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Michael C Ost

Publications and source records attributed to Michael C Ost.

12 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

Hand pain during hand assisted laparoscopic nephrectomy--an ischemic event?

PURPOSE: The etiology of hand discomfort during hand assisted laparoscopic nephrectomy may be ischemic in nature. We determined if pneumoperitoneal pressure sustained to the hand during hand assisted laparoscopic nephrectomy poses an occupational risk, contributing to local hand hypoxia and resultant extremity pain. MATERIALS AND METHODS: A total of 442 measurements of hand oxygen saturation were made during hand assisted laparoscopic nephrectomy. A Nellcor OxiMax Max-1 oxygen sensor was attached to the left index finger of each surgeon and hand assisted laparoscopic nephrectomy was performed using a LapDisc at 15 mm Hg pneumoperitoneal pressures. Local hand oximetry readings and a numerical pain distress scale (range 0 to 10) were recorded every 2 minutes. To control for motion artifact oximetry readings were taken during hand motion and at rest. The Student t test was used to compare differences in local hand oxygen saturation and hand pain in and between study groups. RESULTS: A history of hand pain during hand assisted laparoscopic nephrectomy was significantly associated with local hypoxia during operative motion and at rest (p = 0.023 and 0.012, respectively), even with an adequate fascial incision and standard pneumoperitoneal pressures. During hand assisted laparoscopic nephrectomy hand pain was most significantly associated with local hypoxia after 24 minutes (p = 0.0002), when local oxygen saturation was 56% to 88%. CONCLUSIONS: A cohort of urologists is predisposed to ischemic hand pain during hand assisted laparoscopic nephrectomy. The etiology of this pain may be hypoxic in nature, attributable to pneumoperitoneal pressure decreasing perfusion and causing venous congestion or regional local ischemia. Circumferential antebrachial constriction from the LapDisc does not seem to be a significant contributing factor in the presence of an adequate fascial incision. Hand pain secondary to ischemia is most significant after 24 minutes at 15 mm Hg. Future studies in more subjects are called for to validate these findings to elucidate which surgeons are predisposed to this potential occupational hazard and what perioperative measures can be taken to avoid hand pain during hand assisted laparoscopic nephrectomy.

Adult↗
PubMed2006

Urolithiasis in patients with spinal cord injuries: risk factors, management, and outcomes.

PURPOSE OF REVIEW: Despite major advances in the urological care of spinal cord injury patients, the incidence of urolithiasis has not changed. Although the incidence of kidneys lost to staghorn calculus disease has decreased considerably, stone disease is still a significant cause of morbidity and concern. The purpose of this review is to summarize the risk factors for the development of stone diseases in the spinal cord injury patient population and present the outcomes of current endourologic treatment modalities. RECENT FINDINGS: Recurrent urinary tract infections, indwelling catheters, vesicoureteral reflux, and immobilization hypercalcuria are a few of the major risk factors for the development of urolithiasis among spinal cord injury patients. Retrograde endourologic techniques are often not possible to address stone disease due to lower extremity contractures, spinal curvature, and pelvic tilt. Extracorporeal shockwave lithotripsy success rates vary from 50 to 90%, but clearance rates are often delayed. Success rates for percutaneous nephrolithotomy match those quoted in the general population ( > 90%), but at the expense of a higher rate of complications (6-20%). Meticulous planning with regard to appropriate prophylactic antibiotics and body position will maximize efficacious outcomes. SUMMARY: Early identification and treatment of urolithiasis in spinal cord injury patients will aid in preserving renal function and minimizing associated complications. Despite variation in common urological practices between spinal cord injury units and the lack of clear cut guidelines for follow-up, the increased incidence of risks associated with urolithiasis lends support for routine genitourinary imaging in order to identify and treat those individuals at highest risk.

Humans↗
PubMed2005

Laparoscopic pyeloplasty versus antegrade endopyelotomy: comparison in 100 patients and a new algorithm for the minimally invasive treatment of ureteropelvic junction obstruction.

The aim of this article is to assess the treatment efficacy of percutaneous endopyelotomy and laparoscopic pyeloplasty to establish a new algorithm in the minimally invasive treatment of ureteropelvic junction obstruction (UPJO). Hospital records, office charts, and radiographic studies of patients with UPJO treated either endoscopically (n = 50), laparoscopically (n = 50), or by endopyeloplasty (n = 5) were reviewed. All percutaneous endopyelotomies were performed with a cold hook-knife technique, and all laparoscopic pyeloplasties were performed transperitoneally using an Anderson-Hynes dismembered anastomosis. Successful outcomes were defined as relief of obstruction as quantified by diuretic renal scans and/or relief of obstructive symptoms. All patients were followed for an average of 16.0 months (range, 2 to 42 months). In the endoscopically treated group, the average age was 44.6 +/- 15.6 years, estimated blood loss (EBL) was 152.1 +/- 112.8 mL, and the hospital stay was 2.5 +/- 1.0 days. There was no significant change from preoperative to postoperative creatinine (1.2 +/- 0.7 mg/dL to 1.2 +/- 0.7 [106 +/- 62 micromol/L +/- 106 +/- 62 micromol/L]). Success rates included 92% (35 of 38) for primary percutaneous antegrade endopyelotomy and 58% (7 of 12) for secondary percutaneous antegrade endopyelotomy. All of the primary percutaneous antegrade endopyelotomy failures (n = 3) had either grade 3 or grade 4 hydronephrosis. In the laparoscopic pyeloplasty group the average age was 37.9 +/- 14.8 years, EBL was 108.3 +/- 109.4 mL, and the average hospital stay was 2.6 +/- 0.9 days. There was no significant change from preoperative to postoperative creatinine (1.1 +/- 0.4 mg/dL to 1.0 +/- 0.4 mg/dL [97 +/- 35 micromol/L to 97 +/- 35 micromol/L]). Success rates included 100% (29 of 29) for primary repair and 95.2% (20 of 21) for secondary repair. There was no statistical difference in preoperative patient parameters or objective outcomes when comparing primary endopyelotomy and primary laparoscopic pyeloplasty. In skilled hands, highly successful outcomes can be expected when either antegrade endopyelotomy or laparoscopic pyeloplasty is used to treat a primary UPJO. In the instance of a UPJO associated with a high degree of hydronephrosis, patients may be better served with a laparoscopic pyeloplasty. To maximize an efficacious outcome, minimally invasive UPJO treatment decisions should be based on patient and surgeon preference, as directed by the presented algorithm.

Adult↗
PubMed2005

Endourologic treatment of upper urinary tract transitional cell carcinoma.

The traditional treatment for upper tract transitional cell carcinoma (UTTCC) consists of radical nephroureterectomy. A more conservative approach, however, was required in cases of bilateral UTTCC and in patients with disease in a solitary kidney but who had underlying comorbidities that made them unsuitable candidates for open surgery. Minimally invasive treatment methods were developed for these select groups of patients. Because of technological advancements and refinement in endoscopic techniques, most patients with UTTCC, even those with normal contralateral kidneys, can now be offered minimally invasive treatment with single or multimodal approaches involving ureteroscopy or percutaneous resection. For patients with low-stage, low-grade UTTCC, five-year survival rates are comparable for those treated endourologically and those treated by nephroureterectomy. High-grade lesions have much higher recurrence and progression rates than lower-grade lesions, and nephroureterectomy is therefore recommended in patients with high-grade disease. The use of adjuvant instillation in the treatment of UTTCC, administered via antegrade and retrograde methods, has been shown to improve outcomes. For recurrences to be diagnosed and treated in a timely manner, and acceptable cancer-free survival rates maintained, long-term rigorous follow-up after endourologic treatment, with regular surveillance ureteroscopy, is crucial.

Administration, Intravesical↗
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↗
PubMed2003

C-terminal Hsp-interacting protein slows androgen receptor synthesis and reduces its rate of degradation.

The androgen receptor (AR) is a member of the nuclear receptor superfamily that requires the action of molecular chaperones for folding and hormone binding. C-terminal Hsp-interacting protein (Chip) is a cochaperone that interacts with Hsp70 and Hsp90 molecular chaperones via a tetratricopeptide domain and inhibits chaperone-dependent protein folding in vitro. Chip also stimulates protein degradation by acting as an E3 ubiquitin ligase via a modified ring finger domain called a U box. We analyzed whether Chip affected AR levels using a transient transfection strategy. Chip overexpression led to a large decrease in AR steady state levels and increased levels of AR ubiquitinylation. However, Chip effects were not fully reversed by proteasome inhibitors, suggesting that mechanisms alternative to or in addition to proteasome-mediated degradation were involved. This hypothesis was supported by the finding that Chip overexpression reduced the rate of AR degradation, consistent with an effect on AR folding, perhaps leading to aggregation. The possibility that Chip affected AR folding was further supported by the finding that the effects of exogenous Chip were reproduced by a mutant lacking the U box. These results are discussed in terms of the role played by molecular chaperones in AR biogenesis.

Acetylcysteine↗
PubMed2002

Occult renal cell carcinoma in a patient with polymyositis.

Polymyositis (PM) is associated with an increased risk of malignancy. We report a case in which a 45-year-old patient with PM underwent computed tomography to search for an occult malignant process. The evaluation revealed a left renal mass that was treated successfully by laparoscopic radical nephrectomy. Pathologic evaluation revealed a clear cell renal cell carcinoma. The patient remained free of disease at 2 years postoperatively and required decreasing amounts of medication to manage his PM. This suggests that renal malignancies may contribute to the PM disease process in a paraneoplastic fashion and that screening for occult malignancy in the presence of PM is warranted.

Carcinoma, Renal Cell↗
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↗