This Month in Investigative Urology

Article Outline

• Renal Artery Occlusion for Bloodless Robotic Partial Nephrectomy
• Anti-Adhesive Coating and Device Associated Escherichia coli Cystitis
• Prostatic Tissue Single Frequency Admittivity Properties Versus Spectral Admittivity Properties
• Tissue Factor Expression and Nephroblastoma Prognosis
• Copyright

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Renal Artery Occlusion for Bloodless Robotic Partial Nephrectomy 

The incidence of renal malignancies has increased during the last 30 years, and concurrently the technical feasibility and long-term oncological success of nephron sparing surgery have been demonstrated. During the last decade robotic or laparoscopic partial nephrectomy has emerged as a viable alternative to open surgery. Renal vascular clamping with ensuing warm ischemia is typically necessary during these procedures. Moinzadeh et al (page 1582) from Burlington, Massachusetts developed a technique for angiographic delivery of a novel intra-arterial reverse thermoplastic polymer allowing temporary selective vascular occlusion with normal perfusion of the remaining kidney.

In 8 pigs they performed 16 selective angiographic occlusions of the lower pole segmental artery using LeGoo-XL™. The technical feasibility of the hemostatic techniques of perfusion hemostasis, where the polymer is infused slowly at low concentrations and temperatures, and local plug formation, where the polymer is injected rapidly and at room temperature, was assessed in 4 pigs each. Selective ischemia time was recorded, and the vascular occlusion site was noted radiographically and laparoscopically. The feasibility of reversing the polymer from a solid back to a liquid state to allow reperfusion was determined. The authors achieved selective lower pole ischemia in all 8 cases. Perfusion hemostasis yielded an inconsistent duration of occlusion (ranging from 0 to more than 60 minutes). Vascular occlusion time using local plug formation was more reliable (17 to 30 minutes) with the consistent ability to reverse the plug back to a liquid state by cold saline flush. Two lower pole robotic partial nephrectomies were completed (using the da Vinci® surgical system) with minimal blood loss. The authors conclude that local plug formation allowed reliable angiographic delivery of LeGoo-XL for temporary vascular occlusion of selective renal artery branches. Further studies are under way to assess the consistency of the technique and the long-term effects of the polymer, as well as to determine any long-term pathological and functional renal or systemic complications.

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Anti-Adhesive Coating and Device Associated Escherichia coli Cystitis 

Bacterial attachment and biofilm formation associated with urinary stents and catheters can lead to chronic infections that cannot be resolved without device removal. Decreased uropathogen adherence has been demonstrated using a novel anti-fouling coating consisting of mussel adhesive protein mimics conjugated to poly(ethylene glycol) (mPEG-DOPA3). Pechey et al (page 1628) from London, Ontario, Canada assessed the ability of methoxy polyethylene glycol-dihydroxyphenylalanine (mPEG-DOPA) coated ureteral stents to resist bacterial adherence, infection development and encrustation in a rabbit model of uropathogenic E. coli cystitis. Coated (3 coatings including Surphys™ S002, S008, S009) and uncoated Sof-Flex® stent curls as well as uncoated Percuflex Plus® stents were inserted transurethrally into the bladder of 50 male New Zealand White rabbits followed by instillation of uropathogenic E. Coli strain GR12 (10⁷). Urine was examined for bacteria on days 0, 1, 3 and 7, and for cytokine levels on day 7. On day 7 the animals were euthanized, and stent curls and bladders were harvested for analysis. In a parallel experiment stents were challenged in vitro for 7 days with GR12 in human urine.

Surphys 009 coated devices showed decreased urine and stent bacterial counts compared to controls. Of 10 rabbits in the S009 group 8 had sterile urine by day 3 vs 1 in either control group (p = 0.013) and stent adherent organisms were reduced by more than 75%. No statistical differences were found in encrustation and bladder inflammation across the groups. However, immune scoring was lowest in the uncoated Sof-Flex control and Surphys 009 groups (p = 0.030). The authors conclude that Surphys 009 strongly resisted bacterial attachment, resulting in improved infection clearance compared to uncoated devices. However, encrustation appeared to be independent of infection in this model.

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Prostatic Tissue Single Frequency Admittivity Properties Versus Spectral Admittivity Properties 

Prostate specific antigen (PSA) monitoring has been successful in detecting earlier stage prostate cancers but leads to a significant number of false-positive findings because PSA is produced by malignant and benign processes. More specific diagnostic tools that identify prostate cancers requiring therapeutic intervention are desirable. The electrical properties of the prostate may provide sufficient contrast to distinguish between malignant and benign formations in the gland.

In 2 articles Halter et al (pages 1600 and 1608) from Lebanon, New Hampshire evaluated how well these electrical properties distinguish cancer from noncancer tissues in the prostate. They recorded electrical admittivity (conductivity and permittivity) at 31 discrete frequencies of 100 Hz to 100 kHz from each of 50 ex vivo human prostates using a specifically designed admittivity probe to gauge these electrical properties in sectioned prostate specimens. The specific tissue area probed was marked to provide precise co-localization between the histological assessment of the tissue and the recorded admittivity spectra. Adenocarcinoma, benign prostatic hyperplasia, nonhyperplastic glandular tissue and stromal tissue were the primary tissue types probed. Mean cancer conductivity was significantly less than that of glandular and stromal tissues at all frequencies (p <0.05) while mean cancer permittivity was significantly greater than that of all benign tissues at 100 kHz (p <0.0001). ROC curves showed that permittivity at 100 kHz was optimal for distinguishing cancer from all benign tissues. This parameter displayed 77% specificity at a sensitivity level of 70%, and had an area under the ROC curve of 0.798.

Enhanced discriminatory power was observed when spectral admittivity parameters were used instead of discrete single frequency admittivity properties to discriminate between malignant and benign prostate tissues. The authors conclude that the contrast in electrical admittivity properties of different prostate tissues shows promise for distinguishing cancer from benign tissues. Since the sensitivity and specificity exceed those reported for current PSA screening practices at low PSAs, this is an attractive addition to the clinical repertoire for identifying prostate cancer. While the data reported by the authors are based on ex vivo tissues, technological developments are under way to design clinical tools to gauge these properties in vivo.

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Tissue Factor Expression and Nephroblastoma Prognosis 

Wilms tumor (WT) or nephroblastoma is the most common renal malignancy and the second most common abdominal solid tumor in childhood. Although the overall 4-year survival rate exceeds 90% for favorable histology tumors, there is still a subgroup of patients who experience relapse and respond poorly to second line therapy. Thus, there has been a continuous search for novel potential prognostic markers of poor outcomes to improve therapeutic strategies.

Tissue factor (TF), also known as thromboplastin, is important for the initiation of the extrinsic pathway of coagulation. It is expressed in various solid tumors in association with increased angiogenesis. Maciel et al (page 1594) from Porto Alegre, Brazil describe the expression of TF detected by immunohistochemistry in WTs and its correlation with clinical outcomes. TF expression detected by immunohistochemistry was assessed in 41 formalin fixed, paraffin embedded WTs treated at university hospitals, and they correlated the findings with tumor recurrence and cancer specific survival. Positive immunohistochemistry detection of TF expression was observed in 88.3% of tumors analyzed. TF expression detected by immunohistochemistry was associated with tumor recurrence (p = 0.01) and survival (p = 0.02). The expression of TF assessed by immunohistochemistry was the most important risk factor for recurrence and mortality in the investigated cohort of patients with WT on bivariate and multivariate analysis. Thus, TF expression on immunohistochemistry was an independent prognostic factor for survival of the investigated patients, and TF is a promising research subject as a prognostic factor for WT. The authors acknowledge the limitations of the study (eg retrospective, small sample), and suggest that more studies are necessary to clarify the mechanisms by which TF affects cancer progression and outcome, and to establish its potential role as a therapeutic target.