Browsing by Author "Preminger, Glenn M"

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    Combined Endoscopic and Percutaneous Retrieval of a Retained 4-Wire Ureteral Stone Basket.
    (Journal of endourology case reports, 2015-01) Kaplan, Adam G; Preminger, Glenn M; Lipkin, Michael E
    Complex endourologic procedures may require the use of a combined ureteroscopic and percutaneous approach. Endoscopic removal of a retained 4-wire ureteral stone basket is particularly complex, as broken tines can potentially injure the ureter if the basket is removed in a retrograde manner. The patient in this case presented with a ureteral stone basket embedded within the urothelium of the upper pole of the kidney. Holmium laser incision of the overlying urothelium allowed retrieval of the basket, although the tines were broken. Endoscopically guided percutaneous access to the kidney was obtained to allow for direct passage of the retained basket out of a nephrostomy sheath, thereby protecting the kidney.
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    Defining metabolic activity of nephrolithiasis - Appropriate evaluation and follow-up of stone formers.
    (Asian journal of urology, 2018-10) Wollin, Daniel A; Kaplan, Adam G; Preminger, Glenn M; Ferraro, Pietro Manuel; Nouvenne, Antonio; Tasca, Andrea; Croppi, Emanuele; Gambaro, Giovanni; Heilberg, Ita P
    Considering the variation in metabolic evaluation and medical management of kidney stone disease, this consensus review was created to discuss the metabolic activity of nephrolithiasis, define the difference between single and recurrent stone formers, and develop a schema for metabolic and radiologic follow-up. A systematic review of the literature was performed to identify studies of metabolic evaluation and follow-up of patients with nephrolithiasis. Both single and recurrent stone formers share many similarities in metabolic profiles. The study group determined that based on an assessment of risk for stone recurrence and metabolic activity, single and recurrent stone formers should be evaluated comprehensively, including two 24 h urine studies on a random diet. Targeted medication and dietary recommendations are effective for many patients in reducing the risk of stone recurrence. Follow-up of those with stone disease should be obtained depending on the level of metabolic activity of the patient, the risk of chronic kidney disease and the risk of osteoporosis/osteopenia. A standard scheme includes a baseline metabolic profile, a repeat study 3-6 months after initiation of treatment, and then yearly when stable, with abdominal imaging obtained every 1-2 years.
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    Improving the lens design and performance of a contemporary electromagnetic shock wave lithotripter.
    (Proc Natl Acad Sci U S A, 2014-04-01) Neisius, Andreas; Smith, Nathan B; Sankin, Georgy; Kuntz, Nicholas John; Madden, John Francis; Fovargue, Daniel E; Mitran, Sorin; Lipkin, Michael Eric; Simmons, Walter Neal; Preminger, Glenn M; Zhong, Pei
    The efficiency of shock wave lithotripsy (SWL), a noninvasive first-line therapy for millions of nephrolithiasis patients, has not improved substantially in the past two decades, especially in regard to stone clearance. Here, we report a new acoustic lens design for a contemporary electromagnetic (EM) shock wave lithotripter, based on recently acquired knowledge of the key lithotripter field characteristics that correlate with efficient and safe SWL. The new lens design addresses concomitantly three fundamental drawbacks in EM lithotripters, namely, narrow focal width, nonidealized pulse profile, and significant misalignment in acoustic focus and cavitation activities with the target stone at high output settings. Key design features and performance of the new lens were evaluated using model calculations and experimental measurements against the original lens under comparable acoustic pulse energy (E+) of 40 mJ. The -6-dB focal width of the new lens was enhanced from 7.4 to 11 mm at this energy level, and peak pressure (41 MPa) and maximum cavitation activity were both realigned to be within 5 mm of the lithotripter focus. Stone comminution produced by the new lens was either statistically improved or similar to that of the original lens under various in vitro test conditions and was significantly improved in vivo in a swine model (89% vs. 54%, P = 0.01), and tissue injury was minimal using a clinical treatment protocol. The general principle and associated techniques described in this work can be applied to design improvement of all EM lithotripters.
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    Metabolic evaluation and medical management of staghorn calculi.
    (Asian journal of urology, 2020-04) Terry, Russell S; Preminger, Glenn M
    Staghorn renal calculi are large renal calculi that occupy nearly the entirety of the renal collecting system. They may be composed of metabolic or infection stone types. They are often associated with specific metabolic defects. Infection stones are associated with urease-producing bacterial urinary tract infections. The ideal treatment for staghorn calculi is maximal surgical removal. However, some patients are either unwilling or unable to proceed with that modality of treatment, and therefore other management must be used. One such technique is the metabolic evaluation with directed medical management. Based on contemporary evidence that the majority of staghorn stones are metabolic in etiology, and furthermore that even infection stones are usually associated with metabolic abnormalities, metabolic evaluation with directed medical management is recommended for all staghorn stone formers. The scientific basis of this recommendation is reviewed in the present work.
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    Optimization of treatment strategy used during shockwave lithotripsy to maximize stone fragmentation efficiency.
    (J Endourol, 2011-09) Yong, Daniel Z; Lipkin, Michael E; Simmons, W Neal; Sankin, Georgy; Albala, David M; Zhong, Pei; Preminger, Glenn M
    BACKGROUND AND PURPOSE: Previous studies have demonstrated that treatment strategy plays a critical role in ensuring maximum stone fragmentation during shockwave lithotripsy (SWL). We aimed to develop an optimal treatment strategy in SWL to produce maximum stone fragmentation. MATERIALS AND METHODS: Four treatment strategies were evaluated using an in-vitro experimental setup that mimics stone fragmentation in the renal pelvis. Spherical stone phantoms were exposed to 2100 shocks using the Siemens Modularis (electromagnetic) lithotripter. The treatment strategies included increasing output voltage with 100 shocks at 12.3 kV, 400 shocks at 14.8 kV, and 1600 shocks at 15.8 kV, and decreasing output voltage with 1600 shocks at 15.8 kV, 400 shocks at 14.8 kV, and 100 shocks at 12.3 kV. Both increasing and decreasing voltages models were run at a pulse repetition frequency (PRF) of 1 and 2 Hz. Fragmentation efficiency was determined using a sequential sieving method to isolate fragments less than 2 mm. A fiberoptic probe hydrophone was used to characterize the pressure waveforms at different output voltage and frequency settings. In addition, a high-speed camera was used to assess cavitation activity in the lithotripter field that was produced by different treatment strategies. RESULTS: The increasing output voltage strategy at 1 Hz PRF produced the best stone fragmentation efficiency. This result was significantly better than the decreasing voltage strategy at 1 Hz PFR (85.8% vs 80.8%, P=0.017) and over the same strategy at 2 Hz PRF (85.8% vs 79.59%, P=0.0078). CONCLUSIONS: A pretreatment dose of 100 low-voltage output shockwaves (SWs) at 60 SWs/min before increasing to a higher voltage output produces the best overall stone fragmentation in vitro. These findings could lead to increased fragmentation efficiency in vivo and higher success rates clinically.
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    Outcomes of metallic stents for malignant ureteral obstruction.
    (J Urol, 2012-09) Goldsmith, Zachariah G; Wang, Agnes J; Bañez, Lionel L; Lipkin, Michael E; Ferrandino, Michael N; Preminger, Glenn M; Inman, Brant A
    PURPOSE: Malignant ureteral obstruction often necessitates chronic urinary diversion and is associated with high rates of failure with traditional ureteral stents. We evaluated the outcomes of a metallic stent placed for malignant ureteral obstruction and determined the impact of risk factors previously associated with increased failure rates of traditional stents. MATERIALS AND METHODS: Patients undergoing placement of the metallic Resonance® stent for malignant ureteral obstruction at an academic referral center were identified retrospectively. Stent failure was defined as unplanned stent exchange or nephrostomy tube placement for signs or symptoms of recurrent ureteral obstruction (recurrent hydroureteronephrosis or increasing creatinine). Predictors of time to stent failure were assessed using Cox regression. RESULTS: A total of 37 stents were placed in 25 patients with malignant ureteral obstruction. Of these stents 12 (35%) were identified to fail. Progressive hydroureteronephrosis and increasing creatinine were the most common signs of stent failure. Three failed stents had migrated distally and no stents required removal for recurrent infection. Patients with evidence of prostate cancer invading the bladder at stent placement were found to have a significantly increased risk of failure (HR 6.50, 95% CI 1.45-29.20, p = 0.015). Notably symptomatic subcapsular hematomas were identified in 3 patients after metallic stent placement. CONCLUSIONS: Failure rates with a metallic stent are similar to those historically observed with traditional polyurethane based stents in malignant ureteral obstruction. The invasion of prostate cancer in the bladder significantly increases the risk of failure. Patients should be counseled and observed for subcapsular hematoma formation with this device.
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    Subcapsular Splenic Urinoma and Splenorenal Fistula: A New Complication of Percutaneous Nephrolithotomy.
    (Journal of endourology case reports, 2017-01) Cone, Eugene B; Jibara, Ghalib; Wollin, Daniel; Preminger, Glenn M
    Background: Splenic urinoma has not been previously reported as a complication of percutaneous nephrolithotomy (PNL). Case Presentation: A 46-year-old Caucasian male underwent PNL for two large left renal stones. Surgery was performed in prone split-leg position, with access obtained through combined fluoroscopic guidance and direct ureteroscopic observation of the targeted calix. The tract was dilated to 30F using a pressure balloon, and complete clearance of stones was obtained through a combination of rigid and flexible nephroscopy, as well as antegrade ureteroscopy. The patient was left with a Double-J ureteral stent on a string for removal in 1 week. After overnight observation, his hemoglobin, white blood cell count, and renal function were normal and thus he was discharged home. The day after stent removal, he presented to the emergency department with abdominal pain, was found to have mild left hydronephrosis on CT, and was discharged on 1 week of antibiotics. One week later he re-presented with worsening abdominal pain and was found to have an elevated creatinine and a white blood cell count of 21 × 109/L. On contrasted CT with delayed images, an 18 cm splenic fluid collection was seen with a fistulous connection to the left kidney collecting system. He underwent emergent stent placement and improved clinically without drainage of the urinoma. A renal ultrasonography 1 month after stent placement confirmed resolution of the splenic urinoma, so the stent was removed at 1 month. Follow-up CT 1 month after stent removal was normal without any evidence of fistula or urinoma recurrence. Conclusion: This is the first report of a subcapsular splenic urinoma and splenorenal fistula post-PNL. Ureteral stent placement was sufficient for drainage and to resolve the complication.