Effect of low dose radiation computerized tomography protocols on distal ureteral calculus detection

Can Artificial Intelligence Accurately Detect Urinary Stones? A Systematic Review

Objectives: To perform a systematic review on artificial intelligence (AI) performances to detect urinary stones. Methods: A PROSPERO-registered (CRD473152) systematic search of Scopus, Web of Science, Embase, and PubMed databases was performed to identify original research articles pertaining to AI stone detection or measurement, using search terms ("automatic" OR "machine learning" OR "convolutional neural network" OR "artificial intelligence" OR "detection" AND "stone volume"). Risk-of-bias (RoB) assessment was performed according to the Cochrane RoB tool, the Joanna Briggs Institute Checklist for nonrandomized studies, and the Checklist for Artificial Intelligence in Medical Imaging (CLAIM). Results: Twelve studies were selected for the final review, including three multicenter and nine single-center retrospective studies. Eleven studies completed at least 50% of the CLAIM checkpoints and only one presented a high RoB. All included studies aimed to detect kidney (5/12, 42%), ureter (2/12, 16%), or urinary (5/12, 42%) stones on noncontrast computed tomography (NCCT), but 42% intended to automate measurement. Stone distinction from vascular calcification interested two studies. All studies used AI machine learning network training and internal validation, but a single one provided an external validation. Trained networks achieved stone detection, with sensitivity, specificity, and accuracy rates ranging from 58.7% to 100%, 68.5% to 100%, and 63% to 99.95%, respectively. Detection Dice score ranged from 83% to 97%. A high correlation between manual and automated stone volume (r = 0.95) was noted. Differentiate distal ureteral stones and phleboliths seemed feasible. Conclusions: AI processes can achieve automated urinary stone detection from NCCT. Further studies should provide urinary stone detection coupled with phlebolith distinction and an external validation, and include anatomical abnormalities and urologic foreign bodies (ureteral stent and nephrostomy tubes) cases.

Application of deep learning reconstruction of ultra-low-dose abdominal CT in the diagnosis of renal calculi

BACKGROUND

Renal calculi are a common and recurrent urological disease and are usually detected by CT. In this study, we evaluated the diagnostic capability, image quality, and radiation dose of abdominal ultra-low-dose CT (ULDCT) with deep learning reconstruction (DLR) for detecting renal calculi.

METHODS

Sixty patients with suspected renal calculi were prospectively enrolled. Low-dose CT (LDCT) images were reconstructed with hybrid iterative reconstruction (LD-HIR) and was regarded as the standard for stone and lesion detection. ULDCT images were reconstructed with HIR (ULD-HIR) and DLR (ULD-DLR). We then compared stone detection rate, abdominal lesion detection rate, image quality and radiation dose between LDCT and ULDCT.

RESULTS

A total of 130 calculi were observed on LD-HIR images. Stone detection rates of ULD-HIR and ULD-DLR images were 93.1% (121/130) and 95.4% (124/130). A total of 129 lesions were detected on the LD-HIR images. The lesion detection rate on ULD-DLR images was 92.2%, with 10 cysts < 5 mm in diameter missed. The CT values of organs on ULD-DLR were similar to those on LD-HIR and lower than those on ULD-HIR. Signal-to-noise ratio was highest and noise lowest on ULD-DLR. The subjective image quality of ULD-DLR was similar to that of LD-HIR and better than that of ULD-HIR. The effective radiation dose of ULDCT (0.64 ± 0.17 mSv) was 77% lower than that of LDCT (2.75 ± 0.50 mSv).

CONCLUSION

ULDCT combined with DLR could significantly reduce radiation dose while maintaining suitable image quality and stone detection rate in the diagnosis of renal calculi.

Optimal Delivery of Follow-Up Care for the Prevention of Stone Recurrence in Urolithiasis Patients: Improving Outcomes

Urolithiasis is a common clinical condition with frequent recurrences. Advances in knowledge of pathophysiological mechanisms permit the categorization of patients to low and high risk for recurrence, with specific metabolic abnormalities diagnosed in the second category. Follow-up is essential for patients with urolithiasis and consists of both imaging and metabolic follow-up with urine studies. No formal guidelines or solid evidence currently exists regarding frequency and type of follow-up studies to be performed in each category. This review aims to summarize existing evidence regarding follow-up, in order to guide clinicians on how and when to follow-up urolithiasis patients according to existing clinical scenario.

Ultra-low-dose CTKUB: the new standard of follow-up of ureteric calculi not visible on plain radiograph?

PURPOSE

With sensitivities over 95%, non-contrast computer tomography of kidney, ureter and bladder (CTKUB) is the investigation of choice in renal colic to diagnose or exclude ureteric calculi. CTKUB delivers an average effective radiation dose of 5.4 millisievert (mSv) and is used to follow-up calculi not visible on plain X-ray, whereas plain radiography has a radiation exposure of 0.7 mSv and is used to follow-up radio-opaque calculi. We assessed the effectiveness of using ultra-low-dose CTKUB (ULDCTKUB) for the follow-up of ureteric calculi not visible on plain radiograph of the kidneys, ureter and bladder (KUB), as an emerging option to reduce radiation exposure compared to standard dose CTKUB.

METHODS

Between 2013 and 2016 we retrospectively analysed 86 patients who underwent ULDCTKUB for CTKUB-confirmed ureteric calculi that were not visible on plain radiography. Patients were identified from our Radiology Management System with additional information from electronic patient records.

RESULTS

98% of ULDCTKUBs were of diagnostic quality; two patients required further cross-sectional imaging. 67% of patients had passed their calculi after the initial diagnostic CTKUB. In the remaining 33% who had persistent calculi on ULDCTKUB, 20% required surgical intervention and 13% required no intervention. The mean ULDCTKUB effective radiation dose was six times lower than conventional CTKUB (0.8 vs 5.4 mSv). 67% of patients had a radiation dose equivalent to X-ray KUB (< 1 mSv).

CONCLUSION

ULDCTKUB is a reliable and safe follow-up investigation of ureteric calculi and has absorbed radiation doses similar to plain radiography and lower than annual background radiation. We advocate ULDCTKUB as the primary imaging modality in the follow-up of ureteric calculi not visible on plain radiograph.

Urolithiasis and intracorporeal lithotripsy in 37 Military Hospital, Accra, Ghana

Objective

The purpose of this study was to determine the indications and complications of intracorporeal lithotripsy in our institution.

Methods

Retrospective study carried out at the urology unit of the 37 Military Hospital between 2012-2015. 42 patients had intracorporeal lithotripsy out of 359 patients who had surgery within the period. Records of all patients who had intracorporeal lithotripsy between December 2012 to December 2015 were collected and analysed. An endourology log sheet was used to record data of patient's name, age, sex, indication for operation, location of stone, intraoperative complications, type of instruments/materials used, stone analysis and follow-up dates. All patients between the ages of six months to seventy years presenting with urinary stones diseases within the period were included, whilst patients with urinary stone disease who were managed with open surgery were excluded.Ethical clearance was obtained from the 37 Military Hospital institutional review board.

Results

Lithotripsy constituted 42/359(11.7%) of the methods used in the surgical cases done within the period.The commonest age of presentation was between 31-40 years (26.2%), with a male to female ratio of 2:1. The commonest indications for lithotripsy were pain (92.8%) and hydronephrosis (61.9%). Ureteric stones are more common (50%), followed by renal stones (45%) with the commonest site being the proximal ureter. The commonest procedure was ureteroscopy. Ureteral mucosal injury (5/43) (11.62%), was the commonest intraoperative complication. Postoperative complications were reno-cutaneous fistula (1/43) (2.32%), severe bleeding (1/43) (2.32%) haematuria (4/43) (9.30%).

Conclusion

Pain was the commonest indication for intra-corporeal lithotripsy (92.8%) and also the commonest post-operative complication (9.30%).

Funding

None declared.

Very low-dose computerized tomography for confirmation of urinary stone presence

PURPOSE

To determine whether a modified non-contrast very low-dose computed tomography (VLD-CT) protocol is applicable for confirmation of known urolithiasis.

METHODS AND MATERIALS

Consecutive adult patients with a CT scan showing urinary tract stone(s) between 6/2017-12/2018 were included. They were referred to a modified VLD-CT protocol if stone presence was equivocal or if stone location needed reassessment before an endourological interventional procedure. The scanned area was limited to the level of initial stone location caudally. Data on patients' demographics andbody mass index, were collected. The scanned length and radiation dose were calculated. Images were reviewed by two radiologists who assessed stone size and location. Follow-up reference standard included stone passage, surgical removal, and other imaging and clinical information.

RESULTS

Sixty-three patients [63 stones, mean BMI 28.7 (range 19-41.9)] were included. VLD-CTs revealed 31 stones in 31 patients, with a mean stone length of 5.5 mm. Fifteen stones remained at the same location, and 16 had migrated, of which two appeared in the bladder. Thirty-two stones were not observed on VLD-CT. The mean span scanned on the VLD-CT was 274 mm (± 80). The average radiation exposure was 1.47 mGy (range 1.09-3.3), and the absorbed dose was 0.77 mSv (range 0.39-1.43), compared to 10.24 mGy (range 1.75-28.9) and 7.87 mSv (range 1.44-18.5) in the previous scan. The mean radiation dose reduction between scans was 89%. On follow-up, all VLD-CT findings were confirmed.

CONCLUSION

A modified imaging protocol is applicable for confirmation of stone presence and location by utilizing very low-dose radiation exposure.

Increased urinary bladder volume improves the detectability of urinary stones at the ureterovesical junction in non-enhanced computed tomography (NECT)

OBJECTIVES

To evaluate the influence of the urinary bladder volume on the detectability of urolithiasis at the ureterovesical junction (UVJ) using a low-dose CT (LD-CT) with iterative reconstruction (IR) and a standard-dose CT (SD-CT) without IR in a large cohort.

METHODS

Four hundred patients (278 males (69.5%), mean 44.6 ± 14.7 years) with urolithiasis at the UVJ were investigated either by an LD-CT with IR (n = 289, 72%) or an SD-CT without IR (n = 111, 28%) protocol. The detectability of distal urolithiasis was assessed by a dichotomous assessment (definite or questionable) by two radiologists in consensus and by a quantitative analysis of the signal density distribution across a line drawn parallel to the distal ureter. Based on the resulting graph, minimum/maximum density values and mean/maximum upslopes and downslopes were derived and calculated automatically. In all patients, the total bladder volume was calculated by a slice-by-slice approach on axial CT images.

RESULTS

Patients with definite stones showed significantly higher urinary bladder volumes compared to patients with questionable stones in both LD-CT and SD-CT (p < 0.01). These results were independent of stones' length and patients' BMI values. Using cutoffs of 92 ml for LD-CT and 69 ml for SD-CT, high positive predictive values/accuracy rates of 96%/85% (LD-CT) and 98%/86% (SD-CT) were observed to identify definite urinary stones.

CONCLUSIONS

Urinary bladder volume has a significant impact on the detectability of distal urolithiasis. Moderate bladder filling by pre-CT hydration with subsequent CT scan at the time of high urge to void increases the detectability of urinary stones at the UVJ in clinical routine.

KEY POINTS

• Urinary bladder volume significantly affects the detectability of distal urolithiasis • Higher bladder volumes are associated with improved detectability of distal urinary stones • Oral pre-CT hydration for urolithiasis is easily applicable and cost-effective.

Emergency Department Switching and Duplicate Computed Tomography Scans in Patients With Kidney Stones

OBJECTIVE

To test whether duplicate imaging relates to a lack of information sharing among providers, we measured the association between emergency department (ED) switching during a kidney stone episode and receipt of a repeat computed tomography (CT) scan.

METHODS

Using the MarketScan Commercial Claims and Encounters Database, we identified adults between the ages 18 and 64 with an ED visit for a diagnosis of kidney stones. Among patients who had an abdominal or pelvic CT scan at their initial encounter, we then determined the subset that made an ED revisit within 30 days of their first, distinguishing between those to the same vs a different ED. Finally, we fit multivariable logistic regression models to estimate the risk of receiving a repeat CT scan associated with ED switching.

RESULTS

Twelve percent of patients who received a CT scan at their initial ED encounter had a revisit within 30 days of discharge. One-third of their revisits were made to a different ED than the index one. Duplicate CT scans were obtained at nearly 40% of all revisits. On multivariable analysis, the risk of receiving a repeat CT was 12% higher if this revisit was made to a different ED (risk ratio, 1.12; 95% confidence interval, 1.03-1.21; P = .010).

CONCLUSION

Our study reveals that ED switching during an acute kidney stone episode is associated with higher levels of repeat CT imaging. These findings support the role of better health information exchange among providers to help reduce waste in the health-care system.

Imaging Advances in Urolithiasis

The prevalence of urinary stones in the United States has been described as 1 in 11 persons reporting a history of stones. Imaging plays a crucial role in diagnosis, management, and follow-up for these patients and imaging technology over the last 100 years has advanced as the disease prevalence has increased. CT remains the gold standard for imaging urolithiasis and changes in this technology, with the addition of multidetector CT and dual-energy CT, as well as the changes in utilization of CT, have decreased the radiation dose encountered by patients and allowed for improved stone detection. The use of digital tomography has been introduced for follow-up of recurrent stone formers offering the potential to lower radiation exposure over the course of a patient's lifelong treatment. However, there is still a demand for improved imaging techniques to detect smaller stones and stones in larger patients at lower radiation doses as well as the continued need for the judicious use of all imaging modalities for healthcare cost containment and patient safety.

[S2k guidelines on diagnostics, therapy and metaphylaxis of urolithiasis (AWMF 043/025) : Compendium]

Every tenth German citizen will suffer from at least one urinary calculus during the lifetime. The diagnostics, treatment and follow-up treatment of urolithiasis are, therefore, part of the daily routine practice for all urologists in hospitals and private practices as well as in many other disciplines, such as general practitioners, internists, nephrologists and pediatricians. Although the diagnostics and therapy have experienced substantial alterations over the last 10 years, the possibilities of metabolic diagnostics and secondary prevention for patients at risk are, unfortunately and unjustly, in many places very poorly represented. The present S2k guidelines, which for the first time were established in an interdisciplinary consensus process, represent the current practical recommendations and, whenever possible, use tables and algorithms in order to facilitate easy reference in the routine daily work. Last but not least, this greatly simplifies the measures for metaphylaxis.

[Urolithiasis 2016 : Reliable, effective and low radiation exposure]

BACKGROUND

Urolithiasis is a widespread disease. Diagnostic imaging plays an important role in the evaluation and management of patients with suspected urolithiasis. Furthermore, modern imaging methods may provide information on stone location, size, fragility and composition aiding the urologist to determine the appropriate treatment modality.

PURPOSE

Based on the current literature and guidelines, this review reports on the various new and established diagnostic imaging modalities.

RESULTS

Ultrasound should always be the initial imaging modality. Following ultrasound, noncontrast CT-principally using a low-dose protocol-is the imaging modality of choice in the evaluation of patients with acute flank pain and suspected urolithiasis. New imaging modalities like dual energy CT, Uro Dyna CT and digital tomosynthesis are currently under investigation but not yet part of daily clinical practice. Magnetic resonance imaging can be used to detect obstruction caused by urinary stones but is not a first-line imaging modality.

Epidemiology, pathophysiology, and management of uric acid urolithiasis: A narrative review

An in-depth comprehension of the epidemiology as well as pathophysiology of uric acid urolithiasis is important for the identification, treatment, and prophylaxis of calculi in these patients. Persistently low urinary pH, hyperuricosuria, and low urinary volume are the most important factors in pathogenesis of uric acid urolithiasis. Other various causes of calculus formation comprises of chronic diarrhea, renal hyperuricosuria, insulin resistance, primary gout, extra purine in the diet, neoplastic syndromes, and congenital hyperuricemia. Non-contrast-enhanced computed tomography is the radiologic modality of choice for early assessment of patients with renal colic. Excluding situations where there is acute obstruction, rising blood chemistry, severe infection, or unresolved pain, the initial management ought to be medical dissolution by oral chemolysis since this method has proved to be effective in most of the cases.

Standard vs. reduced-radiation-dose CT in the tracing of the ureter

PURPOSE

To assess the effectiveness of reduced-radiation-dose computed tomography (CT) protocols in the tracing of the ureter in patients with suspected renal colic.

METHODS

The study was approved by our institutional review board, and informed consent was obtained from the participants. From July 2012 to April 2014, 310 consecutive patients with suspected urolithiasis were recruited to undergo unenhanced CT at 280 (n = 62), 200 (n = 62), 140 (n = 62), 100 (n = 62), and 70 (n = 62) reference mA seconds (mAs) while keeping other imaging parameters constant. Images were independently and randomly reviewed by two radiologists blinded to the study to determine the tracing rates of the ureter and the acceptable rates of image quality according to different tube charge settings.

RESULTS

A significant linear association was noted between tube charge settings, the rates for tracing of the ureter, and the acceptability of image quality (linear-by-linear association; p = 0.000 in all rates for both readers). The 140 reference mAs is the point at which the tracing rates deteriorate rapidly, with the tracing rate of 41.5% (95% CI 32.6%-51.0%) in reader 1 and 51.9% (95% CI 42.5%-61.2%) in reader 2, and with the acceptable rate of 82.3% (95% CI 70.8%-90.0%) in reader 1 and 96.8% (95% CI 88.3%-99.8%) in reader 2.

CONCLUSION

Decreasing the tube charge settings from 280 to 70 reference mAs resulted in a significant reduction in the tracing rate of the ureter, with 140 reference mAs being the breaking point.

Ultrasound-Guided Renal Access for Percutaneous Nephrolithotomy: A Description of Three Novel Ultrasound-Guided Needle Techniques

Ultrasound-guided renal access for percutaneous nephrolithotomy (PCNL) is a safe, effective, and low-cost procedure commonly performed worldwide, but a technique underutilized by urologists in the United States. The purpose of this article is to familiarize the practicing urologist with methods for ultrasound guidance for percutaneous renal access. We discuss two alternative techniques for gaining renal access for PCNL under ultrasound guidance. We also describe a novel technique of using the puncture needle to reposition residual stone fragments to avoid additional tract dilation. With appropriate training, ultrasound-guided renal access for PCNL can lead to reduced radiation exposure, accurate renal access, and excellent stone-free success rates and clinical outcomes.

Knowledge-based iterative model reconstruction (IMR) algorithm in ultralow-dose CT for evaluation of urolithiasis: evaluation of radiation dose reduction, image quality, and diagnostic performance

PURPOSE

To evaluate the efficacy of a knowledge-based iterative model reconstruction (IMR) algorithm for reducing image noise in ultralow-dose (ULD) CT for urolithiasis.

MATERIALS AND METHODS

A total of 103 patients diagnosed with urinary stones (n = 276) were enrolled. Regular dose (RD) scans (120 kV and 150 mAs, maximal tube current in dose modulation) were reconstructed using filtered back-projection (FBP, RD-FBP), and ULD scans (100 kV and 20 mAs, fixed tube current) were reconstructed with FBP (ULD-FBP), statistical iterative reconstruction (IR; ULD-iDose), and a knowledge-based IMR algorithm (ULD-IMR). Prospective interpretations of the two scans were performed with respect to radiation dose, objective image noise, and subjective assessment. The subjective assessment was also evaluated with regard to each patient's body mass index (BMI, < 25 or ≥ 25 kg/m(2)). Using RD CT (RD-FBP) as the reference standard, two reviewers assessed the diagnostic performance and inter-observer agreement for ULD-IMR.

RESULT

The average effective doses with RD CT and ULD CT were 8.31 and 0.68 mSv, respectively, and the average radiation dose reduction rate was 91.82% (p < 0.01). The lowest objective image noise was observed with ULD-IMR (p < 0.01). Subjective assessment in ULD-IMR was comparable to that of RD-FBP, although RD-FBP remained statistically superior. For BMI, there was a statistically significant difference in subjective image quality between the normal (4.7 ± 0.54) and overweight or obese groups (4.2 ± 0.5) (p < 0.05). The ULD-IMR showed a greater than 75% concordant rate in overall stones and 100% in ureter stones larger than 3 mm. However, for stones <3 mm, neither reviewer had a good detection rate (45.5% and 56.9% for the general and genitourinary radiologist, respectively). Inter-observer agreement was almost perfect (κ = 0.82).

CONCLUSION

Despite a significant radiation dose reduction, ULD-IMR images were comparable in image quality and noise to RD-FBP images. Furthermore, the diagnostic performance of the ULD non-enhanced CT protocol was comparable to that of the RD scan for diagnosing urinary stones larger than 3 mm.

An overview of kidney stone imaging techniques

Kidney stone imaging is an important diagnostic tool and initial step in deciding which therapeutic options to use for the management of kidney stones. Guidelines provided by the American College of Radiology, American Urological Association, and European Association of Urology differ regarding the optimal initial imaging modality to use to evaluate patients with suspected obstructive nephrolithiasis. Noncontrast CT of the abdomen and pelvis consistently provides the most accurate diagnosis but also exposes patients to ionizing radiation. Traditionally, ultrasonography has a lower sensitivity and specificity than CT, but does not require use of radiation. However, when these imaging modalities were compared in a randomized controlled trial they were found to have equivalent diagnostic accuracy within the emergency department. Both modalities have advantages and disadvantages. Kidney, ureter, bladder (KUB) plain film radiography is most helpful in evaluating for interval stone growth in patients with known stone disease, and is less useful in the setting of acute stones. MRI provides the possibility of 3D imaging without exposure to radiation, but it is costly and currently stones are difficult to visualize. Further developments are expected to enhance each imaging modality for the evaluation and treatment of kidney stones in the near future. A proposed algorithm for imaging patients with acute stones in light of the current guidelines and a randomized controlled trial could aid clinicians.

Low-dose abdominal computed tomography for detection of urinary stone disease - Impact of additional spectral shaping of the X-ray beam on image quality and dose parameters

OBJECTIVES

To evaluate a novel tin filter-based abdominal CT protocol for urolithiasis in terms of image quality and CT dose parameters.

METHODS

130 consecutive patients with suspected urolithiasis underwent non-enhanced CT with three different protocols: 48 patients (group 1) were examined at tin-filtered 150kV (150kV Sn) on a third-generation dual-source-CT, 33 patients were examined with automated kV-selection (110-140kV) based on the scout view on the same CT-device (group 2), and 49 patients were examined on a second-generation dual-source-CT (group 3) with automated kV-selection (100-140kV). Automated exposure control was active in all groups. Image quality was subjectively evaluated on a 5-point-likert-scale by two radiologists and interobserver agreement as well as signal-to-noise-ratio (SNR) was calculated. Dose-length-product (DLP) and volume CT dose index (CTDIvol) were compared.

RESULTS

Image quality was rated in favour for the tin filter protocol with excellent interobserver agreement (ICC=0.86-0.91) and the difference reached statistical significance (p<0.001). SNR was significantly higher in group 1 and 2 compared to second-generation DSCT (p<0.001). On third-generation dual-source CT, there was no significant difference in SNR between the 150kV Sn and the automated kV selection protocol (p=0.5). The DLP of group 1 was 23% and 21% (p<0.002) lower in comparison to group 2 and 3, respectively. So was the CTDIvol of group 1 compared to group 2 (-36%) and 3 (-32%) (p<0.001).

CONCLUSION

Additional shaping of a 150kV source spectrum by a tin filter substantially lowers patient exposure while improving image quality on un-enhanced abdominal computed tomography for urinary stone disease.

Urolithiasis--an interdisciplinary diagnostic, therapeutic and secondary preventive challenge

BACKGROUND

The prevalence of urolithiasis in Germany is 4.7%; its incidence has trebled in the last three decades. The risk of recurrence is 50-80%, depending on the type of stone, unless secondary prevention is instituted. Risk-adapted secondary prevention lowers this risk to 10-15%.

METHODS

This review is based on publications retrieved by a selective search in PubMed using the key words "urolithiasis," "urinary stones," "epidemiology," "lithogenesis," "biominerals," "risk factors," and "diagnosis, therapy, metaphylaxis." These publications were evaluated with the aid of the urolithiasis guideline of the European Association of Urology.

RESULTS

Acute renal colic can usually be diagnosed without sophisticated equipment. Stones can be dealt with by a variety of techniques depending on their size and location, including extracorporeal shock-wave lithotripsy, ureterorenoscopy, percutaneous nephrolitholapaxy, and open surgery. Most ureteric stones of diameter up to 5 mm pass spontaneously. 75% of patients have no complications. The basic evaluation needed for secondary prevention can be carried out by any physician on an ambulatory basis. In the 25% of patients who have complications, a more extensive interdisciplinary evaluation of metabolic parameters should be performed in a clinical center for urinary stones.

CONCLUSION

Urolithiasis has many causes and can be treated in many different ways. An extensive metabolic work-up is often necessary for secondary prevention. The various treatment options must be considered for their suitability in each individual patient. Robust data are now available on surgical and interventional methods, but there are as yet no high-quality trials of secondary prevention. Further research should concentrate on the etiology and pathogenesis of urolithiasis.

Distribution of ureteral stones and factors affecting their location and expulsion in patients with renal colic

Purpose

To evaluate the distribution of ureteral stones and to determine their characteristics and expulsion rate based on their location.

Materials and Methods

We retrospectively reviewed computed tomography (CT) findings of 246 patients who visited our Emergency Department (ED) for renal colic caused by unilateral ureteral stones between January 2013 and April 2014. Histograms were constructed to plot the distribution of stones based on initial CT findings. Data from 144 of the 246 patients who underwent medical expulsive therapy (MET) for 2 weeks were analyzed to evaluate the factors responsible for the stone distribution and expulsion.

Results

The upper ureter and ureterovesical junction (UVJ) were 2 peak locations at which stones initially lodged. Stones lodged at the upper ureter and ureteropelvic junction (group A) had a larger longitudinal diameter (4.21 mm vs. 3.56 mm, p=0.004) compared to those lodged at the lower ureter and UVJ (group B). The expulsion rate was 75.6% and 94.9% in groups A and B, respectively. There was no significant difference in the time interval from initiation of renal colic to arrival at the ED between groups A and B (p=0.422). Stone diameter was a significant predictor of MET failure (odds ratio [OR], 1.795; p=0.005) but the initial stone location was not (OR, 0.299; p=0.082).

Conclusions

The upper ureter and UVJ are 2 peak sites at which stones lodge. For stone size 10 mm or less, initial stone lodge site is not a significant predictor of MET failure in patients who have no previous history of active stone treatment in the ureter.

Effective radiation exposure evaluation during a one year follow-up of urolithiasis patients after extracorporeal shock wave lithotripsy

Introduction

To determine and evaluate the effective radiation exposure during a one year follow-up of urolithiasis patients following the SWL (extracorporeal shock wave lithotripsy) treatment.

Material and methods

Total Effective Radiation Exposure (ERE) doses for each of the 129 patients: 44 kidney stone patients, 41 ureter stone patients, and 44 multiple stone location patients were calculated by adding up the radiation doses of each ionizing radiation session including images (IVU, KUB, CT) throughout a one year follow-up period following the SWL.

Results

Total mean ERE values for the kidney stone group was calculated as 15, 91 mSv (5.10-27.60), for the ureter group as 13.32 mSv (5.10-24.70), and in the multiple stone location group as 27.02 mSv (9.41-54.85). There was no statistically significant differences between the kidney and ureter groups in terms of the ERE dose values (p = 0.221) (p >0.05). In the comparison of the kidney and ureter stone groups with the multiple stone location group; however, there was a statistically significant difference (p = 0.000) (p <0.05).

Conclusions

ERE doses should be a factor to be considered right at the initiation of any diagnostic and/or therapeutic procedure. Especially in the case of multiple stone locations, due to the high exposure to ionized radiation, different imaging modalities with low dose and/or totally without a dose should be employed in the diagnosis, treatment, and follow-up bearing the aim to optimize diagnosis while minimizing the radiation dose as much as possible.

Adverse events are rare among adults 50 years of age and younger with flank pain when abdominal computed tomography is not clinically indicated according to the emergency physician

OBJECTIVE

Many emergency physicians (EPs) order "confirmatory" abdominal computed tomography (CT) in young flank pain patients, despite a high clinical suspicion of renal colic and the risk of radiation exposure. We measured the adverse outcome rate among flank pain patients identified as not requiring abdominal CT by the EP on a data form, regardless of whether CT was eventually ordered. Our secondary objective was to describe diagnoses other than renal colic identified by CT in this population.

METHODS

We conducted a prospective observational study at two community EDs. We asked staff EPs to complete a data sheet on patients ages 18 to 50 years with a first episode of flank pain, recording 1) if the flank pain was consistent with renal colic and 2) if the EP felt abdominal CT was indicated. Adverse outcomes (defined a priori as urgent surgical procedures, disability, or death) were assessed by research assistants at 4 weeks using telephone follow-up and a hospital records search.

RESULTS

We enrolled 389 patients; 353 completed follow-up (91%). The average age was 38.8 years, and 72.0% were male. Of 212 patients identified in the "CT not indicated" group, 2 had another diagnosis identified (unruptured diverticulitis and a ruptured ovarian cyst), but none had adverse outcomes (95% CI 0-1.4).

CONCLUSIONS

Adverse events were rare (< 1.5%) among patients < 50 years old with flank pain when CT was not required according to the clinical assessment of the EP. Future research should assess the adverse outcomes of withholding CT in low-risk patients using a larger patient sample.

Accuracy of reduced-dose computed tomography for ureteral stones in emergency department patients

STUDY OBJECTIVE

Reduced-dose computed tomography (CT) scans have been recommended for diagnosis of kidney stone but are rarely used in the emergency department (ED) setting. Test characteristics are incompletely characterized, particularly in obese patients. Our primary outcome is to determine the sensitivity and specificity of a reduced-dose CT protocol for symptomatic ureteral stones, particularly those large enough to require intervention, using a protocol stratified by patient size.

METHODS

This was a prospective, blinded observational study of 201 patients at an academic medical center. Consenting subjects underwent both regular- and reduced-dose CT, stratified into a high and low body mass index (BMI) protocol based on effective abdominal diameter. Reduced-dose CT scans were interpreted by radiologists blinded to regular-dose interpretations. Follow-up for outcome and intervention was performed at 90 days.

RESULTS

CT scans with both regular and reduced doses were conducted for 201 patients, with 63% receiving the high BMI reduced-dose protocol. Ureteral stone was identified in 102 patients (50.7%) of those receiving regular-dose CT, with a ureteral stone greater than 5 mm identified in 26 subjects (12.9%). Sensitivity of the reduced-dose CT for any ureteral stone was 90.2% (95% confidence interval [CI] 82.3% to 95.0%), with a specificity of 99.0% (95% CI 93.7% to 100.0%). For stones greater than 5 mm, sensitivity was 100% (95% CI 85.0% to 100.0%). Reduced-dose CT identified 96% of patients who required intervention for ureteral stone within 90 days. Mean reduction in size-specific dose estimate was 18.6 milligray (mGy), from 21.7 mGy (SD 9.7) to 3.4 mGy (SD 0.9).

CONCLUSION

CT with substantial dose reduction was 90.2% (95% CI 82.3% to 95.0%) sensitive and 98.9% (95% CI 85.0% to 100.0%) specific for ureteral stones in ED patients with a wide range of BMIs. Reduced-dose CT was 96.0% (95% CI 80.5% to 99.3%) sensitive for ureteral stones requiring intervention within 90 days.

Use of computed tomography scout film and Hounsfield unit of computed tomography scan in predicting the radio-opacity of urinary calculi in plain kidney, ureter and bladder radiographs

Objective:

The objective of this study is to determine the diagnostic utility of computed tomography (CT)- scout film with an optimal non-contrast helical CT scan Hounsfield unit (HU) in predicting the appearance of urinary calculus in the plain kidneys, ureter, urinary bladder (KUB)-radiograph.

Methods:

A prospective cross-sectional study was executed and data were collected from June 2007 to June 2012 at a tertiary hospital. The included subjects were diagnosed to have <10mm urolithiasis with non-contrast helical CT scan and KUB X-ray, which were carried out on the same day. Both KUB radiographs and CT-scout film were read by two qualified radiologists with inter-observer standardization prior to the study. Urolithiasis characteristics such as stone location, CT attenuation value, CT-scout film and KUB radiograph appearance were recorded independently by two observers. Univariate logistic analysis with receiver operating characteristic curve was generated to determine the best cut-off HU value of urolithiases not identified in CT-scout film, but determined radio-opaque in KUB X-ray. Subsequently, its sensitivity, specificity, predictive values and likelihood ratios were calculated. Statistical significance was set at P value of 0.05 or less.

Results:

Two hundred and three valid cases were included. 73 out of 75 CT-scout film detected urolithiasis were identified on plain radiograph and determined as radio-opaque. The determined best cut off value of HU utilized for prediction of radiographic characteristics was 630HU at which urinary calculi were not seen at CT-scout film and were KUB X-ray radio-opaque. The set HU cut-off was established of ideal accuracy with an overall sensitivity of 82.2%, specificity of 96.9% and a positive predictive value of 96.5% and negative predictive value of 83.5%.

Conclusion:

Urolithiases identified on the CT-scout film were also seen as radiopaque on the KUB radiograph while those stones not visible on the CT-scout film, but above the optimal HU cut-off value of 630 are also likely to be radiopaque.

Prospective trial of the detection of urolithiasis on ultralow dose (sub mSv) noncontrast computerized tomography: direct comparison against routine low dose reference standard

PURPOSE

In this prospective trial we compared ultralow dose computerized tomography reconstruction algorithms and routine low dose computerized tomography for detecting urolithiasis.

MATERIALS AND METHODS

A total of 48 consenting adults prospectively underwent routine low dose noncontrast computerized tomography immediately followed by an ultralow dose series targeted at a 70% to 90% reduction from the routine low dose technique (sub mSv range). Ultralow dose series were reconstructed with filtered back projection, and adaptive statistical and model based iterative reconstruction techniques. Transverse (axial) and coronal images were sequentially reviewed by 3 relatively inexperienced trainees, including a radiology resident, a urology fellow and an abdominal imaging fellow. Three experienced abdominal radiologists independently reviewed the routine low dose filtered back projection images, which served as the reference standard.

RESULTS

The mean effective dose for the ultralow dose scans was 0.91 mSv (median 0.82), representing a mean ± SD 78% ± 5% decrease compared to the routine low dose. Overall sensitivity and positive predictive value per stone for ultralow dose computerized tomography at a 4 mm threshold was 0.91 and 0.98, respectively. Sensitivity, specificity, positive and negative predictive values, and accuracy per patient were 0.87, 1.00, 1.00, 0.94 and 0.96, respectively. At a 4 mm threshold the sensitivity and positive predictive value per stone of the ultralow dose series for filtered back projection, and adaptive statistical and model based iterative reconstruction was 0.89 and 0.96, 0.91 and 0.98, and 0.93 and 1.00, respectively. Sensitivity, specificity, positive and negative predictive values, and accuracy per patient at the 4 mm threshold were 0.82, 1.00, 1.00, 0.91 and 0.94 for filtered back projection, 0.85, 1.00, 1.00, 0.93 and 0.95 for adaptive statistical iterative reconstruction, and 0.94, 1.00, 1.00, 0.97 and 0.98 for model based iterative reconstruction, respectively. Sequential review of coronal images changed the final stone reading in 13% of cases and improved diagnostic confidence in 49%.

CONCLUSIONS

At a 4 mm renal calculus size threshold ultralow dose computerized tomography is accurate for detection when referenced against routine low dose series with dose reduction to below the level of a typical 2-view plain x-ray of the kidneys, ureters and bladder. Slight differences were seen among the reconstruction algorithms. There was mild improvement with model based iterative reconstruction over filtered back projection and adaptive statistical iterative reconstruction. Coronal images improved detection and diagnostic confidence over axial images alone.

[Uretero(reno)scopy: management of complications]

Rigid and flexible uretero(reno)scopy (URS) are safe and effective methods in interventional calculus therapy. Complications are rare and can be avoided in advance in many cases. In ureteroliths, URS has in many cases replaced extracorporeal shock wave lithotripsy (ESWL) as the method of first choice. However, it is important to describe in detail the advantages and disadvantages as well as the risks of the procedure to the patient.

Bilateral stones as a cause of acute renal failure in the emergency department

BACKGROUND

Acute renal failure (ARF) due to obstructive uropathy is a urological emergency. The standard radiological investigations in the emergency setting include X-ray, ultrasonography and computed tomography. But occasionally the cause of obstruction may be elusive.

METHODS

We present a case of obstructive uropathy due to bilateral stones presenting as acute renal failure. The patient underwent successful shock wave lithotripsy (SWL) for dissolution of calculi.

RESULTS

The patient was successfully treated, and reported asymptomatic in a follow-up.

CONCLUSION

Close collaboration between nephrological, urological, and radiological services is required.

[Imaging for diagnostics of urolithiasis including dual-energy CT]

Patients with stone disease usually present to the urologist with acute colic pain. For the right choice of therapy the diagnosis needs to be confirmed using one of many imaging methods, including ultrasonography, abdominal radiography, intravenous urography, non-contrast-enhanced computed tomography (CT), CT and magnetic resonance imaging (MRI) urography and dual-energy CT. The techniques differ in the availability, diagnostic sensitivity and specificity and level of radiation exposure. Compared to the others dual-energy CT allows distinction between different stone compositions with high accuracy and can affect the choice of therapy. This article on imaging and diagnosis of urolithiasis discusses the different imaging methods and highlights dual-energy CT and its distinctive features.

[Management of ureteral stones]

Ureteral stones are normally clinically symptomatic as colic or flank pain. The investigation of acute flank pain by diagnostic imaging targets on the confirmation of the suspected ureteral stone and the exclusion of other diseases. Furthermore, imaging using unenhanced computed tomography (NCCT) or excretory urography (IVU) serves as a basis for treatment planning. Depending on the size and location of ureteral stones a spontaneous stone passage, medical expulsive therapy (MET), extracorporeal shock wave lithotripsy (SWL), ureterorenoscopy (URS) or initially just simple stenting can be considered. The aim of this review is to provide the reader with the necessary decision criteria for optimal care of patients in the daily routine.

Recent finding and new technologies in nephrolitiasis: a review of the recent literature

This review summarizes recent literature on advances regarding renal and ureteral calculi, with particular focus in areas of recent advances in the overall field of urolithiasis. Clinical management in everyday practice requires a complete understanding of the issues regarding metabolic evaluation and subgrouping of stone-forming patients, diagnostic procedures, effective treatment regime in acute stone colic, medical expulsive therapy, and active stone removal. In this review we focus on new perspectives in managing nephrolitihiasis and discuss recentadvances, including medical expulsive therapy, new technologies, and refinements of classical therapy such as shock wave lithotripsy, give a fundamental modification of nephrolithiasis management. Overall, this field appears to be the most promising, capable of new developments in ureterorenoscopy and percutaneous approaches. Further improvements are expected from robotic-assisted procedures, such as flexible robotics in ureterorenoscopy.

Ureteral calculi detection using low dose computerized tomography protocols is compromised in overweight and underweight patients

PURPOSE

Low dose computerized tomography protocols have demonstrated a reduction in radiation exposure while maintaining excellent sensitivity and specificity in the detection of stones in patients of average size. Low dose computerized tomography protocols have not yet been evaluated in subjects in the extremes of weight. We evaluated the effect of body weight when using low dose protocols to detect ureteral calculi.

MATERIALS AND METHODS

Three cadavers of increasing weight (55, 85 and 115 kg) were prepared by inserting 721 calcium oxalate stones (range 3 to 7 mm) in 33 random configurations into urinary tracts. Cadavers were then scanned using a GE LightSpeed® at 7 radiation settings. An independent, blinded review by a radiologist was conducted to generate ROC curves, with areas under the curve compared using a 1-way ANOVA (α = 0.05).

RESULTS

Sensitivity and specificity were significantly lower in the low and high weight cadavers compared to the medium weight cadaver at 5 mAs (p <0.001) and 7.5 mAs (p = 0.048). Differences in sensitivity and specificity at radiation settings of 15 mAs or greater were not significant.

CONCLUSIONS

The sensitivity and specificity for the detection of ureteral calculi on computerized tomography were decreased for underweight and overweight subjects when using extremely low dose radiation settings (less than 1 mSv). Low dose protocols of 15 mAs (2 mSv) can still be used for these subjects without jeopardizing the ability to identify ureteral stones.

Current status of low dose multi-detector CT in the urinary tract

Over the past several years, advances in the technical domain of computed tomography (CT) have influenced the trend of imaging modalities used in the clinical evaluation of the urinary system. Renal collecting systems can be illustrated more precisely with the advent of multi-detector row CT through thinner slices, high speed acquisitions, and enhanced longitudinal spatial resolution resulting in improved reformatted coronal images. On the other hand, a significant increase in exposure to ionizing radiation, especially in the radiosensitive organs, such as the gonads, is a concern with the increased utilization of urinary tract CT. In this article, we discuss the strategies and techniques available for reducing radiation dose for a variety of urinary tract CT protocols with metabolic clinical examples. We also reviewed CT for hematuria evaluation and related scan parameter optimization such as, reducing the number of acquisition phases, CT angiography of renal donors and lowering tube potential, when possible.

Perioperative patient radiation exposure in the endoscopic removal of upper urinary tract calculi

BACKGROUND AND PURPOSE

The efficacy of computed tomography (CT) in detailing upper urinary tract calculi is well established. There is no established acceptable annual recommended limit for medical exposure, yet the global accepted upper limit for occupational radiation exposure is <50 millisieverts (mSv) in any one year. We sought to appreciate the CT and fluoroscopic radiation exposure to our patients undergoing endoscopic removal of upper tract calculi during the periprocedure period.

PATIENTS AND METHODS

All patients undergoing upper urinary endoscopic stone removal between 2005 and 2009 were identified. To calculate the cumulative radiation exposure, we included all ionizing radiation imaging performed during a periprocedure period, which we defined as ≤90 days pre- and post-therapeutic procedure.

RESULTS

A total of 233 upper urinary tract therapeutic patient stone procedures were identified; 127 patients underwent ureteroscopy (URS) and 106 patients underwent percutaneous nephrolithotomy (PCNL). A mean 1.58 CTs were performed per patient. Ninety (38.6%) patients underwent ≥2 CTs in the periprocedure period, with an average number in this group of 2.49 CT/patient, resulting in approximately 49.8 mSv of CT radiation exposure. Patients who were undergoing URS were significantly more likely to have multiple CTs (P=0.003) than those undergoing PCNL. Median fluoroscopic procedure exposures were 43.3 mGy for patients who were undergoing PCNL and 27.6 mGy for those patients undergoing URS.

CONCLUSIONS

CT radiation exposure in the periprocedure period for patients who were undergoing endoscopic upper tract stone removal is considerable. Added to this is the procedure-related fluoroscopic radiation exposure. Urologic surgeons should be aware of the cumulative amount of ionizing radiation received by their patients from multiple sources.

Ultra-low-dose protocol for CT-guided lung biopsies

PURPOSE

Computed tomography (CT) scans are a significant source of radiation to patients. It was hypothesized that technical success and complication rates would not be significantly changed by radically lowering the CT dose during lung biopsies with an ultra-low-dose (ULD) protocol.

MATERIALS AND METHODS

A total of 100 consecutive patients aged 11-89 years who underwent biopsies of lung lesions were evaluated. Technical parameters were altered halfway through the study from the standard dose (140 kV localizing/100 kV subsequent guiding scans with auto-mA) to a ULD protocol (100 kV, 7.5 mAs) as part of a quality initiative. ULD studies were evaluated subjectively for image quality on a five-point scale. Patients' body mass indexes, total estimated radiation doses (dose-length product), technical success rates, and complications were compared between the standard-dose and the ULD groups.

RESULTS

Average radiation dose was reduced from 677.5 mGy·cm for the standard-dose group to 18.3 mGy·cm for the ULD group (P < .0001). In the ULD group, image quality was rated as adequate or better in 96% of cases. Pneumothoraces necessitating chest tube placements occurred in 10% and 6% of cases in the ULD and standard dose groups, respectively (P = .715). Technical success rates of 92% and 98% were obtained in the ULD and standard dose groups, respectively (P = .362).

CONCLUSIONS

Radiation dose to the chest during CT-guided percutaneous lung biopsies is reduced greater than 95% versus a standard protocol through the use of a ULD CT protocol without decreasing technical success or patient safety.

Low dose computerized tomography for detection of urolithiasis--its effectiveness in the setting of the urology clinic

PURPOSE

Low dose noncontrast computerized tomography is becoming a common imaging tool to diagnose urolithiasis. We investigated its usefulness as a diagnostic tool in the outpatient setting.

MATERIALS AND METHODS

A total of 62 patients with suspected urolithiasis underwent standard renal stone protocol computerized tomography with a tube current of 160 mA. Images were modified by adding image noise to simulate tube currents of 70, 100 and 130 mA. Three urologists independently interpreted the original and simulated dose scans for stone number, location and associated signs of obstruction. In addition, the investigators rated the ease of interpreting the scans and their overall level of confidence.

RESULTS

There were no statistically significant differences in interobserver and intra-observer variability for stone detection or obstruction signs except significant interobserver variability in hydronephrosis and intra-observer variability in stranding categories. Each 1 mm increase in stone size increased the likelihood of a concordant response 3.55, 2.7 and 2-fold when reducing the tube current level by 19%, 38% and 56%, respectively (p=0.001, 0.008 and 0.021, respectively). Multiple stones or index stone location were not associated with agreement. The overall level of confidence decreased with lower simulated doses, particularly in the bony pelvis (p<0.02).

CONCLUSIONS

Low dose computerized tomography may serve as an effective tool in the setting of the urology clinic in patients with urolithiasis. This imaging tool can better assess urolithiasis and associated obstruction than plain abdominal radiographs, but it may be problematic with small stones (less than 2 mm) and evidence of distal ureteral obstruction. Its effectiveness as a long-term followup tool requires further prospective trials.

Investigation of the location of the ureteral stone and diameter of the ureter in patients with renal colic

Purpose

The objective of this study were to evaluate the location of ureteral stones and the diameter of the ureter in patients with renal colic.

Materials and Methods

We retrospectively reviewed the records of 95 consecutive patients who presented to the emergency department with renal colic in whom urinary stones were diagnosed by computed tomography between January 2009 and August 2009. The size and location of the stones were investigated. The length and diameter of unaffected ureters were also measured.

Results

The mean size of the stones was 4.87±3.49 mm (range, 0.9-22 mm). Stones were located at ureterovesical junction (UVJ) in 44 cases (46.3%), proximal ureter in 29 (30.5%), distal ureter in 16 (16.8%), ureteropelvic junction (UPJ) in 5 (5.2%), and the ureter crossing external iliac vessel (UEIV) in 1 case (1%). The mean length of the ureter was 226.8±20.8 mm (range, 175-286 mm). The mean diameter of the ureter was 3.40±0.61 mm (range, 1.9-5.3 mm). The mean diameter of the UEIV was 3.28±0.59 mm (range, 2.2-5.3 mm).

Conclusions

The UPJ and UEIV were not common sites of ureteral stones. The smaller the stones, the closer to the UVJ that the stones were located. Spontaneous passage of the stones was most frequently observed for stones in the UVJ. The UEIV was not significantly narrower than the other parts of the ureter.