Daniela Ghiculete

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.

Limitations to Ultrasound in the Detection and Measurement of Urinary Tract Calculi

OBJECTIVES To evaluate differences in stone measurement using computed tomography (CT) and ultrasound (US). Axial unenhanced helical CT is the reference-standard imaging modality for the assessment of urinary tract calculi; however, US is also commonly used. Differences in stone measurement using these techniques are poorly described and contributors to measurement error remain unknown. METHODS All patients at our institution undergoing both abdominal CT and renal US less than 1 month apart since June 2004 were reviewed. Solitary renal calculi were identified on both CT and US in all cases. RESULTS We identified 71 calculi in 60 patients. Compared with CT, US overestimated stone size, an effect that was more pronounced with smaller calculi. The mean stone measurement on CT was 7.4 +/- 4.4 mm and on US it was 9.2 +/- 4.5 mm (P = .018). For stones </=5 mm, US measurements were a mean of 1.9 +/- 1.2 mm greater than CT (P <.001). US and CT measurements were discordant for 60% of stones </=5 mm. Discordance was associated with US measurement of skin-to-stone distance (P = .018), but not body mass index (P = .189) or location within the urinary tract (P = .161). Review of the literature revealed that US has a pooled sensitivity and specificity of 45% and 94%, respectively, for the detection of ureteric calculi and 45% and 88%, respectively, for renal calculi. CONCLUSIONS US overestimates stone size in urolithiasis, a finding that may have implications for stone management. Discordance in stone measurement varies with size and is greatest in stones </=5 mm. US measurement of skin-stone-distance is an important determinant of error in US measurement of renal calculi.

A Clinical Nomogram to Predict the Successful Shock Wave Lithotripsy of Renal and Ureteral Calculi

PURPOSE Although shock wave lithotripsy is dependent on patient and stone related factors, there are few reliable algorithms predictive of its success. In this study we develop a comprehensive nomogram to predict renal and ureteral stone shock wave lithotripsy outcomes. MATERIALS AND METHODS During a 5-year period data from patients treated at our lithotripsy unit were reviewed. Analysis was restricted to patients with a solitary renal or ureteral calculus 20 mm or less. Demographic, stone, patient, treatment and 3-month followup data were collected from a prospective database. All patients were treated using the Philips Lithotron® lithotripter. RESULTS A total of 422 patients (69.7% male) were analyzed. Mean stone size was 52.3±39.3 mm2 for ureteral stones and 78.9±77.3 mm2 for renal stones, with 95 (43.6%) of the renal stones located in the lower pole. The single treatment success rates for ureteral and renal stones were 60.3% and 70.2%, respectively. On univariate analysis predictors of shock wave lithotripsy success, regardless of stone location, were age (p=0.01), body mass index (p=0.01), stone size (p<0.01), mean stone density (p<0.01) and skin to stone distance (p<0.01). By multivariate logistic regression for renal calculi, age, stone area and skin to stone distance were significant predictors with an AUC of 0.75. For ureteral calculi predictive factors included body mass index and stone size (AUC 0.70). CONCLUSIONS Patient and stone parameters have been identified to create a nomogram that predicts shock wave lithotripsy outcomes using the Lithotron lithotripter, which can facilitate optimal treatment based decisions and provide patients with more accurate single treatment success rates for shock wave lithotripsy tailored to patient specific situations.

A Comparison of Treatment Modalities for Renal Calculi Between 100 and 300 mm2: Are Shockwave Lithotripsy, Ureteroscopy, and Percutaneous Nephrolithotomy Equivalent?

BACKGROUND AND PURPOSE Shockwave lithotripsy (SWL) is considered a standard treatment for patients with upper-tract stones that are less than 10 mm in diameter, whereas stones that are larger than 20 mm are best managed by percutaneous nephrolithotomy (PCNL). The management of stones between these sizes remains controversial. Our purpose was to review our contemporary series of SWL, ureteroscopy (URS), and PCNL outcomes for intermediate-sized upper tract calculi (100-300 mm(2)). PATIENTS AND METHODS Analysis was restricted to those patients who were treated for a renal calculus that measured between 100 and 300 mm(2) during a 4-year span. Demographic, stone, patient, treatment, and follow-up data were collected from a prospectively maintained database. RESULTS A total of 137 patients were referred with nonstaghorn calculi with an area between 100 and 300 mm(2). Fifty-three (38.7%) patients were treated with SWL, while 41 (29.9%) and 43 (31.4%) underwent ureteroscopy and PCNL, respectively. Mean stone area was higher in the PCNL group (P < 0.001), whereas stone density was higher for patients undergoing SWL (P = 0.002). Single treatment success rates were better for PCNL at 95.3%,vs 87.8% for ureteroscopy and 60.4% for SWL, P < 0.001. When allowing for two SWL treatments, the success rate improved to 79.2%, thus equalizing the success of the three treatment modalities (P = 0.66). Auxiliary treatments were more common after SWL (42.3%; P < 0.01). CONCLUSIONS For intermediate-sized upper-tract stones, when allowing for up to two SWL treatments, there was no significant difference between treatment modalities. Thus, SWL is a reasonably successful treatment alternative for patients who are not fit for a general anesthetic or who prefer SWL over competing treatments, provided they accept a potentially higher number of treatments.

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.

Comparison of Supracostal Versus Infracostal Percutaneous Nephrolithotomy Using the Novel Prone-Flexed Patient Position

BACKGROUND AND PURPOSE Percutaneous nephrolithotomy (PCNL) is considered standard therapy for large and complex renal calculi. The optimal patient position and puncture site for collecting system access remains controversial. This purpose of this retrospective review is to analyze our PCNL series with respect to puncture tracts, success, and complications using our novel prone-flexed position. PATIENTS AND METHODS Perioperative data were collected on consecutive PCNL cases for renal calculi performed in the prone-flexed position from 2004 to 2009. Patient demographic, stone, operative, postoperative, and follow-up data were collected. Successful treatment was defined as stone free or sandlike (≤1  mm) particles visible on CT scan at 3 months. RESULTS A total of 318 patients, with a mean age of 52.9 years and body mass index of 27.8  kg/m(2), underwent PCNL in the prone-flexed position (57.9% male). Sixteen tracts were above the 11th rib, 138 were above the 12th rib, and 164 were infracostal. Multiple tracts were used in 16 patients. There were no significant differences between patients undergoing supracostal vs infracostal puncture with respect to side, stone area, number of tracts, number of stones, or the presence of staghorn or struvite calculi. Success in the supracostal group (89.8%) was not statistically different from the infracostal group (94.1%), P>0.05. Overall complication rates across groups was low (11.6%), with a significant difference in complications between the supracostal and infracostal puncture groups across Clavien grades, P<0.01. No patients needed blood transfusions or angioembolization. CONCLUSION Regardless of supracostal or infracostal renal access, our novel prone-flexed position assists with percutaneous renal access and ease of nephrolithotomy, while maintaining excellent success rates and minimizing procedural morbidity.

The Canadian StoneBreaker Trial: A Randomized, Multicenter Trial Comparing the LMA StoneBreaker™ and the Swiss LithoClast® During Percutaneous Nephrolithotripsy

BACKGROUND AND PURPOSE Percutaneous nephrolithotripsy (PCNL) is the treatment of choice for patients with large renal stones. The StoneBreaker™ (SB) is a novel handheld pneumatic lithotriptor, powered by a compressed carbon dioxide cartridge. The purpose of this study was to compare the efficiency of the SB to a standard pneumatic lithotriptor, the Swiss LithoClast(®) (LC). PATIENTS AND METHODS From January 2008 to December 2009, patients undergoing PCNL were randomized to either the SB or the Swiss LC. Primary outcomes included time to fragment the stone, retrieve the fragments, and remove debris using ultrasonic lithotripsy. Secondary end points were stone-free rate, lithotriptor setup time, ease of use, operator fatigue, endoscopic visualization, damage to mucosa, and device-related complications. RESULTS Of the initial 115 patients recruited, 77 were enrolled and 38 were excluded. The SB had significantly faster stone fragmentation time, total lithotripsy time, and setup time than the Swiss LC (P ≤ 0.05). A significant difference was also noted in the ease of use and operator fatigue in favor of the SB. There were no device-related complications. CONCLUSION The SB pneumatic lithotriptor is easier to set up and use, and it provides faster stone fragmentation than the Swiss LC.

A Prospective Study Examining the Incidence of Bacteriuria and Urinary Tract Infection After Shock Wave Lithotripsy with Targeted Antibiotic Prophylaxis

PURPOSE Controversy exists regarding antibiotic prophylaxis before shock wave lithotripsy. The AUA (American Urological Association) guideline recommends universal antibiotic prophylaxis, whereas the EAU (European Association of Urology) guideline recommends prophylaxis only for select patients. We evaluated the use of targeted antibiotic prophylaxis in preventing urinary tract infections in patients undergoing shock wave lithotripsy. MATERIALS AND METHODS A prospective single cohort study was performed during 6 months with patients undergoing shock wave lithotripsy. All patients underwent urine dipstick and culture before shock wave lithotripsy. Targeted antibiotic prophylaxis was provided at the discretion of the treating urologist. All patients had a urine culture performed after shock wave lithotripsy and completed a survey documenting fevers or urinary symptoms. The primary outcome was the incidence of urinary tract infections, urosepsis and asymptomatic bacteriuria after shock wave lithotripsy. The secondary outcome was the sensitivity and specificity of urinary dipstick leukocytes and nitrites. RESULTS A total of 526 patients were enrolled in the study. Of the 389 patients included in the determination of the primary outcome, urinary tract infection developed in only 1 (0.3%), urosepsis did not develop in any patients and asymptomatic bacteriuria developed in 11 (2.8%). Eight (2.1%) patients were administered antibiotic prophylaxis. The specificity of urine dipstick nitrites was high (95%) while the sensitivity was poor (9.7%). CONCLUSIONS In our cohort study using targeted antibiotic prophylaxis the rates of urinary tract infection after shock wave lithotripsy and rates of asymptomatic bacteriuria were extremely low, with no development of urosepsis. This finding questions the need for universal antibiotic prophylaxis before shock wave lithotripsy.

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.

Shockwave lithotripsy in patients with horseshoe kidney: determinants of success.

BACKGROUND AND PURPOSE Horseshoe kidney (HSK) is the most common renal fusion anomaly, with a prevalence of ∼1 in 400 and an incidence of urolithiasis between 20% and 60%. The role of shock wave lithotripsy (SWL) in patients with HSK remains poorly studied. METHODS Data from all patients treated since January 1994 with a known HSK was reviewed. Analysis was restricted to all patients with a minimum follow-up of 2 weeks after SWL. Success was defined as patients who were stone-free or had asymptomatic, clinically insignificant residual fragments ≤ 4 mm. RESULTS Data from 41 patients with HSK were analyzed (61 calculi). Mean stone size was 91.3 ± 71.6 mm(2); mean body mass index was 27.1 ± 5.3 kg/m(2). At 3 months, the single-treatment success and stone-free rates were 25.0% and 9.1%, respectively. The overall treatment success rate at 3 months was 63.6%, and the stone-free rate was 39.1%. Little incremental benefit was found for more than two SWL treatments per stone. The auxiliary treatment rate was 72.7%, with an efficiency quotient of 10.5%. On multivariate analysis, stone burden (p = 0.074), other calyceal location (p = 0.026), and body mass index (p = 0.013) were found to be prognostic for SWL success. CONCLUSIONS Patients with HSK appear to have lower success and stone-free rates after SWL than patients with normal kidneys. This likely has to do with factors such as greater skin-to-stone distance (particularly for calyceal stones) and restricted urinary drainage. SWL may be offered to patients with a HSK once limitations in stone clearance have been considered.