Interaction of Shockwaves with Infected Kidney Stones: Is There a Bactericidal Effect?

Photothermal nanoparticles for ablation of bacteria associated with kidney stones

OBJECTIVE

To determine whether photothermal polymer nanoparticles (NPs) can interface with bacteria associated with kidney stones, generate heat when stimulated with near infrared (NIR) light, and aid in reducing bacterial burden.

METHODS

Two types of kidney stones, artificial, and those removed during percutaneous nephrolithotomy (PCNL), were inoculated with Escherichia coli (E. coli) and then incubated with NPs composed of FITC-labeled Poly[4,4-bis(2-ethylhexyl)-cyclopenta[2,1-b;3,4-b']-dithiophene-2,6-diyl-alt-2,1,3-benzoselenadiazole-4,7-diyl] (PCPDTBSe). Association of the PCPDTBSe NPs was evaluated using fluorescence microscopy. Infected stones were incubated with NPs and exposed to 800 nm light to generate temperature increases from 25.4 to 68.6 °C on the stones. Following photothermal treatment, the stones were homogenized and the bacteria was enumerated via colony counting assays to evaluate the bactericidal effect. The photothermal effect was also evaluated using scanning electron microscopy of the treated biofilms.

RESULTS

Both kidney stone types sequestered E. coli. Control stones and stones treated with laser only had growth of numerous bacterial colonies, while stones exposed to NPs and laser grew significantly less, or none (p = 0.02).

CONCLUSIONS

The polymer NPs interface with E. coli on artificial and patient-derived kidney stones, and they can impart a bactericidal effect, when stimulated with NIR to generate heat. This technique may possibly be extended to treating infected kidney stones in patients.

Steinstrasse predictive factors and outcomes after extracorporeal shockwave lithotripsy

PURPOSE

Urinary stone disease is a common medical problem. Extracorporeal shockwave lithotripsy (SWL) has been applied with high success and low complication rates. Steinstrasse (SS) is a possible complication after SWL. The aim of the present study was to prospectively evaluate the factors and outcomes associated with SS after SWL.

MATERIALS AND METHODS

We have prospectively evaluated 265 SWL sessions (2005-2009). Two lithotriptors were used randomly: Siemens Lithostar and Dornier Compact S. All patients had imaging exams after 30 and 90 days or according to symptoms.

RESULTS

SS was observed in 14 (5.3%) out of 265 SWL procedures (n = 175 patients, 51.5% women/48.5% men, mean ± SD age = 46.3 ± 15.5 years). SS was more common after SWL for pelviureteral calculi rather than caliceal stones (p = 0.036). There was a trend toward more occurrences of SS after SWL for larger stone area (> 200 mm², p = 0.072). Preoperative ureteral stent didn't prevent SS. SWL machine, intensity, number of pulses and frequency were not associated with SS formation. Post-SWL pain, fever and gravel elimination were factors associated with SS (p = 0.021; p = 0.011; p = 0.078). When SS occurred, treatment modalities included Medical Expulsive Therapy (MET), ureteroscopy and SWL.

CONCLUSIONS

Steinstrasse is an uncommon event after SWL and seems to occur more frequently with larger pelviureteral stones. Impaction of stones is more frequent in the middle ureter. All patients should be followed after SWL, but SS should be specially suspected if there is macroscopic gravel elimination, flank pain and/or fever. When SS occurs, treatment should be promptly introduced, including medical expulsive therapy, surgical approach or SWL in selected cases. Further prospective studies are awaited to evaluated preventive measures for SS occurrence.