Trevor D. Schuler

Stone Attenuation and Skin-to-Stone Distance on Computed Tomography Predicts for Stone Fragmentation by Shock Wave Lithotripsy

OBJECTIVES To determine whether stone attenuation and the skin-to-stone distance (SSD) can predict for stone fragmentation by SWL independently. Identifying the factors predictive of shock wave lithotripsy (SWL) outcome would help streamline the care of patients with stones. METHODS A retrospective review was performed of 111 patients undergoing initial SWL for a solitary, 5-20 mm, renal calculus. Stone size, location, attenuation value, and SSD were determined on pretreatment noncontrast computed tomography. The outcome was categorized as stone free, complete fragmentation <5 mm, and incomplete fragmentation >or=5 mm or unchanged at 2 weeks on kidney/ureter/bladder radiography. RESULTS After SWL, 44 (40%) were stone free, 27 (24%) had complete fragmentation, and 40 (36%) of 111 patients had incomplete fragmentation. The stone attenuation of the successfully treated patients (stone free and complete fragmentation groups) was 837 +/- 277 Hounsfield units (HU) vs 1092 +/- 254 HU for those with treatment failure (incomplete fragmentation; P < .01). The mean SSD also differed: 9.6 cm +/- 2.0 vs 11.1 cm +/- 2.5 for the successful treatment group vs the treatment failure group, respectively (P = .01). On multivariate analysis, the factors that independently predicted the outcome were stone attenuation, SSD, and stone composition. When patients were stratified into 4 risk groups (stone <900 HU and SSD <9.0 cm, stone <900 HU and SSD >or=9.0 cm, stone >or=900 HU and SSD <9.0 cm, and stone >or=900 HU and SSD >or=9.0 cm), the SWL success rate was 91%, 79%, 58%, and 41%, respectively (odds ratio 7.1, 95% confidence interval 1.6-32 for <900 HU and SSD <9.0 cm group vs other 3 risk groups; P = .01). CONCLUSIONS The results of our study have shown that a stone attenuation of <900 HU, SSD of <9 cm, and stone composition predict for SWL success, independent of stone size, location, and body mass index. These factors will be considered important in the prospective design of a SWL treatment nomogram at our center.

Medical expulsive therapy as an adjunct to improve shockwave lithotripsy outcomes: a systematic review and meta-analysis.

BACKGROUND AND PURPOSE Modern shockwave lithotripsy (SWL) is associated with inferior results compared with the original Dornier HM3. To enhance SWL outcomes, improved patient selection based on radiographic features and modulation of shockwave delivery rate have been used. A growing body of evidence demonstrates the positive effect of medical expulsive therapy (MET) to improve spontaneous passage of urinary calculi. The purpose of this review is to tabulate the current available data that examine the addition of MET to SWL to enhance outcomes. MATERIALS AND METHODS MEDLINE was searched with a strategy developed in conjunction with a medical librarian. Trials were included if patients were randomized to receive either a medical expulsive agent or placebo or standard therapy after SWL. Study quality was assessed according to the Cochrane Renal Group criteria. The data were analyzed using RevMan meta-analysis software. Subgroup analysis was performed with respect to MET agent used, stone size, and duration of follow-up. RESULTS Four randomized trials were identified. MET agents varied, with two trials using tamsulosin, one using nifedipine, and a single trial using Phyllanthus niruri extract. Two trials included patients with renal calculi, one had patients with ureteral calculi, and the fourth included patients with both ureteral and renal calculi. The pool results of the four trials included 212 patients who received MET and 206 who received placebo. The absolute risk difference of a successful outcome after SWL with the addition of MET was significantly superior to control at 17% (95% confidence interval [CI] 9%-24%); means six patients need to be treated with MET to prevent a single unsuccessful SWL of six (95% CI 4-11). The effect of MET post-SWL was even more pronounced for stones larger than 10 mm with an absolute risk difference of 26% (95% CI, 9%-43%). CONCLUSIONS MET post-SWL results in a significant increase in successful treatment outcomes. Further powered, randomized studies are encouraged.

A Randomized, Double-Blind Trial to Compare Shock Wave Frequencies of 60 and 120 Shocks per Minute for Upper Ureteral Stones

PURPOSE Recent evidence demonstrates that decreasing shock wave frequency from the previous standard of 120 to 60 shocks per minute results in improved fragmentation of stones located within the renal collecting system. We report the first randomized trial to our knowledge to examine the effect of a slower shock wave frequency for shock wave lithotripsy on stones located in the proximal ureter. MATERIALS AND METHODS A total of 163 patients with a previously untreated radiopaque calculus in the upper ureter measuring at least 5 mm underwent stratified block randomization according to stone size, and shock wave lithotripsy at 60 or 120 shocks per minute. Stone-free status at 3 months was confirmed with noncontrast computerized tomography or a plain abdominal x-ray and ultrasound study. RESULTS Of the patients 77 were randomized to 60 shocks per minute and 86 were randomized to 120 shocks per minute. The groups were similar in gender, age, body mass index and initial stone area. At 3 months the 60 shocks per minute group had a higher overall stone-free rate (64.9% vs 48.8%, p = 0.039). Significantly fewer shocks were administered to patients treated at 60 shocks per minute (mean 2,680 vs 2,940, p <0.001). However, mean treatment times were longer (44.3 vs 24.5 minutes, p <0.001). Patients treated with 60 shocks per minute required fewer auxiliary procedures (29.9% vs 45.4%) (p = 0.031). CONCLUSIONS Decreasing the rate of shock wave administration from 120 to 60 shocks per minute results in improved stone-free rates. A slower treatment rate of proximal ureteral stones reduces the need for additional shock wave lithotripsy or more invasive treatments to render patients stone-free, without any increase in morbidity, and with an acceptable increase in treatment time.

Third Place: Stones Lodge at Three Sites of Anatomic Narrowing in the Ureter: Clinical Fact or Fiction?

UNLABELLED Abstract Background and Purpose: Throughout the literature, the ureter is described as having three anatomic sites of narrowing at which kidney stones typically become lodged: The ureteropelvic junction (UPJ), the ureteral crossing of the iliac vessels, and the ureterovesical junction (UVJ). There is little evidence to support this notion, however. The purpose of our study is to evaluate whether three peaks in stone distribution corresponding to these anatomic landmarks exist. METHODS We retrospectively reviewed the kidneys-ureters-bladder (KUB) films of 622 patients with solitary ureteral calculi referred for shockwave lithotripsy (SWL). Pretreatment KUB films were used to categorize the location of their ureteral stone relative to 1 of 19 levels referenced to the axial skeleton. CT scans of 74 patients were used to determine the location of the UPJ, ureteral crossing of the iliac vessels, and UVJ relative to the 19 levels on KUB radiography. Histograms were then constructed to plot the distribution of stones within the ureter relative to these 19 levels. The effect of sex, stone size and side, and presence of a stent on stone distribution were analyzed. RESULTS There are two peaks in the distribution of stones within the ureter in patients referred for SWL that correspond to the UPJ/proximal ureter and intramural ureter/UVJ. In patients with larger stones (≥100 mm(2)) or a ureteral stent in place, stones were distributed more proximally (P<0.0001). When comparing sexes, there was a difference in stone distribution that approached significance (P=0.0523), with a greater peak more distally in males compared with females. CONCLUSIONS Our review demonstrates a peak in the distribution of stones corresponding to the UPJ/proximal ureter and the intramural ureter/UVJ. We failed to demonstrate a peak in stone distribution corresponding with the ureteral crossing of the iliac vessels.

CUA Guideline: Management of ureteral calculi

The focus of this guideline is the management of ureteral stones. Specifically, the topics covered include: conservative management, medical expulsive therapy, active intervention with either shockwave lithotripsy (SWL) or ureteroscopy (URS), factors affecting SWL treatment success, optimizing success, and special considerations (e.g., pregnancy, urinary diversion). By performing extensive literature reviews for each topic evaluated, we have generated an evidence-based consensus on the management of ureteral stones. The objective of this guideline is to help standardize the treatment of ureteral stones to optimize treatment outcomes.

Predictors of health-related quality of life recovery following laparoscopic simple, radical and donor nephrectomy.

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

Impact of arterial and arteriovenous renal clamping with and without intrarenal cooling on renal oxygenation and temperature in a porcine model.

BACKGROUND As laparoscopic partial nephrectomy increases in prominence, more needs to be understood about the combined effect of the pneumoperitoneum and renal ischemia during tumor resection. The purpose of this study is to investigate the effect of combined renal hilar clamping (arterial only versus arteriovenous) and retrograde intrarenal cooling on renal temperature and oxygenation in a porcine laparoscopic partial nephrectomy model. MATERIALS AND METHODS Under general anesthesia, laparoscopic access with intra-abdominal pressure of 15 mm Hg to the left renal hilum was obtained. Licox tissue oxygenation and temperature probes were placed into the kidney transcutaneously; measurements were taken every 30 seconds. After establishing baseline readings, either the artery alone (n=18) or the artery and vein (n=18) were clamped for 30, 60 or 90 minutes (n=12 each). During vascular clamping, retrograde, intrarenal cooling was performed with ice cold saline infused via a percutaneously placed ureteric catheter in 18 pigs. Changes in renal pO2 and temperature were analyzed with repeated measures ANCOVA in SPSS 16. RESULTS Retrograde cooling decreased renal parenchyma to 75.8% of baseline temperature (27.9 degrees C) within 15 minutes. There were no differences in cooling whether arterial or arteriovenous clamping was used (p=0.79). In uncooled animals, there was no significant difference in the decrease in renal pO2 during the clamp phase (p=0.18) or during the recovery phase (p=0.52). During the recovery phase, renal pO2 in uncooled animals was significantly higher than in those who received cooling (p=0.01). Animals who underwent hilar clamping for extended periods (60 and 90 min) had a slower recovery of renal pO2 to baseline than those with hilar clamping for 30 minutes (p=0.04) CONCLUSION Retrograde intrarenal cooling can reliably cool the porcine kidney to 28 degrees C, regardless of whether arterial or arteriovenous clamping is used. Renal pO2 is not significantly different between animals that undergo artery only versus en bloc hilar clamping. Pigs that were provided with retrograde cooling had a slower return of pO2 to baseline following release of hilar clamps, possibly due to hypothermic vasospasm. Clamp durations greater than 60 minutes were also associated with slower return of renal oxygenation to baseline.

Prospective determination of ureteral orifice location: a guide for fluoroscopic ureteral stent insertion.

PURPOSE Ureteral stents are commonly inserted under fluoroscopic guidance. Our objective was to determine the intravesical landmarks for stent insertion by mapping the fluoroscopic location of the ureteral orifices (UOs) and bladder neck (BN) in relation to the pubic symphysis (PS). METHODS In patients undergoing ureteroscopy, the UO to BN distance was measured during cystoscopy with a 5F ureteral catheter. Radiographic distance between the UO, BN, and superior border of the PS was determined by mapping their locations on digital fluoroscopic images. Measurements were performed with a full (to 50 cm H2O) and empty bladder. RESULTS With an empty bladder, the mean cystoscopic BN to UO distance was 1.8 cm (+/- 0.4) for men (n = 10) and 2.0 cm (+/- 0.4) for women (n = 11). With a full bladder, it was 2.8 cm (+/- 0.5) for men and 2.9 cm (+/- 0.6) for women. Although the intravesical distance lengthened during cystoscopy (by 50%), there was no difference when viewed fluoroscopically; the BN to UO distance lengthened by only 15%. In men, the UOs were located superior to PS in the majority (83% and 95%, empty and full bladder, respectively). In women, however, the UOs resided behind the PS (73% and 50%, empty and full bladder, respectively). The BN in men was also cephalad to that in women (P = 0.01); superior to the PS in 50%; and behind the upper two thirds of the PS in 50%. In women, the BN was behind the lower two thirds of the PS in the majority (81%). CONCLUSIONS During fluoroscopic ureteral stent insertion, the radiopaque marker of the stent positioner is situated at the superior border of the PS in men and behind the lower one third of the PS in women, permitting formation of an intravesical distal coil. One way to remember this is that men are on top and women are on the bottom of the PS.

Are We Banging Our Heads Against the Wall? The Effect of Treatment Head Wear on the Outcomes of Extracorporeal Shockwave Lithotripsy.

INTRODUCTION AND OBJECTIVE The manufacturer for the Storz Modulith SLX-F2 lithotripter recommends treatment head exchange after 1.65 million shocks. However, there is no documentation describing longevity of the treatment head with continued usage. The objective of this study is to determine whether there is a difference in stone fragmentation effectiveness with the treatment head at the beginning versus the end of its treatment life. METHODS We conducted a retrospective chart review of 200 patients-50 consecutive patients treated immediately preceding, and following, two separate treatment head exchanges. Primary outcome measures were stone-free rate (no stone), total stone fragmentation (any decrease in size), and fragmentation rate ≤4 mm (decrease in size with largest residual fragment ≤4 mm), based on most recent follow-up imaging post shockwave. RESULTS There were no baseline characteristic differences between the pre-exchange and postexchange groups with respect to first time lithotripsy for the stone (85% vs. 77%), stone location, preoperative stenting (3% vs. 4%), mean stone density (912 hounsfield units [HU] vs. 840 HU), mean stone size (9.0 mm vs. 8.1 mm), stone location, and mean number of shocks delivered (3105 vs. 3089). Mean time to follow-up was 2.7 weeks in both groups, with most follow-up imaging consisting of a kidney ureter bladder X-ray (87% pre-exchange vs. 85% postexchange). Stone free (34% vs. 27%), total stone fragmentation (76% vs. 76%), fragmentation ≤4 mm (48% vs. 42%), re-treatment rates (38% vs. 51%), and complication rates (6% vs. 7%), were not statistically different between the pre and postexchange groups, respectively. CONCLUSIONS Exchanging the Storz Modulith F2 lithotripter head at the manufacturer recommended 1.65 million shocks does not affect the stone-free or fragmentation rate. If the manufacturers recommendation for treatment head longevity is based on clinical outcomes, then there is likely room to extend this number without affecting treatment efficacy.