The CROES percutaneous nephrolithotomy global study: the influence of body mass index on outcome.

PURPOSE: In addition to more commonly forming stones, obese patients present a number of challenges when undergoing percutaneous nephrolithotomy. We evaluated percutaneous nephrolithotomy outcomes in 3,709 patients stratified by body mass index. MATERIALS AND METHODS: A prospective database administered by CROES (Clinical Research Office of the Endourological Society) captured data on 5,803 patients treated with percutaneous nephrolithotomy between November 2007 and December 2009. Patients with known solitary kidney, previous percutaneous nephrolithotomy and congenital abnormalities were excluded from analysis. For statistical analysis patients were categorized as normal weight--body mass index 18.5 to 25 kg/m(2), overweight--25 to 30, obese--30 to 40 and super obese--greater than 40. RESULTS: During the study period 5,803 patients underwent percutaneous nephrolithotomy, of whom 3,709 met the inclusion criteria. As expected, obesity was associated with significantly higher rates of comorbid conditions and anticoagulant use (p < 0.001). Operative time was significantly longer in obese patients and use of a balloon device for tract dilation was more common (each p < 0.001). The stone-free rate decreased with obesity (p = 0.009), corresponding to a significantly higher re-treatment rate in this group (p < 0.001). No difference was seen in length of stay or the transfusion rate. No significant difference was seen in the overall complication rate among the 4 groups (p = 0.707). CONCLUSIONS: Percutaneous nephrolithotomy may be done safely in obese patients, although with a longer operative time, an inferior stone-free rate and a higher re-intervention rate.

Ni-Cr-Co alloy ureteral stent: scanning electron microscopy and elemental analysis characterization after long-term indwelling.

We report the first preliminary study on metal-alloy ureteral stent after long indwelling times. The aim is to analyze by physical-chemical characterization of the stent after use and to evaluate the material performance in this human in vivo case study. Six Resonance metallic stents (Cook Ireland) were inserted in six patients for 6, 10, 11, 12, 24, and 36 months. The stents were then collected and studied by Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive Spectroscopy (EDS), gaining information about the metal stent surface and the amount and nature of the formed encrustation. The stents were all draining adequately, despite the presence of the bacterial biofilm layer in all stents. This layer was more dense and compact as the indwelling time increased. Some slight precipitation of inorganic compounds, such as brushite and calcium oxalate was observed. No epithelial tissue in growth was recorded. These preliminary results with Resonance metallic ureteral stents suggest the feasibility of a long-term approach in patients with chronic ureteral obstruction. The durability of the metal stent, the lack of epithelial tissue ingrowths and limited pain or discomfort to patients were proven over long time periods. The long-term use of these stents is therefore feasible, avoiding the continuous exchange of the stent, decreasing hospital costs and increasing the quality of life of patients affected by malignant pelvic tumors.

Heparin coating on ureteral Double J stents prevents encrustations: an in vivo case study.

PURPOSE: To evaluate the ability of heparin coating to inhibit Double J stent encrustation and compare it with the classic polyurethane Double J stent. PATIENTS AND METHODS: The study involved five patients with bilateral obstructions, who required bilateral ureteral Double J stent placement. Every patient received a heparin-coated Double J stent and a traditional polyurethane Double J stent for 1 month. After removal, the stents were analyzed using field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and micro-infrared spectrophotometry (Micro-IR). These same techniques were used to analyze the heparin-coated and uncoated stents before insertion. The thickness, extension, and composition of encrustation of the coated and uncoated stents were compared. Moreover, two heparin-coated stents were analyzed with the same techniques after they had been in place for 10 and 12 months. RESULTS: FESEM analysis showed that the difference in encrustation thickness and extension between the two groups was significant. EDS and Micro-IR confirmed that in the heparinized stents the encrustations were not as uniform and compact as those in the uncoated stents. The stents that were left in place long-term were free of encrustations and had no changes in the heparin layer. CONCLUSIONS: Heparin coating reduces stent encrustation. Moreover, as no changes were seen in the heparin layer, we concluded that covalent heparin bonding enhances its adhesion to the polyurethane surface and ensures its stability for long periods. The heparin-coated stent appears to be a useful tool for long-term urinary drainage.