Accuracy of Radiology Reports for Obstructing Ureteral Stone Size in the Emergency Department

OBJECTIVE

To evaluate the number of dimensions of obstructing ureteral stones in the emergency department (ED) described in present-day radiology computed tomography reports and assess for measurement discrepancies between radiologist and urologist review.

METHODS

We conducted a single-center retrospective study of patients who presented to the ED with unilateral, solitary, obstructing ureteral stones from March 2018 to March 2021. Stone size in each reported dimension recorded by the radiologist was extracted from the chart and then compared to size independently measured by one of our urologists for all 3 stone dimensions. Our primary outcome was the number of stone dimensions included in the radiology report.

RESULTS

In total, 181 patients were included for analysis. 82.3% of radiology reports described the stone in one dimension, 15% in two dimensions, and 2.7% in three dimensions. There was a significant difference in median maximal stone size between radiologist and urologist measurement (5.5 vs 6.5 mm, respectively, P < .001). One hundred fourteen stones (62%) had the maximal measurement recorded in the craniocaudal (CC) dimension by urologist review. Only 26% of radiology reports had the CC measurement included in the radiology report.

CONCLUSION

Ureteral stone size in a present-day ED cohort is still frequently measured in only 1 or 2 dimensions. In many cases, this is associated with an absence of a reported CC measurement. Inadequate characterization of stone size may affect acute management. This study hopes to encourage reporting of all three dimensions of obstructing ureteral stones in the ED setting for improvements in patient management.

Interdisciplinary planning improves radiologist obtained access for percutaneous nephrolithotomy

INTRODUCTION

Proper antegrade access for percutaneous nephrolithotomy (PCNL) is essential for success but can be challenging. Previous work evaluating access obtained by interventional radiology (IR), largely in the emergent setting, has shown high rates of additional access at the time of PCNL. We hypothesize that efforts to improve pre-procedural communication between urology and IR can impact the utility of the access for subsequent PCNL.

MATERIAL AND METHODS

We conducted a retrospective review of patients undergoing PCNL at a single hospital from January 2011 to December 2022. Adult patients undergoing PCNL with established preoperative access were included.

RESULTS

A total of 141 cases were identified with preoperative access. A total of 111 patients had evidence of planning with IR prior to antegrade access. There were high rates of anatomic abnormality (50%) and staghorn calculus (53%). Patients with planned access had higher body mass index (BMI). While preoperative access was initially utilized in 97% of cases, 6% required additional access to be obtained intraoperatively; this included a low rate of new access in those that were previously discussed with IR (4% vs. 17%, p = 0.02). Overall stone free rates (91%), rates of second stage procedures (55%) and complications (14%) were similar between planned and unplanned groups.

CONCLUSION

In this retrospective study of complex patients with large stone burden presenting for PCNL with preoperative antegrade access obtained by IR, the rate of new access was far lower than prior reports. This was likely influenced by urologist involvement in planning access.

Linear relationship between absorbed radiation dose and pulse rate during fluoroscopy

PURPOSE

To identify the relationship between fluoroscopy pulse rate and absorbed radiation dose. We compared absorbed radiation dose with common proxy measurements such as fluoroscopy time and C-arm reported dose.

METHODS

Using a simulated patient model, 60 s fluoroscopy exposures were performed using pulse rates of 30, 8, 4, 2, and 1 pulse(s) per second. Each experiment was performed with both standard and low-dose settings using a GE OEC 9800 plus C-arm. Landauer nanoDot™ OSL dosimeters were used to measure the absorbed radiation dose.

RESULTS

Fluoroscopy pulse rate and absorbed radiation dose demonstrated a linear correlation for both standard (R² = 0.995, p < 0.001) and low-dose (R² = 0.998, p < 0.001) settings. For any given pulse rate, using the low-dose setting reduced absorbed radiation dose by 58 ± 2.8%. Fluoroscopy time demonstrated a linear relationship with absorbed radiation dose for both standard (R² = 0.996, p < 0.001) and low-dose (R² = 0.991, p < 0.001) settings, but did not change with use of the low-dose setting. C-arm reported radiation dose correlated linearly with absorbed dose (R² = 0.999) but consistently under-estimated measured values by an average of 49 ± 3.5%. Using a combination of 1 pulse-per-second and low-dose fluoroscopy, absorbed dose was reduced by 97.7 ± 0.1% compared to standard dose and 30 pulse-per-second settings.

CONCLUSION

Absorbed radiation dose decreases linearly with fluoroscopy pulse rate during equivalent exposure times. Adjusting fluoroscopy pulse rate and utilizing low-dose settings significantly reduces overall absorbed radiation exposure by up to 98%.

Prospective randomized trial of 2 versus 12-weeks of postoperative antibiotics after percutaneous nephrolithotomy in complex patients with infection-related kidney stones

PURPOSE

Treatment of struvite kidney stones requires complete surgical stone removal combined with antibiotic therapy to eliminate urinary tract infections and preventive measures to reduce stone recurrence. The optimal duration of antibiotic therapy is unknown. We sought to determine if 2- or 12-weeks of antibiotics post percutaneous nephrolithotomy (PNL) for infection stones resulted in better outcomes for stone recurrence and positive urine cultures.

MATERIAL AND METHODS

This multi-center, prospective randomized trial evaluated patients with the clinical diagnosis of infection stones. Patients were randomized to 2- or 12-weeks of postoperative oral antibiotics (nitrofurantoin or culture-specific antibiotic) and included if residual fragments were ≤4 mm on computed tomography imaging after PNL. Imaging and urine analyses were performed at 3-, 6-, and 12-months post-procedure.

RESULTS

Thirty-eight patients were enrolled and randomized to either 2-weeks (n = 20) or 12-weeks (n = 18) of antibiotic therapy post-PNL. Eleven patients were excluded due to residual fragments >4 mm, and 3 patients were lost to follow-up. The primary outcome was the stone-free rate (SFR) at 6 months post-PNL. At 3-, 6-, and 12-months follow-up, SFRs were 72.7% versus 80.0%, 70.0% versus 57.1%, 80.0% versus 57.1% (p = ns), between 2- and 12-week-groups, respectively. At 3-, 6-, and 12-months follow-up, positive urine cultures were 50.0% versus 37.5%, 50.0% versus 83.3%, and 37.5% versus 100% between 2- and 12-week groups, respectively (p = ns).

CONCLUSIONS

For patients with stone removal following PNL, neither 2-weeks nor 12-weeks of postoperative oral antibiotics is superior to prevent stones and recurrent positive urine cultures.

Subcapsular hematoma in a solitary kidney: successful conservative management

Subcapsular renal hematoma (SRH) is an infrequent complication of urologic interventions but can lead to serious consequences in patients with a solitary kidney. We present our experience with conservative management of a patient with a solitary kidney and multiple medical comorbidities who developed a SRH and subsequent renal failure after nephroureteral catheter placement. Literature on the management of this unique clinical scenario is limited. Herein, we share our experience with supportive care and temporary dialysis in a medically complex patient whose outcome is complete renal recovery.

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/day, 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/day to 614 mg/day (p<0.01), pH decreased from 6.59 ± 0.54 to 6.33 ± 0.47 (p = 0.06). In addition, 114 stone events occurred in 73 distinct patients, with 50% of stones either pure or majority (≥ 50%) calcium phosphate by composition.

CONCLUSIONS

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.

Safety During Ureteroscopy: Radiation, Eyes, and Ergonomics

It is known that urologic surgeons are at risk of work-place injury due to the physical requirements of operating and exposure to hazards. These hazards include radiation, exposure to body fluids, use of laser energy, and orthopedic injury due to the physical nature of operating. The risks that these hazards present can be mitigated by implementing several evidence-based safety measures. The methods to protect against radiation exposure include keeping radiation usage in the operating room as low as reasonably achievable, donning lead aprons, and wearing protective glasses. Additionally, protective glasses decrease the risk of eye injury from laser injury and exposure to body fluids. Finally, practicing sound surgical ergonomics is essential to minimize the risk of orthopedic injury and promote career longevity. The interventions discussed herein are simple and easy to implement in one's daily practice of urology.

Minimizing radiation dose in management of stone disease: how to achieve 'ALARA'

PURPOSE OF REVIEW

Exposure to radiation is known to have adverse effects such as secondary malignancies. Patients with nephrolithiasis are exposed to radiation in the workup and treatment of their condition. Furthermore, exposure to radiation is often repeated due to the high recurrence rate of nephrolithiasis.

RECENT FINDINGS

We discuss practices inside and outside of the operating room to strive to keep radiation exposure as low as reasonably achievable (ALARA) for patients being treated for nephrolithiasis. These efforts include reduced dose computed tomography scans, fluoroless surgical techniques and new alternative technologies.

SUMMARY

Maintaining radiation exposure ALARA for our patients is increasingly practical. The urologist must make every effort to adhere to ALARA principles to protect patients from the stochastic effects of radiation.

Endoscopic diagnosis of renal pseudoaneurysm following ureteroscopy

Renal pseudoaneurysm following ureteroscopy is a rare cause of hematuria usually diagnosed and treated with angiography and embolization. Here we present a case of a small pseudoaneurysm causing intermittent flank pain and gross hematuria associated with clot retention initially diagnosed during ureteroscopy and subsequently treated with a combined endourologic and endovascular approach.

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%.

Defining the Rate of Primary Ureteroscopic Failure in Unstented Patients: A Multi-Institutional Study

PURPOSE

Primary ureteroscopic intervention for kidney or ureteral stones occasionally encounters difficulty with passage of the ureteroscope in the initial procedure. These patients require a second procedure after stenting. We aim to define the contemporary failure rate of primary ureteroscopy (URS) and identify predictive factors that necessitate prestenting. This will assist in preoperative patient counseling, informed consent, and clinical decision-making.

MATERIALS AND METHODS

We conducted a multi-institutional retrospective review of 535 unstented patients undergoing primary URS from August 2011 to August 2013. The primary outcome was gaining access to the unstented ureter.

RESULTS

The failure rate for accessing the unstented ureter was 7.7% (41/535). The median age of females with primary ureteroscopic failure was significantly lower than in females who had successful ureteroscopic access (34 vs 52 years; p = 0.0041). There was no difference in the median age of males with access vs failure (58 vs 57 years; p = 0.3683). Proximal ureteral stones had the highest failure rate for ureteral access at 18.28% (p = 0.006). On multivariable logistic regression, proximal ureteral stone location remained a significant predictor of failure when compared to renal stones (odds ratio [OR] 3.14, p = 0.006). When including only ureteral stones in the multivariable analysis, stone location in the proximal ureter compared to the distal ureter remained the only significant predictor of access failure (OR 0.24, p = 0.015).

CONCLUSIONS

A low overall rate of ureteral access failure in unstented patients is shown. Young female patients and proximal ureteral stones were less likely to be accessed primarily. This study provides information that will help urologists counsel their patients preoperatively regarding their likelihood of failing primary URS necessitating a second procedure. This will also help the patient to make an informed decision during the consent process and may guide urologists on selective prestenting in higher risk patients.

A prospective, multi-institutional study of flexible ureteroscopy for proximal ureteral stones smaller than 2 cm

PURPOSE

Flexible ureteroscopy is rapidly becoming a first line therapy for many patients with renal and ureteral stones. However, current understanding of treatment outcomes in patients with isolated proximal ureteral stones is limited. Therefore, we performed a prospective, multi-institutional study of ureteroscopic management of proximal ureteral stones smaller than 2 cm to better define clinical outcomes associated with this approach.

MATERIALS AND METHODS

Adult patients with proximal ureteral calculi smaller than 2 cm were prospectively identified. Patients with concomitant ipsilateral renal calculi or prior ureteral stenting were excluded from study. Flexible ureteroscopy, holmium laser lithotripsy and ureteral stent placement was performed. Ureteral access sheath use, laser settings and other details of perioperative and postoperative management were based on individual surgeon preference. Stone clearance was determined by the results of renal ultrasound and plain x-ray of the kidneys, ureters and bladder 4 to 6 weeks postoperatively.

RESULTS

Of 71 patients 44 (62%) were male and 27 (38%) were female. Mean age was 48.2 years. ASA(®) score was 1 in 12 cases (16%), 2 in 41 (58%), 3 in 16 (23%) and 4 in 2 (3%). Mean body mass index was 31.8 kg/m(2), mean stone size was 7.4 mm (range 5 to 15) and mean operative time was 60.3 minutes (range 15 to 148). Intraoperative complications occurred in 2 patients (2.8%), including mild ureteral trauma. Postoperative complications developed in 6 patients (8.7%), including urinary tract infection in 3, urinary retention in 2 and flash pulmonary edema in 1. The stone-free rate was 95% and for stones smaller than 1 cm it was 100%.

CONCLUSIONS

Flexible ureteroscopy is associated with excellent clinical outcomes and acceptable morbidity when applied to patients with proximal ureteral stones smaller than 2 cm.

Acute renal vein thrombus and renal atrophy following shock wave lithotripsy: a unique complication

Serious complications of shock wave lithotripsy (SWL) are rare, but can have significant long term effects. We present a case of acute renal vein thrombus following SWL leading to subsequent renal atrophy and loss of renal function. To our knowledge this is a newly reported complication of SWL.

Kidney stones and pregnancy

Kidney stones are common and do not spare the pregnant population. Although a simple stone event is usually straightforward in the general population, it is complex during pregnancy. Acute nephrolithiasis is associated with a unique set of complications during pregnancy and, because of imaging limitations, diagnosis is challenging. Multidisciplinary care is the key in proper management decisions. The pathophysiology of kidney stone formation in the pregnant state is also unique. Herein, we discuss the complexity of kidney stones and pregnancy.

Half Fourier single-shot turbo spin-echo magnetic resonance urography for the evaluation of suspected renal colic in pregnancy

OBJECTIVE

To report our experience with magnetic resonance urography (MRU) in pregnant women suspected of having obstructing upper tract calculi. The diagnosis of an upper tract calculus in the pregnant woman can be challenging. Recent evidence suggests that MRU can be used to effectively evaluate renal colic.

METHODS

From 2008-2011, 9 pregnant women were referred for evaluation of suspected renal colic caused by an obstructing upper tract stone. All patients underwent MRU with a half Fourier single-shot turbo spin-echo (HASTE) protocol. Medical records and imaging studies were reviewed for demographic and clinical data as well as outcome measures.

RESULTS

The mean age of the subjects was 25 years (range 20-34); average gestational age of the fetus was 23 weeks (range 9-36). In all cases, a renal ultrasound was the initial imaging study obtained, with nondiagnostic findings. HASTE MRU detected 4 ureteral stones and 4 cases of physiological hydronephrosis of pregnancy. In one case, interpretation of the MRU was limited as a result of patient motion. Of the patients with obstructing stones, 1 required endourologic management during her pregnancy and 3 were followed conservatively. No adverse events related to MRU occurred.

CONCLUSION

HASTE MRU is an informative imaging study for pregnant women with suspected upper tract stone disease. Information gathered from this study augments that gained from alternative modalities, and aids in medical decision-making. The lack of ionizing radiation exposure, coupled with the capture of detailed anatomic imaging, makes HASTE MRU a particularly useful study in this setting.

How to improve results with extracorporeal shock wave lithotripsy

OBJECTIVE

Shock wave lithotripsy (SWL) has greatly revolutionized the treatment of patients suffering from stone disease. There are a number of patient- and device-specific factors that can affect treatment outcome. Herein, we review practices that can increase the likelihood of SWL treatment success.

METHODS

A systematic literature review was performed to identify studies of SWL treatment parameters.

RESULTS

Among the factors affecting the outcome of SWL were patient selection criteria, such as stone burden, stone location, and anatomic features. Additionally, technical aspects of the SWL procedure also can affect outcome; these factors include the acoustic output of the lithotripter, the coupling of the lithotripter to the patient, and the power, total number, and rate of shock wave delivery.

CONCLUSIONS

The outcome of SWL can be optimized with close attention to patient selection criteria as well as the manner in which the treatment is performed.

Novel instrumentation in urologic surgery: Shock wave lithotripsy

Extracorporeal shock wave lithotripsy (SWL) was first introduced in 1980 and it rapidly revolutionized the treatment of stone disease. SWL is a non-invasive, outpatient procedure that now accounts for the majority of stone removal procedures. Since the introduction of first generation lithotripter, the Dornier HM3 machine, SWL devices have undergone many modifications secondary to limitations, in efforts to create a more effective and efficient way to treat stones and decrease possible morbidities. Herein, we review the evolution of the technology and advances in the instrumentation over the last three decades.

Ureteroscopy during pregnancy

Urolithiasis during pregnancy is an uncommon, but a serious medical problem. Options for the treatment of pregnant women with obstructing stones include ureteral stent placement, percutaneous nephrostomy tube placement, and ureteroscopic stone removal (URS). Although ureteral stent and nephrostomy tube placement have been the historically standard treatment option for pregnant women with obstructing stones, there is an emerging collection of literature that reviews the safety of URS for pregnant women. We performed a systematic review of MEDLINE and EMBASE from January 1966 through April 2009 to identify all literature on URS in pregnant women. Herein, we review the literature on URS during pregnancy, with a focus on the safety of this approach. We conclude that URS is an appropriate intervention in the pregnant population with urolithiasis; in all cases the procedure should be performed on a properly selected patient by a surgeon with appropriate experience and equipment. With such an approach, complication rates are low and success rates are high. A multidisciplinary approach should be emphasized as a key to a successful outcome.

Validity of administrative coding in identifying patients with upper urinary tract calculi

PURPOSE

Administrative databases are increasingly used for epidemiological investigations. We performed a study to assess the validity of ICD-9 codes for upper urinary tract stone disease in an administrative database.

MATERIALS AND METHODS

We retrieved the records of all inpatients and outpatients at Johns Hopkins Hospital between November 2007 and October 2008 with an ICD-9 code of 592, 592.0, 592.1 or 592.9 as one of the first 3 diagnosis codes. A random number generator selected 100 encounters for further review. We considered a patient to have a true diagnosis of an upper tract stone if the medical records specifically referenced a kidney stone event, or included current or past treatment for a kidney stone. Descriptive and comparative analyses were performed.

RESULTS

A total of 8,245 encounters coded as upper tract calculus were identified and 100 were randomly selected for review. Two patients could not be identified within the electronic medical record and were excluded from the study. The positive predictive value of using all ICD-9 codes for an upper tract calculus (592, 592.0, 592.1) to identify subjects with renal or ureteral stones was 95.9%. For 592.0 only the positive predictive value was 85%. However, although the positive predictive value for 592.1 only was 100%, 26 subjects (76%) with a ureteral stone were not appropriately billed with this code.

CONCLUSIONS

ICD-9 coding for urinary calculi is likely to be sufficiently valid to be useful in studies using administrative data to analyze stone disease. However, ICD-9 coding is not a reliable means to distinguish between subjects with renal and ureteral calculi.

Fluoroscopy-guided percutaneous renal access

Percutaneous renal surgery is dependent upon appropriate access to the targeted portion of the collecting system. Obtaining a well-positioned nephrostomy tract improves the urologist's ability to both obtain the desired surgical outcome and minimize attendant morbidities. The two primary methods of obtaining fluoroscopic-guided percutaneous renal access-"bull's eye" targeting and triangulation-are reviewed. The authors' preferred techniques are outlined, technical refinements are noted, and recent modifications and future directions are reviewed.

The association of increasing body mass index and kidney stone disease

PURPOSE

Previous epidemiological works have reported that obesity is a risk factor for kidney stone disease. However, the effect of increasing degrees of obesity on stone formation has yet to be defined. To address this question we examined how an increasing body mass index affects the risk of kidney stone disease.

MATERIALS AND METHODS

We evaluated claims from a 5-year period (2002 to 2006) in a national private insurance database to identify subjects diagnosed with or treated for kidney stones. From a data set of 95,598 patients, subjects were identified by ICD-9 or CPT codes specific to kidney stone disease. Descriptive analyses were performed and odds ratios were calculated.

RESULTS

Gender distribution of the 3,257 stone formers was 42.9% male and 57.1% female. Obesity (body mass index greater than 30 kg/m(2)) was associated with a significantly greater likelihood of being diagnosed with a kidney stone. However, when obese patients were stratified by body mass index there were no significant differences in the likelihood of a kidney stone diagnosis, suggesting a stabilization of risk once body mass index increased above 30 kg/m(2). The association of body mass index and a stone removal procedure was significant only for men and women with a body mass index between 30 and 45 kg/m(2) relative to a body mass index less than 25 kg/m(2) (p <0.001).

CONCLUSIONS

An obese body mass index is associated with an increased risk of kidney stone disease. However, the magnitude of this risk appears to be stable in the morbidly obese population. Once body mass index is greater than 30 kg/m(2), further increases do not appear to significantly increase the risk of stone disease.

The effect of gastric banding on kidney stone disease

OBJECTIVES

To evaluate the likelihood of being diagnosed with, or treated for, an upper urinary tract calculus after gastric banding. Bariatric surgical procedures are being increasingly utilized in the treatment of patients with morbid obesity. Certain malabsorptive bariatric procedures have been associated with an increased risk for kidney stone formation. However, the kidney stone risk of gastric banding, a restrictive bariatric procedure, is unknown.

METHODS

We identified 201 patients who underwent gastric banding and a control group of 201 obese patients who did not have bariatric surgery in a national private insurance claims database within a 5-year period from 2002-2006. All patients had at least 2 years of continuous claims data follow-up. Our 2 primary outcomes were the diagnosis and the surgical treatment of a urinary calculus.

RESULTS

After gastric banding, the diagnosis of an upper urinary tract calculus occurred in 3 subjects (1.49%), as compared with 12 subjects (5.97%) in the comparison cohort (P = .0179). One subject in each cohort (0.50%) underwent a surgical procedure for the treatment of an upper urinary tract (P = 1.0000).

CONCLUSIONS

Gastric banding is not associated with an increased risk for kidney stone disease or kidney stone surgery in the postoperative period. Additional long-term studies are required to confirm these findings.

The safety of ureteroscopy during pregnancy: a systematic review and meta-analysis

PURPOSE

We performed a literature review and analysis to compare the safety of ureteroscopic stone removal during pregnancy with findings from a set of contemporary studies of that procedure in nonpregnant patients.

MATERIALS AND METHODS

A systematic review of MEDLINE(R) and EMBASE(R) was done to identify all reports of ureteroscopic stone removal in pregnant women. Complications were stratified according to modified Clavien criteria. We then reviewed a contemporary, multi-national meta-analysis of ureteroscopic stone removal (American Urological Association/European Association of Urology 2007 Guideline for the Management of Ureteral Calculi) to define the complication rate in a series of nonpregnant patients. Complication rates in the 2 reviews were compared using Fisher's exact test.

RESULTS

A total of 14 reports of ureteroscopic stone removal in pregnant women were identified, representing 108 patients. Nine complications were noted. By Clavien criteria 2 complications were level 1, 6 were level 2 and 1 was level 3. When compared to the multinational meta-analysis of ureteroscopy in nonpregnant women, there was no significant difference in the ureteral injury and urinary tract infection complication rates (p = 0.191 and 0.597, respectively).

CONCLUSIONS

Our analysis shows that the safety of ureteroscopic stone removal in pregnant patients is not significantly different from the safety of that procedure in nonpregnant patients and in each cohort the complication rate is low. Therefore, ureteroscopic stone removal may reasonably be considered appropriate first line therapy in pregnant patients with stone disease.

Effects of 6-cyano-7-nitroquinoxaline-2,3-dione on nicotinic receptor subunit transcript expression in the rat brain

The nicotinic cholinergic system exerts potent modulatory effects on glutamatergic neurotransmission, an effect mediated in part by increased glutamate release following activation of presynaptic nicotinic cholinergic receptors. Ionotropic glutamate receptor agonists also stimulate release of acetylcholine, suggesting that these neurotransmitter systems reciprocally regulate one another. We investigated an interface between the nicotinic cholinergic and glutamatergic systems by measuring nicotinic receptor subunit transcript expression following administration of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), an antagonist of the AMPA and kainate subtypes of glutamate receptors. Using [(35)S] in situ hybridization, we measured expression of alpha 2, alpha 3, alpha 4, alpha 5, alpha 7, beta 2, beta 3, and beta 4 nicotinic receptor subunit transcripts in the rat forebrain. Following 7 days of treatment with vehicle or CNQX (1 mg/kg/day or 10 mg/kg/day), changes in nicotinic receptor subunit transcript expression were restricted to subunits that form heteromeric receptors. We found increased levels of transcripts for alpha 2 and beta 2 nicotinic receptor subunits in the hippocampus, decreased alpha 4 subunit transcripts in the medial habenula and amygdala, and increased beta 2 subunit transcripts in the septum and piriform cortex. We did not detect changes in expression of transcripts for the alpha 7 subunit, which forms homomeric nicotinic receptors. Our findings indicate that expression of nicotinic cholinergic receptor subunit transcripts are regulated in a subunit- and region-specific fashion by CNQX, an antagonist of non-NMDA ionotropic glutamate receptors.