Can noncontrast helical computed tomography replace intravenous urography for evaluation of patients with acute urinary tract colic?

Hematuria as a Sign of Kidney Stone Disease Evaluated Using Computed Tomography: A Review

Kidney stone is a common cause of acute pain in the abdomen in patients presenting to casualty. Being present in roughly 12% of the world's population makes it the most prevalent pathology of the urinary system. The ureters, kidneys, and bladder frequently develop calculi, resulting in hematuria. The most effective imaging technique for evaluating calculi is unenhanced helical computed tomography. The population, intervention, control, and outcomes (PICO)-formatted question was used to generate methodological medical subject heading (MeSH) phrases, which increased the search strategy's sensitivity in finding research. Some of these names ("hematuria") included "renal calculi" (MeSH) and "cone-beam computed tomography" (MeSH). Studies that satisfied these requirements were subjected to critical evaluation. The merits of the listed studies were evaluated using a unique quality assessment scale. The most accurate imaging diagnostic test for people with hematuria is multidetector computed tomography. If a patient over 40 presents with microscopic hematuria, a non-contrast computed tomography or ultrasound study should be performed, and if gross hematuria is observed, cystoscopy should be added. Pre- and post-contrast computed tomography scans and cystoscopy should be carried out on elderly patients.

Essentials of Computed Tomography Imaging of Hematuria

Hematuria is defined usually as the presence of blood in the urine, either on voiding or in a catheterized specimen. Hematuria is broadly divided into microscopic and gross hematuria and may be symptomatic or asymptomatic. The causes of hematuria include a very wide spectrum of conditions. However, here, we have filtered the causes causing gross hematuria, including calculus, trauma, tumors, vascular, and miscellaneous causes. Plain X-rays of the kidney, ureter, and bladder; ultrasound; intravenous urography; computed tomography (CT); magnetic resonance imaging; retrograde ureterography and pyelography (RGP); cystoscopy; and ureteroscopy are techniques that are useful for diagnosis. In the past, one or a combination of several techniques was used to evaluate hematuria but recently, advances in CT urography mean that it can be used alone for this task. This article briefly reviews the common causes of gross hematuria in adults and their evaluation by CT-based urography. Gross hematuria is evaluated well with CT scan urography which includes an unenhanced scan, the nephrographic phase, and the excretory phase. Unenhanced scans are routinely performed to evaluate the basic parameters such as the size, shape, position, and outline of the kidneys and calculus disease, which is the most common cause of hematuria. Renal parenchymal diseases including masses are best visualized in the nephrographic phase along with other abdominal organs. Delayed excretory phases including the kidneys, ureters, and bladder are useful for detecting urothelial diseases. CT urography's protocol permits evaluations of hematuria through a single examination.

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.

Development of a computational tool for estimating computed tomography dose parameters

BACKGROUND

Computed Tomographic (CT) imaging procedures have been reported as the main source of radiation in diagnostic procedures compared to other modalities. To provide the optimal quality of CT images at the minimum radiation risk to the patient, periodic inspections and calibration tests for CT equipment are required. These tests involve a series of measurements that are time consuming and may require specific skills and highly-trained personnel.

OBJECTIVE

This study aims to develop a new computational tool to estimate the dose of CT radiation outputs and assist in the calibration of CT scanners. It may also provide an educational resource by which radiological practitioners can learn the influence of technique factors on both patient radiation dose and the produced image quality.

METHODS

The computational tool was developed using MATLAB in order to estimate the CT radiation dose parameters for different technique factors. The CT radiation dose parameters were estimated from the calibrated energy spectrum of the x-ray tube for a CT scanner.

RESULTS

The estimated dose parameters and the measured values utilising an Adult CT Head Dose Phantom showed linear correlations for different tube voltages (80 kVp, 100 kVp, 120 kVp, and 140 kVp), with R2 nearly equal to 1 (0.99). The maximum differences between the estimated and measured CTDIvol were under 5 %. For 80 kVp and low tube currents (50 mA, 100 mA), the maximum differences were under 10%.

CONCLUSIONS

The prototyped computational model provides a tool for the simulation of a machine-specific spectrum and CT dose parameters using a single dose measurement.

Sensitivity of Noncontrast Computed Tomography for Small Renal Calculi With Endoscopy as the Gold Standard

OBJECTIVE

To compare the sensitivity of noncontrast computed tomography (CT) with endoscopy for detection of renal calculi. Imaging modalities for detection of nephrolithiasis have centered on abdominal x-ray, ultrasound, and noncontrast CT. Sensitivities of 58%-62% (abdominal x-ray), 45% (ultrasound), and 95%-100% (CT) have been previously reported. However, these results have never been correlated with endoscopic findings.

METHODS

Idiopathic calcium oxalate stone formers with symptomatic calculi requiring ureteroscopy were studied. At the time of surgery, the number and the location of all calculi within the kidney were recorded followed by basket retrieval. Each calculus was measured and sent for micro-CT and infrared spectrophotometry. All CT scans were reviewed by the same genitourinary radiologist who was blinded to the endoscopic findings. The radiologist reported on the number, location, and size of each calculus.

RESULTS

Eighteen renal units were studied in 11 patients. Average time from CT scan to ureteroscopy was 28.6 days. The mean number of calculi identified per kidney was 9.2 ± 6.1 for endoscopy and 5.9 ± 4.1 for CT (P <.004). The mean size of total renal calculi (sum of the longest stone diameters) per kidney was 22.4 ± 17.1 mm and 18.2 ± 13.2 mm for endoscopy and CT, respectively (P = .06).

CONCLUSION

CT scan underreports the number of renal calculi, probably missing some small stones and being unable to distinguish those lying in close proximity to one another. However, the total stone burden seen by CT is, on average, accurate when compared with that found on endoscopic examination.

Ultrasound vs. Computed Tomography for Severity of Hydronephrosis and Its Importance in Renal Colic

Introduction

Supporting an “ultrasound-first” approach to evaluating renal colic in the emergency department (ED) remains important for improving patient care and decreasing healthcare costs. Our primary objective was to compare emergency physician (EP) ultrasound to computed tomography (CT) detection of hydronephrosis severity in patients with suspected renal colic. We calculated test characteristics of hydronephrosis on EP-performed ultrasound for detecting ureteral stones or ureteral stone size >5mm. We then analyzed the association of hydronephrosis on EP-performed ultrasound, stone size >5mm, and proximal stone location with 30-day events.

Methods

This was a prospective observational study of ED patients with suspected renal colic undergoing CT. Subjects had an EP-performed ultrasound evaluating for the severity of hydronephrosis. A chart review and follow-up phone call was performed.

Results

We enrolled 302 subjects who had an EP-performed ultrasound. CT and EP ultrasound results were comparable in detecting severity of hydronephrosis (x²=51.7, p<0.001). Hydronephrosis on EP-performed ultrasound was predictive of a ureteral stone on CT (PPV 88%; LR+ 2.91), but lack of hydronephrosis did not rule it out (NPV 65%). Lack of hydronephrosis on EP-performed ultrasound makes larger stone size >5mm less likely (NPV 89%; LR− 0.39). Larger stone size > 5mm was associated with 30-day events (OR 2.30, p=0.03).

Conclusion

Using an ultrasound-first approach to detect hydronephrosis may help physicians identify patients with renal colic. The lack of hydronephrosis on ultrasound makes the presence of a larger ureteral stone less likely. Stone size >5mm may be a useful predictor of 30-day events.

Answers to Common Questions About the Use and Safety of CT Scans

Articles in the scientific literature and lay press over the past several years have implied that computed tomography (CT) may cause cancer and that physicians and patients must exercise caution in its use. Although there is broad agreement on the latter point--unnecessary medical tests of any type should always be avoided--there is considerable controversy surrounding the question of whether, or to what extent, CT scans can lead to future cancers. Although the doses used in CT are higher than those used in conventional radiographic examinations, they are still 10 to 100 times lower than the dose levels that have been reported to increase the risk of cancer. Despite the fact that at the low doses associated with a CT scan the risk either is too low to be convincingly demonstrated or does not exist, the magnitude of the concern among patients and some medical professionals that CT scans increase cancer risk remains unreasonably high. In this article, common questions about CT scanning and radiation are answered to provide physicians with accurate information on which to base their medical decisions and respond to patient questions.

The utility of renal ultrasonography in the diagnosis of renal colic in emergency department patients

Objective:

Computed tomography (CT) is an imaging modality used to detect renal stones. However, there is concern about the lifetime cumulative radiation exposure attributed to CT. Ultrasonography (US) has been used to diagnose urolithiasis, thereby avoiding radiation exposure. The objective of this study was to determine the ability of US to identify renal colic patients with a low risk of requiring urologic intervention within 90 days of their initial emergency department (ED) visit.

Methods:

We completed a retrospective medical record review for all adult patients who underwent ED-ordered renal US for suspected urolithiasis over a 1-year period. Independent, double data extraction was performed for all imaging reports and US results were categorized as “normal,” “suggestive of ureterolithiasis,” “ureteric stone seen” or “disease unrelated to urolithiasis.” Charts were reviewed to determine how many patients underwent subsequent CT and urologic intervention.

Results:

Of the 817 renal US procedures ordered for suspected urolithiasis during the study period, the results of 352 (43.2%) were classified as normal, and only 2 (0.6%) of these patients required urologic intervention. The results of 177 (21.7%) renal US procedures were suggestive of ureterolithiasis. Of these, 12 (6.8%) patients required urologic intervention. Of the 241 (29.5%) patients who had a ureteric stone seen on US, 15 (6.2%) required urologic intervention. The rate of urologic intervention was significantly lower in those with normal results on US (p &lt; 0.001) than in those with abnormal results on US.

Conclusion:

A normal result on renal US predicts a low likelihood for urologic intervention within 90 days for adult ED patients with suspected urolithiasis.

The comparison of ultrasound and non-contrast helical computerized tomography for children nephrolithiasis detection

AIMS

Nephrolithiasis is less common in children than adults, but its diagnosis and management in children may be more perplexing. In this article, we compare two imaging ultrasound (US) and non-contrast helical computerized tomography (CT) for diagnosis of nephrolithiasis.

SUBJECTS AND METHODS

A total of 20 children who diagnosed as nephrolithiasis by US were imaged simultaneously by non-contrast helical CT. Their history like as family history in first and second degree relatives and urine analysis for hematuria and urine randomly calcium to creatinine ratio was obtained. All data analyzed by χ(2) and Mann-Whitney U-test in SPSS 16 and P < 0.05 was considered to be significant.

RESULTS

Out of 20 cases, only 5 cases diagnosed as nephrlithiasis by US were confirmed by CT method 2 out of 20 cases had another extrarenal origin for their complaint who diagnosed wrongly as nephrolithiasis by US. Stone size based of US that was confirmed by CT method was larger 4.6 ± 1.5 (minimum 3 max 6 mm) than non-confirmed ones 2.3 ± 0.7 mm (P 0.002). Hematuria occurred more in correct diagnosed compared with misdiagnosed (P 0.005). Positive family history and urine calcium ratio was not differed between two groups.

CONCLUSIONS

Non contrast helical CT is essential to confirm of nephrolithiasis and other extrarenal origin of complaints, which diagnosed wrongly as nephrolithiasis in children. Stone size and presence of hematuria are two major factors for right diagnosis of nephrolithiasis as US method but Urine calcium excretion ratio or positive family history cannot be predictive as this study.

Haematuria: an imaging guide

This paper discusses the current status of imaging in the investigation of patients with haematuria. The physician must rationalize imaging so that serious causes such as malignancy are promptly diagnosed while at the same time not exposing patients to unnecessary investigations. There is currently no universal agreement about the optimal imaging work up of haematuria. The choice of modality to image the urinary tract will depend on individual patient factors such as age, the presence of risk factors for malignancy, renal function, a history of calculus disease and pregnancy, and other factors, such as local policy and practice, cost effectiveness and availability of resources. The role of all modalities, including conventional radiography, intravenous urography/excretory urography, ultrasonography, retrograde pyelography, multidetector computed tomography urography (MDCTU), and magnetic resonance urography, is discussed. This paper highlights the pivotal role of MDCTU in the imaging of the patient with haematuria and discusses issues specific to this modality including protocol design, imaging of the urothelium, and radiation dose. Examination protocols should be tailored to the patient while all the while optimizing radiation dose.

Applications of dual-energy CT in urologic imaging: an update

This article discusses modern dual-energy computed tomography (DECT) and the unique material-specific information these scanners can provide. A description of the technical aspects of the various DECT techniques is provided. Specific clinical applications in urologic imaging, including chemical composition of urolithiasis, evaluation of renal masses, detection of urothelial neoplasms, and adrenal adenoma imaging, are discussed. The unique postprocessed image sets, including virtual noncontrast, iodine overlay, and stone composition, are described.

Computed tomography versus ureteroscopy in identification of renal tract stone with ureteral stent in situ

INTRODUCTION

The aim of this study was to validate the use of non-contrast computed tomography (CT) with a ureteral stent in situ instead of ureteroscopy for identification of renal tract stones.

METHODS

All patients who had stents inserted for renal tract stones and underwent non-contrast CT with the stent in situ followed by ureteroscopy between May 2008 and October 2009 at The Canberra hospital, Australia, were analysed retrospectively. Statistical analysis was performed to compare any differences between CT and ureteroscopy in the identification of stones.

RESULTS

Overall, 57 patients were included in the study. The difference between CT and ureteroscopy findings was statistically significant. CT identification of stones with a stent in situ had a sensitivity of 86%, a specificity of 46%, a positive predictive value of 63%, a negative predictive value of 76% and an accuracy of 67%.

CONCLUSIONS

Our study suggests that non-contrast CT is inferior to the 'gold standard' of ureteroscopy. It lacks sensitivity, specificity, positive predictive value, negative predictive value and accuracy. Therefore, we cannot recommend using non-contrast CT to replace ureteroscopy.

Genitourinary applications of dual-energy CT

OBJECTIVE

Recent advances in CT technology provide improved diagnostic characterization of materials using dual-energy CT methods. Application of these methods improves lesion conspicuity and detection. In addition, improved material characterization and creation of virtual unenhanced techniques potentially result in decreased radiation dose. We will review the role of dual-energy CT as applied to the genitourinary system.

CONCLUSION

Dual-energy CT is beginning to play an important role in patients with genitourinary diseases by providing unique characterization tools for calculi and masses.

Thick curved planar reformation of unenhanced multislice computed tomography demonstrating urolithiasis

OBJECTIVES

To determine what slice thickness provides optimal curved planar reformation (CPR) images of the urinary tract.

METHODS

A total of 75 consecutive patients with acute flank pain were included in a retrospective pilot study and underwent unenhanced multislice computed tomography (MSCT) (collimation 3.75 mm, pitch 6, reconstruction increment 3 mm, working voltage 120 kV, and tube current 100 mA) with CPR reconstruction of the urinary tract. CPRs with differing slice thicknesses of 3-20 mm at 1-mm increments to reformat each ureter were assessed in each patient separately. Two radiologists and a urologist evaluated the quality of the reformatted images by judging each ureter in terms of the delineation of all its parts using a 5-point scale (insufficient, poor, moderate, good, and excellent).

RESULTS

Of the 75 patients in our cohort, 52 (69%) had urolithiasis. CPR images could be made of all ureters in all patients. Good to excellent image quality was found in the CPRs performed with a slice thickness of 8-12 mm: 27.7% at 8 mm, 14.3% at 9 mm, 26.9% at 10 mm, 12.6% at 11 mm, and 18.5% at 12 mm. Thus, a slice thickness of 8-12 mm determined a cumulative likelihood of 96.7% to demonstrate the ureter totally.

CONCLUSIONS

The results of our study have shown that CPR is a feasible and quick useful tool. CPRs of the urinary tract with a slice thickness of 8-12 mm are best for good delineation of the whole ureter.

Predictive role of renal resistance indices in the extracorporeal shock-wave lithotripsy outcome of ureteral stones

OBJECTIVE

Doppler ultrasonography (US) can be used to measure renal blood flow and calculate resistance indices. Increased renal resistance indices have been suggested to be associated with upper urinary tract obstruction and may help clinical physicians to differentiate physiological hydronephrosis from urinary tract obstruction. The aims of this study were to investigate the value of renal resistance indices before extracorporeal shock-wave lithotripsy (ESWL) and to determine whether they were predictive of the ESWL outcome.

MATERIAL AND METHODS

Between May 2005 and May 2006, a total of 84 patients who suffered from ureteral stones with renal colic and were treated with ESWL in the emergency department were enrolled in this study. Blood urea nitrogen and serum creatinine were determined and urinalysis, abdominal plain film X-ray and color Doppler US were performed. The resistive index (RI) and pulsatility index (PI) of the three different measurements of renal upper, middle and lower poles were calculated for both the affected and contralateral kidneys.

RESULTS

Sixty of the 84 patients were found to be stone-free after follow-up, and the total stone-free rate was 71%. There was a statistically significant difference between the mean RI of the affected and contralateral kidneys in all patients: 0.672+/-0.046 vs 0.616+/-0.054 (p<0.001). Moreover, there were statistically significant differences between the stone-free group and the residual stone group regarding the RI (0.651+/-0.046 vs 0.723+/-0.029, respectively; p=0.003) and PI (1.143+/-0.162 vs 1.262+/-0.145, respectively; p=0.03) of the affected kidney.

CONCLUSIONS

Intrarenal resistance indices represent the integration of arterial compliance, pulsatility, and peripheral resistance. Higher pre-ESWL resistance indices correlate with lower ESWL treatment success rates. Doppler US performed before ESWL treatment can therefore aid in making a correct clinical decision.

Radiology of urolithiasis: implications of radiation exposure and new imaging modalities

Computed tomography (CT) scanning is now the standard imaging technique for detecting and characterizing urolithiasis. However, the potential effects of the radiation exposure from CT examinations have raised concern among some physicians. This article describes the radiation doses for various urolithiasis-imaging techniques and describes techniques to optimize and reduce radiation exposures to patients undergoing these examinations. Potential future directions in radiologic techniques used for studying urolithiasis are also discussed.

Radiation exposure in the acute and short-term management of urolithiasis at 2 academic centers

PURPOSE

Diagnostic imaging has a central role in the evaluation and management of urolithiasis. A variety of modalities are available, each with benefits and limitations. Without careful consideration of imaging modalities in quantity and type patients may receive excessive doses of radiation during initial diagnostic and followup evaluations. Therefore, we determined the effective radiation dose associated with an acute stone episode and short-term followup.

MATERIALS AND METHODS

A multicenter retrospective study of all patients who presented with an acute stone episode was performed. The analysis included all imaging studies related to stone disease performed within 1 year of the acute event. Using accepted effective radiation dose standards for each of these examinations, the total radiation dose administered was calculated and compared by patient characteristics including stone location, stone number and intervention strategy. The primary outcome assessed was a total radiation dose greater than 50 mSv, the recommended yearly dose limit for occupational exposure by the International Commission on Radiological Protection.

RESULTS

We identified 108 patients who presented to our respective institutions with a primary acute stone episode between 2000 and 2006. The mean age in our cohort was 48.6 years and 50% of the patients were men. Patients underwent an average of 4 radiographic examinations during the 1-year period. Studies performed included a mean of 1.2 plain abdominal films of the kidneys, ureters and bladder (range 0 to 7), 1.7 abdominopelvic computerized tomograms (range 0 to 6) and 1 excretory urogram (range 0 to 3) during the first year of followup. The median total effective radiation dose per patient was 29.7 mSv (IQR 24.2, 45.1). There were 22 (20%) patients who received greater than 50 mSv. Analysis of stone location, number of stones, stone composition, patient age, sex and surgical intervention indicated no statistically significant difference in the probability of receiving a total radiation dose greater than 50 mSv.

CONCLUSIONS

A fifth of patients receive potentially significant radiation doses in the short-term followup of an acute stone event. Radiographic imaging remains an integral part of the diagnosis and management of symptomatic urolithiasis. While debate exists regarding the threshold level for radiation induced fatal malignancies, urologists must be cognizant of the radiation exposure to patients, and seek alternative imaging strategies to minimize radiation dose during acute and long-term stone management.

Evaluation of patients with suspected ureteral calculi using sonography as an initial diagnostic tool: how can we improve diagnostic accuracy?

OBJECTIVE

The purpose of this study was to evaluate the usefulness of sonography as an initial diagnostic tool in patients with suspected ureterolithiasis.

METHODS

We performed a prospective study of 318 patients with suspected ureteral stones over a 14-month period. All patients underwent sonography after fasting for 8 hours and bladder filling. If no cause of the flank pain was found by sonography, computed tomography or intravenous urography was performed immediately to confirm the absence of ureteral stones.

RESULTS

We found urolithiasis with sonography in 291 of 296 patients with confirmed urolithiasis. The 5 remaining cases were identified after non-contrast-enhanced computed tomography (n = 3), intravenous urography (n = 1), or the passage of a stone (n = 1, pregnant patient). We detected 313 calculi in the 291 patients with sonography as follows: 307 ureteral calculi in 285 patients, 5 urinary bladder calculi that were probably passed from the ureter in 5 patients, and 1 urethral calculus. The locations of the 313 calculi in the 291 patients with a sonographic diagnosis were as follows: 21 were in the ureteropelvic junction, 96 in the proximal half of the ureter, 69 in the distal half of the ureter, 121 in the ureterovesical junction, 5 in the urinary bladder, and 1 in the urethra. Hydronephrosis was seen in 200 of the 291 patients with calculi identified by sonography (68.7%). Twinkling artifacts helped confirm the presence of tiny calculi in 184 of the 214 calculi (86%).

CONCLUSIONS

Sonography can be used as an initial diagnostic tool in patients with suspected ureterolithiasis.

Imaging of hematuria

Hematuria may have a number of causes, of which the more common are urinary tract calculi, urinary tract infection, urinary tract neoplasms (including renal cell carcinoma and urothelial tumors), trauma to the urinary tract, and renal parenchymal disease. This article discusses the current status of imaging of patients suspected of having urologic causes of hematuria. The role of all modalities, including plain radiography, intravenous urography or excretory urography, retrograde pyelography, ultrasonography, and multidetector computed tomography (MDCT) in evaluation of these patients is discussed. The article highlights the current status of MDCT urography in imaging of patients with hematuria, and discusses various-often controversial-issues, such as optimal protocol design, accuracy of the technique in imaging of the urothelium, and the significant issue of radiation dose associated with MDCT urography.

Value of automated coronal reformations from 64-section multidetector row computerized tomography in the diagnosis of urinary stone disease

PURPOSE

We determined the value of automated coronal reformation using 64-detector computerized tomography for the detection of urinary stones.

MATERIALS AND METHODS

A total of 72 patients underwent unenhanced 64-detector computerized tomography to diagnose urinary stones. Two radiologists independently reviewed coronal reformations and axial images at separate reading sessions. The stone detection rate, reader confidence and interpretation time per radiologist were recorded. Two radiologists reviewed coronal and axial images in consensus and served as the reference standard.

RESULTS

A total of 175 stones were diagnosed by consensus. Using coronal reformations 162 stones (92.6%) were detected by reader 1 and 157 (89.7%) were detected by reader 2. Using axial images 157 stones (90.3%) were detected by reader 1 and 155 (88.6%) were detected by reader 2. The reading time of coronal reformations was significantly shorter than that of axial images for each reader (p <0.01). Using coronal imaging to complement axial imaging 12 additional stones were detected and 23 were diagnosed with increased confidence by reader 1, while an additional 15 were detected and 8 were diagnosed with increased confidence by reader 2. The mean size of stones detected with coronal reformations alone was significantly smaller than that of the total stones. Excellent interobserver agreement was noted for coronal reformations and axial images (kappa coefficient: 0.91 and 0.904, respectively).

CONCLUSIONS

Review of automated coronal reformations allows equally accurate and more rapid detection of urinary stones compared with axial images alone. In addition, coronal reformation of 64-detector computerized tomography adds value when used in conjunction with axial data sets.

Acute Flank Pain Secondary to Urolithiasis: Radiologic Evaluation and Alternate Diagnoses

This article discusses the radiologic management of the patient who has acute flank pain. It describes the evolution of radiologic imaging in patients who present with acute symptoms caused by suspected urolithiasis, the advantages of unenhanced helical CT and the limitations of abdominal radiography, intravenous urography, and ultrasonography in this setting, and the alternative diagnoses encountered within the urinary tract, abdomen, and pelvis.

Imaging for percutaneous renal access and management of renal calculi

Percutaneous renal stone surgery requires detailed imaging to define stone burden and delineate the anatomy of the kidney and nearby organs. It is also essential to carry out safe percutaneous access and to assess postoperative outcomes. The emergence of CT as the imaging modality of choice for detecting renal calculi and the ability of CT urography with or without three-dimensional reconstruction to delineate the collecting system makes this the most versatile and sensitive imaging modality for pre- and postoperative evaluation. At present, intravenous urogram continues to play an important role in the evaluation of patients considered for percutaneous nephrostolithotomy. Fluoroscopy re-mains the mainstay of intraoperative imaging, although ultrasound is a useful alternative. Selection and application of appropriate imaging modalities for patients undergoing per-cutaneous nephrostolithotomy enhances the safety and success of the procedure.

Is fluid ingestion really necessary during ultrasonography for detecting ureteral stones? A prospective randomized study

OBJECTIVE

Ultrasonographic evaluation of ureteral stones is usually performed after fluid ingestion for filling the bladder to visualize the ureterovesical junction better. We hypothesized that water ingestion may decrease the imaging quality of ultrasonography for detecting ureter stones. In our prospective randomized study, the accuracy of ultrasonography for detecting ureteral stones performed with or without fluid intake were evaluated.

METHODS

The study population comprised 150 consecutive patients thought to have ureteral stones who underwent ultrasonography. Patients were divided into 2 groups. Group A patients ingested 500 mL of water to distend the bladder before ultrasonographic examination. Group B patients were restricted from drinking any water at least 4 hours before the procedure.

RESULTS

Ultrasonography showed 35 (67.30%) of 52 stones in group A and 68 (93.15%) of 73 stones in group B. The difference of detection rates between the 2 groups was statistically significant (P < .001). The greatest improvement in detection rates was noted in the middle ureter stones. The evaluated sensitivity and specificity rates for group A were 67% and 82%, respectively, and those for group B were 93% and 94%. When the 2 methods were compared, total accuracy of ultrasonography increased from 71% in group A to 93% in group B.

CONCLUSIONS

This prospective randomized study showed that the diagnostic accuracy of ultrasonography for detection of middle ureteral stones increased significantly when performed without any water ingestion before the procedure. We recommend that patients thought to have ureteral stones should be first examined without any fluid ingestion.

Quantitation of stone burden: imaging advances

The accurate diagnosis and quantitation of nephrolithiasis in patients with primary hyperoxaluria (PH) often directly impacts the medical and surgical management for individuals with both symptomatic and asymptomatic calculi. Traditionally, depiction of the size, location and appearance of urinary calculi has been provided by kidney, ureter and bladder plain film radiographs with or without tomography. Given advances in imaging technology there is a shift from conventional radiographs to cross-sectional imaging technology, namely unenhanced computed tomography (CT), CT urography, ultrasound and magnetic resonance imaging. These diagnostic techniques provide differing advantages and disadvantages for imaging stone disease. This review outlines imaging advances in the accurate diagnosis and quantitation of patients with metabolically active stone disease such as PH.

Low-dose and standard-dose unenhanced helical computed tomography for the assessment of acute renal colic: prospective comparative study

PURPOSE

To compare the efficacy of low-dose and standard-dose computed tomography (CT) for the diagnosis of ureteral stones.

MATERIAL AND METHODS

Unenhanced helical CT was performed with both a standard dose (260 mAs, pitch 1.5) and a low dose (50 mAs, pitch 1.5) in 121 patients suspected of having acute renal colic. The two studies were prospectively and independently interpreted for the presence and location of ureteral stones, abnormalities unrelated to stone disease, identification of secondary signs, i.e. hydronephrosis and perinephric stranding, and tissue rim sign. The standard-dose CT images were interpreted by one reviewer and the low-dose CT images independently by two reviewers unaware of the standard-dose CT findings. The findings of the standard and low-dose CT scans were compared with the exact McNemar test. Interobserver agreements were assessed with kappa analysis. The effective radiation doses resulting from two different protocols were calculated by means of commercially available software to which the Monte-Carlo phantom model was given.

RESULTS

The sensitivity, specificity, and accuracy of standard-dose CT for detecting ureteral stones were 99%, 93%, and 98%, respectively, whereas for the two reviewers the sensitivity of low-dose CT was 93% and 95%, specificity 86%, and accuracy 92% and 94%. We found no significant differences between standard-dose and low-dose CT in the sensitivity and specificity for diagnosing ureter stones (P >0.05 for both). However, the sensitivity of low-dose CT for detection of 19 stones less than or equal to 2 mm in diameter was 79% and 68%, respectively, for the two reviewers. Low-dose CT was comparable to standard-dose CT in visualizing hydronephrosis and the tissue rim sign. Perinephric stranding was far less clear on low-dose CT. Low-dose CT had the same diagnostic performance as standard-dose CT in diagnosing alternative diseases. Interobserver agreement between the two low-dose CT reviewers in the diagnosis of ureter stones and alternative diseases, the identification of secondary signs, and tissue rim sign were high, with kappa values ranging from 0.769 to 0.968. On standard-dose CT scans, the calculated mean effective radiation dose was 7.30 mSv for males and 10.00 mSv for females. On low-dose CT scans, the calculated mean effective radiation dose was 1.40 mSv for males and 1.97 mSv for females.

CONCLUSION

Compared with standard scans using 260 mAs, low-dose unenhanced helical CT using a reduced tube current of 50 mAs results in a concomitant decrease in the radiation dose of 81%. Although low-dose CT was limited in its ability to depict small-sized calculi less than or equal to 2 mm, it is still comparable to standard-dose CT for the diagnosis of ureter stones and alternative disease.

Investigation of acute flank pain: how do practices of U.K.and Irish urologists compare with those of transatlantic and continental European colleagues?

BACKGROUND AND PURPOSE

Noncontrast-enhanced spiral CT (NESCT) is more accurate and reliable than intravenous urography (IVU) in diagnosing the cause of acute flank pain. This study aimed to determine the impact of current literature on the choice of imaging modality used to investigate acute flank pain within the UK and the Republic of Ireland.

MATERIALS AND METHODS

A questionnaire regarding the preferred investigation for acute flank pain was sent to all consultant urologists registered as British Association of Urological Surgeons members.

RESULTS

Of the 548 consultants from 210 institutions surveyed, 293 (54%) from 171 (81.4%) institutions returned their questionnaires. Intravenous urography is used in the majority of institutions (146; 85.4%) for investigating acute flank pain. Only 18 (10.5%) use NESCT, while 4.1% use ultrasonography. Among those using IVU as the investigation of choice, the main reason given was limited CT services (82.4%). Others included familiarity with IVU features (51.2%), limited availability of radiologists for out-of-hours reporting of CT (26%), more rapid procedure (20.8%), lower cost (20%), and lower radiation exposure (19.6%). Only 52.4% of consultants using IVU would prefer NESCT if both were equally available.

CONCLUSIONS

Urography remains the commonest modality for the investigation of acute flank pain in the UK and Ireland primarily because of limited CT services and greater familiarity with the images. Given the opportunity, only half of consultant urologists would select NESCT in preference to IVU, suggesting that improving the availability of CT services alone may not lead to practice paralleling that of our transatlantic and continental European colleagues.

[New techniques in computed tomography. Significance for urology]

Computed tomographic (CT) imaging has become the modality of choice for the assessment of patients with urological malignancies. Recently, multi-slice CT imaging was introduced, providing faster acquisition times and higher resolution leading to improved image quality. Several studies show that thin-slice, high-resolution acquisition strategies lead to an improved accuracy for T-staging, especially of renal cell carcinomas. Three-dimensional post-processing techniques for the visualization of the vascular supply as well as the ureter (CT-angiography and CT-urography) are helpful for surgical planning. Compared to conventional imaging strategies unenhanced CT images render higher sensitivities and specificities for detecting stone disease in patients with acute flank pain. In the USA unenhanced CT imaging has almost replaced conventional urography, as no contrast agent is administered and the examination time is shorter. PET/CT examinations provide information on the morphology and function of tumors in one examination. However, there are only few data available for the assessment of urologic tumors.

Impact of CT scan in patients with first episode of suspected nephrolithiasis

This prospective observational outcome study assessed the impact of helical computed tomography (CT) scan in patients with a first episode of suspected nephrolithiasis. Before CT scanning, Emergency Physicians completed a questionnaire, including diagnostic certainty of nephrolithiasis and anticipated patient disposition. Primary outcome measure was the comparison of physician diagnostic certainty and CT scan results. Secondary outcome measures included alternate diagnoses and changes in patient disposition after CT scan. Four categories grouped the pre-CT diagnostic certainty: 0-49%, 50-74%, 75-90%, and 90-100%. The CT scan found urinary calculi in 28.6%, 45.7%, 74.2%, and 80.5% of patients in each category, respectively. CT scanning revealed alternate diagnoses in 40 cases (33.1%). Of these, 19 (47.5%) included other significant pathology. Before CT scanning, physicians planned to discharge 115 patients and admit six patients. After CT scanning, six of the former group were admitted, and five of the latter group were discharged. Patients presenting with a first episode of clinically suspected nephrolithiasis should undergo CT scanning because it enhances diagnostic certainty by identifying alternate diagnoses not suspected on clinical grounds alone.

Renal ultrasound

Renal US is one of several imaging modalities available to the EP in the evaluation of patients with acute urologic disorders. It offers excellent anatomic detail without exposure to radiation or contrast agents but is limited in its assessment of renal function. It is an important alternative to helical CT scanning for evaluating renal colic, especially in children and pregnant women. It has an important role in excluding bilateral renal obstruction as the cause of acute renal failure. It is likely that Doppler renal US also will take on a prominent role in the evaluation of renal vascular disorders. It already has become the standard of care in the management of renal transplant patients. Bedside emergency renal US performed and interpreted by EPs with limited training and experience is increasing in use and gaining acceptance. At present, the primary role of renal US is to identify hydronephrosis in patients with renal colic or acute renal failure but, in the future, its role likely will expand as technology advances and its use increases. In many patients, bedside renal US may obviate the need for further diagnostic workup and speed the diagnosis and treatment of an emergency patient.

Diagnostic value of attenuation measurements of the kidney on unenhanced helical CT of obstructive ureterolithiasis

OBJECTIVE

The objective of this study was to assess the diagnostic value of attenuation measurements of the kidney on unenhanced helical CT in patients with obstructive ureterolithiasis.

MATERIALS AND METHODS

Consecutive unenhanced helical CT scans of patients referred for acute unilateral renal colic were retrospectively reviewed. Patients with CT evidence of other urinary system diseases were excluded. Included scans (n = 145) were assessed for ureteral stone and secondary signs of obstruction such as unilateral collecting system or ureteral dilatation, perinephric stranding, and periureteral edema. Renal attenuation in Hounsfield units was measured in the upper, middle, and lower portions of the parenchyma, and a mean value was determined for each kidney.

RESULTS

Ureteral stones were present in 76 patients. Renal attenuation on the side with lithiasis was lower than on the opposite kidney: 27.2 +/- 3.9 H vs 32.6 +/- 3.4 H (p < 0.001). Attenuation differences between kidneys were higher for patients with ureterolithiasis: 5.4 +/- 3.2 H (range, -3.3 to 13.0 H) versus 1.2 +/- 1.0 H (range, 0-4.7 H) (p < 0.001). An attenuation difference between kidneys greater than or equal to 5.0 H had 61% sensitivity, 100% specificity, 100% positive predictive value, 69% negative predictive value, and 79% accuracy for diagnosis of ureteral lithiasis.

CONCLUSION

Attenuation difference between kidneys greater than or equal to 5.0 H was a valuable sign and had diagnostic performance similar to other secondary signs of obstructive ureterolithiasis. Furthermore, attenuation difference had the advantage of being an objective, measurement-based indicator.

The presence of microscopic hematuria detected by urine dipstick test in the evaluation of patients with renal colic

Urolithiasis is a common diagnosis in patients presenting at our hospital with flank pain. One of the most important steps in the diagnostic algorithm of renal colic is the presence of hematuria, but this fact has been challenged by authors reporting a negative urinalysis for microscopic hematuria in about 9-18% of such patients. Our aim was to investigate whether the same results are obtained when a sample of urine is tested with a urine dipstick test (UDT) at the time of the initial examination. Data from patients with the clinical diagnosis of renal colic examined at the emergency department of our hospital were reviewed, and the sensitivity of hematuria in urine samples tested by UDT was recorded in a group consisting of patients for whom imaging showed evidence of a stone >3 mm in size. In cases in which UDT was negative, or showed only traces of red blood cells (RBCs), a formal urinalysis was performed. A total of 609 patients were finally included in the study, with a mean age of 49.2 years. Average stone size was 5.8 mm, located mainly in the lower part of the ureter. Dipstick analysis was positive for hematuria in 92.9%. A urinalysis, with a cut-off point of less than three red blood cells per high power field, was used as a means to verify the results of the UDT in 17.8% of cases: in 7.1% of UDT negative patients and 10.7% of patients with traces of blood. The urinalysis was negative in 5.1% of patients, adding only 2% to the diagnostic accuracy of UDT. Therefore, our findings suggest that the sensitivity of a UDT for hematuria in cases of suspected renal colic has a high degree of accuracy when performed at the emergency department, and can be used as a first-line, low cost examination. A microscopic analysis may be useful when the UDT is negative or not clear enough, to verify the results.

Acute Ureterolithiasis: Incidence of Secondary Signs on Unenhanced Helical CT and Influence on Patient Management

AIM

The purpose of this study was to determine the incidence of secondary signs associated with ureteral stones on unenhanced helical computed tomography (CT) of patients with acute renal colic, and to correlate these with patient management and outcome.

MATERIALS AND METHODS

One hundred and ten patients with ureterolithiasis were evaluated prospectively for the secondary signs of obstruction on unenhanced helical CT. Our attention was focused primarily on the presence or absence of seven secondary signs on unenhanced helical CT, including hydronephrosis, unilateral renal enlargement, perinephric oedema, unilateral absence of the white pyramid, hydroureter, periureteral oedema and lateroconal fascial thickening.

RESULTS

Of the 110 patients, 91 (82.7%) had hydroureter, 88 (80%) had hydronephrosis, 65 (59%) had periureteric oedema and 63 (57.2%) had unilateral renal enlargement. Ninety stones passed spontaneously and 21 required intervention.

CONCLUSION

Secondary signs of urinary tract obstruction are useful and supportive findings in interpretation of the CT examination. In our experience, the most reliable signs indicating ureteral obstruction are hydroureter, hydronephrosis, periureteral oedema and unilateral renal enlargement, respectively. In addition, stones larger than 6 mm, located within the proximal two thirds of the ureter, and seen associated with five or more the secondary signs of obstruction, are more likely to require endoscopic removal and/or lithotripsy.

CT evaluation of urinary lithiasis

Unenhanced CT has been demonstrated to be the most accurate and efficient diagnostic imaging means to evaluate urinary lithiasis, with capability of directing management, and has become well accepted by radiologists, urologists, and emergency department physicians such that it is now the standard of practice. It is the duty of the radiologist to be aware of proper technique and the details of interpretation. The radiologist also has a duty to be aware of the limitations of unenhanced CT for detection and evaluation of various nonstone disorders, particularly with poor patient selection, and to extend the examination if appropriate. Controversies and future developments include cost containment with care for the selection of patients. Further attempts to reduce radiation exposure should be made. Optimal CT technique is not needed in general merely to detect urinary lithiasis. A consensus should be developed regarding use of CT in pregnant patients. Further improvements in the digital scout view would be useful for following patients.

Helical CT for nephrolithiasis and ureterolithiasis: comparison of conventional and reduced radiation-dose techniques

PURPOSE

To determine the accuracy of unenhanced helical computed tomography (CT) performed at reduced milliampere-second, and therefore at a reduced patient radiation dose, by using conventional unenhanced helical CT as the standard.

MATERIALS AND METHODS

Fifty patients with acute flank pain who weighed less than 200 lb (90 kg) were prospectively recruited for this study. Conventional helical CT scans were obtained with patients in the prone position by using 5-mm-thick sections, 140 kVp, 135-208 mAs (mean, 160 mAs), and a pitch of 1.5 (single-detector row CT) or 0.75 (multi-detector row CT, 4 x 5-mm detector configuration). Conventional CT was immediately followed by low-dose scanning, whereby the tube current was reduced to 100 mA (mean, 76 mAs). All other technical parameters and anatomic coverage remained constant. Three independent readers who were blinded to patient identity interpreted the scans in random order. The observers noted the location, size, and number of calculi; secondary signs of obstruction; and other clinically relevant findings. High- and low-dose scans were compared by using paired t tests and the signed rank test.

RESULTS

Calculi were found in 33 (66%) patients; 25 (50%) had renal calculi and 19 (38%) had an obstructing ureteral calculus. The accuracy rates (averaged over the three readers) for determining the various findings on the low-dose scan compared with the high-dose scan were as follows: nephrolithiasis, 91%; ureterolithiasis, 94%; obstruction, 91%; and normal findings, 92%. When interpretations between readers were compared, agreement rates were 90%-95% for standard-dose scans and 90%-92% for reduced-dose scans (P >.5). Uncomplicated mild diverticulitis was found in three patients. No other clinically important abnormality was identified. A reduction in the tube current to 100 mA resulted in a dose reduction of 25% for multi-detector row CT and 42% for single-detector row CT.

CONCLUSION

In patients who weighed less than 200 lb, unenhanced helical CT performed at a reduced tube current of 100 mA, and therefore at a reduced patient dose, resulted in scans of high accuracy.