Instrumentation and Surgical Technique

Obesity Triples the Radiation Dose of Stone Protocol Computerized Tomography

Patients with recurrent nephrolithiasis are often evaluated and followed with computerized tomography. Obesity is a risk factor for nephrolithiasis. We evaluated the radiation dose of computerized tomography in obese and nonobese adults.We scanned a validated, anthropomorphic male phantom according to our institutional renal stone evaluation protocol. The obese model consisted of the phantom wrapped in 2 Custom Fat Layers (CIRS, Norfolk, Virginia), which have been verified to have the same radiographic tissue density as fat. High sensitivity metal oxide semiconductor field effect transistor dosimeters were placed at 20 organ locations in the phantoms to measure organ specific radiation dose…

Contemporary Management of Struvite Stones Using Combined Endourologic and Medical Treatment: Predictors of Unfavorable Clinical Outcome

Struvite stones have been associated with significant morbidity and mortality, yet there has not been a report on the medical management of struvite stones in almost 20 years. We report on the contemporary outcomes of the surgical and medical management of struvite stones in a contemporary series.A retrospective review of patients who were treated with percutaneous nephrolithotomy (PCNL) for struvite stones at Duke University Medical Center between January 2005 and September 2012 identified a total of 75 patients. Of these, 43 patients had adequate follow-up and were included in this analysis. Stone activity, defined as either stone recurrence or stone-related events, and predictors of acti…

Assessment of a Modified Acoustic Lens for Electromagnetic Shock Wave Lithotripters in a Swine Model

The acoustic lens of the Modularis electromagnetic shock wave lithotripter (Siemens, Malvern, Pennsylvania) was modified to produce a pressure waveform and focal zone more closely resembling that of the original HM3 device (Dornier Medtech, Wessling, Germany). We assessed the newly designed acoustic lens in vivo in an animal model.Stone fragmentation and tissue injury produced by the original and modified lenses of the Modularis lithotripter were evaluated in a swine model under equivalent acoustic pulse energy (about 45 mJ) at 1 Hz pulse repetition frequency. Stone fragmentation was determined by the weight percent of stone fragments less than 2 mm. To assess tissue injury, shock wave trea…

Digital Tomosynthesis: A New Technique for Imaging Nephrolithiasis. Specific Organ Doses and Effective Doses Compared With Renal Stone Protocol Noncontrast Computed Tomography

Objective To determine organ-specific doses (ODs) and effective dose (ED) for digital tomosynthesis (DT) and compare it with our institutional renal stone protocol noncontrast computed tomography (NCCT). Methods A validated anthropomorphic male phantom was placed supine on a digital GE Definium 8000 radiological scanner. Thermoluminescent dosimeters were placed in 256 locations and used to measure OD. A routine DT study was performed consisting of 2 scout images and 1 tomographic sweep in a 14.2-degree arc over the phantom. Software is used to recreate a series of coronal images from the sweep. ODs were determined as the sum of the doses for the study. Equivalent doses were calculated by mu…

Treatment Response in Patients with Stones, and Low Urinary pH and Hypocitraturia Stratified by Body Mass Index.

Obesity has been shown to be a risk factor for kidney stone formation. Obesity leads to insulin resistance which subsequently leads to low urinary pH. Low urinary pH is typically treated with potassium citrate. We determined if the response to potassium citrate for the treatment of low urinary pH and hypocitraturia varied when patients were stratified by body mass index.We retrospectively reviewed the records of patients with urolithiasis and concomitant hypocitraturia and low urinary pH as unique abnormalities upon metabolic evaluation treated exclusively with potassium citrate. Based on body mass index the cohort was divided into the 4 groups of normal weight, overweight, obese and morbid…