Imaging in Suspected Renal Colic: Systematic Review of the Literature and Multispecialty Consensus.

PURPOSE: Renal colic is common and CT (computerized tomography) is frequently utilized when the diagnosis of kidney stone is suspected. CT is accurate, but exposes patients to ionizing radiation and has not been shown to alter either interventional approaches or hospital admission rates. This multi-organizational transdisciplinary collaboration sought evidence-based, multispecialty consensus on optimal imaging across different clinical scenarios in patients with suspected renal colic in the acute setting. MATERIALS AND METHODS: In conjunction with the ACEP (American College of Emergency Physicians®) E-QUAL (Emergency Quality Network) we formed a nine-member panel with three physician representatives each from the ACEP, the ACR® (American College of Radiology) and the AUA (American Urological Association). A systematic literature review was used as the basis for a 3-step modified Delphi process to seek consensus on optimal imaging in 29 specific clinical scenarios. RESULTS: From an initial search yielding 6,337 records there were 232 relevant articles of acceptable evidence quality to guide the literature summary. At the completion of the Delphi process consensus, agreement was rated as perfect in 15 (52%), excellent in 8 (28%), good in 3 (10%) and moderate in 3 (10%) of the 29 scenarios. There were no scenarios where at least moderate consensus was not reached. CT was recommended in 7 scenarios (24%) with ultrasound in 9 (31%) and no further imaging needed in 13 (45%). CONCLUSIONS: Evidence and multispecialty consensus support ultrasound or no further imaging in specific clinical scenarios, with reduced-radiation dose CT to be employed when CT is needed in patients with suspected renal colic.

Imaging in Suspected Renal Colic: Systematic Review of the Literature and Multispecialty Consensus.

STUDY OBJECTIVE: Renal colic is common and computed tomography (CT) is frequently used when the diagnosis of kidney stone is suspected. CT is accurate but exposes patients to ionizing radiation and has not been shown to alter either interventional approaches or hospital admission rates. This multiorganizational transdisciplinary collaboration seeks evidence-based, multispecialty consensus on optimal imaging across different clinical scenarios in patients with suspected renal colic in the acute setting. METHODS: In conjunction with the American College of Emergency Physicians (ACEP) Emergency Quality Network, we formed a 9-member panel with 3 physician representatives each from ACEP, the American College of Radiology, and the American Urology Association. A systematic literature review was used as the basis for a 3-step modified Delphi process to seek consensus on optimal imaging in 29 specific clinical scenarios. RESULTS: From an initial search yielding 6,337 records, there were 232 relevant articles of acceptable evidence quality to guide the literature summary. At the completion of the Delphi process consensus, out of the 29 scenarios agreement was rated as perfect in 15 (52%), excellent in 8 (28%), good in 3 (10%), and moderate in 3 (10%). There were no scenarios in which at least moderate consensus was not reached. CT was recommended in 7 scenarios (24%), with ultrasonography in 9 (31%) and no further imaging needed in 12 (45%). CONCLUSION: Evidence and multispecialty consensus support ultrasonography or no further imaging in specific clinical scenarios, with reduced-radiation-dose CT to be used when CT is needed for patients with suspected renal colic.

Retrospective comparison of measured stone size and posterior acoustic shadow width in clinical ultrasound images.

PURPOSE: Posterior acoustic shadow width has been proposed as a more accurate measure of kidney stone size compared to direct measurement of stone width on ultrasound (US). Published data in humans to date have been based on a research using US system. Herein, we compared these two measurements in clinical US images. METHODS: Thirty patient image sets where computed tomography (CT) and US images were captured less than 1 day apart were retrospectively reviewed. Five blinded reviewers independently assessed the largest stone in each image set for shadow presence and size. Shadow size was compared to US and CT stone sizes. RESULTS: Eighty percent of included stones demonstrated an acoustic shadow; 83% of stones without a shadow were ≤ 5 mm on CT. Average stone size was 6.5 ± 4.0 mm on CT, 10.3 ± 4.1 mm on US, and 7.5 ± 4.2 mm by shadow width. On average, US overestimated stone size by 3.8 ± 2.4 mm based on stone width (p < 0.001) and 1.0 ± 1.4 mm based on shadow width (p < 0.0098). Shadow measurements decreased misclassification of stones by 25% among three clinically relevant size categories (≤ 5, 5.1-10, > 10 mm), and by 50% for stones ≤ 5 mm. CONCLUSIONS: US overestimates stone size compared to CT. Retrospective measurement of the acoustic shadow from the same clinical US images is a more accurate reflection of true stone size than direct stone measurement. Most stones without a posterior shadow are ≤ 5 mm.

Discharge materials provided to patients with kidney stones in the emergency department may be a source of misinformation.

INTRODUCTION: Renal colic is commonly seen in the emergency department (ED), where the focus is on diagnosis and symptom control. Educational materials are sometimes provided upon discharge, however, no standard content has been established. We characterized the educational materials given to patients reporting to EDs in different regions across the U.S. for symptomatic kidney stones, specifically evaluating disease-specific information, symptom management, prevention strategies including dietary recommendations (DRs), and patient follow up plans. MATERIALS AND METHODS: Generic discharge instructions for patients presenting to EDs with renal colic were obtained from community hospitals and academic medical centers between October 2016 and November 2017. Hospitals were called directly. If the same discharge instructions were used by more than one hospital, each was included in our analysis. We assessed the different types of information provided with a focus on stone prevention and DRs by characterizing them into specific nutritional categories. RESULTS: Of 266 hospitals contacted, 79 provided discharge instructions. Of these, 51 (65%) provided some information on diet. While most recommended higher fluid intake, almost 40% endorsed unnecessary fluid restrictions. Recommendations to reduce protein and oxalate intake were common, but erroneous information for both was given. Nearly 1 in 5 EDs recommended lower calcium intake. Less than 30% of EDs mentioned that stones can have different composition or causes. Less than 30% referenced consultation with a registered dietitian nutritionist (RDN) or that dietary approaches to stone prevention are optimally individualized. Only 9 summaries recommended urologic follow up. CONCLUSIONS: Many ED discharge materials contain DRs for stone prevention. These recommendations can be inaccurate and/or inappropriate. Advice on diet and stone prevention is more appropriately addressed in the outpatient setting when more data (stone composition, serum and urine parameters) and expert consultants are available.

Revisiting Prostate Cancer Screening Practices Among Vermont Primary Care Physicians.

The objective of this study was to assess the prostate cancer screening practices of Vermont primary care physicians and compare them with a prior study in 2001. An electronic survey was created and emailed to all currently practicing primary care physicians in Vermont. Data was stratified by practice length, practice location, university affiliation, and internal medicine versus family practice. Surveys were received from 123 (27.2%) primary care physicians. 27.7% of physicians in practice <10 years recommended prostate specific antigen (PSA) testing, compared with 55.9% of those practicing ≥10 years (p = 0.006). Of those who modified their recommendations in the past 5 years, 96.1% reported that the United States Preventive Services Task Force (USPSTF) 2012 statement influenced them. Respondents who continued to use PSA testing were less likely to stop screening after age 80 compared with those surveyed in 2001 (51% in 2014 vs. 74% in 2001; p <0.001). Primary care physicians in practice for 10 or more years were more likely to recommend PSA-based screening than those in practice for less time. The USPSTF statement discouraging PSA-based screening for prostate cancer has had significant penetrance among Vermont primary care physicians.

Trends in Imaging Use for the Evaluation and Followup of Kidney Stone Disease: A Single Center Experience.

PURPOSE: Recent reports support renal ultrasound as the initial imaging study to evaluate patients with suspected renal colic. However, urologists often advocate for computerized tomography to better define stone size and location, especially before proceeding with endourological intervention. One concern with using ultrasound as initial imaging is that computerized tomography may be required later, obviating the reduction in costs and radiation gained by using ultrasound. MATERIALS AND METHODS: We retrospectively reviewed the electronic health records of 10,680 episodes of stone disease in a total of 7,659 patients who presented to the emergency department or walk-in clinic with a chief complaint or visit diagnosis of urolithiasis from 2009 to 2015 at a single institution. Images obtained during the index encounter and in the following 90 days were recorded. RESULTS: The index encounter included computerized tomography in 47% of episodes, ultrasound in 20%, plain x-ray of the kidneys, ureters and bladder in 12% and no imaging in 29%. Of the index visits 49% included multiple testing. If no computerized tomography was obtained during the index visit, 10% of patients underwent computerized tomography later in the episode. Total imaging costs and radiation exposure during 90 days were significantly higher when computerized tomography was done at the index visit. If the initial image obtained during an episode was ultrasound, computerized tomography was performed in 20% of cases within 90 days. CONCLUSIONS: Of patients who underwent an initial ultrasound 80% avoided computerized tomography imaging. Avoiding computerized tomography at the index visit was associated with substantial reductions in radiation exposure and imaging costs.

Profile of metabolic and infectious stone-formers in a contemporary PCNL cohort.

INTRODUCTION: To identify factors associated with stone composition in patients undergoing percutaneous nephrolithotomy (PCNL). MATERIAL AND METHODS: A retrospective analysis of patients who underwent PCNL at two academic institutions between 2002 and 2014. Stone composition, stone characteristics based on non-contrast computer tomography (NCCT), patient demographics, and the S.T.O.N.E nephrolithometry scores were compared. Stones were characterized as either infection or metabolic. Metabolic stones were classified as calcium phosphate-containing and all others. RESULTS: A total of 192 renal units underwent PCNL. Retrieved stones were found to be 75% (144) metabolic and 25% (48) infection by stone analysis. Of the metabolic stones, 51% (73) were phosphate-containing calculi. Overall, infection stones were found to have a significantly higher S.T.O.N.E nephrolithometry score than metabolic stones (9.2 versus 8.1, p < 0.001). Average Hounsfield units (HU) were significantly lower in infection stones (765 versus 899, p < 0.05). Sixty-three percent of patients with infection stones were female as compared to 46% of patients with metabolic stones. Patients with phosphate-containing stones in the metabolic group were significantly more likely to be female (56% versus 35%, p < 0.01), younger (mean 49 versus 60 years of age, p < 0.02), and have lower BMI's (30 versus 32, p < 0.02) compared with other metabolic stones. CONCLUSIONS: Patient demographics including age, sex and BMI differ between patients with phosphate and non-phosphate containing metabolic stones. Higher S.T.O.N.E nephrolithometry scores were found in infection stones. These findings may serve as useful tools in the identification of stone compositions that are being seen more frequently in large and complicated stones undergoing PCNL.

Is Hydronephrosis on Ultrasound Predictive of Ureterolithiasis in Patients with Renal Colic?

PURPOSE: Renal ultrasound accurately identifies hydronephrosis but it is less sensitive than computerized tomography for the detection of ureterolithiasis. We investigated whether the presence of hydronephrosis on ultrasound was associated with a ureteral stone in patients who underwent both ultrasound and computerized tomography during the evaluation of acute renal colic. MATERIALS AND METHODS: We retrospectively reviewed the records of patients from 3 institutions who were evaluated for acute renal colic by both ultrasound and computerized tomography between 2012 and 2015. Patients were included in analysis if ultrasound and computerized tomography were performed on the same day. The presence of ureterolithiasis, stone location and hydronephrosis was reviewed and compared between imaging modalities. RESULTS: Ureteral stones were present in 85 of 144 patients. Ultrasound identified hydronephrosis in 89.8% of patients and a ureteral stone in 25.9%. Computerized tomography identified hydronephrosis in 91.8% of patients and a ureteral stone in 98.8%. In 75.0% of cases the presence or absence of hydronephrosis on ultrasound correctly predicted the presence or absence of a ureteral stone on computerized tomography. Hydronephrosis on ultrasound had a positive predictive value of 0.77 for the presence of a ureteral stone and a negative predictive value of 0.71 for the absence of a ureteral stone. CONCLUSIONS: Hydronephrosis on ultrasound did not accurately predict the presence or absence of a ureteral stone on computerized tomography in 25.0% of the patients in this study. Ultrasound is an important tool for evaluating hydronephrosis associated with renal colic but patients may benefit from other studies to confirm the presence or absence of ureteral stones.

CT Urography for Evaluation of the Ureter.

Over the past decade, computed tomographic (CT) urography has emerged as the primary imaging modality for evaluating the urinary tract in various clinical settings, including the initial workup of hematuria. With the widespread implementation of CT urography, it is critical for radiologists to understand normal ureteral anatomy and the varied appearance of pathologic ureteral conditions at CT urography. Pathologic findings at CT urography include congenital abnormalities, filling defects, dilatation, narrowing, and deviations in course. These abnormalities are reviewed, along with the indications for CT urography, current imaging protocols with specific techniques for optimal evaluation of the ureter, and dose reduction strategies.

The prone ureteroscopic technique for managing large stone burdens.

Percutaneous nephrolithotomy (PCNL) is the standard treatment for patients with large stone burdens, but can be associated with significant complications. Flexible ureteroscopy is an alternative approach that is less invasive, but often requires multiple procedures. Typically, many factors play a role in the decision to perform PCNL or ureteroscopy. The challenge is that it is difficult to predict which stone burdens will be able to be cleared ureteroscopically. We describe our approach using initial prone ureteroscopy with the transition to standard prone PCNL if required.

Urological Education in United States Medical Schools: Where Are We Now and How Can We Do Better?

INTRODUCTION: While urological complaints increase in aging populations and conditions commonly require management by multiple physician specialty types, exposure to formal urological education in United States medical schools is limited and has been decreasing over time. We aim to update the current status of urological education in the United States curriculum and delve further into the subject matter being taught and the type and timing of this education. METHODS: An 11-question survey was developed to describe the current status of urological education. The survey was distributed using Survey Monkey to the American Urological Association's medical student listserv in November 2021. Descriptive statistics were used to summarize survey findings. RESULTS: Of 879 invitations sent, 173 responded (20%). Most (112/173, 65%) of respondents were in their fourth year. Only 4 (2%) reported that their school had a required clinical urology rotation. Kidney stones (98%) and urinary tract infections (100%) were the most frequent topics taught. The least exposure included infertility (20%), urological emergencies (19%), bladder drainage (17%), and erectile dysfunction (13%). Videos and case vignettes were the preferred learning modalities and the majority (84%) of respondents were familiar with the American Urological Association's medical student curriculum material. CONCLUSIONS: The majority of United States medical schools do not have a required clinical urology rotation and some core urological topics are not taught at all. Future incorporation of urological educational material through video and case vignette learning may be the best opportunity to provide exposure to clinical topics that will commonly be encountered regardless of chosen medical discipline.

Association of Urine Findings with Metabolic Syndrome Traits in a Population of Patients with Nephrolithiasis.

Background: The odds of nephrolithiasis increase with more metabolic syndrome (MetS) traits. We evaluated associations of metabolic and dietary factors from urine studies and stone composition with MetS traits in a large cohort of stone-forming patients. Methods: Patients >18 years old who were evaluated for stones with 24-hour urine collections between July 2009 and December 2018 had their records reviewed retrospectively. Patient factors, laboratory values, and diagnoses were identified within 6 months of urine collection and stone composition within 1 year. Four groups with none, one, two, and three or four MetS traits (hypertension, obesity, dyslipidemia, and diabetes) were evaluated. Trends across groups were tested using linear contrasts in analysis of variance and analysis of covariance. Results: A total of 1473 patients met the inclusion criteria (835 with stone composition). MetS groups were 684 with no traits, 425 with one trait, 211 with two traits, and 153 with three or four traits. There were no differences among groups for urine volume, calcium, or ammonium excretion. There was a significant trend (P<0.001) for more MetS traits being associated with decreasing urine pH, increasing age, calculated dietary protein, urine uric acid (UA), oxalate, citrate, titratable acid phosphate, net acid excretion, and UA supersaturation. The ratio of ammonium to net acid excretion did not differ among the groups. After adjustment for protein intake, the fall in urine pH remained strong, while the upward trend in acid excretion was lost. Calcium oxalate stones were most common, but there was a trend for more UA (P<0.001) and fewer calcium phosphate (P=0.09) and calcium oxalate stones (P=0.01) with more MetS traits. Conclusions: Stone-forming patients with MetS have a defined pattern of metabolic and dietary risk factors that contribute to an increased risk of stone formation, including higher acid excretion, largely the result of greater protein intake, and lower urine pH.

Laboratory Reporting Parameters of Microhematuria: Implications for Interpreting the 2020 AUA Guideline.

OBJECTIVE: To explore how laboratories in the United States (U.S.) report red blood cell per high powered field (RBC/HPF) counts on urinalysis and to evaluate whether this methodology permits effective risk stratification in accordance with the 2020 AUA/SUFU microhematuria guidelines. MATERIALS AND METHODS: Reporting methods for RBC/HPF counts (ranges, or actual counts) were collected by querying urologists in U.S. academic medical institutions or commercial laboratories. We explore whether (1) the reporting schemes were concordant with the risk strata in the new microhematuria guideline (3-10 [low risk], 11-25 [intermediate risk], and more than 25 [high risk]), and (2) evaluate the potential for risk group misclassification based on reporting methodology. RESULTS: Data were available for 141 laboratories. Seventy-two (51%) use RBC/HPF ranges, while the remainder use actual counts (or counts to a threshold). Sixty (42%) report range cutoffs which are not concordant with the microhematuria guidelines risk groups. Furthermore, fifty-six (40%) do not include the cutoff of 25 RBC/HPF which could potentially misclassify intermediate and high risk groups. Finally, sixteen (11%) do not include the cut-off of 3 RBC/HPF that defines the presence of microhematuria. CONCLUSION: A significant number of laboratories report RBC/HPF counts in ranges that differ from thresholds in the 2020 AUA/SUFU guideline. The implication is potential misclassification of microhematuria both at minimum threshold diagnosis (3 RBC/HPF), and additionally between intermediate and high risk groups. Standardization of reporting schemes to actual RBC/HPF counts may allow improved adherence to guidelines while providing data for future guideline development.

Patterns of opioid prescription post ureteroscopy among members of the Endourological Society.

BACKGROUND: Postoperative opioid prescribing has been linked with persistent opioid use. Ureteroscopy (URS) is a common urologic procedure and a potential area to focus on opioid reduction. We aim to characterize international practice patterns of opioid prescribing post URS and what measures may decrease the need for opioid prescription. METHODS: We developed a survey directed to members of the Endourological Society. The survey queried the frequency of opioid prescribing post URS, challenges when opioids are not prescribed, and measures thought to reduce the need for opioids. RESULTS: We received 159 responses with the majority reported practicing urology for >20 years (37.1%), and performing 10-20 ureteroscopies/month (45.3%). Forty-one percent were from the United States (US) and Canada. Sixty-six percent completed a fellowship, 84% in endourology. Twenty-six percent prescribe opioids more than half the time and the majority do so less than 10% of the time (61.6%). Thirty-eight percent had no challenges when opioids were omitted. Measures felt to decrease the need for opioids were preoperative counseling, nonsteroidal anti-inflammatory drugs use, and use of adjunct medications. After adjusting for location and type of practice, endourology fellowship completion, years of practice, and number of ureteroscopies/month, we found that respondents from the US and Canada were more likely to prescribe opioids more than half the time post URS compared to respondents from the rest of the world [odds ratio (OR): 87.5, P<0.001, 95% confidence interval (CI): 17.3-443.5]. CONCLUSIONS: Despite proven feasibility of non-opioid pathway, nearly one-quarter of participants in our survey prescribe opioids >50% of the time post URS. Most important factors felt to reduce opioid prescription post URS were preoperative counseling, nonsteroidal anti-inflammatory drugs use. US and Canadian urologists were more likely to prescribe opioids >50% of the time post URS compared to the rest of the world. We believe best practice guidelines should be considered by the American and Canadian Urological Associations to address post URS opioid prescribing.

Imaging in Suspected Renal Colic: Systematic Review of the Literature and Multispecialty Consensus.

BACKGROUND: Renal colic is common, and CT is frequently utilized when the diagnosis of kidney stones is suspected. CT is accurate but exposes patients to ionizing radiation and has not been shown to alter either interventional approaches or hospital admission rates. This multi-organizational transdisciplinary collaboration sought evidence-based, multispecialty consensus on optimal imaging across different clinical scenarios in patients with suspected renal colic in the acute setting. METHODS: In conjunction with the American College of Emergency Physicians (ACEP) eQual network, we formed a nine-member panel with three physician representatives each from ACEP, the ACR, and the American Urology Association. A systematic literature review was used as the basis for a three-step modified Delphi process to seek consensus on optimal imaging in 29 specific clinical scenarios. RESULTS: From an initial search yielding 6,337 records, there were 232 relevant articles of acceptable evidence quality to guide the literature summary. At the completion of the Delphi process consensus, agreement was rated as perfect in 15 (52%), excellent in 8 (28%), good in 3 (10%), and moderate in 3 (10%) of the 29 scenarios. There were no scenarios where at least moderate consensus was not reached. CT was recommended in 7 scenarios (24%), with ultrasound in 9 (31%) and no further imaging needed in 12 (45%). SUMMARY: Evidence and multispecialty consensus support ultrasound or no further imaging in specific clinical scenarios, with reduced-radiation dose CT to be employed when CT is needed in patients with suspected renal colic.

The use of Twitter to facilitate sharing of clinical expertise in urology.

The use of social media in the urologic community is common and increasing. Although the potential benefits of platforms like Twitter have been described in the literature, the use of social media in the clinical context of Urology has not been explored.In this case report, we describe how we used Twitter to share ideas about the clinical management of a complex urologic patient. By posting a clinical scenario, a timely discussion was generated with global participation and expert suggestions. This knowledge was applied to the surgical management of a patient with positive clinical outcomes.The ability of Twitter to facilitate rapid communication with a wide network of contributors makes it a potentially useful tool for clinical decision making. Care must be taken to ensure patient confidentiality and caution used appropriately when evaluating the sources and content of the clinical information shared.

Measurement of Posterior Acoustic Stone Shadow on Ultrasound Is a Learnable Skill for Inexperienced Users to Improve Accuracy of Stone Sizing.

INTRODUCTION: Studies suggest that the width of the acoustic shadow on ultrasound (US) more accurately reflects true stone size than the stone width in US images. We evaluated the need for training in the adoption of the acoustic shadow sizing technique by clinical providers. METHODS: Providers without shadow sizing experience were recruited and assigned in a stratified, alternating manner to receive a training tutorial ("trained") or no intervention ("control"). Each conducted a baseline assessment of 24 clinical US images; where present, shadow width was measured using custom calipers. The trained group subsequently completed a standardized training module on shadow sizing. All subjects repeated measurements after ∼1 week. Group demographics were compared using Fisher's exact test. Measurements were compared to clinically reported stone sizes on corresponding CT and US using mixed-effects models. One millimeter concordance between shadow and CT size was compared using a generalized linear mixed-effects model. RESULTS: Twenty-six subjects were included. There was no significant difference between groups in demographics, clinical role, or US experience. Mean reported CT and US stone sizes were 6.8 ± 4.0 mm and 10.3 ± 4.1 mm, respectively. At baseline, there was no difference in shadow size measurements between groups (p = 0.18), and shadow size was no more accurate than US stone size (p = 0.28 trained; p = 0.81 control), compared to CT. After training, overestimation bias of shadow size in the trained group decreased to 1.6 ± 0.5 mm (p < 0.01), relative to CT. This was not significantly associated with clinical rank, US experience, or stone-measuring experience. One millimeter concordance with CT size significantly increased from 23% to 35% of stones after training (p = 0.01). No significant improvement occurred in the control group. CONCLUSION: Acoustic shadow sizing was readily adopted by inexperienced providers, but was not more accurate than reported US stone sizes without training. Education on shadow sizing may be warranted before clinical adoption.

Ultrasonography Significantly Overestimates Stone Size When Compared to Low-dose, Noncontrast Computed Tomography.

OBJECTIVE: To evaluate the differences between low-dose noncontrast computed tomography (NCCT) and renal ultrasound (US) in the identification and measurement of urinary calculi. MATERIALS AND METHODS: A retrospective review was conducted at 3 institutions of patients evaluated for flank pain with both renal US and NCCT, within 1 day of one another, from 2012 to 2015. Stone presence and size were compared between imaging modalities. Stone size was determined by largest measured diameter. Stones were grouped into size categories (≤5 mm, 5.1-10 mm, and >10 mm) based on NCCT and compared with US. Statistical analysis was performed using 2-sided t tests. RESULTS: One hundred fifty-five patients received both a renal US and NCCT within 1 day. In 79 patients (51.0%), both US and NCCT identified a stone for size comparison. Fifty-eight patients (37.4%) had a stone visualized on NCCT but not on US, and 2 patients (1.3%) had a stone documented on US but not seen on NCCT. The average NCCT size of the stones missed on US was 4.5 mm. When comparing the average largest stone diameter for US (9.1 mm) vs NCCT (6.9 mm), US overestimated stone size by 2.2 mm (P < .001). US overestimated stone size by 84.6% for stones ≤5 mm, 27.1% for stones 5.1-10 mm, and 3.0% for stones >10 mm. CONCLUSION: US significantly overestimated stone size and this was most pronounced for small (≤5 mm) stones. The potential for systematic overestimation of stone size with standard US techniques should be taken into consideration when evaluating endourologic treatment options.