Dorit Zilberman

Factors Affecting Patient Radiation Exposure During Percutaneous Nephrolithotomy

PURPOSE We identified patient and stone characteristics that may contribute to increased radiation exposure during percutaneous nephrolithotomy and offer technique modifications to limit the radiation dose. MATERIAL AND METHODS We reviewed the records of 96 patients who underwent percutaneous nephrolithotomy in the last 2 years. The effective radiation dose was calculated using accepted conversion tables. We performed multivariate linear regression to determine the association of the effective radiation dose with specific patient, stone and procedural characteristics. RESULTS Mean±SD patient age was 51.5±13.4 years and 62.5% of the patients were female. Median body mass index was 32.0±9.7 kg/m2 (range 16.2 to 59.6) and the median stone burden was 4 cm2. Increased body mass index (p<0.001), higher stone burden (p=0.013), stone nonbranched configuration (p=0.002) and a greater number of percutaneous access tracts (p=0.040) were significantly associated with an increased effective radiation dose. Specifically obese patients with a body mass index of 30 to 39.9 kg/m2 had a more than 2-fold increase in the mean adjusted effective radiation dose and morbidly obese patients with a body mass index of 40 kg/m2 or greater had a greater than 3-fold increase vs that in normal weight patients with a body mass index of less than 25 kg/m2 (6.49 and 9.13 mSv, respectively, vs 2.66, p<0.001). Other stone specific parameters, including site and composition, percutaneous access site and estimated blood loss were not associated with the effective radiation dose. CONCLUSIONS Patients with higher body mass index, greater stone burden, nonbranched stones and multiple nephrostomy access tracts are at risk for increased radiation exposure during percutaneous nephrolithotomy. Urologists must seek alternative strategies to minimize radiation exposure, such as tighter collimation to the region of interest, judicious use of magnification and the acquisition of as few images as possible during stone removal.

In Vivo Determination of Urinary Stone Composition Using Dual Energy Computerized Tomography With Advanced Post-Acquisition Processing

PURPOSE We assessed whether dual energy computerized tomography with advanced post-image processing can accurately differentiate urinary calculi composition in vivo. MATERIALS AND METHODS A total of 25 patients scheduled to undergo ureteroscopic/percutaneous nephrolithotomy were prospectively identified. Dual energy computerized tomography was performed using 64-slice multidetector computerized tomography. Novel post-processing (DECTSlope) used pixel by pixel analyses to generate data sets grayscale encoding ratios of relative differences in attenuation of low (DECT80 kVp) and high energy (DECT140 kVp) series. Surgical extraction and Fourier spectroscopy resulted in 82 calculi. Of these stones 51 showed minor admixtures (uric acid, ammonium urate, struvite, calcium oxalate monohydrate and brushite) and 31 were polycrystalline (mixtures of calcium oxalate monohydrate/dihydrate and calcium phosphate). Analyses identified stone clusters of equal composition and distinct attenuation descriptors on DECT140 kVp, DECT80 kVp and DECTSlope. Iterative cross-validation of the 3 dual energy computerized tomography data sets was used to identify characteristic attenuation limits for each stone type. RESULTS Attenuatio profiles showed substantial overlap among various stones on DECT140 kVp (uric acid 427.3±168.1 HU, ammonium urate 429.9±99.7 HU, struvite 480.2±123.5 HU, calcium oxalate monohydrate 852.4±301.4 HU, brushite 863.7±180.1 HU and polycrystalline 858.1±210.5 HU) and on DECT80 kVp (uric acid 493.6±182.8 HU, ammonium urate 591.5±157.9 HU, struvite 712.4±173.9 HU, calcium oxalate monohydrate 1,240.5±494.7 HU, brushite 1,532.1±273.1 HU and polycrystalline 1,358.7±316.8 HU). Statistically spectral separation was not sufficient to characterize stones unambiguously based on DECT140 kVp/DECT80 kVp attenuation. Analysis of attenuation showed sufficient spectral separation on DECTSlope (uric acid 14.9±10.9 U, ammonium urate 56.1±1.8 U, struvite 42.7±1.4 U, calcium oxalate monohydrate 62.8±1.8 U and brushite 113.2±5.3 U). Polycrystalline stones (51.8±3.7 U) overlapped with struvite and ammonium urate stones. This overlap was resolved as all struvite/ammonium urate stones measured 900 HU or less and all polycrystalline stones measured more than 900 HU on DECT80 kVp. CONCLUSIONS Dual energy computerized tomography with novel post-processing allows accurate discrimination among main subtypes of urinary calculi in vivo and, thus, may have implications in determining the optimum clinical treatment of urinary calculi from a noninvasive, preoperative radiological assessment.

Complications of Laparoscopic and Percutaneous Renal Cryoablation in a Single Tertiary Referral Center

BACKGROUND Laparoscopic cryoablation (LCA) and percutaneous cryoablation (PCA) of small renal masses have gained popularity, but only limited data exist on the complication rates. OBJECTIVES In this study, we report on postoperative complications associated with LCA and PCA in a single tertiary center experience. DESIGN, SETTING, AND PARTICIPANTS We conducted a retrospective review of electronic medical records for patients undergoing LCA or PCA between 2001 and 2008 at our institution. INTERVENTIONS All patients underwent LCA or PCA. MEASUREMENTS Demographics, radiographic variables, and complication rates were compared between the two groups. Complications were classified according to the modified Clavien system. RESULTS AND LIMITATIONS Of a total of 195 patients included in this study, 72 underwent LCA and 123 underwent PCA. There were no differences in demographics between the groups. We observed complications in 10 LCA procedures (13.9%) and 26 PCA procedures (21.1%) (p=0.253). The distribution of the complications differed significantly between the groups with mild complications (grades 1 and 2) more common in the PCA group (20.3% vs 5.6%, respectively; p=0.001), whereas severe events (grades 3 and 4) were more frequent in the LCA group (8.3% vs 0.8%, respectively; p=0.011). On multivariate analysis, age and body mass index were inversely associated with complications, whereas female gender, multiple tumors, and preexisting comorbidities showed a trend toward increased risk. CONCLUSIONS LCA and PCA, although minimally invasive, are not void of complications. Most of the complications encountered are mild; however, severe (grade 3 or 4) events may occur in up to 3.6% of patients. PCA may be associated with a higher rate of complications, although most of these are mild and transient. However, on multivariate analysis, the chosen ablative approach (laparoscopic or percutaneous) is not associated with the risk of complications.

Low dose computerized tomography for detection of urolithiasis-its effectiveness in the setting of the urology clinic

PURPOSE Low dose noncontrast computerized tomography is becoming a common imaging tool to diagnose urolithiasis. We investigated its usefulness as a diagnostic tool in the outpatient setting. MATERIALS AND METHODS A total of 62 patients with suspected urolithiasis underwent standard renal stone protocol computerized tomography with a tube current of 160 mA. Images were modified by adding image noise to simulate tube currents of 70, 100 and 130 mA. Three urologists independently interpreted the original and simulated dose scans for stone number, location and associated signs of obstruction. In addition, the investigators rated the ease of interpreting the scans and their overall level of confidence. RESULTS There were no statistically significant differences in interobserver and intra-observer variability for stone detection or obstruction signs except significant interobserver variability in hydronephrosis and intra-observer variability in stranding categories. Each 1 mm increase in stone size increased the likelihood of a concordant response 3.55, 2.7 and 2-fold when reducing the tube current level by 19%, 38% and 56%, respectively (p=0.001, 0.008 and 0.021, respectively). Multiple stones or index stone location were not associated with agreement. The overall level of confidence decreased with lower simulated doses, particularly in the bony pelvis (p<0.02). CONCLUSIONS Low dose computerized tomography may serve as an effective tool in the setting of the urology clinic in patients with urolithiasis. This imaging tool can better assess urolithiasis and associated obstruction than plain abdominal radiographs, but it may be problematic with small stones (less than 2 mm) and evidence of distal ureteral obstruction. Its effectiveness as a long-term followup tool requires further prospective trials.

Reduced Radiation Exposure with the Use of an Air Retrograde Pyelogram During Fluoroscopic Access for Percutaneous Nephrolithotomy

INTRODUCTION Fluoroscopy with retrograde pyelogram is commonly used to obtain access for percutaneous nephrolithotomy (PNL). Our practice uses room air for retrograde identification of calyceal anatomy. Herein we explore whether an air pyelogram was associated with a decrease in radiation exposure compared with standard retrograde pyelogram. METHODS We retrospectively reviewed all PNL procedures performed at our institution over the past 2 years. Of the 260 PNL procedures performed during the study period, 96 had information on radiation dosage required for analysis. The effective dose (ED) was calculated using accepted conversion tables. Multivariable linear regression was used to determine the association between ED and the use of air pyelogram controlling for factors thought to affect radiation exposure. RESULTS Of the 96 PNL procedures included in the study, 60 (63%) were performed with an air retrograde pyelogram (AP) and 36 (37%) used contrast retrograde pyelogram (CP). Both groups were matched in terms of age, body mass index, stone burden, and number of access tracts. Multivariable linear regression showed significantly lower radiation exposure in the AP group than in the CP group (p = 0.001). There was no difference in fluoroscopy time between the two groups. Using an AP lowered the mean adjusted ED nearly twofold, from 7.67 (CI = 5.99-9.81) to 4.45 (CI = 3.68-5.38) mSv. CONCLUSIONS An air retrograde pyelogram is associated with decreased radiation exposure during PNL when compared with a contrast retrograde pyelogram.

Third Prize: The Role of Endoscopic Nephron-Sparing Surgery in the Management of Upper Tract Urothelial Carcinoma

INTRODUCTION Upper tract urothelial carcinoma (UT-UC) is an uncommon disease with pronounced difference in 5-year survival for noninvasive (96%) versus invasive (17%) disease. High survival rate of early disease questioned the accepted norm of using radical nephroureterectomy (RNU) for all stages. This review assesses effectiveness of endoscopic management for UT-UC. METHODS A review of 131 UT-UC patients seen between January 1999 and October 2009 was performed. Demographic, clinicopathologic, and outcomes data were collected and compared between patients initially managed with RNU versus those initially managed with nephron-sparing surgery (NSS). The chi-square or Fishers exact tests for categorical variables and the Wilcoxon-Mann-Whitney test for continuous variables were used. Clinical and pathologic stages of RNU patients were evaluated with chi-square testing, whereas difference in length of stay was detected using linear regression. Recurrence rates were compared using multivariate Cox regression. RESULTS The two arms had similar distributions of age, sex, frequency of medical comorbidities, American Society of Anesthesiologists (ASA), and Charlson scores. Mean-adjusted length of stay was 2.1 (95% confidence interval [1.6, 2.5]) and 5.5 days (95% confidence interval [5.3, 6.4]) for the NSS and RNU groups, respectively (p < 0.001). Comparison of clinical and pathologic stages of RNU patients showed a difference (p < 0.001), with under-staging noted in 32%. Men (Hazards Ratio = 2.9 [1.5-5.5], p = 0.001) and NSS patients (hazards ratio [HR] = 3.5 [1.7-7.3], p < 0.001) had threefold increased recurrence risk. CONCLUSION NSS offered shorter hospital stay but had increased risk of recurrence. Therefore, extreme care should be made to rule out occult invasive tumors preoperatively. Patients being managed endoscopically must be informed of the necessity for close follow-up.

The digital flexible ureteroscope: in vitro assessment of optical characteristics

INTRODUCTION Recent advances in endoscope design have placed the charged coupled device chip on the tip of the endoscope. The image is instantly digitalized and converted into an electrical signal for transmission. Digital technology was first introduced into flexible cystoscopes/nephroscopes and subsequently into rigid and flexible ureteroscopes. Herein, we assess the image characteristics and advantages of a new generation of digital flexible ureteroscopes. METHODS The Olympus URF-V flexible digital ureteroscope and the Olympus URF-P3 fiberoptic ureteroscope were assessed in vitro for image resolution, distortion, color representation, grayscale imaging, field of view, and depth of field. RESULTS The digital ureteroscope had a higher resolution at 3, 5, 10, and 20 mm (25.2 lines/mm vs. 8.0, 14.1 vs. 5.0, 6.3 vs. 2.8, and 3.2 vs. 1.3), respectively. Distortion with the digital flexible ureteroscope was lower, though not statistically significant. Color representation was better with the digital ureteroscope, whereas contrast evaluation was comparable between both scopes. The digital flexlible ureteroscope produced a 5.3 times larger image size compared with the standard fiberoptic flexible uretersocpe with a narrower field of view. The depth of field was limited by light and not the optic or the camera for both ureteroscopes. CONCLUSIONS The development of digital flexible ureteroscopes represents a significant technological advance in urology. These devices offer significantly improved resolution and color reproduction as compared with traditional fiberoptic flexible ureteroscopes. Future clinical trials are warranted to ultimately determine the advantages of these innovative endoscopes.

The impact of societal changes on patterns of urolithiasis.

Purpose of review The purpose of the present review is to track changes in prevalence and composition of stone disease as a result of lifestyle changes over the past century. Recent findings Increasing rates of obesity, diabetes mellitus and metabolic syndrome have resulted in increasing rates of nephrolithiasis among women, decreasing the male-to-female ratio from 1.3: 1 to 1.7: 1. Urine composition results have revealed a decrease in urinary pH (<5.5) and an increase in urinary uric acid supersaturation. This has resulted in increased rates of uric acid stones. Modern bariatric surgeries have further increased the risk of calcium oxalate stone formation. Offending agents, intentionally or unintentionally added to food or drug products, have also led to the appearance of previously unrecognized stone types, that is, melamine and indinavir calculi. Summary Societal changes have had a tremendous impact on stone prevalence and composition. Prompt healthier lifestyle education as well as tighter quality control in the Food and Drug Industry is paramount to reducing nephrolithiasis rates and its complications.

Surgical Steps That Elongate Operative Time in Robot-Assisted Radical Prostatectomy Among the Obese Population

INTRODUCTION The association between increased body mass index (BMI) and prolonged operative time (OT) in robot-assisted laparoscopic radical prostatectomy (RLRP) has been suggested before. It is unclear, however, which RLRP step contributes to this finding. We aimed to assess the association between BMI and duration of RLRP steps. PATIENTS AND METHODS Records of patients who underwent RLRP between 2003 and 2009 were reviewed retrospectively. Demographics (including BMI) and OT were recorded. We reviewed total OT (incision to closure) and separate duration of sequential steps of RLRP: In room to incision (preparation), incision to robot docking (port-placement), docking to endopelvic fascia dissection end (retroperitoneal space development), dorsal vein complex (DVC) control, DVC-control end to prostate detachment (prostate dissection), vesicourethral anastomosis (anastomosis), and undocking time (undocking). We divided this cohort into BMI groups (<25, 25.0 to 29.9, 30.0 to 34.9, and ≥35) and compared their characteristics and OT. RESULTS A total of 555 patients were analyzed. OT was significantly different across BMI groups with medians of 159, 181, 178, and 191 minutes for BMI <25, 25 to 29.9, 30 to 34.9, and ≥35 kg/m2, respectively (P = 0.002). For BMI <25, preparation and prostate dissection were significantly shorter. There was a correlation between higher BMI and longer time of prostate dissection with nerve-sparing technique (P = 0.016), but not with a non-nerve-sparing approach (P = 0.658). Higher BMI was associated with longer times of DVC-control and vesicourethral anastomosis (P = 0.048 and P = 0.035, respectively). CONCLUSIONS Higher BMI is significantly associated with prolonged total OT for RLRP with specific steps (preparation, nerve-sparing dissection, DVC-control, anastomosis) responsible for this result. These data need to be considered when planning RLRP in the obese population.

Predictors of prolonged operative time during robot-assisted laparoscopic radical prostatectomy.

Study Type – Therapy (case series)
Level of Evidence 4