Biomedical subjects

Ricardo M Brizuela

Publications and source records attributed to Ricardo M Brizuela.

5 recordsLinked to original sources

PubMed2005

Citrate and vitamin E blunt the shock wave-induced free radical surge in an in vitro cell culture model.

Free radical formation plays a major role in shock wave lithotripsy induced renal damage. Moreover, previous studies suggest that free radicals may also promote de novo calcium oxalate crystallization of previously damaged urothelium. Citrate is a known inhibitor of renal stone formation and has also been used as a free radical scavenger. Using an in vitro model with Madin-Darby canine kidney (MDCK) cells, we investigated the influence of two free radical scavengers, citrate and vitamin E, on the prevention of the shock wave-induced free radical surge. Suspensions of MDCK cells were placed in containers for shock wave exposure. Six groups of six containers each were examined: (a) no scavengers 0 shocks, (b) no scavengers 100 shocks, (c) citrate 0 shocks, (d) citrate 100 shocks, (e) vitamin E 0 shocks, (f) vitamin E 100 shocks. An unmodified HM3 was used to deliver 100 shocks at 24 kV. The cell groups that were not shocked acted as the control group and were handled identically, except for the lack of shock wave exposure. After shock wave administration, the containers were emptied and cell suspensions were immediately centrifuged. The supernatant was examined for lactate dehydrogenase (LDH) and 8-isoprostane (8-IP), markers of cellular injury and free radical formation, respectively. Intracellular LDH uniformly increased in all groups exposed to shock wave energy. Similarly, 8-IP increased in all shocked groups. However, the 8-IP increase was significantly reduced when the free radical scavengers were employed. As citrate is a well-known inhibitor of calcium nephrolithiasis, its mechanism of action may be further enhanced, based on its ability to reduce free radical formation, by a protective effect on the urothelium. These data further support the use of citrate based medications during the peri-operative period of shock wave lithotripsy, not only to inhibit stone formation and facilitate fragment passage, but also to reduce the incidence of shock wave induced renal damage. Further studies are warranted to clinically test this hypothesis.

Animals↗

PubMed2003

Assessment of stricture formation with the ureteral access sheath.

OBJECTIVES: To analyze the long-term incidence of ureteral stricture formation in a series of patients in whom a new-generation ureteral access sheath was used. A new generation of ureteral access sheaths has been developed to facilitate ureteroscopic procedures. However, some have questioned their safety and whether the device might cause significant ureteral trauma. METHODS: Between September 1999 and July 2001, 150 consecutive ureteroscopic procedures with adjunctive use of an access sheath were performed. A retrospective chart review to April 2002 was done. Of the 150 patients, 130 underwent ureteroscopy for ureteral stones. Patients who underwent endoureterotomy or treatment of transitional cell carcinoma were excluded from this analysis. Sixty-two patients had follow-up greater than 3 months and were included in the analysis. Overall, 71 ureteroscopic procedures were performed, with 9 patients undergoing multiple procedures. Ninety-two percent of the patients had pathologic findings above the iliac vessels. The average patient age was 45.3 years (range 17 to 76), and 70% and 30% of the patients were male and female, respectively. The mean clinical follow-up was 332 days (range 95 to 821), and follow-up imaging was performed within 3 months after ureteroscopy in all patients. RESULTS: The 10/12F access sheath was used in 8 ureteroscopic procedures (11.2%), the 12/14F access sheath in 56 (78.9%), and the 14/16F access sheath in 7 (9.8%). One stricture was identified on follow-up imaging of 71 procedures performed, for an incidence of 1.4%. The patient developed the stricture at the ureteropelvic junction after multiple ureteroscopic procedures to manage recurrent struvite calculi. The access sheath did not appear to be a contributing factor. CONCLUSIONS: The results of our series indicate that the ureteral access sheath is safe and beneficial for routine use to facilitate flexible ureteroscopy. However, awareness of the potential ischemic effects with the use of unnecessarily large sheaths for long periods in patients at risk of ischemic injury should be considered. We advocate the routine use of the device for most flexible ureteroscopic procedures proximal to the iliac vessels.

Adolescent↗

PubMed2003

In vitro analysis of stone fragmentation ability of the FREDDY laser.

BACKGROUND AND PURPOSE: The Frequency-Doubled Double-Pulse Nd:Yag) (FREDDY) laser (World of Medicine, Berlin Germany) is a short-pulsed, double-frequency solid-state laser with wavelengths of 532 and 1064 nm. This low-power, low-cost laser was developed for intracorporeal lithotripsy. We designed an experimental set-up to test its fragmentation efficiency at different energy and frequency settings. MATERIALS AND METHODS: Forty previously weighed plaster-of-Paris stone phantoms were divided into four groups in order to test fragmentation at 5 and 10 Hz for 2 and 4 minutes. A hands-off underwater laboratory set-up including a holder to keep the stone phantom in contact with the quartz laser fiber was utilized. The 280-microm laser fiber was cleaved and stripped between runs to ensure optimal energy delivery. After fragmentation was completed, all of the stone fragments remaining within the holder were allowed to desiccate for 48 hours and reweighed. Fragmentation was measured as the percentage weight loss. RESULTS: Stone phantoms fragmented at 5 Hz for 2 minutes sustained a mean 24% loss of weight, whereas the 4-minute treatment at 5 Hz reduced stone weight by 54%. Treatment at 10 Hz for 2 minutes demonstrated results similar to those of stones treated for 4 minutes at 5 Hz, reducing stone weight by 51%. Fragmentation at 10 Hz for 4 minutes revealed a 64% loss of mass, less than expected for these power settings. Fiber deterioration observed at the higher energy settings may be the cause of the reduced stone-fragmentation efficiency. CONCLUSIONS: Fragmentation with the FREDDY laser in the 5 Hz, 4 minutes and 10 Hz, 2 minutes protocols is comparable, suggesting that stone fragmentation correlates well with the total energy delivered to the stone. The slight drop in fragmentation efficiency at 10 Hz, 4 minutes is most likely explained by fiber damage occurring consistently at these higher energy settings. The safety profile and low investment and running costs of this laser are advantages that suggest the laser warrants further clinical trials.

In Vitro Techniques↗

PubMed2002

Computed tomography urography, three-dimensional computed tomography and virtual endoscopy.

Spiral computed tomography technology allows an entire body region to be imaged as a continuous volume of computed tomography data. The acquisition of genitourinary images can be performed at different intervals after intravenous contrast injection in order to characterize the renal vasculature, the renal parenchyma or the collecting system. Computed tomography scanning as contrast is excreted into the collecting system is termed a 'computed tomography urogram'. Volumetric data from spiral computed tomography can be rendered into conventional two-dimensional images or even reformatted into three-dimensional views of organ systems or hollow structures, as in 'fly-through' virtual endoscopy. Although virtual endoscopy of the urinary tract remains in its infancy, three-dimensional imaging is currently a useful adjunct in the evaluation of renal transplant and donor patients and partial nephrectomy candidates. The role of computed tomography urography compared with intravenous urography in the evaluation of hematuria is discussed.

Humans↗

PubMed2002

Routine postoperative imaging is important after ureteroscopic stone manipulation.

PURPOSE: Improved fiber optics and advanced intracorporeal lithotripsy devices have significantly decreased the incidence of complications during ureteroscopic procedures. Despite recent reports suggesting that radiographic imaging may not be necessary in all individuals after routine ureteroscopy silent obstruction may develop in some, ultimately resulting in renal damage. We determined the incidence of postoperative silent obstruction at our institution and assessed the need for routine functional radiographic studies after ureteroscopy. MATERIALS AND METHODS: We retrospectively reviewed the charts of 320 patients who underwent a total of 459 ureteroscopic procedures for renal or ureteral calculi in a 3-year period. Complete followup with imaging was available for 241 patients (75%). Average patient age was 47.2 years. The variables of interest reviewed included preoperative pain, preoperative obstruction, targeted calculous site, stone-free rate, postoperative pain and postoperative obstruction. Mean followup was 5.4 months (range 2 to 43). RESULTS: A total of 241 patients with complete followup were identified in this analysis. Preoperative pain was present in 202 patients (84%) and 168 (70%) had preoperative obstruction. Overall targeted calculous clearance was successful in 73% of the patients and an additional 15.8% had residual fragments less than 4 mm. The renal, proximal or mid and distal ureteral stone-free rate was 32.1%, 81.9% and 90.5%, while in an additional 46.4%, 6.3% and 6.7% of cases, respectively, residual fragments were less than 4 mm. Of the 241 patients 30 (12.3%) had obstruction postoperatively due to residual stone in 25 (83.3%), stricture in 3 (10%), edema of the ureteral orifice in 1 (3.3%) and a retained encrusted stent in 1 (3.3%). Postoperatively obstruction correlated with postoperative pain in 23 of the 30 patients (76.7%). Pain was present postoperatively in 30 of the 211 patients (14%) without evidence of ureteral obstruction postoperatively. However, silent obstruction developed in 7 patients (23.3%) or 2.9% of the total cohort. All 7 patients underwent secondary ureteroscopy to alleviate obstruction. A single patient ultimately received chronic hemodialysis for renal failure, 1 was lost to followup and in 5 there was documented successful resolution of the cause of obstruction. CONCLUSIONS: Our analysis suggests that silent obstruction remains a potentially significant complication after stone management. Relying on postoperative pain to determine the necessity of postoperative imaging places patients at risk for progressive renal failure due to unrecognized obstruction. Therefore, we recommend that imaging of the collecting system should be performed by excretory urography, spiral computerized tomography or ultrasound within 3 months after routine ureteroscopic stone treatment to avoid the potential complications of unrecognized ureteral obstruction.

Adult↗