Recent advances in ureteral stents.

PURPOSE OF REVIEW: Conventional ureteral stents, which have been in use for almost 30 years, are undergoing several changes in materials, designs and purposes of use. RECENT FINDINGS: Recent advances in ureteroscopes reduced the numbers of double-J insertions. In addition, because of the frequent failures of the double-J stents in malignant obstructions of the ureter coiled metal stents, metal coil-reinforced stents and large-caliber self-expanding stents are being developed for such patients. In the near future, a new application will be stent-based drug delivery. SUMMARY: The conventional double-J stents and the concept of ureteral stenting is undergoing several changes. New generation stents will allow the physician to choose better-fitting stents according to the needs of the individual patient.

Feasibility of fluid volume conductance to assess bladder volume.

AIM: Ambulatory urodynamics has the potential to provide measurements of bladder function during activities of daily living; however, no method of real-time continuous bladder volume measurement exists. The present study was conducted to determine the feasibility of using fluid volume conductance to continuously assess bladder volume. METHODS: Prototype devices consisted of four electrodes mounted on a polymer body. Each was tested in an in vitro organ bath system using latex vessels filled to 500 ml with saline matching the conductivity of urine. One device was selected and used to test the effects of fluid concentration (25%, 50%, 100%, 200%, and 400% physiological saline) in latex vessels as well as the effects of fluid concentration (25%, 50%, 100%, 200%, and 400% Tyrodes solution) and temperature (32, 37, and 42 degrees C) in excised pig bladders. RESULTS: Conductance demonstrated a linear increase at low volumes but approached an asymptotic value at high volumes. Conductivity increased with increased temperature or concentration. With the exception of the differences between 25% and 50% concentrations, 32 degrees C and 37 degrees C, and 37 degrees C and 42 degrees C temperatures, each concentration and temperature produced statistically different conductance measurements from all others. CONCLUSIONS: The conductance method is sensitive to changes in both concentration and temperature of the intravesical solution, likely due to changes in solution conductivity. Clinical application of conductance for measurement of bladder volume will require real-time conductivity compensation for the dynamically varying properties of urine. However, improved sensitivity at high volumes is necessary before this method has the potential to provide real-time bladder volume measurement for use in ambulatory urodynamics.

Povidone-iodine sclerotherapy is ineffective in the treatment of symptomatic renal cysts.

PURPOSE: To evaluate the efficacy of povidone-iodine sclerotherapy after percutaneous drainage of simple renal cysts in the treatment of symptomatic patients. PATIENTS AND METHODS: Sixteen patients with symptomatic renal cysts were treated by percutaneous drainage and injection of povidone-iodine solution. The cysts were drained by a nephrostomy tube catheter, and povidone- iodine injections were repeated every 24 hours for 3 days. All patients were followed up by ultrasound examination during a period ranging from 1 to 4 years (mean 1.8 years). RESULTS: Thirteen patients experienced recurrence of cysts, while complete resolution was observed in only three patients. Of the cysts that recurred, only partial resolution in cyst diameter was observed (from 3-10.5 cm to 2.4-8.6 cm). During the follow-up period, 12 of the 16 patients (75%) continued to have pain that necessitated additional treatments. CONCLUSION: Povidone-iodine sclerotherapy is followed by a high rate of recurrence and is therefore not indicated for the treatment of symptomatic simple renal cysts.

Comparison of nitinol urethral stent infections with indwelling catheter-associated urinary-tract infections.

BACKGROUND AND PURPOSE: To determine the efficacy of intraurethral metal stents in preventing or eradicating urinary-tract infections (UTI) during the management of bladder outlet obstruction (BOO) by comparing the frequency and nature of the infections with indwelling-catheter-associated UTI. PATIENTS AND METHODS: The SAS relative-risk test was used to compare the risks of UTI in 76 patients with temporary urethral stents, 60 patients with BOO who had never been catheterized nor stented, and 34 patients with a permanent indwelling urethral catheter (PIUC). Infection was assessed 1 month after placement of the devices. Scanning electron microscopy (SEM) of the proximal and distal pieces of the stents removed from five patients with and five patients without UTI was carried out in a search for predisposing changes on the surfaces. RESULTS: After insertion of the catheter, UTI developed in 79.4% of the patients who originally had sterile urine. However, after insertion of the stent, UTI developed in only 40.9% of the patients with sterile urine. In 21 (44.6%) of the catheterized patients who had infected urine, UTI was eradicated after stent insertion. The SEM analysis of the stents showed that a thick organic layer had formed only on the infected devices but with no sign of erosion. CONCLUSION: Urinary infection is a significant problem in patients with PIUC but is significantly less frequent and less severe in patients with urethral stents. This advantage of stents over the conventional urethral catheter, in addition to their obvious convenience for the patient, make them good alternatives to reduce the risk of UTI.

New approach to the management of stress urinary incontinence in patients with treatment failure.

Urinary incontinence affects about 40 million adults in the Western world. Many mechanical, behavioral, and surgical approaches have been used for its treatment. Many of the surgical techniques are successful, but about 50% of patients need re-treatment after 5 to 7 years. Although intraurethral plug-like devices could block the leak, they create a communication between the bladder and vulva, resulting in high rates of ascending urinary infections. To prevent this communication but block the bladder outlet while allowing it to open voluntarily, a new intravesical device was designed. The device could be inserted easily into the bladder of 35 patients and activated using a remote control. The use of a completely intravesical device for the management of anatomic incontinence is a novel approach. The results obtained in pilot studies showed that the device is effective in the management of stress incontinence in patients who were failures after surgery or who refused surgery.