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

Assessment of the efficacy of reduced-radiation noncontrast computed tomography scan compared with the standard noncontrast computed tomography scan for detecting urolithiasis: A prospective single-center study

Background

Noncontrast computed tomography (CT) scan of the kidneys, ureter and bladder is the standard investigative modality for diagnosing and following up patients with urolithiasis. With each scan, a patient receives radiation of 18-34 mGy. Dose considerations become pertinent because of a 10% lifetime incidence rate and higher than 50% risk of recurrence, necessitating repeated imaging in the lifetime of a stone former. Hence, this study aimed to assess the sensitivity of "reduced-radiation" CT imaging by altering scan settings to lower than the "standard" norms.

Materials and methods

Altogether, 222 patients (255 "kidney-ureter" stone-bearing units or "renal units") with urolithiasis and patients undergoing CT for other reasons with incidental findings of renal/ureteric calculi between 2017 and 2019 were included. All patients were subjected to 3 sequential scans at tube current settings of 250 mA (CT-N/Standard), 100 mA (CT-100), and 50 mA (CT-50) at a constant voltage of 120 kV. Their clinicodemographic and radiological findings were recorded and assessed for significance.

Results

Of the 255 renal units, 117 were between 30 and 44 years of age, 75% were men. Of the 255 patients, 178 (70.1%) reported a first stone episode and 77 had recurrence. Lower ureteric calculi were predominant (40.4%). All calculi were identified on CT-N; CT-100 failed to detect calculi in 1 patient, and CT-50 failed in 3 patients, where all calculi were <3 mm in size. Meanwhile, none were undetected among patients with obesity. The sensitivity was 99.61% for the CT-100 and 98.82% for the CT-50, which indicated a 2.5 and 5 times lower radiation and dose/length, respectively, than CT-N.

Conclusions

The reduced-radiation CT scan is safe, sensitive, and accurate for the diagnosis and follow-up of patients with urolithiasis with significantly lower radiation exposures. Our study lays the foundation to accept low-dose CT in general and CT-50 in particular, as the new "standard of care," and attempt further dose reduction without loss of diagnostic efficacy.

A systematic review and meta-analysis of clinical signs, symptoms, and imaging findings in patients with suspected renal colic

Study Objective

The objective of this study was to conduct a systematic review and meta-analysis of the diagnostic accuracy of the clinical signs, symptoms, laboratory investigations, and imaging modalities commonly used in patients with clinically suspected renal colic.

Methods

We conducted this systematic review and meta-analysis according to an a priori, registered protocol (PROSPERO CRD42017055153). A literature search was performed using MEDLINE and EMBASE from inception to July 2, 2020. We assessed the risk of bias using Quality Assessment of Diagnostic Accuracy Studies-2, calculated likelihood ratios (LRs), and applied a random-effects model for meta-analysis.

Results

Among 7641 references screened, 76 were included in the systematic review and 53 were included in the meta-analyis. The overall pooled prevalence for ureteral stones was 63% (95% confidence interval [CI], 58%-67%). No individual demographic feature, symptom, or sign when present had an LR+ ≥2.0 for identifying ureterolithiasis. A (Sex, Timing and Origin of pain, race, presence or absence of Nausea, and Erythrocytes) STONE score ≥10 increased (sensitivity 0.49, specificity 0.91, LR 5.3 [95% CI, 4.1-6.7]) and a STONE score <6 reduced the likelihood of ureteral stones (sensitivity 0.94, specificity 0.43, LR 0.15 [95% CI, 0.10-0.22]). Standard-dose (sensitivity 0.96, specificity 0.94, LR+ 16 [95% CI, 11-23], LR- 0.05 [95% CI, 0.03-0.07]) and low-dose computed tomography (CT) scanning (sensitivity 0.93, specificity 0.94, LR+ 17 [95% CI, 8.8-31], LR- 0.08 [95% CI, 0.03-0.19]) were the most useful imaging techniques for identifying patients with or without ureteral stones.

Conclusions

Individual signs, symptoms, or the presence of microscopic hematuria do not substantially impact the likelihood of ureteral stones in patients with clinically suspected renal colic. The STONE score at high and low thresholds and a modified STONE score at a high threshold may sufficiently guide physicians' decisions to obtain imaging. Low-dose, non-contrast CT imaging provides superior diagnostic accuracy compared with all other imaging index tests that are comparable with standard CT imaging. Limitations of the evidence include methodological shortcomings and considerable heterogeneity of the included studies.

Multi-institutional variation in performance of low dose computerized tomography for the evaluation of suspected nephrolithiasis

Introduction and Objective Guidelines from the American Urological Association (AUA) and American College of Radiology (ACR) recommend that patients with suspected nephrolithiasis undergo low dose computerized tomography (LD CT KUB) as opposed to higher dose conventional imaging. We hypothesized that even at institutions with established LD protocols, higher dose imaging is common. Methods We identified four academic medical centers where LD CT KUB protocols were implemented to yield an Effective Dose (EDose) consistent with national guidelines. Fifty consecutive adult patients who underwent CT KUB specifically for the evaluation of nephrolithiasis were retrospectively reviewed at each site. Patient age, sex, BMI, imaging location, and EDose (millisieverts, mSv) were recorded. Results 200 patients with a mean age of 54 years were identified. 46 patients (23%) underwent CT KUB with EDose ≤ 4 mSv, accounting for 10-48% of each institution's cohort. 116 patients had a BMI < 30, and would have been expected to receive LD CTs by the AUA criteria for LD CT KUB. Within this subset, only 37 patients (32%) actually underwent LD CT KUB. The highest dose CT KUB at each institution resulted in EDose of 33.8-44.6 mSv, exceeding the recommended exposure of LD CT KUB by tenfold. Conclusions At academic institutions where LD CT KUB was implemented for the evaluation of nephrolithiasis, a minority of patients with BMI < 30 receive guideline-concordant imaging. Differences in patient BMI did not account for the variation in radiation exposure. Further research is necessary to elucidate barriers to low dose CT implementation.

Strategies to Optimize Nephrolithiasis Emergency Care (STONE): Prospective Evaluation of an Emergency Department Clinical Pathway

OBJECTIVE

To convene a multi-disciplinary panel to develop a pathway for Emergency Department (ED) patients with suspected nephrolithiasis and then prospectively evaluate its effect on patient care.

MATERIALS AND METHODS

The STONE Pathway was developed and linked to order sets within our Electronic Health Record in April 2019. Records were prospectively reviewed for ED patients who underwent ultrasound or Computerized Tomography (CT) to evaluate suspected nephrolithiasis between January 2019 and August 2019 within our institution. The primary outcome measure was the proportion of patients whose ED CT was low dose (<4 mSv). Secondary outcome measures included receipt of pathway-concordant pain medications and urine strainers. Order set utilization was evaluated as a process measure. Balance measures assessed included repeat ED visits, imaging, hospitalizations, and a urologic clinic visit or surgery within 30 days of discharge.

RESULTS

441 patients underwent ED imaging, of whom 261 (59%) were evaluated for suspected nephrolithiasis. The STONE Pathway was used in 50 (30%) eligible patients. Patients treated with the Pathway were more likely to undergo low-dose CTs (49% vs. 23%, p<0.001), and receive guideline-concordant pain medications such as NSAIDs (90% vs. 62%, p<0.001), and were less likely to return to the ED within 30 days (13% vs. 2%, p=0.01). These measures demonstrated special cause variation following Pathway release.

CONCLUSIONS

Clinical pathways increase compliance with evidence-based practices for pain control and imaging in nephrolithiasis emergency care and may improve the delivery of value-based care.

Radiation Dose Reduction in Kidney Stone CT: A Randomized, Facility-Based Intervention

OBJECTIVE

Kidney stones are common, tend to recur, and afflict a young population. Despite evidence and recommendations, adoption of reduced-radiation dose CT (RDCT) for kidney stone CT (KSCT) is slow. We sought to design and test an intervention to improve adoption of RDCT protocols for KSCT using a randomized facility-based intervention.

METHODS

Facilities contributing at least 40 KSCTs to the American College of Radiology dose index registry (DIR) during calendar year 2015 were randomized to intervention or control groups. The Dose Optimization for Stone Evaluation intervention included customized CME modules, personalized consultation, and protocol recommendations for RDCT. Dose length product (DLP) of all KSCTs was recorded at baseline (2015) and compared with 2017, 2018, and 2019. Change in mean DLP was compared between facilities that participated (intervened-on), facilities randomized to intervention that did not participate (intervened-off), and control facilities. Difference-in-difference between intervened-on and control facilities is reported before and after intervention.

RESULTS

Of 314 eligible facilities, 155 were randomized to intervention and 159 to control. There were 25 intervened-on facilities, 71 intervened-off facilities, and 96 control facilities. From 2015 to 2017, there was a drop of 110 mGy ∙ cm (a 16% reduction) in the mean DLP in the intervened-on group, which was significantly lower compared with the control group (P < .05). The proportion of RDCTs increased for each year in the intervened-on group relative to the other groups for all 3 years (P < .01).

DISCUSSION

The Dose Optimization for Stone Evaluation intervention resulted in a significant (P < .05) and persistent reduction in mean radiation doses for engaged facilities performing KSCTs.

External validation of the CHOKAI score for the prediction of ureteral stones: A multicenter prospective observational study

OBJECTIVE

The CHOKAI and STONE scores are clinical prediction rules to predict ureteral stones in patients presenting with renal colic. Both systems contribute to reducing diagnostic radiation exposure; however, few studies have compared the two scoring systems. Therefore, we aimed to compare these systems and assess their diagnostic accuracy for ureteral stones.

METHODS

This was a multicenter prospective observational study performed between 2017 and 2018, including patients aged >15 years with renal colic and suspected with ureteral stones. We calculated the CHOKAI and STONE scores of each patient based on their medical interviews and physical and laboratory findings. Primary outcome was differences in the area under the receiver operating characteristic curve in each model, and secondary outcome was diagnostic accuracy at the optimal cut-off point.

RESULTS

Of the 124 patients included, 84 were diagnosed with ureteral stones. The area under the curve of the CHOKAI score was 0.95, showing a sensitivity of 0.93, specificity of 0.90, positive likelihood ratio of 9.3, and negative likelihood ratio of 0.079, at an optimal cut-off point of 6. The area under the curve of the STONE score was 0.88, showing a sensitivity of 0.68, specificity of 0.90, positive likelihood ratio of 6.8, and negative likelihood ratio of 0.36, at an optimal cut-off point of 9. Thus, the area under the curve was significantly higher for the CHOKAI score than for the STONE score (p = 0.0028).

CONCLUSIONS

The CHOKAI score has a diagnostic performance superior to that of the STONE score in this population.

Narcotic Pain Control for Ureterolithiasis Is Associated With Unnecessary Repeat Imaging in the Emergency Department

A subset of patients with ureteral stones who present to the emergency department (ED) will return with recurring symptoms and will receive unnecessary repeat imaging. We retrospectively identified 112 patients from 2012 to 2016 diagnosed with at least one ureteral stone on computerized tomography (CT) at our institution who returned to the ED within 30 days. Patients were stratified based on the presence or absence of repeat CT scan imaging. Mean values were compared with independent t-test and proportions with chi-square analysis. Multivariate logistic regression was performed to determine independent predictors of repeat imaging. Sixty-eight patients (60.7%) underwent repeat CT scan imaging upon representation to the ED within 30 days of being diagnosed with ureterolithiasis. Ureteral stone position changed in 34 patients (30.4%) who underwent repeat imaging. On univariate analysis, younger age, nondiabetics, narcotics prescribed on discharge from first ED visit, and longer mean time between ED visits were associated with repeat CT scan imaging being performed (p < .05). Only prescription of narcotic pain medications was an independent predictor of repeat CT scan imaging (odds ratio: 3.18, 95% confidence interval: 1.22-8.28; p = .018). Nonsteroidal anti-inflammatory drugs or nonnarcotic pain medications, therefore, should primarily be used for pain control in these patients to avoid unnecessary testing.

Image Quality and Patient-Specific Organ Doses in Stone Protocol CT: A Comparison of Traditional CT to Low Dose CT with Iterative Reconstruction

Objective

To compare organ specific radiation dose and image quality in kidney stone patients scanned with standard CT reconstructed with filtered back projection (FBP-CT) to those scanned with low dose CT reconstructed with iterative techniques (IR-CT).

Materials and Methods

Over a one-year study period, adult kidney stone patients were retrospectively netted to capture the use of noncontrasted, stone protocol CT in one of six institutional scanners (four FBP and two IR). To limit potential CT-unit use bias, scans were included only from days when all six scanners were functioning. Organ dose was calculated using volumetric CT dose index and patient effective body diameter through validated conversion equations derived from previous cadaveric, dosimetry studies. Board-certified radiologists, blinded to CT algorithm type, assessed stone characteristics, study noise, and image quality of both techniques.

Results

FBP-CT (n=250) and IR-CT (n=90) groups were similar in regard to gender, race, body mass index (mean BMI = 30.3), and stone burden detected (mean size 5.4 ± 1.2 mm). Mean organ-specific dose (OSD) was 54-62% lower across all organs for IR-CT compared to FBP-CT with particularly reduced doses (up to 4.6-fold) noted in patients with normal BMI range. No differences were noted in radiological assessment of image quality or noise between the cohorts, and intrarater agreement was highly correlated for noise (AC2=0.873) and quality (AC2=0.874) between blinded radiologists.

Conclusions

Image quality and stone burden assessment were maintained between standard FBP and low dose IR groups, but IR-CT decreased mean OSD by 50%. Both urologists and radiologists should advocate for low dose CT, utilizing reconstructive protocols like IR, to reduce radiation exposure in their stone formers who undergo multiple CTs.

Radiation dose reduction for CT assessment of urolithiasis using iterative reconstruction: A prospective intra-individual study

OBJECTIVE

To assess the performance of hybrid (HIR) and model-based iterative reconstruction (MIR) in patients with urolithiasis at reduced-dose computed tomography (CT).

METHODS

Twenty patients scheduled for unenhanced abdominal CT for follow-up of urolithiasis were prospectively included. Routine dose acquisition was followed by three low-dose acquisitions at 40%, 60% and 80% reduced doses. All images were reconstructed with filtered back projection (FBP), HIR and MIR. Urolithiasis detection rates, gall bladder, appendix and rectosigmoid evaluation and overall subjective image quality were evaluated by two observers.

RESULTS

74 stones were present in 17 patients. Half the stones were not detected on FBP at the lowest dose level, but this improved with MIR to a sensitivity of 100%. HIR resulted in a slight decrease in sensitivity at the lowest dose to 72%, but outperformed FBP. Evaluation of other structures with HIR at 40% and with MIR at 60% dose reductions was comparable to FBP at routine dose, but 80% dose reduction resulted in non-evaluable images.

CONCLUSIONS

CT radiation dose for urolithiasis detection can be safely reduced by 40 (HIR)-60 (MIR) % without affecting assessment of urolithiasis, possible extra-urinary tract pathology or overall image quality.

KEY POINTS

• Iterative reconstruction can be used to substantially lower the radiation dose. • This allows for radiation reduction without affecting sensitivity of stone detection. • Possible extra-urinary tract pathology evaluation is feasible at 40-60% reduced dose.

Evaluation of Kidney Stones with Reduced-Radiation Dose CT: Progress from 2011-2012 to 2015-2016-Not There Yet

Purpose To determine if the use of reduced-dose computed tomography (CT) for evaluation of kidney stones increased in 2015-2016 compared with that in 2011-2012, to determine variability in radiation exposure according to facility for this indication, and to establish a current average radiation dose for CT evaluation for kidney stones by querying a national dose registry. Materials and Methods This cross-sectional study was exempt from institutional review board approval. Data were obtained from the American College of Radiology dose registry for CT examinations submitted from July 2015 to June 2016. Study descriptors consistent with single-phase unenhanced CT for evaluation of kidney stones and associated RadLex® Playbook identifiers (RPIDs) were retrospectively identified. Facilities actively submitting data on kidney stone-specific CT examinations were included. Dose metrics including volumetric CT dose index, dose-length product, and size-specific dose estimate, when available, were reported, and a random effects model was run to account for clustering of CT examinations at facilities. A z-ratio was calculated to test for a significant difference between the proportion of reduced-radiation dose CT examinations (defined as those with a dose-length product of 200 mGy · cm or less) performed in 2015-2016 and the proportion performed in 2011-2012. Results Three hundred four study descriptors for kidney stone CT corresponding to data from 328 facilities that submitted 105 334 kidney stone CT examinations were identified. Reduced-dose CT examinations accounted for 8040 of 105 334 (7.6%) CT examinations, a 5.6% increase from the 1010 of 49 903 (2%) examinations in 2011-2012 (P < .001). Mean overall dose-length product was 689 mGy · cm (95% confidence interval: 667, 712), decreased from the mean of 746 mGy · cm observed in 2011-2012. Median facility dose-length product varied up to sevenfold, from less than 200 mGy · cm to greater than 1600 mGy · cm. Conclusion Use of reduced-radiation dose CT for evaluation of kidney stones has increased since 2011-2012, but remains low; variability of radiation dose according to facility continues to be wide. National mean CT radiation exposure for evaluation of renal colic during 2015-2016 decreased relative to 2011-2012 values, but remained well above what is reasonably achievable. ^© RSNA, 2017.

The Diagnosis and Management of Patients with Renal Colic across a Sample of US Hospitals: High CT Utilization Despite Low Rates of Admission and Inpatient Urologic Intervention

Objectives

Symptomatic ureterolithiasis (renal colic) is a common Emergency Department (ED) complaint. Variation in practice surrounding the diagnosis and management of suspected renal colic could have substantial implications for both quality and cost of care as well as patient radiation burden. Previous literature has suggested that CT scanning has increased with no improvements in outcome, owing at least partially to the spontaneous passage of kidney stones in the majority of patients. Concerns about the rising medical radiation burden in the US necessitate scrutiny of current practices and viable alternatives. Our objective was to use data from a diverse sample of US EDs to examine rates of and variation in the use of CT scanning, admission, and inpatient procedures for patients with renal colic and analyze the influence of patient and hospital factors on the diagnostic testing and treatment patterns for patients with suspected renal colic.

Methods

We conducted a retrospective cohort study of adult patients who received a diagnosis of renal colic via a visit to an ED at 444 US hospitals participating in the Premier Healthcare Alliance database from 2009–2011. We modeled use of CT, admission, and inpatient urologic intervention as functions of both patient characteristics and hospital characteristics.

Results

Over the 2-year period, 307,612 patient visits met inclusion criteria. Among these patients, 254,211 (82.6%) had an abdominal CT scan, with 91.5% being non-contrast (“renal protocol”) CT scans. Nineteen percent of visits (58,266) resulted in admission or transfer, and 9.8% of visits (30,239) resulted in a urologic procedure as part of the index visit. On multivariable analysis male patients, Hispanic patients, uninsured patients, and privately insured patients were more likely to have a CT scan performed. Older patients and those covered by Medicare were more likely to be admitted, and once admitted, white patients and privately insured patients were more likely to have a urologic intervention. Only hospital region was associated with variation in CT rates, and this variation was minimal. Region and size of the hospital were associated with admission rates, and hospitals with more practicing urologists had higher intervention rates.

Conclusions

In this dataset, the majority of patients did not require admission or immediate intervention. Despite this, the large majority received CT scans, in a cohort representing 15–20% of all US ED visits. The CT rate was minimally variable at the hospital level, but the admission rates varied 2-fold, suggesting that hospital-level factors affect patient management. The high rate of CT usage coupled with the low rate of immediate intervention suggests that further research is warranted to identify patients who are at low risk for an immediate intervention, and could potentially be managed with ultrasound alone, expectant management, or delayed CT.

Ultra-low-dose, low-dose, and standard-dose CT of the kidney, ureters, and bladder: is there a difference? Results from a systematic review of the literature

AIM

To investigate whether reducing the radiation dose of computed tomography (CT) of the kidney, ureters, and bladder (KUB) for acute renal colic impacts upon the specificity, sensitivity, and detection of urolithiasis.

MATERIALS AND METHODS

A systematic review of the literature over a 20-year period between 1995 and 2015 was conducted of all prospective studies in the English language reporting on adult patients who underwent CT KUB or non-contrast CT for renal colic or urolithiasis. Retrospective studies and those that included pregnant females, children, non-human test subjects, cadaveric use, and simulations were excluded. Data were collected using an Excel spreadsheet and ultra-low-dose (ULD CT) and low-dose CT KUB (LD CT) was defined as a radiation dose ≤1.9 and <3.5 mSv, respectively.

RESULTS

A total of 417 articles were identified, and after screening, seven articles (1,104 patients) were included in the present study with a male:female ratio of 3:2. Of the four studies with ULD CT for both males and females, the prevalence of urolithiasis ranged from 36% and 73%, with additional pathologies found in 12-15%. The effective radiation dose of ULD CT ranged from 0.5-1.9 mSv. Overall, ULD CT and LD CT had a sensitivity of 90-100% and a specificity of 86-100% across all studies.

CONCLUSIONS

ULD CT and LD CT are effective techniques and yield high sensitivity and specificity. Although they yield comparable results against standard-dose CT KUB in detecting alternative diagnoses, they may not be as effective in detecting stones <3 mm in size or in patients with a body mass index of >30 kg/m²; however, this should be the first-line investigation for the majority of renal colic patients in the modern era.

CT Radiation: Key Concepts for Gentle and Wise Use

Use of computed tomography (CT) in medicine comes with the responsibility of its appropriate (wise) and safe (gentle) application to obtain required diagnostic information with the lowest possible dose of radiation. CT provides useful information that may not be available with other imaging modalities in many clinical situations in children and adults. Inappropriate or excessive use of CT should be avoided, especially if required information can be obtained in an accurate and time-efficient manner with other modalities that require a lower radiation dose, or non-radiation-based imaging modalities such as ultrasonography and magnetic resonance imaging. In addition to appropriate use of CT, the radiology community also must monitor scanning practices and protocols. When appropriate, high-contrast regions and lesions should be scanned with reduced dose, but overly zealous dose reduction should be avoided for assessment of low-contrast lesions. Patients' cross-sectional body size should be taken into account to deliver lower radiation dose to smaller patients and children. Wise use of CT scanning with gentle application of radiation dose can help maximize the diagnostic value of CT, as well as address concerns about potential risks of radiation. In this article, key concepts in CT radiation dose are reviewed, including CT dose descriptors; radiation doses from CT procedures; and factors and technologies that affect radiation dose and image quality, including their use in creating dose-saving protocols. Also discussed are the contributions of radiation awareness campaigns such as the Image Gently and Image Wisely campaigns and the American College of Radiology Dose Index Registry initiatives.

Ureteral Stones: Implementation of a Reduced-Dose CT Protocol in Patients in the Emergency Department with Moderate to High Likelihood of Calculi on the Basis of STONE Score

Purpose To determine if a reduced-dose computed tomography (CT) protocol could effectively help to identify patients in the emergency department (ED) with moderate to high likelihood of calculi who would require urologic intervention within 90 days. Materials and Methods The study was approved by the institutional review board and written informed consent with HIPAA authorization was obtained. This was a prospective, single-center study of patients in the ED with moderate to high likelihood of ureteral stone undergoing CT imaging. Objective likelihood of ureteral stone was determined by using the previously derived and validated STONE clinical prediction rule, which includes five elements: sex, timing, origin, nausea, and erythrocytes. All patients with high STONE score (STONE score, 10-13) underwent reduced-dose CT, while those with moderate likelihood of ureteral stone (moderate STONE score, 6-9) underwent reduced-dose CT or standard CT based on clinician discretion. Patients were followed to 90 days after initial imaging for clinical course and for the primary outcome of any intervention. Statistics are primarily descriptive and are reported as percentages, sensitivities, and specificities with 95% confidence intervals. Results There were 264 participants enrolled and 165 reduced-dose CTs performed; of these participants, 108 underwent reduced-dose CT alone with complete follow-up. Overall, 46 of 264 (17.4%) of patients underwent urologic intervention, and 25 of 108 (23.1%) patients who underwent reduced-dose CT underwent a urologic intervention; all were correctly diagnosed on the clinical report of the reduced-dose CT (sensitivity, 100%; 95% confidence interval: 86.7%, 100%). The average dose-length product for all standard-dose CTs was 857 mGy · cm ± 395 compared with 101 mGy · cm ± 39 for all reduced-dose CTs (average dose reduction, 88.2%). There were five interventions for nonurologic causes, three of which were urgent and none of which were missed when reduced-dose CT was performed. Conclusion A CT protocol with over 85% dose reduction can be used in patients with moderate to high likelihood of ureteral stone to safely and effectively identify patients in the ED who will require urologic intervention. (©) RSNA, 2016 Online supplemental material is available for this article.

Low-Dose (10%) Computed Tomography May Be Inferior to Standard-Dose CT in the Evaluation of Acute Renal Colic in the Emergency Room Setting

Introduction: Noncontrast CT is the standard of care to evaluate nephrolithiasis. We evaluated the performance of low-dose CT (LDCT) scan for evaluation of renal colic in the emergency room (ER).

Materials and Methods: Patients visiting the ER with suspected nephrolithiasis received a standard-dose CT (SDCT) and an LDCT. Two urologists read the LDCTs and later they read SDCTs. Stone information was recorded on a diagram of the renal system. Findings on SDCTs and LDCTs were correlated through side-by-side comparison of the diagrams. Later, the two urologists adjudicated all nonconcordance between SDCTs and LDCTs in an unblinded manner.

Results: Twenty-seven patients were included. SDCTs revealed 27 stones in 18 patients. Mean stone size was 3.81 mm. LDCTs revealed 27 stones in 18 patients with a mean stone size of 4.7 mm (p = 0.23). Overall sensitivity and specificity of LDCTs were 70% and 39%, respectively. There were eight false-positive and eight false-negative stones. All the false-positive stones on LDCTs were placed in the ureter, in which all of the corresponding SDCTs were visible calcifications outside the ureter. Of the eight false-negative stones on LDCTs, seven were visible calcifications on the SDCTs and the eighth stone was 1 mm and was not visible.

Conclusion: LDCT may not perform well in the evaluation of suspected nephrolithiasis in the acute setting. LDCT scan accurately demonstrates calcifications; however, accurate placement of calcifications in or out of the urinary tract may be diminished due to impaired resolution of soft tissue structures.

Predictors for urologic intervention and alternate diagnoses in people having computed tomography urography for suspected renal colic

OBJECTIVE

The majority of ureteric calculi pass spontaneously and are uncomplicated, yet use of computed tomography urography (CTU) has increased in recent years. This study describes a cohort of ED patients undergoing CTU for renal colic and assesses the predictors of urologic intervention.

METHODS

A retrospective cohort study enrolled patients who underwent CTU at three Melbourne EDs. Demographic data, clinical assessments, laboratory and radiological findings and interventions were abstracted. Univariate analysis was performed and significant predictors were entered into a multivariate logistic regression model to calculate adjusted odds ratios for associations with urologic intervention.

RESULTS

Six hundred and seventeen patients underwent 626 CTUs; mean age was 48 and 67.7% were male. 58.2% of scans found calculi, of which median size was 4 mm. 9.2% of scans revealed an alternate diagnosis, of which 2.7% were acutely important. 14.6% of patients with calculi received an intervention. Multivariate analysis found the factors associated with intervention were female sex (OR 3.9, 95% CI 1.8-8.7), proximal calculus site (OR 4.1, 95% CI 1.5-11.7), single kidney (OR 9.0, 95% CI 1.7-49.0) and calculus size > 5 mm (OR 7.0, 95% CI 3.3-14.7).

CONCLUSION

Factors associated with urologic intervention included female sex, single kidney, calculus size >5 mm and proximal calculus. Information on acute alternate diagnoses was uncommon. A prospective study is needed to further clarify clinical parameters that could predict intervention to allow targeting of CTU to those most likely to benefit.

STONE PLUS: Evaluation of Emergency Department Patients With Suspected Renal Colic, Using a Clinical Prediction Tool Combined With Point-of-Care Limited Ultrasonography

STUDY OBJECTIVE

We determine whether renal point-of-care limited ultrasonography (PLUS) used in conjunction with the Sex, Timing, Origin, Nausea, Erythrocytes (STONE) clinical prediction score can aid identification of emergency department (ED) patients with uncomplicated ureteral stone or need for urologic intervention.

METHODS

This was a prospective observational study of adult ED patients undergoing computed tomography (CT) scan for suspected ureteral stone. The previously validated STONE score classifies patients into risk categories of low (≈10%), moderate (≈50%), or high (≈90%) for symptomatic stone. Renal PLUS assessed for presence of hydronephrosis before CT scanning. The primary outcomes of symptomatic ureteral stone or acutely important alternative finding were abstracted from CT reports. The secondary outcome, urologic intervention, was assessed by 90-day follow-up interview and record review.

RESULTS

Of 835 enrolled patients, ureteral stone was identified in 53%, whereas 6.5% had an acutely important alternative finding on CT. Renal PLUS modestly increased sensitivity for symptomatic stone among low and moderate STONE score categories. Moderate or greater hydronephrosis improved specificity from 67% (62% to 72%) to 98% (93% to 99%) and 42% (37% to 47%) to 92% (86% to 95%) in low- and moderate-risk patients, with likelihood ratios of 22 (95% CI, 4.2-111) and 4.9 (95% CI, 2.9-8.3), respectively. Test characteristics among high-risk patients were unchanged by renal PLUS. For urologic intervention, any hydronephrosis was 66% sensitive (57% to 74%), whereas moderate or greater hydronephrosis was 86% specific overall (83% to 89%) and 81% (69% to 90%) sensitive and 79% 95% CI, (73-84) specific among patients with the highest likelihood of symptomatic stone.

CONCLUSION

Hydronephrosis on renal PLUS modestly improved risk stratification in low- and moderate-risk STONE score patients. The presence or absence of hydronephrosis among high-risk patients did not significantly alter likelihood of symptomatic stone but may aid in identifying patients more likely to require urologic intervention.

Predictive value of low tube voltage and dual-energy CT for successful shock wave lithotripsy: an in vitro study

This study investigates the capabilities of low tube voltage computed tomography (CT) and dual-energy CT (DECT) for predicting successful shock wave lithotripsy (SWL) of urinary stones in vitro. A total of 33 urinary calculi (six different chemical compositions; mean size 6 ± 3 mm) were scanned using a dual-source CT machine with single- (120 kVp) and dual-energy settings (80/150, 100/150 Sn kVp) resulting in six different datasets. The attenuation (Hounsfield Units) of calculi was measured on single-energy CT images and the dual-energy indices (DEIs) were calculated from DECT acquisitions. Calculi underwent SWL and the number of shock waves for successful disintegration was recorded. The prediction of required shock waves regarding stone attenuation/DEI was calculated using regression analysis (adjusted for stone size and composition) and the correlation between CT attenuation/DEI and the number of shock waves was assessed for all datasets. The median number of shock waves for successful stone disintegration was 72 (interquartile range 30-361). CT attenuation/DEI of stones was a significant, independent predictor (P < 0.01) for the number of required shock waves with the best prediction at 80 kVp (β estimate 0.576) (P < 0.05). Correlation coefficients between attenuation/DEI and the number of required shock waves ranged between ρ = 0.31 and 0.68 showing the best correlation at 80 kVp (P < 0.001). The attenuation of urinary stones at low tube voltage CT is the best predictor for successful stone disintegration, being independent of stone composition and size. DECT shows no added value for predicting the success of SWL.