The materials used in the fabrication of self-retained internal ureteral stents should provide strength, flexibility, low surface friction, radiopacity, biodurability, biocompatibility, and reasonable unit cost. Polymeric biomaterials currently used for stent construction include polyurethane, silicone, Silitek, C-Flex, and Percuflex. Comparative evaluation of these materials in the context of the requirements for stent structure and function suggests advantages and disadvantages for all of them. We believe that the most important attributes for an internal ureteral stent are ease of insertion, effective restoration and maintenance of flow, resistance to migration, significant biodurability, and biocompatibility. Based on our physical testing of stents fabricated from these materials, as well as clinical and laboratory experience, we believe that C-Flex and Percuflex are the most suitable materials for stent construction.

Definitive surgical treatment of ureteral obstruction may not be appropriate in patients with advanced malignancy, complex benign ureteral disease or even simple obstructive disease accompanied by unacceptable operative risk. Endoscopic placement of self-retained internal ureteral catheters (stents) offers satisfactory relief for many of these patients. A new 6F pigtail ureteral stent and placement technique are described. These stents are placed easily, effective and well tolerated for short-term drainage in selected patients with ureteral obstruction.

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Nephrostomy has been the standard procedure for urinary diversion when ureters are obstructed by cancer. However, recent reports have revealed significant problems related directly to the nephrostomy. The indwelling, internal ureteral stent eliminates many of these problems. We herein describe the course and survival of 20 patients in whom the pigtail ureteral stent was used to relieve ureteral obstruction caused by cancer. In these cases an over-all prolonged longevity, better quality of life and fewer complications have been noted when compared to cases of nephrostomy diversions.

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Despite the need for sample transport, resulting in the inevitable aging of samples, and variations in diet and details of sample collection, supersaturation values measured in only 2, 24-hour urine collections accurately reflected stone composition. This finding indicates that supersaturation values are reasonably stable in most patients during the months to years required for stones to form. In addition, samples collected in standard practice settings and sent to a central laboratory may accurately reflect these supersaturation values.

Patients with low calcium oxalate monohydrate supersaturation (less than 7) are unlikely to have calcium oxalate dihydrate in renal stones. However, many patients with no calcium oxalate dihydrate have higher calcium oxalate monohydrate supersaturation values, and so prediction of calcium oxalate dihydrate or its absence from urine findings is imperfect. Urine magnesium and the calcium-to-oxalate ratio are unrelated to calcium oxalate dihydrate.

Despite the need for sample transport, resulting in the inevitable aging of samples, and variations in diet and details of sample collection, supersaturation values measured in only 2, 24-hour urine collections accurately reflected stone composition. This finding indicates that supersaturation values are reasonably stable in most patients during the months to years required for stones to form. In addition, samples collected in standard practice settings and sent to a central laboratory may accurately reflect these supersaturation values.