The role of radiologic imaging and biopsy in renal tumor ablation.

PURPOSE: The rate of unintentionally discovered renal masses has been increasing along with a parallel increased incidence of renal cell carcinoma both in men and women. Ablation therapy has emerged as an alternative for the treatment of these small renal tumors. Several techniques have been developed for renal tumor ablation with cryoablation (CA) and radiofrequency ablation (RFA) being among the most widely used and studied. The purpose of this article is to review the role of imaging and renal mass biopsy in renal tumor ablation with focus on CA and RFA. METHODS: We performed a PubMed database search from January 2000 to January 2010 using the terms: renal tumor ablation, renal biopsy, indications, imaging, computed tomography (CT) guided, magnetic resonance imaging (MRI) guided and ultrasound (US) guided. CONCLUSION: Nephron-sparing procedures, such as cryoablation and RFA, offer an adequate treatment option for selected patients. Imaging techniques such as ultrasonography, CT and MRI are critical to targeting thermal ablation of renal masses. Intra-operative biopsy prior to treatment is becoming a standard procedure but controversy remains regarding pre-operative biopsy. Additionally, contradictory data exist on the value of post-ablation biopsy.

Patient-centered medical therapy for nephrolithiasis.

OBJECTIVE: To elucidate the effect of a patient-centered combined nutritional and medical therapy approach on stone disease management, guided by 24-hour urinary stone risk. MATERIALS AND METHODS: We retrospectively analyzed the records of patients treated at our multidisciplinary stone clinic from July 2007 to February 2009. Included were adult stone formers who presented with severe urinary abnormalities or whose urinary parameters failed to improve with dietary changes. Urinary risk factors for stone disease were evaluated before and after intervention with 24-hour urine collections. Hypercalciuria was treated with hydrochlorothiazide/indapamide, hypocitraturia with potassium/calcium citrate, and hyperuricosuria with allopurinol. The primary end point was the effect of combined dietary and medical intervention on levels of urinary metabolites. Statistical comparisons of postintervention urine collection values with baseline values were performed using a paired t test. Two-tailed P <.05 was considered statistically significant. RESULTS: Data for 137 patients with a mean follow-up of 14.39 months were analyzed. Mean age was 47.2 years, and the male-to-female ratio was 1.04. Hypocitraturia was detected in 70 patients (51%), hypercalciuria in 49 (37%) and hyperuricosuria in 18 (13%). A significant improvement was found in 67% of patients with hypocitraturia (urinary citrate levels: 380.28 to 663.96 mg/d; P <.0001), in 82% of patients with hypercalciuria (urinary calcium levels: 337.4 to 183.6 mg/d; P <.0001), and in 72% of patients with hyperuricosuria (urinary citric acid level: 927 to 600 mg/d; P <.0001). CONCLUSION: Medical management of stone disease instituted based on individual risk factors impacts subsequent urinary stone risk, supporting its use for stone disease when patients do not respond to lifestyle and dietary changes.

Nature of crossing vessels in patients with radiographically normal ureteropelvic junctions: prevalence and anatomic characteristics.

OBJECTIVE: To evaluate the prevalence and characteristics of crossing vessels in asymptomatic patients with a radiographically normal ureteropelvic junction. MATERIALS AND METHODS: We retrospectively reviewed the computed tomography angiography images of 601 patients who were evaluated for possible living organ donation at the University of Minnesota from 2005 to 2008. One patient had asymptomatic hydronephrosis and was excluded from the analysis. The prevalence and characteristics of crossing vessels at the ureteropelvic junction were determined, including vessel location, origin, size, distance from the ureteropelvic junction, and vessel type (artery or vein). RESULTS: The prevalence of crossing vessels at the radiographically normal ureteropelvic junction was 22.7%. A total of 163 crossing vessels were present in 136 patients; 60.1% were left-sided and 39.9% were right-sided. Arteries accounted for 81.0% of the crossing vessels and veins for 19.0%. Accessory lower pole renal vessels originating from the great vessels constituted 59.5% of the crossing vessels. The location of the crossing vessel relative to the ureteropelvic junction varied and included anterior (25.8%), anterolateral (36.8%), medial (14.6%), anteromedial (2.5%), lateral (12.9%), and posterior (7.4%). The mean diameter and mean distance of the crossing vessel from the ureteropelvic junction was 3.3 mm and 1.8 mm, respectively. CONCLUSION: The prevalence of crossing vessels in asymptomatic, healthy patients with a radiographically normal ureteropelvic junction was 22.7%, lower than that seen in association with ureteropelvic junction obstruction. The location of the crossing vessels varied about the ureteropelvic junction, and no location was consistently free of traversing vessels.

Correlation between stress and kidney stone disease.

BACKGROUND AND PURPOSE: Prevalence of kidney stone disease is increasing worldwide, and several factors may be involved. We aimed to establish a correlation between stress and kidney stones. PATIENTS AND METHODS: We prospectively evaluated 200 patients with a diagnosis of kidney stone disease having them self-respond to a validated questionnaire to measure stress (Perceived Stress Scale-10 [PSS-10]). Stone-related characteristics and potential stressing factors were assessed. Variables that were significant on the univariate analysis were used to construct a model that was able to explain the variability in PSS-10 score in our patients. RESULTS: Mean PSS-10 score was 15.3 ± 1.1. Female sex (P=0.014), occurrence of death or serious illness of a family member or close friend within the last 6 months of the interview (P=0.044), occurrence of other psychological trauma (P<0.0001) all proved to be significant factors. Stone-related aspects associated with stress were presence of symptoms at the time of the interview (P=0.012) and passage of two or more stones per year (P=0.022). We were able to construct a model that explains 34% of the variability of the PSS-10 between subjects. Employment status was the only significant variable, but sex, age, and presence of symptoms at the time of questionnaire administration had to be kept in to achieve a model that explains the largest variability. CONCLUSIONS: Passage of two or more stones per year and presence of symptoms proved to be factors related to elevated stress in patients with a diagnosis of kidney stone disease. Female sex, age, and unemployment may also contribute to a stressed state in this population.

Omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid in the management of hypercalciuric stone formers.

OBJECTIVE: To investigate the use of fish oil in the dietary management of hypercalciuric stone formers. Prostaglandins have been linked to urinary calcium excretion, suggesting a role for omega-3 fatty acids in the treatment of hypercalciuric urolithiasis. METHODS: We retrospectively studied a cohort of patients treated at our stone clinics from July 2007 to February 2009. Patients' urinary risk factors for stone disease were evaluated with pre- and post-intervention 24-hour urine collections. All patients received empiric dietary recommendations for intake of fluids, sodium, protein, and citric juices. All subjects with hypercalciuria (urinary calcium>250 mg/d for males or >200 mg/d for females) on at least two 24-hour urine collections were counseled to supplement their diet with fish oil (1200 mg/d). RESULTS: Twenty-nine patients were followed for 9.86±8.96 months. The mean age was 43.38±13.78 years. Urinary calcium levels decreased in 52% of patients, with 24% converting to normocalciuria. The average urinary calcium (mg/d) decreased significantly from baseline (329.27±96.23 to 247.47±84.53, P<.0001). Urinary oxalate excretion decreased in 34% of patients. The average urinary oxalate (mg/d) decreased significantly from baseline (45.40±9.90 to 32.9±8.21, P=.0004). Urinary citrate (mg/d) increased in 62% of subjects from baseline (731.67±279.09 to 940.22±437.54, P=.0005). Calcium oxalate supersaturation decreased in 38% of the subjects significantly from baseline (9.73±4.48 to 3.68±1.76, P=.001). CONCLUSION: Omega-3 fatty acids combined with empiric dietary counseling results in a measurable decrease in urinary calcium and oxalate excretion and an increase in urinary citrate in hypercalciuric stone formers.

A dual-channel flexible ureteroscope: evaluation of deflection, flow, illumination, and optics.

BACKGROUND AND PURPOSE: Despite the evolution and progressive improvements of ureteroscopes, problems related to visibility and maneuverability can still hinder the goals of surgical intervention. We evaluate the attributes of a dual-channel flexible ureteroscope compared with a single-channel device and discuss the implications for expanded techniques afforded by this new technology. MATERIALS AND METHODS: In vitro measurements of active deflection, irrigant flow through the working channel, luminescence, and optical resolution were performed between the single-channel Wolf Viper and the dual-channel Wolf Cobra ureteroscopes. Characteristics were obtained with the working channels both empty and with combinations of a 200 µ holmium aser fiber, 3.0F biopsy forceps, and 1.5F, 2.4F, and 2.8F nitinol basket. Luminescence from each scope was measured using a commercial luminometer. Three blinded physicians rated the optical resolution captured electronically using a standard test image. RESULTS: The single-channel scope has improved upward deflection both empty and with all but the largest single tools, with an improved range of 4 to 15 degrees. The dual-channel scope has superior downward deflection across all comparisons (average increase of 24.5 degrees) and superior upward deflection with large or multiple instruments in the working channel. Baseline flows through each individual-channel of the dual-channel scope were slower than the larger single-channel ureteroscope. Because flow can be provided through a dedicated port in the dual-channel configuration, however, overall flow, depending on instrumentation, can be up to 37 times faster than the single-channel (range 1.5-37×). Optical resolution and luminescence are comparable between the two scopes. CONCLUSION: The dual-channel flexible ureteroscope provides similar deflection characteristics to the current single-channel scope. Deflection and flow characteristics are superior, however, when larger or multiple simultaneous instruments are used in the working channel. These benefits may facilitate the development and implementation of novel endoscopic procedures.

Pyridoxine and dietary counseling for the management of idiopathic hyperoxaluria in stone-forming patients.

OBJECTIVES: To examine the effects of dietary manipulation and pyridoxine medical management for idiopathic hyperoxaluria in patients with nephrolithiasis. METHODS: A retrospective longitudinal study of the patients treated in our stone clinics from July 2007 to February 2009 was performed. All patients were evaluated with pre- and postintervention 24-hour urine collection and met a registered dietician. Recommendations to keep urine volume above 2 L per day, sodium restriction, protein moderation, increased calcium intake with meals and low oxalate diet combined with oral pyridoxine were given. Initial dosage ranged from 50 to 100 mg per day depending on the baseline oxalate level, and was titrated to a maximum of 200 mg daily. Subjects with at least two 24-hour urine collections were included in the study. RESULTS: Of 314 patients with complete metabolic and urinary profile evaluation, 95 subjects were identified with idiopathic hyperoxaluria. Mean follow-up was 18.4 ± 14.8 months and mean age was 50.3 ± 12.8 years. In patients treated with the combination of dietary counseling and pyridoxine, there was a significant change in urinary parameters in 75% of patients with a significant decrease in urinary oxalate excretion (58.26 ± 27.05 to 40.61 ± 15.04, P < .0001). In all, 39% of the patients had a decrease from a high urine oxalate levels (>40 mg/d) to a normal range urine oxalate (55.30 ± 22.04 to 33.45 ± 3.93, P = .0004). No peripheral neuropathy was reported. CONCLUSIONS: Dietary management and medical treatment using pyridoxine may be an effective first-line therapy to decrease hyperoxaluria in patients who form stones.

Impact of dietary counseling on urinary stone risk parameters in recurrent stone formers.

OBJECTIVES: The aim of this study was to investigate the current impact of dietary counseling on the risk for urolithiasis. METHODS: A retrospective cohort study of the patients treated in our stone clinics from July 2007 to February 2009 was carried out. Patients' urinary risk factors for stone disease were evaluated with pre- and postintervention 24-hour urine collections. All patients received dietary recommendations from a registered dietician at each visit. RESULTS: One hundred thirty-seven subjects were identified and managed initially with only dietary interventions to address their urinary stone risk parameters. Average follow-up for this group was 15.19 ± 13.7 months. Subjects showed significant changes in urine volume (71.1%, 1.68 ± 0.68 to 2.59 ± 0.80 L/day, p < 0.0001), urine sodium (58.1%, 229.68 ± 72.51 to 144.65 ± 52.70 mmol/day, p < 0.0001), urine calcium (43.8%, 314.33 ± 95.75 to 216.81 ± 80.90 mg/day, p < 0.0001), urinary uric acid (50%, 0.821 ± 0.210 to 0.622 ± 0.128 g/day, p < 0.0001), urinary citrate (50.7%, 583.19 ± 330.86 to 797.36 ± 412.31, p < 0.0001), and urine oxalate (55.5%, 46.28 ± 10.31 to 32.56 ± 9.02 mg/day, p < 0.0001). The supersaturation for calcium oxalate also decreased significantly from baseline (9.34-5.03, p < 0.0001). CONCLUSION: Urolithiasis is a multifactorial disease requiring a multidisciplinary approach. Our results support the use of dietary counseling by a registered dietician in the management of urolithiasis.

Durability of the next-generation flexible fiberoptic ureteroscopes: a randomized prospective multi-institutional clinical trial.

OBJECTIVES: To evaluate the durability of 4 next-generation flexible ureteroscopes in a randomized, multi-institutional, prospective study. METHODS: Patients at 3 institutions were randomized to 1 of 4 flexible ureteroscopes: the Wolf Viper, Olympus URF-P5, Gyrus-ACMI DUR-8 Elite (DUR-8E), and Stryker FlexVision U-500. Each center used 1 scope from each manufacturer until it needed major repair (primary endpoint). Intraoperative data included total time of use, number of scope insertions through an access sheath, working time in the lower pole, number of insertions and total time for accessory instrumentation in the working channel, number of laser insertions through the working channel, and total laser energy used. RESULTS: A total of 175 patients were randomized. The DUR-8E experienced early catastrophic failure (< or = 10 cases) at all 3 sites; however, this also occurred at 1 site each for the Stryker and Wolf scopes. The DUR-8E required major repair after the fewest average number of cases (5.3), the lowest average total time of usage (108 minutes), the fewest insertions through an access sheath (20.3), the shortest duration of laser firing (31.3 minutes), and the shortest instrument in the working channel time (224.7 minutes). As such, due to variation in durability within manufacturers, no differences could be demonstrated. Visibility ratings for the Wolf iper were significantly better than the DUR-8E (P = .034) and the Flexvision (P = .038). CONCLUSIONS: The Wolf Viper, Olympus URF-P5, and Stryker Flexvision U-500 flexible ureteroscopes seem comparable with regard to durability. However, larger prospective registry-based studies are needed to document significant differences between them.