Biomedical subjects

Beng Jit Tan

Publications and source records attributed to Beng Jit Tan.

9 recordsLinked to original sources

PubMed2006

Novel dual-lumen ureteral stents provide better ureteral flow than single ureteral stent in ex vivo porcine kidney model of extrinsic ureteral obstruction.

OBJECTIVES: In the instance of extrinsic ureteral obstruction, indwelling ureteral stents have a high failure rate. Although technically challenging, simultaneous insertion of two ipsilateral stents can achieve better flow rates with time. A novel dual-lumen stent, composed of two adhered ureteral stents, offers the additional benefit of easier placement than a single guidewire. Using a novel ex vivo porcine model, the flow rates within an extrinsically obstructed renal unit were evaluated using two internal ipsilateral stents and two prototype double-lumen stents. METHODS: Sixteen renal units were harvested from eight adult Yorkshire female pigs. To quantify flow, the kidneys were infused at a constant pressure, and the corresponding ureteral drainage was measured for a defined interval. The flow was measured with a standard 7F double-pigtail stent, two ipsilateral 7F double-pigtail stents, a 7F novel double-lumen stent designed with both distal lumens open, and a 7F novel double-lumen stent with one distal lumen closed. The intraluminal and extraluminal flow in obstructed and nonobstructed systems was measured. RESULTS: The two ipsilateral standard stents or prototype double stents achieved better flow down the ureter than did one standard stent (P <0.05). The intraluminal and extraluminal flow in the novel stents was statistically greater than the corresponding flow in the standard double-pigtail stent (P <0.01). The extraluminal and obstructed flow was lowest for the standard double-pigtail stent. CONCLUSIONS: Novel dual-lumen prototype ureteral stents provided better flow than a single stent in extrinsically obstructed ureters with the proposed added benefit of easier retrograde insertion compared with a single guidewire.

Animals↗

PubMed2006

Is carbon dioxide insufflation safe for laparoscopic surgery? A model to assess the effects of carbon dioxide on transitional-cell carcinoma growth, apoptosis, and necrosis.

PURPOSE: To study the effects of carbon dioxide insufflation pressure and concentration on the adhesion, growth, apoptosis, and necrosis of transitional-cell carcinoma (TCC). MATERIALS AND METHODS: Adhesion and growth of the AY-27 rat TCC cell line was measured after CO2 insufflation in vitro at different pressures ranging from 0 to 15 mm Hg and after incubation in CO2-air mixtures at 5%, 10%, and 15% CO2 by volume. RESULTS: Tumor adhesion decreased significantly after CO2 insufflation. For all insufflation pressures, there was an increase in cell growth, apoptosis, and necrosis for the first 24 hours followed by a steady decline. High concentrations of CO2 (>5%) inhibited cell growth for only the first 48 hours. The effects of CO2 pneumoperitoneum on tumor-cell adhesion, growth inhibition, apoptosis, and necrosis were more prominent at high CO2 pressure (> or =15 mm Hg) and concentration (>5% CO2). However, insufflation pressure had a greater inhibitory effect on tumor growth than did CO2 concentration. High insufflation pressures and CO2 concentrations significantly decreased extracellular pH. CONCLUSION: The short-term effect of CO2 on TCC growth and apoptosis is complex. Overall, CO2 has a toxic effect on TCC and inhibits cell adhesion and growth. High CO2 concentrations (>5%) and high insufflation pressures (> or =15 mm Hg) are most effective in decreasing tumor-cell adhesion and growth.

Animals↗

PubMed2006

The use of robotically assisted surgery for treating urachal anomalies.

OBJECTIVE: To report the management of urachal anomalies using a robotically assisted approach. PATIENTS AND METHODS: Between January 2005 and February 2006, five patients (mean age 51 years, range 24-68) were diagnosed with urachal anomalies. Two basic robot-assisted surgical approaches were used for excising the urachal anomalies: excision of the urachal remnant via partial cystectomy, and radical cystectomy for excision of urachal adenocarcinoma. RESULTS: All five cases were successful and the excised specimens were assessed histologically. The short-term oncological outcome in the three patients with histologically confirmed moderately differentiated adenocarcinoma showed no evidence of recurrent disease within a median interval of 8 months. Surveillance follow-up cystoscopy in the patients who had a partial cystectomy showed a well-healed bladder mucosa with no evidence of recurrence. CONCLUSIONS: Radical excision of the urachal tract with partial cystectomy or radical cystectomy using the da Vinci robot is safe, effective and technically feasible.

Adult↗

PubMed2005

Trends in ureteropelvic junction obstruction management among urologists in the United States.

OBJECTIVES: To determine current practice patterns in the surgical treatment of ureteropelvic junction obstruction (UPJO) among urologists in the United States. METHODS: Using the American Urological Association directory, an electronic mail survey regarding the surgical management of UPJO was sent to 1040 urologists in the United States with an electronic mail address listed in the roster. RESULTS: The response rate was 37.6%. Of the respondents, 67.4% were in community practice and 32.6% in academic practice. Nearly 53% of the respondents would perform a workup for a crossing vessel before definitive therapy; if no crossing vessel was found, 43.5% would consider Acucise endopyelotomy as the first-line procedure. However, if a crossing vessel was found, 57.4% would perform open pyeloplasty and 34.3% would choose laparoscopic pyeloplasty as their first-line procedure. If pyeloplasty was chosen, community urologists preferred open pyeloplasty (77.6%), and academic urologists preferred laparoscopic pyeloplasty (66.9%). The surgeon's training and experience was the most influential factor in choosing between laparoscopic and open pyeloplasty. If the patient had a failed endopyelotomy in the past, most respondents (90.8%) would perform pyeloplasty for definitive treatment of the UPJO. CONCLUSIONS: Demonstration of a crossing vessel remains an important factor in determining the course of management of a UPJO. During the past 5 years, a growing number of urologists in both academic and nonacademic practices have been performing laparoscopic pyeloplasty for the management of UPJO in adults. Several factors, especially the surgeon's training, have an impact on the choice of procedure. Open pyeloplasty is still performed by a significant number of urologists. These data may be useful in designing physician education programs and/or future investigations to help define standard treatment practices for UPJO.

Adult↗

PubMed2005

Effects of pneumoperitoneal gases and pressures on transitional cell carcinoma adhesion, growth, apoptosis and necrosis: an in vitro study.

PURPOSE: We studied the effects of insufflation gas and pressure on the adhesion, growth, apoptosis and necrosis of transitional cell carcinoma (TCC) in an in vitro model. MATERIALS AND METHODS: Tumor adhesion and cell growth of AY-27 rat TCC was measured after 3-hour incubation with CO2, N2 and He insufflation at different pressures (0, 10 and 15 mm Hg) in vitro. The effects of these gases on the rate of tumor cell apoptosis and necrosis were compared. RESULTS: In vitro the tumor adhesion rate was lowest with CO2 and highest with N2. Higher gas pressures resulted in decreased adhesion rates for CO2 and He but increased adhesion rates for N2. N2 enhanced tumor cell proliferation at all pressures studied. He and CO2 resulted in an initial increase in cell proliferation in the first 24 hours, followed by a decrease in tumor growth. Extracellular medium turned acidic in CO2 (pH 6.27 to 6.39) but basic in N2 and He (pH 8.39 to 8.84). At all insufflation pressures studied apoptosis and necrosis rates were increased in the first 24 hours, followed by a decrease for CO2 and N2. He resulted in increasing apoptosis and necrosis throughout the study period. CONCLUSIONS: The type of gas and insufflation pressure affects cell adhesion and tumor growth. There was a significant increase in tumor adhesion and proliferation with N2 insufflation compared with CO2 and He at 0 to 15 mm Hg pressures. CO2 demonstrated the greatest decrease in TCC adhesion and proliferation at 15 mm Hg pressure. Apoptosis and necrosis were highest for He compared with the other gases.

Animals↗

PubMed2005

Urological laparoscopy: basic physiological considerations and immunological consequences.

PURPOSE: The applications of laparoscopy to urological surgery continue to grow at a steady pace. A complete understanding of the physiological and immunological changes associated with pneumoperitoneum is required. We reviewed the physiology of laparoscopy with regard to the major organ systems and summarize the effects of pneumoperitoneum on immune function. MATERIALS AND METHODS: Articles published in the scientific literature from 1990 to 2004 with relevance to laparoscopic physiology and the immune response to pneumoperitoneum were reviewed using PubMed. RESULTS: Pneumoperitoneum induces predictable pulmonary and renal responses. The cardiovascular and hemodynamic responses are phasic and dynamic in nature, and only generalizations regarding cardiac function can be made. Renal parenchymal and venous compression during pneumoperitoneum are the etiology of oliguria during laparoscopy. The effects are reversible and cause no adverse effects on renal function. There is a general trend toward systemic immune preservation and peritoneal immune depression during insufflation based laparoscopy. Attenuated peritoneal immunity has been demonstrated most consistently by altered macrophage function. CONCLUSIONS: Physiological changes incurred as a result of pneumoperitoneum have minimal adverse effects in healthy individuals undergoing laparoscopic surgery. Interest has grown in the impaired peritoneal immune response to CO2 pneumoperitoneum. Altered intraperitoneal immunity may represent a new avenue for the development of adjuvant therapies for minimally invasive treatments of urological malignancies and for the prevention of port site metastasis. Further elucidation and investigation into the immunological responses to pneumoperitoneum during urological laparoscopic procedures is called for.

Animals↗

PubMed2004

Ureteropelvic junction obstruction repair: when, how, what?

PURPOSE OF REVIEW: To review factors that affect the success of ureteropelvic junction obstruction repair and recent developments in minimally invasive procedures for the repair of ureteropelvic junction obstruction. RECENT FINDINGS: Recent reports and studies further confirm earlier findings that the success rate of endopyelotomy is decreased when a crossing vessel is the primary cause of ureteropelvic junction obstruction, poor renal function and significant hydronephrosis. Various minimally invasive procedures have emerged recently for the treatment of ureteropelvic junction obstruction. These include laparoscopic pyeloplasty, robotically assisted laparoscopic procedures, and percutaneous endopyeloplasty. These procedures offer potential advantages over conventional endopyelotomy, including better success rates in the presence of crossing vessels, wider caliber reconstruction of the ureteropelvic junction, and full-thickness healing with primary intent. SUMMARY: With such a large variety of minimally invasive procedures for the treatment of ureteropelvic junction obstruction available, the treatment choice for ureteropelvic junction obstruction must be based on several factors, including the success and morbidity of the procedures, the surgeon's experience, the cost of the procedure, and the patient's choice.

Age Factors↗

PubMed2004

Comparison of laparoscopic saline infused to dry radio frequency ablation of renal tissue: evolution of histological infarct in the porcine model.

PURPOSE: We investigated and compared the gross and histopathological features of radio frequency (RF) ablated renal tissue using saline infused RF ablation (RFA) vs dry RFA in a porcine model. MATERIALS AND METHODS: Ten porcine kidneys underwent laparoscopic RFA. The lower and upper poles of each right kidney were treated with 1 and 2 cycles of saline augmented (wet) RFA, respectively. The upper pole of each left kidney was RF ablated without saline infusion (dry RFA) and a control lesion was created in the lower pole. The animals were sacrificed immediately after ', 2 and 9 days after (subacute), and 14 and 21 days after (chronic) treatment, respectively. Gross pathological and histological changes caused by the different RF treatments were compared. RESULTS: Mean time to attain target temperature was shorter with wet than with dry RFA. Grossly the lesion sizes achieved were larger using wet RFA but independent of the number of wet RFA treatment cycles. Gross lesion sizes decreased with time for each treatment modality. No histopathological differences were seen between the 2 RFA treatment modalities as well as between 1 vs 2 cycles of wet RFA. In the acute phase hematoxylin and eosin staining of ablated tissue revealed focal areas of alterations in renal tubular histology. However, nicotinamide adenine dinucleotide staining of corresponding areas confirmed the lack of cellular viability except for glomeruli. In the subacute phase there were focal coagulation necrosis and thrombosed blood vessels. Within the necrotic areas the glomeruli were the last structures to lose viability. In the chronic phase fibrosis with decreased lesion size was seen. Nicotinamide adenine dinucleotide staining demonstrated that the cellular kill was permanent during the entire study period. CONCLUSIONS: The effects of RFA of renal tissue has 2 phases, namely initial direct thermal ablation causing acute cell death and a later subacute phase causing subsequent infarction of the distal arterial vascular supply to the ablated region, resulting in more cell death and coagulative necrosis. Glomeruli are the last structures to lose viability in necrotic areas. Most importantly cellular death caused by RFA is permanent.

Animals↗

PubMedDate not supplied

Laparoscopic nephroureterectomy with bladder-cuff resection: techniques and outcomes.

Advancements in minimally invasive instrumentation and technique have provided the impetus to performing urologic procedures with reduced perioperative morbidity, shorter hospital stays, and, most importantly, efficacious oncologic results. At multiple centers of excellence, laparoscopic nephroureterectomy (LNU) has evolved into a new standard for the management of upper-tract transitional-cell carcinoma (TCC) that is not amenable to endoscopic resection. An LNU may be performed via a transperitoneal or retroperitoneal approach together with excision of the distal ureter and a bladder cuff. Analysis of present-day studies comparing LNU with open techniques demonstrates equivalent oncologic outcomes. In addition, those patients undergoing LNU fare better than their counterparts having open surgery with respect to hospital stay, analgesic requirements, and convalescence. With multiple options for excision of a cuff of bladder, a consensus has not been established. However, LNU has emerged as the new standard of care for the treatment of upper- tract TCC. Review of the techniques and outcomes of LNU from the minimally invasive urology community are described.

Carcinoma, Transitional Cell↗