Vol. 181, No. 4, Supplement, Tuesday, April 28, 2009 THE JOURNAL OF UROLOGY® 585

(.49%), 4 blood transfusions (0.03%) and 1 rib fracture (0.006%). Clavien 3 included 431 patients (2.8%) who required intervention for management of obstructing stone fragments. Clavien 4 included 3 patients. (0.019%). 2 of these had significant renal hemorrhage requiring 4 units and 8 units of blood and management by interventional radiology embolization. 1 patient (0.006%) required a splenectomy for splenic rupture. One patient was classified as Clavien 5 who died secondary to renal and splenic rupture and subsequent coagulopathy and sepsis. Of interest the Clavien 4 and 5 patients all had 1-1.5cm ureteropelvic junction calculi, were treated with an average of 2,425 shocks at level 5/6. Also, 3 of the 4 patients had preoperatively unidentified connective tissue disorders.

CONCLUSIONS: Although severe adverse events following ESWL, (Clavien 4 or 5), are rare, they can occur. Physicians should be aware of this possibility during preoperative counseling. Further reports of severe adverse events should be collected to try and identify underlying risk factors that could identify and prevent these catastrophic outcomes.

Source of Funding: None

1626STRATEGIES TO IMPROVE SWL FOR OBESE PATIENTS: IN VITRO ASSESSMENT OF TARGETING STONES ALONG THE DISTAL ACOUSTIC AXIS

Yuri A Pishchalnikov*, Anthony J. Zancanaro, Jonathan N. VonDerHaar, James C. Williams, Jr, Andrew P. Evan, James E. Lingeman, James A. McAteer, Indianapolis, IN

INTRODUCTION AND OBJECTIVES: Obese stone patients typically have poor outcomes with SWL, particularly when the skin-to-stone distance is greater than ~9-10 cm. A practical problem with such a patient is that the stone cannot be positioned at the target point of the lithotripter. Over 20 years ago Whelan et al (J Urol 140: 410, 1988) introduced the concept of the “blast path” and showed that with the Dornier HM3, stones could be broken even if they were targeted distal to F2. One might expect that undershooting a stone could significantly reduce treatment efficiency, but this may depend on the acoustic characteristics of the lithotripter. To test the idea that some lithotripters may be better suited to treat obese patients we assessed the ability of several clinical lithotripters to break stones at various points along the acoustic axis.

METHODS: U30 gypsum stones held in a 2 mm mesh basket were broken at various points along the acoustic axis (z-axis) of several clinical lithotripters including a Dornier HM3, XiXin XX-ES, TRT LG380 and AST LithoSpace. In each case the target point was determined by x-ray alignment and the stone basket was moved using x-y-z positioners. Water in the test system was filtered and degassed to ~30% saturation. Axial scans of acoustic pressure were conducted using a fiberoptic probe hydrophone.

RESULTS: Stone breakage for the HM3 was better at the target point (F2 focal point) compared to points proximal (-) or distal (+) (F2>-25 mm or +25mm, p<0.001), but in all three positions U30 stones were completely comminuted in <800 shots. For the XX-ES, breakage was functionally equivalent over the distance from -45mm to +40 mm from the target point. For the LG380, stone breakage was significantly lower pre-focus (-20mm, p<0.05) but was equivalent from the target point to as far away as +50mm distally. Stone breakage for the LithoSpace was equivalent from -20mm to +70mm along the z-axis, a span of 9 cm.

CONCLUSIONS: This in vitro survey suggests that lithotripters vary in their ability to break stones at different depths along the acoustic axis, and for many machines effective stone breakage is not limited to the target point of the lithotripter. Indeed, for some lithotripters, such as the LithoSpace and the LG380, breakage equivalent to that at the target point can be achieved over a considerable distance (+40-50mm) along the distal acoustic axis. Such a machine may offer flexibility in targeting, as in the case of an obese patient when skin-to-stone distance is large. (Supported by DK43881)

Source of Funding: NIH DK43881

1627MULTI-INSTITUTIONAL ANALYSIS DEMONSTRATES THAT STONE SIZE IS ONLY INDEPENDENT PREDICTOR OF SWL SUCCESS IN CHILDREN

Sean McAdams, Nicholas Kim, Indupur R. Ravish, Manoj Monga, Roland Ugarte, Aseem R Shukla*, Minneapolis, MN

INTRODUCTION AND OBJECTIVES: We sought to determine whether age, BMI, number of stones, and total stone diameter can independently predict stone fragmentation after extracorporeal shock wave lithotripsy (SWL) in the pediatric population. Identifying the factors predictive of ESWL outcome would help streamline the care of pediatric patients with stones.

METHODS: We reviewed 149 pediatric patients (age 3-17) undergoing SWL from 2001-2008, retrieved from a regional SWL database. Variables included in the database were age, BMI, number of stones, and total stone diameter. The outcome of SWL was categorized as stone free with or without stenting, repeat procedure required, or incomplete fragmentation at 1-6 month on follow up imaging. We defined SWL success as stone free with or without stenting. 32 of 149 patients had multiple stones, and all stones were fragmented for those cases to be considered successful.

RESULTS: After ESWL, 106 (71%) were stone free, 12 (8%) required a repeat procedure, and 31 (21%) had incomplete fragmentation. Only three patients in the stone free group required stenting. BMI of the successfully treated patients was 21.92 ± 4.75 (for 99 of 106; 8 records were missing height) vs 22.26 ± 6.14 (for 38 of 43) for those with treatment failure (P = 0.76). The number of stones per patient ranged from 1 to 18 with a mean of 2.14 ± 2.60. The mean number of stones of the successfully treated patients was 1.87 ± 2.42 vs 2.81 ± 2.92 for those with treatment failure (P = 0.065). The total stone diameter ranged from 2 to 90 mm with the mean total stone diameter of 14.03 ± 16.68 mm. The mean total stone diameter of successfully treated patients was 11.1 ± 13.4 mm vs 21.3 ± 21.4 mm for those with treatment failure (P < 0.005).

CONCLUSIONS: To our knowledge, we present the first multi-institutional cohort study in the pediatric population demonstrating no significant relationship between a successful outcome and the patient age, BMI, or number of stones. Only total stone diameter independently predicted SWL success.

Source of Funding: None

1628PREDICTION OF STONE-FREE RATE OF EXTRACORPOREAL SHOCK WAVE LITHOTRIPSY IN THE TREATMENT OF PROXIMAL URETERAL STONE

Shun-Fa Hung*, Taipei, Taiwan; Shiu-Dong Chung, Ban Ciao, Taipei, Taiwan; Hong-Jeng Yu, Shuo-Meng Wang, Ho-Shiang Huang, Jun Chen, Taipei, Taiwan

INTRODUCTION AND OBJECTIVES: To evaluate the factors affecting stone-free rate after Extracorporeal Shock Wave Lithotripsy (ESWL) for the proximal ureteral stone (PUS) and to develop a prediction model.

METHODS: From January 2005 to December 2007, 1534 patients with urolithiasis underwent ESWL in our institution. Among them, 319 patients with PUS who received in situ ESWL were retrospectively reviewed. Patients requiring simultaneous treatment of kidney stones or placement of double pigtail stent, or percutaneous pigtail nephrostomy tube were excluded. The stone-free status was defined as no visible stone fragments on KUB at 3 months after ESWL. We substrated patients into two groups by Chronic Kidney Disease (CKD) Stage according to the estimated glomerular filtration rate (eGFR). Logistic regression model was used to evaluate the possible significant factors that influence the stone-free rate of PUS after ESWL.

RESULTS: Overall stone-free rate after ESWL for PUS in the 319 patients was 86.5%. In patients with eGFR 60, their stone-free rate was 93%, whereas stone-free rate was 50% in eGFR<60 group (P<0.001). The mean stone width was 6.13 ± 0.13 mm (range 1~12mm)