Noncontrast Helical Computed Tomography Research Articles

Reproducibility of a semiautomatic lobar lung tissue assignment technique on noncontrast CT scans: a study on swine animal model

BackgroundTo evaluate the reproducibility of a vessel-specific minimum cost path (MCP) technique used for lobar segmentation on noncontrast computed tomography (CT).MethodsSixteen Yorkshire swine (49.9 ± 4.7 kg, mean ± standard deviation) underwent a total of 46 noncontrast helical CT scans from November 2020 to May 2022 using a 320-slice scanner. A semiautomatic algorithm was employed by three readers to segment the lung tissue and pulmonary arterial tree. The centerline of the arterial tree was extracted and partitioned into six subtrees for lobar assignment. The MCP technique was implemented to assign lobar territories by assigning lung tissue voxels to the nearest arterial tree segment. MCP-derived lobar mass and volume were then compared between two acquisitions, using linear regression, root mean square error (RMSE), and paired sample t-tests. An interobserver and intraobserver analysis of the lobar measurements was also performed.ResultsThe average whole lung mass and volume was 663.7 ± 103.7 g and 1,444.22 ± 309.1 mL, respectively. The lobar mass measurements from the initial (MLobe1) and subsequent (MLobe2) acquisitions were correlated by MLobe1 = 0.99 MLobe2 + 1.76 (r = 0.99, p = 0.120, RMSE = 7.99 g). The lobar volume measurements from the initial (VLobe1) and subsequent (VLobe2) acquisitions were correlated by VLobe1 = 0.98VLobe2 + 2.66 (r = 0.99, p = 0.160, RSME = 15.26 mL).ConclusionsThe lobar mass and volume measurements showed excellent reproducibility through a vessel-specific assignment technique. This technique may serve for automated lung lobar segmentation, facilitating clinical regional pulmonary analysis.Relevance statementAssessment of lobar mass or volume in the lung lobes using noncontrast CT may allow for efficient region-specific treatment strategies for diseases such as pulmonary embolism and chronic thromboembolic pulmonary hypertension.Key points• Lobar segmentation is essential for precise disease assessment and treatment planning.• Current methods for segmentation using fissure lines are problematic.• The minimum-cost-path technique here is proposed and a swine model showed excellent reproducibility for lobar mass measurements.• Interobserver agreement was excellent, with intraclass correlation coefficients greater than 0.90.Graphical

Deep Learning-Based Digitally Reconstructed Tomography of the Chest in the Evaluation of Solitary Pulmonary Nodules: A Feasibility Study.

Computed tomography (CT) is preferred for evaluating solitary pulmonary nodules (SPNs) but access or availability may be lacking, in addition, overlapping anatomy can hinder detection of SPNs on chest radiographs. We developed and evaluated the clinical feasibility of a deep learning algorithm to generate digitally reconstructed tomography (DRT) images of the chest from digitally reconstructed frontal and lateral radiographs (DRRs) and use them to detect SPNs. This single-institution retrospective study included 637 patients with noncontrast helical CT of the chest (mean age 68 years, median age 69 years, standard deviation 11.7 years; 355 women) between 11/2012 and 12/2020, with SPNs measuring 10-30 mm. A deep learning model was trained on 562 patients, validated on 60 patients, and tested on the remaining 15 patients. Diagnostic performance (SPN detection) from planar radiography (DRRs and CT scanograms, PR) alone or with DRT was evaluated by two radiologists in an independent blinded fashion. The quality of the DRT SPN image in terms of nodule size and location, morphology, and opacity was also evaluated, and compared to the ground-truth CT images RESULTS: Diagnostic performance was higher from DRT plus PR than from PR alone (area under the receiver operating characteristic curve 0.95-0.98 versus 0.80-0.85; p < 0.05). DRT plus PR enabled diagnosis of SPNs in 11 more patients than PR alone. Interobserver agreement was 0.82 for DRT plus PR and 0.89 for PR alone; and interobserver agreement for size and location, morphology, and opacity of the DRT SPN was 0.94, 0.68, and 0.38, respectively. For SPN detection, DRT plus PR showed better diagnostic performance than PR alone. Deep learning can be used to generate DRT images and improve detection of SPNs.

Study of non-contrast helical computed tomography in evaluating holmium laser lithotripsy for urinary calculus.

The present study aimed to investigate the correlation between the parameters of non-contrast helical computed tomography (NCHCT) and the total energy of holmium laser lithotripsy, and establish a correlative mathematical model. From March 2016 to February 2017, 120 patients with a single urinary calculus were examined by NCHCT prior to holmium laser lithotripsy. The calculus location was confirmed, the CT value was measured and the volume of the calculus in the established three-dimensional reconstruction model was calculated. The total energy of lithotripsy (TEL) was recorded post-operatively. A significant difference in the TEL between renal calculi and ureteral calculi was identified (P<0.001) and a high and significant correlation between the volume of the calculus and the TEL was determined (Spearman r=0.827, P<0.001). A moderate correlation was identified between the CT value of the calculus and the TEL (Spearman r=0.468, P<0.001). Multivariate linear regression analysis revealed that the location, the volume and the CT value of the calculus were independently associated with the TEL (F=288.858, adjusted R2=0.879, P<0.01). A mathematical model correlating the parameters of NCHCT with the TEL was established, which may provide a foundation to guide the use of energy in holmium laser lithotripsy, and it was possible to estimate the TEL by the location, the volume and the CT value of the calculus.

Using computed tomography to predict in vivo stone chemical composition

OBJECTIVES. Several authors hypothesized the usefulness of the non-contrast helical computed tomography (NCHCT) with the determination of stone Hounsfield Unit (HU) values in order to predict urinary stone compositions. Preoperative knowledge of stone composition might be interesting in pre-operative decision-making process. The aim of this study was to evaluate the possible correlation between stone chemical composition and correspondent stone HU value in an in-vivo experience. METHODS. Forty patients with urinary stones were preoperatively studied with abdominal NCHCT, where stone HU values were reported. Stone chemical composition was obtained in each patient, using the colorimetric method. The HU value of each stone was compared with the correspondent chemical analysis. Results. The median HU values of calcium oxalate (n=10), mixed calcium oxalate and phosphate (n=19), calcium phosphate (n=2), uric acid (n=6) and mixed uric acid and calcium oxalate (n=3) stones were 1060 HU [interquartile range (IQR) 743.75-1222.5]; 900 HU (IQR 588.5-1108.5); 774 HU (range 720-828); 371 HU (IQR 361.25-436.25) and 532 HU (range 476-626), respectively. CONCLUSIONS. Our results confirmed a statistically significant difference of the HU values between calcium and pure uric acid calculi, suggesting a correlation between stone chemical composition and CT-density. Hounsfield unit.

Improved image quality of helical computed tomography of the head in children by iterative reconstruction

Iterative reconstruction (IR) offers noise reduction and improved image quality of computed tomography (CT). Our aim was to assess the imaging quality of non-contrast helical CT of the head in children using IR. This study recruited 78 consecutive children aged ≤5 years (range: from 3 months to 5 years; mean: 1.7 years) who underwent an emergent non-enhanced helical CT of the head with no abnormal findings. The acquired data were reconstructed using filtered back projection (FBP) and sinogram-affirmed IR (SAFIRE) with strength levels of 2 (IR2) and 4 (IR4). The imaging quality of FBP, IR2 and IR4 was scored by two experienced neuroradiologists in terms of the contrast between the gray-white matter junction and artifacts from the skull at the level of the semioval center, basal ganglia and fourth ventricle. FBP, IR2 and IR4 scores were compared at each slice level. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated for FBP, IR2 and IR4 and were compared among the three reconstruction algorithms. The score of IR2 and IR4 was significantly higher than that of FBP in terms of both the contrast between the gray-white matter junction and artifacts from the skull at each slice level (P<0.001). SNR and CNR on IR4 were the highest followed by those on IR2 and FBP (P<0.001). IR may improve the image quality of helical CT of the head in children.

DIAGNOSTIC VALUE OF NON-CONTRAST HELICAL CT-SCAN AND INTRAVENOUS UROGRAPHY IN UROLITHIASIS EVALUATION

Objective: To evaluate the diagnostic value of Non Contrast Helical Computed Tomography (NCHCT) scanning as the first choice diagnostic modality for detecting urolithiasis cases in Soetomo General Hospital Surabaya and evaluate the feasibility as alternative to Intravenous Urography (IVU). Material &amp; Methods: Seventeen patients with clinical manifestation of suspected urolithiasis underwent NCHCT and IVU to evaluate suspected urolithiasis. Reformatted three-dimensional CT was performed in all patients. The images were correlated with findings from surgical procedure (ureteroscopy, percutaneous nephrolithotomy, and open surgery). Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy were determined for NCHCT and IVU. Results: The diagnosis of urolithiasis was defined as unequivocal evidence of urolithiasis on either NCHCT or IVU. Sixteen of seventeen patients evaluated were diagnosed with urolithiasis. NCHCT established the diagnosis in 16 of 17 patients while IVU was positive in 11 of 17 patients. IVU was negative in 6 of the 17 cases. The sensitivity, specificity and accuracy of NCHCT was 100%, 100%, and 100% respectively (p = 0.05) and the sensitivity, specificity, and accuracy of IVU was 68%, 100% and 70% respectively (p = 0.35). There was no statistically significant difference between IVU and NCHCT using Fisher’s exact test. Conclusions: NCHCT accurately diagnosed urolithiasis in patients with suspected urolithiasis. Considering that NCHCT is more effective and efficient than IVU as diagnostic modality in determining the presence of urolithiasis, it may be considered to replace IVU as the first line diagnostic tool for urolithiasis in Soetomo General Hospital Surabaya.&#x0D; Keywords: Non Contrast Helical CT Scan, Intravenous Urography, 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 χ2 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.

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.

Imaging-Based Assessment of the Mineral Composition of Urinary Stones: An In Vitro Study of the Combination of Hounsfield Unit Measurement in Noncontrast Helical Computerized Tomography and the Twinkling Artifact in Color Doppler Ultrasound

We evaluated the value of combining noncontrast helical computerized tomography (NCHCT) and color Doppler ultrasound in the assessment of the composition of urinary stones. In vitro, we studied 120 stones of known composition, that separate into the five main types: 18 calcium oxalate monohydrate (COM) stones, 41 calcium oxalate dihydrate (COD) stones, 24 uric acid stones, 25 calcium phosphate stones and 12 cystine calculi. Stones were characterized in terms of their Hounsfield density (HU) in NCHCT and the presence of a twinkling artifact (TA) in color Doppler ultrasound. There were statistically significant HU differences between calcium and non-calcium stones (p < 0.001), calcium oxalate stones and calcium phosphate stones (p < 0.001) and uric acid stones and cystine calculi (p < 0.001) but not between COM and COD stones (p = 0.786). Hence, the HU was a predictive factor of the composition of all types of stones, other than for COM and COD stones within the calcium oxalate class (p > 0.05). We found that the TA does not enable differentiation between calcium and non-calcium stones (p > 0.999), calcium oxalate stones and calcium phosphate stones (p = 0.15), or uric acid stones and cystine calculi (p = 0.079). However, it did reveal a significant difference between COM and COD stones (p = 0.002). The absence of a TA is a predictive factor for the presence of COM stones (p = 0.008). Hence, the association of NCHCT and Doppler enables the accurate classification of the five types of stones in vitro.

Using Computed Tomography to Predict in Vivo Stone Chemical Composition

Objectives Several authors hypothesized the usefulness of the non-contrast helical computed tomography (NCHCT) with the determination of stone Hounsfield Unit (HU) values in order to predict urinary stone compositions. Preoperative knowledge of stone composition might be interesting in pre-operative decision-making process. The aim of this study was to evaluate the possible correlation between stone chemical composition and correspondent stone HU value in an in-vivo experience. Methods Forty patients with urinary stones were preoperatively studied with abdominal NCHCT, where stone HU values were reported. Stone chemical composition was obtained in each patient, using the colorimetric method. The HU value of each stone was compared with the correspondent chemical analysis. Results The median HU values of calcium oxalate (n=10), mixed calcium oxalate and phosphate (n=19), calcium phosphate (n=2), uric acid (n=6) and mixed uric acid and calcium oxalate (n=3) stones were 1060 HU [interquartile range (IQR) 743.75–1222.5]; 900 HU (IQR 588.5–1108.5); 774 HU (range 720–828); 371 HU (IQR 361.25–436.25) and 532 HU (range 476–626), respectively. Conclusions Our results confirmed a statistically significant difference of the HU values between calcium and pure uric acid calculi, suggesting a correlation between stone chemical composition and CT-density. Hounsfield unit

Discrimination between ureteral stent and stone by non‐contrast helical computed tomography in the clinical setting

In urolithiasis with indwelling ureteral stent, an adequate visualization of retained stone is often obscured by the stent. In functional solitary kidney, it is essential to detect retained fragments before stent removal. We examined the capability of non-contrast helical computed tomography (NCHCT) in discriminating stone from stent. We assessed the CT of 21 radiopaque stones of 3-5 mm and four stents, and compared their attenuation values. In addition, two other cases with stent, in which only NCHCT by manipulating the setting could detect retained fragments. No overlaps of attenuation value were found between the stones and stents. Although they had the same appearance in NCHCT with abdominal-window setting, in bone-window setting the contrasts of stones were reduced, while stents were still bright white. We would discriminate the residual stone from the stent by manipulating window and level setting, and bone-window setting is easy to use.

Value of Hounsfield unit on CT in prediction of stone-free rate of upper urinary calculi after extracorporeal shockwave lithotripsy

To study the value of Hounsfield unit (HU) on CT in prediction of stone-free rate of upper urinary calculi after extracorporeal shockwave lithotripsy (ESWL). Fifty-two patients suffering from solitary stone in the upper urinary tract 0.5 - 1.5 cm in size, 34 males and 18 females, aged 15 - 77, underwent non-contrast helical computerized tomography (NCHCT), and then ESWL. One day, 2 weeks, 4 weeks, and 3 months after the ESWL the patients underwent kidney, ureter, and bladder examination and B mode ultrasonography. The patients with the residual fragments less than 3 mm in size were categorized into the stone-free group. The relationship among the HU, number of shock wave, and the characteristics of the patients were analyzed. Thirty-six of the 52 patients were categorized into the stone-free group (69.2%) and 16 of the 52 were categorized into the residual stone group (30.8%). The CT value of the stone-free group was 579.65 +/- 194.65 HU, significantly lower than that of the residual stone group (1032.18 +/- 270.49 HU, t = 6.842, P < 0.01). The number of shock wave of the stone-free group was 1526.67 +/- 723.01, significantly lower than that of the residual stone group (2612.50 +/- 518.81, t = 5.407, P < 0.01). The OR values for the HU and number of shock wave were 0.993 (95% CI: 0.988 - 0.998) and 0.998 (95% CI: 0.997 - 1.000). The HU value on pretreatment NCHCT of the upper urinary tract stones can be used to predict the stone-free rate after ESWL. ESWL is not indicated to the patients of upper urinary tract stones with high values of HU.

Prediction of differential creatinine clearance in chronically obstructed kidneys by non-contrast helical computerized tomography

We investigate the use of non-contrast helical computerized tomography (NCHCT) in the measurement of differential renal parenchymal volume as a surrogate for differential creatinine clearance (CrCl) for unilateral chronically obstructed kidney. Patients with unilateral chronically obstructed kidneys with normal contralateral kidneys were enrolled. Ultrasonography (USG) of the kidneys was first done with the cortical thickness of the site with the most renal substance in the upper pole, mid-kidney, and lower pole of both kidneys were measured, and the mean cortical thickness of each kidney was calculated. NCHCT was subsequently performed for each patient. The CT images were individually reviewed with the area of renal parenchyma measured for each kidney. Then the volume of the slices was summated to give the renal parenchymal volume of both the obstructed and normal kidneys. Finally, a percutaneous nephrostomy (PCN) was inserted to the obstructed kidney, and CrCl of both the obstructed kidney (PCN urine) and the normal side (voided urine) were measured two 2 after the relief of obstruction. From March 1999 to February 2001, thirty patients were enrolled into the study. Ninety percent of them had ureteral calculi. The differential CrCl of the obstructed kidney (%CrCl) was defined as the percentage of CrCl of the obstructed kidney as of the total CrCl, measured 2 weeks after relief of obstruction. The differential renal parenchymal volume of the obstructed kidney (%CTvol) was the percentage of renal parenchymal volume as of the total parenchymal volume. The differential USG cortical thickness of the obstructed kidney (%USGcort) was the percentage of mean cortical thickness as of the total mean cortical thickness. The Pearson's correlation coefficient (r) between %CTvol and %CrCl and that between %USGcort and %CrCl were 0.756 and 0.543 respectively. The regression line was %CrCl = (1.00) x %CTvol - 14.27. The %CTvol overestimated the differential creatinine clearance by about 14%, but the correlation is good. The differential renal parenchymal volume measured by NCHCT provided a reasonable prediction of differential creatinine clearance in chronically obstructed kidneys.

How accurate are emergency clinicians at interpreting noncontrast computed tomography for suspected renal colic?

To assess the accuracy of emergency physicians and trainees in the interpretation of noncontrast helical computed tomography (NCHCT) for suspected renal colic by examining the interrater reliability between emergency department (ED) clinicians and radiologists. Information was collected prospectively on all ED patients undergoing NCHCT for suspected renal colic over a 12-month period. Emergency physicians and trainees were asked to report the absence or presence of specific renal parameters (renal tract abnormality, calculus, hydroureter, hydronephrosis, perinephric stranding, and renal parenchymal edema) and nonrenal parameters (nonrenal abnormality, free gas, free fluid, and aortic diameter >3 cm). These reports were compared with the formal radiology report, which was used as the reference standard. The sensitivity, specificity, accuracy, and kappa coefficient were calculated for each of the parameters. Over the 12-month period, 212 patients underwent NCHCT for suspected renal colic, of whom 127 had both ED and formal radiological reporting. There was an excellent degree of interrater reliability between the ED clinicians and the radiologists (kappa > 0.75) for the presence of renal tract abnormality and renal tract calculus. There was intermediate interrater reliability (kappa 0.4-0.75) for nonrenal tract abnormalities, hydroureter, hydronephrosis, and perinephric stranding. Four patients had potentially significant nonrenal abnormalities missed by ED clinicians. Emergency clinicians are able to identify renal calculi with a high degree of accuracy but may miss important nonrenal abnormalities. Therefore, all patients without evidence of renal tract calculus on NCHCT must have early and appropriate follow-up.

Nonobstructive renal causes of flank pain: findings on noncontrast helical CT (CT KUB).

Depending on the experience and clinical acumen of the referring physician, 25-60% of patients with flank pain who are referred for noncontrast helical computed tomography (CT) of the abdomen (CT KUB) prove to have an obstructing stone. In our institution, with many different emergency physicians and house staff requesting imaging examinations, the yield of obstructing ureteral stones is approximately one in four patients. Of the remainder, 20-35% have a nonurinary cause of pain, such as appendicitis, diverticulitis, unsuspected bowel obstruction, or twisted ovarian cyst, demonstrated on the CT KUB. In approximately 50% of our patients, CT KUB does not furnish an explanation for the patients' symptoms. In this article, we present a spectrum of genitourinary tract surprises discovered in patients presenting to the Emergency Department or Urgent Care Clinic with flank pain, with or without hematuria. These masquerades of stone colic are based on one institution's experience from January 1995, when we abandoned intravenous urography for flank pain, to September 2001. Practical lessons learned along the way may help the reader get it right when unexpected imaging findings are encountered. For almost all such cases, contrast-enhanced CT should be performed to pursue the diagnosis.

The efficacy of non-contrast helical computed tomography in the prediction of urinary stone composition in vivo.

The composition of urinary stones was predicted on the basis of the differences in their Hounsfield unit (HU) densities as detected by in vivo non-contrast helical computed tomography (NCHCT). A total of 87 stones, which had been obtained from patients admitted to the emergency department with acute flank pain, were analysed biochemically. These stones had been visualized by NCHCT before spontaneous passage, ureteroscopic extraction or surgical removal, and their HU densities had been recorded. The HU densities of the stones were compared with the results of biochemical analysis. The mean HU densities of the stones composed of calcium oxalate (n = 54), struvite (n = 19) and uric acid (n = 14) were 812 +/- 135, 614 +/- 121 and 413 +/- 143, respectively. The differences between the mean HU densities of these three stone types were statistically significant. This initial clinical study demonstrated that in vivo NCHCT analysis may be used to predict the composition of urinary stones.

The accuracy of noncontrast helical computed tomography versus intravenous pyelography in the diagnosis of suspected acute urolithiasis: A meta-analysis

Study objectives: We determine the accuracy of noncontrast helical computed tomography (NHCT) compared with that of intravenous pyelography (IVP) in diagnosing acute urolithiasis. Methods: Computerized searches of MEDLINE and EMBASE were combined with hand reviews of major journals and of articles from reference lists. Articles were assessed according to a priori criteria for inclusion. Study eligibility was independently assessed by 2 reviewers in a blinded fashion. Test results were combined and analysis of log-transformed data was conducted by using general linear models. Results: No disagreement was found between the 2 investigators in terms of articles that met the inclusion criteria or between the results of the studies. Four studies involving a total of 296 patients met all of the a priori criteria. The pooled positive likelihood ratios (LR+) for NHCT and IVP are 23.15 (95% confidence interval [CI] 11.53 to 47.23) and 9.32 (95% CI 5.23 to 16.61), respectively. The pooled negative likelihood ratios (LR−) for NHCT and IVP are 0.05 (95% CI 0.02 to 0.15) and 0.33 (95% CI 0.23 to 0.48), respectively. The differences between NHCT and IVP were statistically significant for both LR+ (P =.046) and LR− (P =.013). Differences among trials were not statistically significant in either analysis (P =.125 for LR+; P =.114 for LR−). Conclusion: The studies analyzed consistently demonstrated NHCT to be superior to IVP in accurately diagnosing acute urolithiasis, and differences between the 2 tests for both LR+ and LR− were statistically significant. [Ann Emerg Med. 2002;40:280-286.]

COMPARISON OF HELICAL COMPUTERIZED TOMOGRAPHY AND PLAIN RADIOGRAPHY FOR ESTIMATING URINARY STONE SIZE

We evaluated the accuracy of noncontrast spiral computerized tomography (CT) for determining urinary stone size compared with plain x-ray. We retrospectively analyzed noncontrast helical CT and plain x-ray of the kidneys, ureters and bladder images of 39 patients with urolithiasis who underwent each study from July 1997 to February 1999. Stone size on x-ray was measured in the craniocaudal and transverse dimensions by a single radiologist (I.C.B.). The size of the same stone was then determined on blinded noncontrast spiral CT images. Stones that were less than 3 mm. were excluded from study. On CT estimated craniocaudal dimension was based on collimation thickness, the reconstruction interval and the number of images on which the stone was visualized. We evaluated 58 stones 3 mm. or larger in the greatest dimension on plain x-ray of the kidneys, ureters and bladder, and noncontrast spiral CT, including 15 in the distal ureter, 7 in the mid or proximal ureter and 36 in the kidneys. Stone size was 3 to 18 mm. in the greatest dimension. Mean transverse dimension of the stone plus or minus standard deviation on noncontrast spiral CT was 5.1 +/- 1.08 versus 4.9 +/- 1.08 mm. on plain x-ray of the kidneys, ureters and bladder (paired t test; p = 0.335). The mean craniocaudal dimension on noncontrast spiral CT was 7.5 +/- 1.98 versus 6.7 +/- 1.98 mm. on plain x-ray paired t test (p = 0.005). Noncontrast spiral CT enables a similar measurement of stone size along the transverse dimension as plain x-ray of the kidneys, ureters and bladder. In individuals noncontrast spiral CT does not accurately measure the craniocaudal dimension of stones compared with plain x-ray when standard acquisition and reconstruction techniques are used. In this regard it has a tendency to overestimate stone size by an average of 0.8 mm.

A prospective comparative study of non-contrast helical computed tomography and intravenous urogram for the assessment of renal colic

Objective: To compare noncontrast helical computed tomography (NCHCT) and intravenous urography (IVU) for diagnosis of urinary calculi in evaluation of renal colic. Materials and methods: A 4-month prospective paired study compared NCHCT and IVU in patients being evaluated for renal colic. Each patient was studied with NCHCT followed by an IVU. An IVU was regarded as positive if any of the following were identified: delayed filling, hydronephrosis, hydroureter, ureteral calculus, or extravasation of contrast. A NCHCT was regarded as positive if any of the following were identified: hydronephrosis, hydroureter, ureteral calculus, or perinephric or ureteral inflammatory change. The sensitivity (Se), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV) were reported using the clinical outcome as the gold standard, by either observation of passage or retrieval of calculus. Bladder distention was noted on NCHCT relative to the level of the acetabulum. The charts were also reviewed retrospectively for the results of urinalysis. Results: One hundred sixty-eight patients had both examinations interpreted. Nineteen positive NCHCT and IVU studies were eliminated due to lack of observation or retrieval of calculus, leaving 149 studies for interpretation. NCHCT had Se 0.98, Sp 0.95, PPV 0.98, and NPV 0.95. IVU had Se 0.83, Sp 0.95, PPV 0.97, and NPV 0.67. In 13/168 (8 %) cases, and in 9/37 (24 %) negative cases, NCHCT offered an alternative diagnosis. Ureterovesical junction (UVJ) calculus was identified on 84 NCHCT scans, with near-even distribution between well, partially, and poorly distended bladder. No UVJ calculus was identified on IVU that was not present on NCHCT. Absence of hematuria was found in 26 % of patients with proven urolithiasis. Conclusion: NCHCT is superior to IVU for the evaluation of renal colic. NCHCT identifies significant pathology in 24 % of cases negative for ureteral obstruction/calculus. Bladder distention does not play an important role in detection of UVJ calculus. Hematuria is not universally present in patients with painful urolithiasis.

Central lucency of pelvic phleboliths: Comparison of radiographs and noncontrast helical CT

To compare how often the central lucency of pelvic phleboliths is seen on plain radiographs and noncontrast helical computed tomography (CT), both images in 70 patients with renal colic were analyzed. Both images revealed the same number of phleboliths in all cases except one in which one of two phleboliths demonstrated by CT was not seen on radiographs. Radiography revealed central lucency in 95 of 149 pelvic phleboliths (63%), but CT failed to depict a hypodense center in any of 150 phleboliths. The presence or absence of central lucency on CT images cannot, therefore, be used to differentiate phleboliths from distal ureteral calculi.