Julie Riley

Retrograde Ureteroscopy for Renal Stones Larger Than 2.5 cm

INTRODUCTION AND OBJECTIVES Because of the advances in endoscopic technology, retrograde flexible ureteroscopy (URS) is being applied to larger renal stone burdens. For stones greater than 2.5 cm, percutaneous nephrolithotomy has long been considered the standard of care. We have encountered a growing population of patients who desire a less invasive, less disruptive approach to large renal stones. We present our experience with retrograde ureteroscopic management of renal stones larger than 2.5 cm. METHODS Twenty-two patients between October 2004 and June 2008 underwent retrograde flexible URS with holmium laser lithotripsy. Each patient underwent retrograde URS using the Storz Flex-X and a ureteral access sheath. Patients were evaluated for number of procedures, stone clearance rates, and hospital admissions. Postoperative kidney, ureter, and bladder radiograph was used to determine stone-free rates. RESULTS Mean stone size was 3.0 cm. The average number of procedures was 1.82 with 5 patients requiring one, 14 requiring two, and 1 requiring three procedures. There were two failures who went on to have percutaneous nephrolithotomy, both of whom had significant lower pole stone burden. Overall stone-free rate was 90.9%. There were three overnight admissions for stent pain, and one 3-day admission for bacteremia in a patient who was noncompliant with preoperative antibiotics. CONCLUSIONS Planned staged URS is a viable option for the treatment of renal stones larger than 2.5 cm with excellent stone-free results. Significant lower pole stone burden is a limiting factor.

Effect of magnesium on calcium and oxalate ion binding.

BACKGROUND AND PURPOSE Magnesium (Mg(2+)) has been shown to be a kidney stone inhibitor; however, the exact mechanism of its effect is unknown. Using theoretical models, the interactions of calcium and oxalate were examined in the presence of Mg(2+). METHODS Molecular dynamics simulations were performed with NAMD and CHARMM27 force field. The interaction between calcium (Ca(2+)) and oxalate (Ox(2-)) ions was examined with and without magnesium. Concentrations of calcium and oxalate were 0.1 M and 0.03 M, respectively, and placed in a cubic box of length ~115 Angstrom. Na(+) and Cl(-) ions were inserted to meet system electroneutrality. Mg(2+) was then placed into the box at physiologic concentrations and the interaction between calcium and oxalate was observed. In addition, the effect of citrate and pH were examined in regard to the effect of Mg(2+) inhibition. Each system was allowed to run until a stable crystalline structure was formed. RESULTS The presence of Mg(2+) reduces the average size of the calcium oxalate and calcium phosphate aggregates. This effect is found to be Mg(2+) concentration-dependent. It is also found that Mg(2+) inhibition is synergistic with citrate and continues to be effective at acidic pH levels. CONCLUSION The presence of magnesium ions tends to destabilize calcium oxalate ion pairs and reduce the size of their aggregates. Mg(2+) inhibitory effect is synergistic with citrate and remains effective in acidic environments. Further studies are needed to see if this can be applied to in vivo models as well as extending this to other stone inhibitors and promoters.

Resonance Metallic Stents Do Not Effectively Relieve Extrinsic Ureteral Compression in Pediatric Patients

BACKGROUND AND PURPOSE Use of metallic stents (Resonance) has been reported in the literature to be effective in relieving extrinsic obstruction in adults. Successful patency rates have been reported to be around 83.3%. The use of Resonance stents in children has not been reported. We present our experience with these stents in addressing extrinsic ureteral obstruction in the pediatric population. PATIENTS AND METHODS We identified two patients who underwent placement of Resonance stents for extrinsic compression at the Childrens Hospital of the University of Pittsburgh Medical Center. The first patient is a 12-year-old girl with a solitary left kidney who had a diagnosis of pelvic rhabdomyosarcoma; she was treated with surgery followed by adjuvant chemoradiation. Two years post-treatment, worsening renal function secondary to ureteral strictures developed. The second patient is a 14-year-old girl with a history of Gardner syndrome. Recurrent desmoid tumors developed in her pelvis and retroperitoneum that led to right ureteral obstruction, necessitating a nephrostomy tube. RESULTS Both patients underwent successful technical placement of a Resonance stent. The time to failure for patient 1 was 3 months and for patient 2, 3 weeks. The first patient presented to the emergency department 3 months poststent in renal failure with a creatinine level of 13.7 mg/dL. This necessitated nephrostomy tube placement and hemodialysis. Ultimately, she needed an ileal ureter to preserve renal function. She is off hemodialysis and has a creatinine level of 2.2 mg/dL.The second patient, recurrent episodes of pyelonephritis, worsening hydronephrosis, and flank pain developed with just the Resonance stent in place. It was elected to remove the Resonance stent and replace the nephrostomy tube. She needed extensive ureterolysis, a right subtotal ureterectomy with a right to left ureteroureterostomy. CONCLUSION We did not find the use of these stents to be effective in children. The time to failure was significantly shorter in children than those reported in the literature for adults.

Stone Management for the Patient on Anticoagulation

Use of chronic anticoagulation has increased recently, leading to more surgical intervention on patients taking chronic anticoagulation. This review discusses anticoagulation and the management of urolithiasis.

Dietary management of idiopathic hyperoxaluria and the influence of patient characteristics and compliance.

OBJECTIVE To assess the efficacy of dietary management for the treatment of idiopathic hyperoxaluria in a large tertiary care center and examine the influence of patient factors, compliance, and follow-up on oxalate reduction, which has not been previously investigated. METHODS Retrospectively, 149 patients with kidney stones with idiopathic hyperoxaluria who received dietary management at our stone clinic were evaluated. Changes in urinary parameters on 24-hour urine collections were calculated for all patients and those with abnormal values in the overall short-term (30-240 days) and long-term (>240 days) time periods. Changes in urinary oxalate were evaluated with respect to patient characteristics and compliance measures. RESULTS Urine oxalate and supersaturation of calcium oxalate were significantly (P < .001) reduced by 8.9 ± 19.2 mg/d and 1.7 ± 4.3, respectively. A total of 48.3% of the patients reduced their urinary oxalate to normal. Urine oxalate reductions were similar in the short-term and long-term periods. Women lowered urine oxalate nearly twice as much as men (12.7 ± 2.0 mg/d vs 6.7 ± 2.2 mg/d, P = .022) and body mass index (BMI) negatively correlated with oxalate reduction (Pearsons r = -0.213). Reported noncompliance and keeping follow-up appointments did not affect oxalate, however, there was a significant correlation between increasing urine volume and reducing oxalate (Pearsons r = -0.21). CONCLUSION This study confirms that meaningful reductions of urine oxalate and supersaturation of calcium oxalate can be achieved with dietary management of hyperoxaluria on a larger clinical scale. Furthermore, we identified that women and patients with low BMIs had greater urine oxalate reductions and urine volume may also be used by clinicians as a measure of dietary compliance.

Use of preoperative embolization prior to Transplant nephrectomy

ABSTRACT Introduction After a failed transplant, management of a non-functional graft with pain or recurrent infections can be challenging. Transplant nephrectomy (TN) can be a morbid procedure with the potential for significant blood loss. Embolization of the renal artery alone has been proposed as a method of reducing complications from an in vivo failed kidney transplant. While this does yield less morbidity, it may not address an infected graft or refractory hematuria or rejection. We elected to begin preoperative embolization to assess if this would help decrease the blood loss and transfusion rate associated with TN. Materials and Methods We performed a retrospective analysis of all patients who underwent non-emergent TN at our institution. Patients who had functioning grafts that later failed were included in analysis. TN was performed for recurrent infections, pain or hematuria. We evaluated for blood loss (EBL) during TN, transfusion rate and length of hospital stay. Results A total of 16 patients were identified. Nine had preoperative embolization or no blood flow to the graft prior to TN. The remaining 7 did not have preoperative embolization. The shortest time from transplant to TN was 8 months and the longest 18 years with an average of 6.3 years. Average EBL for the embolized patients (ETN) was 143.9cc compared to 621.4cc in the non-embolized (NETN) group (p=0.041). Average number of units of blood transfused was 0.44 in the ETN with only 3/9 patients requiring transfusion. The NETN patients had average of 1.29 units transfused with 5/7 requiring transfusion. The length of stay was longer for the ETN (5.4 days) compared to 3.9 in the NETN. No intraoperative complications were seen in either group and only one patient had a postoperative ileus in the NETN. Conclusion Embolization prior to TN significantly decreases the EBL but does not significantly decrease transfusion rate. However, patients do require a significantly longer hospitalization with embolization due to the time needed for embolization. Larger studies are needed to determine if embolization before transplant nephrectomy reduces the transfusion rates and overall complications.

MP96-09 PREDICTING PROBABILITY OF MISSED CLINIC VISITS AT AN ACADEMIC MULTI-PROVIDER UROLOGY CLINIC

INTRODUCTION AND OBJECTIVES: Regionalization of cystectomy has been associated with improved outcomes but it may exacerbate geographic disparity by increasing travel distance. We sought to examine the association between travel distance to a highvolume cystectomy center and the probability of receiving a cystectomy among patients with muscle-invasive bladder cancer. METHODS: Using Surveillance, Epidemiology, and End Results (SEER)-Medicare data, we identified patients diagnosed with non-metastatic muscle-invasive bladder cancer between 2004 and 2011. We further identified patient treatment (i.e, cystectomy, bladdersparing alternative) using the inpatient, outpatient, and carrier files. Patients were then grouped into quartiles according to travel distance to the nearest high-volume cystectomy center (<1⁄48, 9-22, 23-53, and >53 miles). High-volume cystectomy centers included those with cystectomy volumes in the top quartile. The relationship between distance to a high-volume cystectomy center and treatment was assessed using a multivariable logistic regression model, adjusting for age, sex, race, comorbidity, marital status, county population, education level and median household income in ZIP code of residence, grade, and stage. RESULTS: Among 5149 patients with non-metastatic muscleinvasive bladder cancer, 1998 (39%) underwent a radical cystectomy. The adjusted probability of receiving a cystectomy according to travel distance to a high-volume cystectomy center is summarized in Figure 1. Compared to patients with a travel distance of 8 miles or less, those with a travel distance of 9-22 miles were less likely to receive a cystectomy (adjusted OR 0.79, 95% CI 0.66-0.96). However, this difference was mitigated in those with travel distances beyond 22 miles CONCLUSIONS: Our findings demonstrated a complex relationship between travel distances to a high-volume cystectomy center and the probability of receiving a radical cystectomy. While increasing distance decreased the likelihood of receiving a cystectomy for patients that live easily commutable distance, this disparity dissipated once the travel distance increased beyond 22 miles.

2081 EFFECT OF URIC ACID AND MAGNESIUM ON CALCIUM AND OXALATE ION BINDING

INTRODUCTION AND OBJECTIVES: Hyperuricosuria has been known to be a risk factor for calcium oxalate stones and Magnesium has been known to inhibit stone formation. However, the exact mechanism is unknown for both of these molecules. Using theoretical models, the interaction of calcium and oxalate were examined in the presence of uric acid and magnesium. METHODS: Molecular dynamic simulations were performed with NAMD and CHARMM27 force field. The interaction between calcium and oxalate ions were examined with and without uric acid and repeated with and without magnesium. Concentrations of calcium and oxalate were 0.15 M and placed in electroneutral cubic box of length 48 Angstrom. Uric acid (UA1 ) or magnesium (Mg2 ) was then placed into the box and the interaction between calcium and oxalate was observed. Oxalate was found to have two forms with a binding pair consisting of Ox1 (OACAO) and Ox2 (OACOCAO). RESULTS: In the presence of UA1-, calcium is in contact with Ox1 five times longer and in contact with Ox2 in excess of 100 times longer. In the presence of Mg2 , the oxalate binding pair is disrupted and shortens the contact between Ca and oxalate. This reduction is between 100 and 1000 times shorter then without Mg2 present. The density of Mg2 increases this effect and is most prominent when 2 Mg2 ions bind. However, when both calcium and Mg2 bind to Ox1, the effect of Mg2 is negated. CONCLUSIONS: Calcium and oxalate ions in the presence of uric acid have prolonged contact time and in the presence of magnesium, the contact time is significantly reduced. The effect of Mg2 is appears to be effected by density and binding position. Further studies are needed to see if this can be applied to in vivo models as well as extending this to other stone inhibitors and promoters.

Laparoscopic donor nephrectomy – safety in a small-volume transplant center

Riley J, Troxel S, Wakefield M, Ross G, Weinstein S. Laparoscopic donor nephrectomy – safety in a small‐volume transplant center.
Clin Transplant 2010: 24: 429–432.