.

PURPOSE: To develop a technique for laparoscopic partial nephrectomy (LPN) without the use of hilar occlusion that allows large renal resection and excellent hemostasis. MATERIALS AND METHODS: Five female domestic pigs underwent right laparoscopic transperitoneal lower-pole partial nephrectomy after placement of pledgeted parenchymal compression sutures tied intracorporeally to induce regional renal hypoperfusion. Postoperatively, serial serum creatinine measurements were obtained to monitor renal function. The pigs were allowed to recover and 2 weeks later underwent an identical procedure on the left side. The animals were sacrificed after the second procedure, and both renal units were removed for ex vivo retrograde urograms and histologic analysis. RESULTS: The median operative time was 154.5 minutes (range 110-305 minutes), and the median blood loss was 137.5 mL (range 100-300 mL). On average, 35% (range 31%-36.8%) of the kidney was resected. All cases required use of adjunctive hemostatic clips to control bleeding from central vessels. All animals survived 2 weeks and had no evidence of urinary extravasation clinically or on ex vivo retrograde urograms. CONCLUSIONS: In the porcine model, LPN with placement of pledgeted sutures allows resection of large renal segments, although technical refinements are required to improve hemostasis. Currently, the need for adjunctive hemostatic measures limits the initial clinical application of this technique to small, exophytic tumors.

Animals↗
PubMed2002

Laparoscopic versus open retroperitoneal lymph node dissection: a cost analysis.

PURPOSE: Laparoscopic retroperitoneal lymph node dissection is significantly less morbid than open retroperitoneal lymph node dissection but it is generally more costly due to longer operative time and disposable equipment. In response to budgetary pressure at our large county hospital we identified the cost components of laparoscopic retroperitoneal lymph node dissection that could be targeted to decrease procedure costs before expanding our laparoscopic retroperitoneal lymph node dissection program. MATERIALS AND METHODS: A comprehensive literature review of open and laparoscopic retroperitoneal lymph node dissection was performed and certain parameters were abstracted, including operative time and equipment, hospital stay, perioperative complications and surgical success rates. Using these data the projected overall cost and individual cost centers at our institution were compared for open and laparoscopic retroperitoneal lymph node dissection. Decision tree analysis models were devised to estimate the cost of each treatment using commercially available software. We performed 1 and 2-way sensitivity analysis to evaluate the effect of individual treatment variables on overall cost. Base case analysis involved a young man with clinical stage I nonseminomatous testicular cancer who was a candidate for retroperitoneal lymph node dissection. RESULTS: Based on a review of the costs at our institution open retroperitoneal lymph node dissection was a less costly procedure at $7,162 versus $7,804 for the laparoscopic approach. The slight cost superiority of the open approach was due to significantly lower costs associated with operating room time and equipment. On the other hand, the laparoscopic procedure showed a cost advantage for hospital stay. On 1-way sensitivity analysis laparoscopic dissection was less costly when operative time was less than 3.6 hours, hospitalization was less than 2.2 days or laparoscopic equipment costs were less than $768. On 2-way sensitivity analysis the laparoscopic approach was cost advantageous when performed in less than 5 hours or when the patient was discharged home within 2 days postoperatively. CONCLUSIONS: The primary cost variables for surgical treatment for testicular cancer include operative time, hospital stay and equipment cost. According to published data and decision tree analysis open retroperitoneal lymph node dissection is slightly less costly (less than $650) than laparoscopic retroperitoneal lymph node dissection for the surgical treatment of clinical stage I nonseminomatous testicular cancer at our institution. Our model identifies several measures that can be applied at any institution to render laparoscopic retroperitoneal lymph node dissection economically superior to the open approach.

Adult↗
PubMed2002

Oops we got in the chest: fluoroscopic chest tube insertion for hydrothorax after percutaneous nephrostolithotomy.

Percutaneous supracostal renal puncture provides ideal access to the collecting system or proximal ureter but is associated with an increased risk of pleural injury. We describe a simplified approach to intraoperative thoracostomy tube placement that uses urologic techniques and protects against recurrent hydrothoraces at second-look nephroscopy, without increasing patient morbidity or length of hospital stay.

Drainage↗
PubMed2002

Percutaneous radiofrequency ablation of renal tumors: technique, limitations, and morbidity.

OBJECTIVES: To evaluate our evolving experience with percutaneous radiofrequency (RF) renal tumor ablation and focus on our technique to ensure maximal treatment efficacy and reduce the possibility of complications. METHODS: Fifteen patients with small (less than 4 cm) posterior or lateral contrast-enhancing (more than 10 Hounsfield units) renal tumors were candidates for RF treatment. Of these patients, 12 (13 tumors) received computed tomography-guided percutaneous RF ablation. General anesthesia was administered in all but our first 2 patients, who received intravenous sedation. After treatment, patients were closely followed up with computed tomography scans at 6 weeks and 3, 6, and 12 months, and every 6 months thereafter. Successful ablation was defined as a lesion along with a margin of normal parenchyma that no longer enhanced (less than 10 Hounsfield units) on follow-up contrast imaging. RESULTS: The mean tumor size was 2.4 +/- 0.6 cm. The average procedure time was 95 minutes (range 60 to 150) and length of stay 0.9 days. All patients underwent the procedure without any major complications. At a mean follow-up of 4.9 months, 12 (93%) of 13 tumors were successfully ablated. In 3 patients, the procedure was not performed because of intervening bowel or lung parenchyma when positioned in the prone position before the procedure. Computed tomography-guided percutaneous RF ablation of small renal tumors is a viable minimally invasive treatment option with a high short-term success rate and low morbidity. This new technology must be uniformly applied to assess its long-term efficacy.

Adult↗