Jessica N. Lange

Glyoxal Formation and Its Role in Endogenous Oxalate Synthesis

Calcium oxalate kidney stones are a common condition affecting many people in the United States. The concentration of oxalate in urine is a major risk factor for stone formation. There is evidence that glyoxal metabolism may be an important contributor to urinary oxalate excretion. Endogenous sources of glyoxal include the catabolism of carbohydrates, proteins, and fats. Here, we review all the known sources of glyoxal as well as its relationship to oxalate synthesis and crystal formation.

The association of cardiovascular disease and metabolic syndrome with nephrolithiasis.

Purpose of review This review describes the relationship between nephrolithiasis, vascular disease and metabolic syndrome. Recent findings There is increasing evidence that kidney stone formation is associated with a number of systemic problems including cardiovascular disease, metabolic syndrome and its components. Some of these associations are bidirectional. The reasons for these associations are not totally clear, but potential factors include metabolic responses associated with these disorders that promote a stone forming milieu in urine, environmental factors such as diet, oxidative stress and inflammation and molecular changes impacting the transport of certain analytes in urine. Summary Urologists need to be cognizant of these associations as they may be able to contribute to an early diagnosis of a significant medical problem, or provide counseling to patients to prevent their occurrence.

The effects of oxazyme on oxalate degradation: Results and implications of in vitro experiments

UNLABELLED Abstract Background and Purpose: Urinary oxalate excretion influences the development of calcium oxalate kidney stones. Urinary oxalate is derived from dietary sources and endogenous synthesis. Oxalate decarboxylase metabolizes oxalate and, if consumed, could theoretically accomplish this in the gastrointestinal tract. This study aimed to determine whether a commercially produced form of oxalate decarboxylase (Oxazyme(®)) could degrade oxalate in simulated gastric and intestinal environments. MATERIALS AND METHODS One buffer (pH 3.6) simulated the gastric environment, while another (pH 6.5), approximated the proximal intestine. Potassium oxalate (soluble form of oxalate) and whole and homogenized spinach (a high oxalate containing food) were incubated in the different buffered solutions, with or without Oxazyme. Oxalate content, after incubation, was measured using established ion chromatographic techniques. RESULTS Oxazyme resulted in complete degradation of oxalate derived from potassium oxalate in the intestinal buffer; meanwhile, oxalate derived from potassium oxalate in the gastric buffer was profoundly digested by Oxazyme. Adding Oxazyme also substantially reduced the oxalate content of both whole and homogenized spinach preparations, in either buffer. CONCLUSIONS These in vitro findings demonstrate that Oxazyme can metabolize oxalate in both simulated gastric and small intestinal environments.

Gas-containing Renal Stones: Findings From Five Consecutive Patients

OBJECTIVE To describe the clinical course, microbiology, and metabolic findings of 5 patients presenting to our institution with gas-containing renal stones. MATERIALS AND METHODS During a 20-month period beginning in 2009, 5 patients were identified by computed tomography scanning to harbor gas-containing renal calculi. Despite similar imaging and referral practice patterns, no such cases had been seen at our institution in the preceding 20 years. The records of these patients were reviewed to better characterize this unique condition. RESULTS All 5 subjects were premenopausal women. One patient presented with urosepsis and 4 presented with flank pain. All had urinary tract infections, and Escherichia coli was isolated from a voided urine specimen in 3. Stone culture was positive in 2 and was concordant with the voided specimen in 1. The stones were solitary in 4 and multiple in 1 patient. All the stones were composed of calcium phosphate. Of the 5 patients, 3 had pure calcium phosphate stones and 2 had stones with calcium oxalate monohydrate components. Also, 3 subjects had diabetes mellitus, 3 had hypertension, and 1 had a history of gout. Two subjects underwent 24-hour urine metabolic testing, and abnormalities were identified in both. All patients were rendered stone free: 4 with percutaneous nephrostolithotomy and 1 using robotic pyelolithotomy. CONCLUSION Gas-containing renal stones are rare but might be increasing in prevalence. The pathophysiology is unknown but is most likely influenced by a combination of metabolic and infectious factors.

Safety and Efficacy of Removable Inferior Vena Cava Filters in Anticoagulated Patients Undergoing Percutaneous Nephrostolithotomy

BACKGROUND AND PURPOSE Increasing numbers of patients are receiving a diagnosis of thrombophilic conditions necessitating chronic anticoagulation therapy. The best management approach for such patients needing percutaneous nephrostolithotomy (PCNL) has not been established. Discontinuing anticoagulation therapy before PCNL is needed to prevent hemorrhage, placing some of these patients at risk for thromboembolic events. We describe the use of removable inferior vena cava filters (RIVCF) in patients undergoing PCNL who are at risk for a venous thromboembolic event. PATIENTS AND METHODS A retrospective study of outcomes of PCNL with RIVCF placement was conducted. RESULTS Four patients underwent PCNL with RIVCF placement on the same day of the procedure. The mean age was 49 years (range 35-69 years). PCNL was performed on a total of six renal units with a mean of 2.2 (range 1-3) operations per renal unit. Five of six (83%) renal units were rendered stone free. There were no complications associated with either the PCNL or RIVCF placement. No patient had a thromboembolic event or received blood products. Two of the four patients underwent successful removal of the RIVCF, and one elected to keep the device in place. The device could not be extracted in the other patient. The average length that the filters were in place was 52.5 days. Patients resumed anticoagulation therapy shortly after RIVCF removal. CONCLUSION RIVCF placement is a safe and effective method of preventing venous thromboembolic complications in thrombophilic patients needing PCNL. Patients should be informed, however, that RIVCF removal is not always possible.

Comparative Outcomes of Conventional PCNL and Miniaturized PCNL in the Treatment of Kidney Stones: Does a Miniaturized Tract Improve Quality of Care?

Introduction: Percutaneous nephrostolithotomy is the method of choice to treat renal stones larger than 2 cm due to its high stone‐free rates but it has potentially increased blood loss, postoperative pain and hospital stay compared to other treatments. Miniaturizing the percutaneous tract has recently gained interest. We performed a quality improvement study to investigate whether mini percutaneous nephrostolithotomy would reduce postoperative analgesic use, blood loss, operative time and/or hospital stay relative to the conventional approach while maintaining stone‐free rates in our patient population. Methods: The outcomes of 29 consecutive mini percutaneous nephrostolithotomies were compared to 27 conventional procedures performed by a single surgeon at our institution. Inclusion criteria were age 18 years or older, body mass index 18 to 40 kg/m2 and first look percutaneous nephrostolithotomy for stones 1 to 3.5 cm. Conventional percutaneous nephrostolithotomy was performed through a 30Fr tract, whereas the mini approach was done through a 16.5Fr tract. All percutaneous access was performed by the surgeon. Results: A total of 17 patients in the conventional percutaneous nephrostolithotomy group and 19 in the mini approach group were stone‐free after 1 procedure. There was no significant difference in residual stone burden, operative time or postoperative analgesic use between groups. There was significantly less blood loss (p = 0.02) in the mini percutaneous nephrostolithotomy group. Conclusions: Conventional and mini percutaneous nephrostolithotomies are effective methods of removing renal stones 1 to 3.5 cm in greatest dimension. There is no difference in residual stone volume, postoperative analgesic use or operative time between the 2 modalities, but blood loss is less in the mini percutaneous nephrostolithotomy group.

Fish Oil Supplementation and Urinary Oxalate Excretion in Normal Subjects on a Low-oxalate Diet

OBJECTIVE To determine if fish oil supplementation reduces endogenous oxalate synthesis in healthy subjects. MATERIALS AND METHODS Fifteen healthy non-stone-forming adults participated in this study. Subjects first abstained from using vitamins, medications, or foods enriched in omega-3 fatty acids for 30 days. Next, they collected two 24-hour urine specimens while consuming a self-selected diet. Subjects consumed an extremely low-oxalate and normal-calcium diet for 5 days and collected 24-hour urine specimens on the last 3 days of this diet. Next, the subjects took 2 fish oil capsules containing 650-mg eicosapentaenoic acid and 450-mg docosahexaenoic acid twice daily for 30 days. They consumed a self-selected diet on days 1-25 and the controlled diet on days 26-30. Twenty-four-hour urine samples were collected on days 28-30. Excretion levels of urinary analytes including oxalate and glycolate were analyzed. RESULTS Although there was a significant reduction in urinary oxalate, magnesium, and potassium excretions and an increase in uric acid excretion during the controlled dietary phases compared with the self-selected diet, there were no significant differences in their excretion during controlled diet phases with and without fish oil supplementation. CONCLUSION These results suggest that fish oil supplementation does not reduce endogenous oxalate synthesis or urinary oxalate excretion in normal adults during periods of extremely low oxalate intake. However, these results do not challenge the previously described reduction in urinary oxalate excretion demonstrated in normal subjects consuming a moderate amount of oxalate in conjunction with fish oil.

MP95-20 THE PERSISTENCE OF OPEN STONE SURGERY IN THE UNITED STATES IN THE 21ST CENTURY

INTRODUCTION AND OBJECTIVES: NHS outpatient waiting lists are ever increasing. In January 2016, 976 patients were awaiting a Urology appointment in Brighton. Urgent referrals to a dedicated stone clinic were seen after 12-14 weeks, with routine referrals seen after 6 months. Patient experience was poor, with stone clinic DNA rates of 14%. Innovative changes were needed and a virtual stone clinic (VSC) was set up to improve the service. METHODS: VSC set up was based on Brighton0s award-winning virtual fracture clinic. A consultant-led once-weekly VSC was supported by a MDT of the stone registrar, ESWL radiographer and stone nurse. Referrals were triaged direct from source (ED, GPs, inpatient teams, post-lithotripsy). A target of 20-30 patients per week was set and a tariff of £64 agreed. We aimed to assess the effectiveness following the first 2 months of running the service. RESULTS: 212 patients were seen. 90 (42.5%) were discharged without any further investigations after the first VSC. Of the 122 (57.5%) who required follow up, 89 were brought back to the VSC, and only 33 patients (15%) were invited to attend face-to-face outpatient appointment, to either discuss more invasive treatment (PCNL) or for metabolic evaluation. 83% were discharged following a second virtual clinic review. Treatment was offered to 38 patients (18%); 23 had ESWL, 10 URS, 3 PCNL, and 2 stent/stent removal. Total income, over 2 months, from the 1h-long weekly VSC was £13 568, vs. £24 960 from 4h-long comparable outpatients clinics. The projected income, had the VSC run for 4h, would have however been £54 272. The 6 month waiting list was cleared in the 2 months period. All new referrals are now reviewed by a Consultant in less than 1 week. Feedback from patients was good with only 1 complaint (0.5%) and 8 DNAs (3.8%). We expect to see nearer a 1000 patients by May 2017, and will present updated results. CONCLUSIONS: VSC is a viable and appropriate way for managing patients0 stones. It is cost effective and has a clear advantage with regards to reducing waiting lists. VSCs avoid the time consuming telephone follow-up clinic and free-up traditional outpatient appointments for other activity or complex metabolic stone patients. Early experience suggests patients enjoy the service. Virtual clinics have been gaining popularity across the world, improving the quality and access to care for patients. To the best of our knowledge, this is the first virtual clinic dedicated to patients with urolithiasis in the world. Given the encouraging preliminary results of our study, VSC has the scope to be introduced on a much wider scale.

Robot-Assisted Laparoscopic Extended Pyelolithotomy and Ureterolithotomy

This chapter provides an overview of the latest robotic approaches to stone-removing surgery. These include transperitoneal pyelolithotomy, retroperitoneal pyelolithotomy, ureterolithotomy, and anatrophic nephrolithotomy. We provide diagrams to assist with optimal port placement for all versions of the da Vinci robot platform. Finally, we provide suggestions as to when the robotic approach to stone-removing surgery may be preferred.