Urinary Metabolic Disturbances During Topiramate Use and their Reversibility Following Drug Cessation.

OBJECTIVE: To understand the metabolic disturbances of stone formers currently taking topiramate and to examine the reversibility of these disturbances with cessation of the medication. MATERIALS AND METHODS: All progress notes written by 5 endourologists from a single academic center were retrospectively reviewed from January 2010 to July 2020 containing the words "topiramate" or "topamax." Inclusion criteria were age >18 and presence of either a 24-hour urine sample or stone analysis while on topiramate. In addition, a subgroup of 18 patients with 24-hour urine samples before and after stopping topiramate were identified. RESULTS: A total of 93 patients were identified and included for final analysis. Twenty-four hour urine samples were available in 67 patients and showed mean citrate excretion of 331 ± 322 mg/d, mean pH of 6.6 ± 0.5, and mean calcium phosphate supersaturation of 1.9 ± 1.1. In the subgroup analysis urinary citrate excretion increased from 225 mg/d to 614 mg/d (P <.01) and pH decreased from 6.59 ± 0.54 to 6.33 ± 0.47 (P = .06) after stopping topiramate. In addition, 114 stone events occurred in 73 distinct patients, with 50% of stones either pure or majority (≥50%) calcium phosphate by composition. CONCLUSION: Hypocitraturia and elevated pH is seen during topiramate use with resultant higher rate of calcium phosphate stone formation compared to the general population. Stopping topiramate leads to significant increase in citrate excretion and normalization of pH. These metabolic disturbances appear to be reversible with medication cessation.

Trends in renal calculus composition and 24-hour urine analyses in patients with neurologically derived musculoskeletal deficiencies

ABSTRACT Purpose: To better characterize metabolic stone risk in patients with neurologically derived musculoskeletal deficiencies (NDMD) by determining how patient characteristics relate to renal calculus composition and 24-hour urine parameters. Materials and Methods: We performed a retrospective cohort study of adult patients with neurologically derived musculoskeletal deficiencies presenting to our multidisciplinary Kidney Stone Clinic. Patients with a diagnosis of NDMD, at least one 24-hour urine collection, and one chemical stone analysis were included in the analysis. Calculi were classified as primarily metabolic or elevated pH. We assessed in clinical factors, demographics, and urine metabolites for differences between patients who formed primarily metabolic or elevated pH stones. Results: Over a 16-year period, 100 patients with NDMD and nephrolithiasis were identified and 41 met inclusion criteria. Thirty percent (12 / 41) of patients had purely metabolic calculi. Patients with metabolic calculi were significantly more likely to be obese (median body mass index 30.3kg / m2 versus 25.9kg / m2), void spontaneously (75% vs. 6.9%), and have low urine volumes (100% vs. 69%). Patients who formed elevated pH stones were more likely to have positive preoperative urine cultures with urease splitting organisms (58.6% vs. 16.7%) and be hyperoxaluric and hypocitraturic on 24-hour urine analysis (37mg / day and 265mg / day versus 29mg / day and 523mg / day). Conclusions: Among patients with NDMD, metabolic factors may play a more significant role in renal calculus formation than previously believed. There is still a high incidence of carbonate apatite calculi, which could be attributed to bacteriuria. However, obesity, low urine volumes, hypocitraturia, and hyperoxaluria suggest an underrecognized metabolic contribution to stone formation in this population.

Trends in the Usage of Contrast Allergy Prophylaxis for Endourologic Procedures.

OBJECTIVE: To characterize current practice patterns of urologists in the management of intravenous (IV) contrast allergy in the setting of endourologic procedures. METHODS: A survey was administered to all members of the Endourological Society to assess management of IV contrast allergy prior to ureteroscopy (URS) and percutaneous nephrolithotomy (PCNL). Treatment regimens, reports of adverse outcomes, and demographics of respondents were also collected. Data were analyzed using chi-square tests. RESULTS: The response rate was 15% (325/2100). A total of 21% and 28% of respondents reported giving prophylaxis prior to URS and PCNL, respectively. Nearly 3% of respondents reported having observed a severe adverse reaction to intraluminal contrast in the past. Approximately half reported giving prophylaxis only 1 hour prior to the procedure. Most respondents (77%) completed a fellowship, the most common being endourology. Chi-square analysis revealed a significant difference between giving prophylaxis for URS or PCNL and the respective case volumes (for URS, X2 = 8.3, P= .004; for PCNL, X2 = 8.5, P= .003) where urologists with the lowest and highest case volumes were more likely to give prophylaxis (Fig. 1). There was no significant difference between giving prophylaxis for URS or PCNL and recency of residency, fellowship training, practice setting, or practice type. CONCLUSION: Most urologists do not give prophylaxis for patients with IV contrast allergy prior to URS and PCNL. Further studies are needed to evaluate the necessity of prophylaxis as well as to establish clear guidelines.

Trends in renal calculus composition and 24-hour urine analyses in patients with neurologically derived musculoskeletal deficiencies.

PURPOSE: To better characterize metabolic stone risk in patients with neurologically derived musculoskeletal deficiencies (NDMD) by determining how patient characteristics relate to renal calculus composition and 24-hour urine parameters. MATERIALS AND METHODS: We performed a retrospective cohort study of adult patients with neurologically derived musculoskeletal deficiencies presenting to our multidisciplinary Kidney Stone Clinic. Patients with a diagnosis of NDMD, at least one 24-hour urine collection, and one chemical stone analysis were included in the analysis. Calculi were classified as primarily metabolic or elevated pH. We assessed in clinical factors, demographics, and urine metabolites for differences between patients who formed primarily metabolic or elevated pH stones. RESULTS: Over a 16-year period, 100 patients with NDMD and nephrolithiasis were identified and 41 met inclusion criteria. Thirty percent (12 / 41) of patients had purely metabolic calculi. Patients with metabolic calculi were significantly more likely to be obese (median body mass index 30.3kg / m2 versus 25.9kg / m2), void spontaneously (75% vs. 6.9%), and have low urine volumes (100% vs. 69%). Patients who formed elevated pH stones were more likely to have positive preoperative urine cultures with urease splitting organisms (58.6% vs. 16.7%) and be hyperoxaluric and hypocitraturic on 24-hour urine analysis (37mg / day and 265mg / day versus 29mg / day and 523mg / day). CONCLUSIONS: Among patients with NDMD, metabolic factors may play a more significant role in renal calculus formation than previously believed. There is still a high incidence of carbonate apatite calculi, which could be attributed to bacteriuria. However, obesity, low urine volumes, hypocitraturia, and hyperoxaluria suggest an underrecognized metabolic contribution to stone formation in this population.

Single Pulse-per-second Setting Reduces Fluoroscopy Time During Ureteroscopy.

OBJECTIVE: To evaluate the effect of 1 pulse-per-second (pps) fluoroscopy on fluoroscopy time and surgeon radiation exposure during ureteroscopy. MATERIALS AND METHODS: A retrospective review of a single endourologist's operative records was performed over a 12-month period. Adult patients undergoing ureteroscopy were included. At the 6-month point, the switch from continuous "low-dose" to 1 pps "low-dose" fluoroscopy was made. Surgeon radiation exposure was measured using 1 dosimeter placed at the torso under the lead apron and 1 dosimeter overlying the chest outside the lead apron. RESULTS: A total of 84 and 70 patients underwent ureteroscopy using continuous and 1 pps fluoroscopy, respectively. No differences were identified between the 2 groups with regard to patient age (P = .96), sex (P = .26), body mass index (P = .95), stone multiplicity (P = .31), bilateral ureteroscopy (P = .07), pre-stenting (P = .99), staged (P = .84) or failed (P = .99) primary ureteroscopy, ureteral access sheath utilization (P = .10), or case duration (P = .54). Patients in the 1 pps cohort had a larger median stone burden (P = .04). The median fluoroscopy time was reduced from 77 (interquartile range: 54-115) to 16 seconds (interquartile range: 13-24) using 1 pps fluoroscopy (P < .001). Monthly surgeon radiation exposure was reduced by 64%, from 6.8 ± 8.3 to 1.8 ± 2.7 mRad deep dose equivalent (P = .11), from 120.6 ± 101.4 to 49.2 ± 66.6 mRad lens dose equivalent (P = .10), and from 116.2 ± 97.8 to 47.6 ± 64.0 mRad shallow dose equivalent (P = .11). Reversion to continuous fluoroscopy was never required during the study period. CONCLUSION: Single pps fluoroscopy is feasible, significantly reduces fluoroscopy time, and lowers surgeon radiation exposure by 64%.

Radiation Practice Patterns and Exposure in the High-volume Endourologist.

OBJECTIVE: To define radiation exposure among high-volume endourologists and characterize surgeon exposure patterns as previous literature has focused primarily on patient exposure. METHODS: Surveys were obtained from the Research on Calculus Kinetics Society members from 14 different institutions across North America. All surgeons practice at high-volume academic institutions as surgical stone specialists. Protective equipment, fluoroscopy variables, and practice patterns were recorded. Dosimeter readings from the past year were analyzed when available. RESULTS: Fifteen surveys were returned, with a response rate of 94%. Fluoroscopic procedures comprised 87% of surgeon cases. Surgeon mean experience was 12.4 years (range, 1-32 years). Lead aprons were worn in 99.3% of cases, thyroid shields in 98.7%, radiation glasses in 52.7%, and lead gloves in 9.7%. Only 33.3% of surgeons regularly wore dosimeters. Of these surgeons, average deep-dose equivalent was 816.6 mrem/y. Lens dose equivalent was 1303.4 mrem/y. Shallow-dose equivalent was 1286 mrem/y. CONCLUSION: Endourologists receive moderate radiation exposure, and dosimetry use remains low. As Low As Reasonably Achievable principles should be in place and judiciously followed. Improved monitoring and education should assist with reduction of radiation exposure to both the patient and the endourologist.