Detection Of Calculi Research Articles

Invivo characterization of urinary calculi on dual-energy CT: going a step ahead with sub-differentiation of calcium stones.

The role of dual-energy computed tomography (DECT) in characterization of urinary calculi is evolving and literature regarding differentiation of calcium calculi is sparse and confounding. To evaluate the capability of DECT in assessing the urinary calculi composition invivo, especially in differentiating various types of calcium calculi. One hundred and twenty patients underwent DECT for characterization of urinary calculi. Seventy patients with 114 calculi, including 93 calcium stones, were retrospectively analyzed. DE ratios and attenuation differences were compared using ANOVA and receiver-operating-characteristic (ROC) analysis was done to predict cut-off values, in particular for detecting calcium-oxalate-monohydrate (COM) stones. DE ratio ≤1.14 accurately detected uric acid calculi, ≥1.29 was definitive for calcium and intermediate values were characteristic of cystine stones. DE ratios were significantly different between group 1 (COM [n = 32]; mean 1.376 ± 0.041), group 2 ([calcium oxalate dihydrate (COD) + COM] [n = 51]; 1.416 ± 0.048), and group 3 ([carbonate apatite (CaP) + COD + COM] [n = 10]; 1.468 ± 0.038) (group 1 vs. 2, P = 0.001; 1 vs. 3, P = 0.000; 2 vs. 3, P = 0.004). More importantly, pure COM calculi (group 1) had significantly lower DE ratio compared with mixed calcium calculi (groups 2 and 3) (P = 0.000). Attenuation differences (between low and high kV images) could not distinguish between COM and mixed calculi. ROC analysis for detection of COM calculi yielded AUC of 0.770 with cut-off DE ratio 1.385 (sensitivity 65.6%, specificity 82%) and value <1.335 was seen only with COM calculi (100% specificity). DECT can be employed for invivo differentiation of various types of calculi and for detection of relatively lithotripsy-resistant COM calculi.

Computer-aided detection of renal calculi from noncontrast CT images using TV-flow and MSER features.

Renal calculi are common extracolonic incidental findings on computed tomographic colonography (CTC). This work aims to develop a fully automated computer-aided diagnosis system to accurately detect renal calculi on CTC images. The authors developed a total variation (TV) flow method to reduce image noise within the kidneys while maintaining the characteristic appearance of renal calculi. Maximally stable extremal region (MSER) features were then calculated to robustly identify calculi candidates. Finally, the authors computed texture and shape features that were imported to support vector machines for calculus classification. The method was validated on a dataset of 192 patients and compared to a baseline approach that detects calculi by thresholding. The authors also compared their method with the detection approaches using anisotropic diffusion and nonsmoothing. At a false positive rate of 8 per patient, the sensitivities of the new method and the baseline thresholding approach were 69% and 35% (p < 1e - 3) on all calculi from 1 to 433 mm(3) in the testing dataset. The sensitivities of the detection methods using anisotropic diffusion and nonsmoothing were 36% and 0%, respectively. The sensitivity of the new method increased to 90% if only larger and more clinically relevant calculi were considered. Experimental results demonstrated that TV-flow and MSER features are efficient means to robustly and accurately detect renal calculi on low-dose, high noise CTC images. Thus, the proposed method can potentially improve diagnosis.

Urinary stone detection and characterisation with dual-energy CT urography after furosemide intravenous injection: preliminary results

To investigate the added advantage of IV furosemide injection and the subsequent urine dilution in the detection of urinary calculi in the excretory phase of dual-source dual-energy (DE) computed tomography (CT) urography, and to investigate the feasibility of characterising the calculi through diluted urine. Twenty-three urinary calculi were detected in 116 patients who underwent DECT urography for macroscopic haematuria with a split bolus two- or three-acquisition protocol, including a true unenhanced series and at least a mixed nephrographic excretory phase. Virtual unenhanced images were reconstructed from contrast-enhanced DE data. Calculi were recorded on all series and characterised based on their X-ray absorption characteristics at 100kVp and 140kVp in both true unenhanced and nephrographic excretory phase series. All calculi with a diameter more than 2mm were detected in the virtual unenhanced phase and in the nephrographic excretory phase. Thirteen of these calculi could be characterised in the true unenhanced phase and in the mixed nephrographic excretory phase. The results were strictly identical for both phases, six of them being recognised as non-uric acid calculi and seven as uric acid calculi. Mixed nephrographic excretory phase DECT after furosemide administration allows both detection and characterisation of clinically significant calculi, through the diluted urine. • Urinary tract stones can be detected on excretory phase through diluted urine. • Urinary tract stone characterisation with dual-energy CT (DECT) is possible through diluted urine. • A dual energy split-bolus CT urography simultaneously enables urinary stone detection and characterisation.

Natural history of acalculous biliary symptoms

The radiological criteria for the diagnosis of gallbladder disease rely largely on the detection of calculi using ultrasonography. Patients may, however, suffer symptoms typical of biliary pain without detectable gallstones. The aim of this study was to identify a cohort of patients presenting with recurrent episodes of biliary symptoms in the absence of identifiable pathology on ultrasonography and to record the outcome of subsequent imaging investigations. Records of patients having abdominal ultrasonography during a four-month period in 2006 were accessed retrospectively and those with symptoms suggesting biliary disease were identified. Radiology records were reviewed over a five-year follow-up period to identify patients undergoing further imaging for recurrent biliary symptoms and outcomes were recorded. A total of 512 patients had ultrasonography for investigation of symptoms consistent with biliary disease. Almost half (41.2%) of these were found to have gallbladder pathology on ultrasonography and 4.7% of patients went on to have further investigations for similar symptoms without achieving a diagnosis. The median age of this group was 47 years and 75% of these patients were female. During the follow-up period, 2.6% of patients with biliary symptoms and initially normal ultrasonography developed gallstones and in 1.3% pancreatitis was demonstrated on imaging. A small minority of patients who present with biliary symptoms and have no abnormality on ultrasonography present with recurrent symptoms or develop significant biliary pathology. These patients should be identified by interview at routine follow-up visits and further investigations should be considered.

How Reliable Is Sonography in the Assessment of Sialolithiasis?

The purpose of this study was to determine the value of sonography for the diagnosis of salivary gland calculi. In this study, 82 salivary glands in 79 consecutively registered patients with acute or recurrent parotid or submandibular gland swelling were examined with 7.5-12 MHz linear probes. All sonographic examinations were performed by two experienced radiologists without knowledge of the final diagnosis. The reference standard was digital sialography and sialendoscopy with or without surgery for 54 salivary glands and digital sialography alone for 28 glands. Sialolithiasis was present in 44 glands and was absent in 38 glands as confirmed by the final diagnosis. The overall sensitivity, specificity, accuracy, and positive and negative predictive values of sonography in the detection of calculi were 77%, 95%, 85%, 94%, and 78%, respectively. False-negative sonographic findings were associated with calculi with a diameter less than 3 mm in nondilated or dilated salivary ducts; most calculi with a diameter of 3 mm or greater were correctly identified. False-positive findings were caused by ductal stenosis with wall fibrosis, which was erroneously interpreted as lithiasis. Because of its limited sensitivity and limited negative predictive value, sonography does not allow reliable exclusion of small salivary gland calculi. Therefore, further diagnostic investigations are recommended to detect calculi in patients with normal sonographic findings and suspected lithiasis.

The use of a fully integrated electronic medical record to minimize cumulative lifetime radiation exposure from CT scanning to detect urinary tract calculi

In order to determine the effects of implementation of an electronic medical record on rates of repeat computed tomography (CT) scanning in the emergency department (ED) setting, we analyzed the utilization of CT of the kidneys, ureters, and bladder (CT KUB) for the detection of urinary tract calculi for periods before and after the implementation of a hospital-wide electronic medical record system. Rates of repeat CT scanning within a 6-month period of previous scan were determined pre- and post-implementation and compared. Prior to implementation, there was a 6-month repeat rate of 6.2 % compared with the post-implementation period, which was associated with a 6-month repeat rate of 4.1 %. Statistical analysis using a two-sample, one-tailed t test for difference of means was associated with a p value of 0.00007. This indicates that the implementation of the electronic medical record system was associated with a 34 % decrease in 6-month repeat CT KUB scans. We conclude that the use of an electronic medical record can be associated with a decrease in utilization of unnecessary repeat CT imaging, leading to decreased cumulative lifetime risk for cancer in these patients and more efficient utilization of ED and radiologic resources.

US detection of renal and ureteral calculi in patients with suspected renal colic

PurposeThe purpose of this study was to determine whether the color Doppler twinkling sign could be considered as an additional diagnostic feature of small renal lithiasis (_5mm).Methods181 patients underwent CT scans performed for other pathologies; the images were also analyzed by a radiologists to identify the incidental presence of renal lithiasis equal to or smaller than 5 mm.These patients underwent an abdominal ultrasound examination, including grayscale analysis of the kidneys and color Doppler. Lithiasis were divided into three groups, on the basis of the diagnostic agreement provided by CT and gray scale results. Then, the twinkling sign sensitivity was assessed in the three groups.ResultsThe twinkling sign was positive in 177 out of 206 lithiasis (86 %) visible on CT, while the grayscale was absolutely positive in 98 out of 206 lithiasis (47.6%) and doubtful positive in 71 out of 206 lithiasis (31%).The twinkling sign was positive in 100% of absolutely positive and doubtful positive lithiasis on bmode, and in 8 out of 31 lithiasis not visible on b-mode.ConclusionsIn the diagnosis of small renal lithiasis, integrating gray-scale with color Doppler may be the most suitable procedure, because the color-Doppler twinkling sign is able to confirm the doubtful diagnosis of renal lithiasis and to detect some lithiasis that are not visible on b-mode.

Editorial comment on “The value of unenhanced multi-detector computed tomography versus three-dimensional ultrasound in evaluating patients with impaired renal function and hematuria”

The issue of how best to image patients with hematuria and impaired renal function has always been controversial and remains controversial, particularly in recent years with the development and continued refinement of multi-detector computed tomography (MDCT).Patients with impaired renal function are more likely to have urinary stone disease and urothelial cancer than those with normal renal function. Thus, retrograde pyelography (RP) is more valuable for evaluating hematuria in patients with impaired renal function than in patients with normal renal function. Among the patients with impaired renal function, uremic patients are at higher risk of having urothelial cancer. Therefore, for the noncalcular causes of hematuria, it is crucial to perform RP and/or cystoscopy, as standard of reference, for patients with impaired renal function, especially for those with uremia [1]. Low-dose CT offers much greater sensitivities for the detection of urinary tract calculi than radiography at doses equivalent to conventional radiography. Ultrasound (US) alone is insufficient for imaging

Sonographic diagnosis of symptomatic ureteral calculi: usefulness of the twinkling artifact

Our aim was to analyze the value of ultrasound using the twinkling sign in the diagnosis of ureteral stones in patients with renal colic in the emergency setting. Prospective study of 100 patients with suspected renal colic who underwent an US examination, including color Doppler mode. We analyzed sensitivity, specificity, predictive values, and accuracy. We evaluated whether the stone was observed before or after the twinkling artifact, and whether the use of the Doppler color increased the examination time. US including color Doppler detected 76 of the 84 confirmed lithiasis. The sensitivity and specificity were 90 % and 100 %, respectively. The positive predictive value was 100 % and the negative 67 %. The accuracy was 92 %. A total of 59 calculi (78 %) examined by color Doppler sonography showed the twinkling artifact. Seventy percent of the twinkling-positive calculi showed the artifact before the stone itself was detected. Considering the location of the stones the twinkling sign was seen before the stone in 92 % of lithiasis located in the mid lumbar ureter (p = 0.02). The use of the twinkling artifact showed a trend to facilitate the detection of smaller calculi (<10 mm) (p = 0.08). The average examination time was 5.8 min [± 4.3] (without differences between the stones detected before or after the twinkling artifact, p = 0.75). Doppler US examination shows good sensitivity and specificity for the diagnosis of symptomatic ureteral stones. The twinkling artifact is useful for the early detection of the calculi, especially in the middle tract of the ureter, usually the most difficult place in sonographic diagnosis. It also seems helpful for the detection of smaller stones. The use of color Doppler does not increase the exploration time.

Virtual Nonenhanced Dual-Energy CT Urography with Tin-Filter Technology: Determinants of Detection of Urinary Calculi in the Renal Collecting System

To retrospectively determine which features of urinary calculi are associated with their detection after virtual elimination of contrast medium at dual-energy computed tomographic (CT) urography by using a novel tin filter. The institutional ethics committee approved this retrospective study, with waiver of informed consent. A total of 152 patients were examined with single-energy nonenhanced CT and dual-energy CT urography in the excretory phase (either 140 and 80 kV [n=44] or 140 and 100 kV [n=108], with tin filtration at 140 kV). The contrast medium in the renal pelvis and ureters was virtually removed from excretory phase images by using postprocessing software, resulting in virtual nonenhanced (VNE) images. The sensitivity regarding the detection of calculi on VNE images compared with true nonenhanced (TNE) images was determined, and interrater agreement was evaluated by using the Cohen k test. By using logistic regression, the influences of image noise, attenuation, and stone size, as well as attenuation of the contrast medium, on the stone detection rate were assessed. Threshold values with maximal sensitivity and specificity were calculated by means of receiver operating characteristic analyses. Eighty-seven stones were detected on TNE images; 46 calculi were identified on VNE images (sensitivity, 52.9%). Interrater agreement revealed a κ value of 0.95 with TNE images and 0.91 with VNE data. Size (long-axis diameter, P=.005; short-axis diameter, P=.041) and attenuation (P=.0005) of the calculi and image noise (P=.0031) were significantly associated with the detection rate on VNE images. As threshold values, size larger than 2.9 mm, maximum attenuation of the calculi greater than 387 HU, and image noise less than 20 HU were found. After virtual elimination of contrast medium, large (>2.9 mm) and high-attenuation (>387 HU) calculi can be detected with good reliability; smaller and lower attenuation calculi might be erased from images, especially with increased image noise.

Noncontrast multidetector-row computed tomography scanning for detection of radiolucent calculi in acute renal insufficiency caused by bilateral ureteral obstruction of ceftriaxone crystals

Noncontrast computed tomography (CT) has great advantage with higher sensitivity and more clear modalities in detecting urinary tract radiolucent calculi in patients with acute renal insufficiency (ARI) compared to other image diagnosis approaches. We report two cases (female, 28 years old; male, 39 years old) with persistent flank pain and acute anuria after the administration of ceftriaxone (4.0 g daily) for 2 days intravenously. No abnormality was found in the kidney-ureter- bladder (KUB) areas with plain abdomen X-rays. A diagnosis of bilateral hydronephrosis was made by ultrasound examination in both cases. Serum creatinine levels reached up to 257 and 810 μ mol/L (normal serum creatinine level is 40-130 μ mol/L), respectively. Vague density spots were noticed in the pelvis with noncontrast multidetector-row CT (MDCT) scanning. However, distinguishable clusters of high-density shadows were seen in pelvic areas with maximum intensity projections (MIP, CT values in 30-128 HU). Ceftriaxone crystal calculi were found on both sides of distal ureters under endoscopy. Renal function recovered in both patients after double-J ureteral stents were installed. Out results demonstrated that noncontrast MDCT scanning and MIP reconstruction as an effective diagnostic tool could provide clear images in detection of radiolucent calculi in urinary tract when conventional X-rays image are not suitable in the patients with obstructive anuria and ARI of unknown origin.

Role of Endoscopic Ultrasound in Gastrointestinal Surgery

Endoscopic Ultrasound is an emerging diagnostic tool in the field of Gastrointestinal Surgery. Our review article focuses on role of EUS in staging cancers (esophageal, gastric, biliary and rectal), detection of bilio-pancreatic calculi and diagnosis of chronic pancreatitis. Potential for performing EUS based therapeutic interventions are been explored and looks promising from the initial reports.

Imaging of Hematuria

In this article, we will discuss the current status of imaging in patients with hematuria of urologic origin. Issues impacting evaluation of these patients with radiography, excretory urography, retrograde pyelography, and sonography will be discussed. Conventional radiography has no role in the detection of renal or urothelial carcinoma. Low-dose CT offers much greater sensitivities for the detection of urinary tract calculi than radiography at doses equivalent to conventional radiography. Ultrasound alone is insufficient for imaging of hematuria. Using ultrasound alone, it is often difficult to differentiate renal transitional cell carcinoma from other causes of filling defects of the renal collecting system such as blood clots, sloughed papillae, or fungus balls. The prominence of the role of excretory urography in the evaluation of patients with hematuria has diminished, and MDCT urography is now preferred to excretory urography in most cases.

Urinary Calculi Composed of Uric Acid, Cystine, and Mineral Salts: Differentiation with Dual-Energy CT at a Radiation Dose Comparable to That of Intravenous Pyelography

To retrospectively evaluate radiation dose, image quality, and the ability to differentiate urinary calculi of differing compositions by using low-dose dual-energy computed tomography (CT). The institutional review board approved this retrospective study; informed consent was waived. A low-dose dual-energy CT protocol (tube voltage and reference effective tube current-time product, 140 kV and 23 mAs and 80 kV and 105 mAs; collimation, 64 × 0.6 mm; pitch, 0.7) for the detection of urinary calculi was implemented into routine clinical care. All patients (n = 112) who were examined with this protocol from July 2008 to August 2009 were included. The composition of urinary calculi was assessed by using commercially available postprocessing software and was compared with results of the reference standard (ex vivo infrared spectroscopy) in 40 patients for whom the reference standard was available. Effective doses were calculated. Image quality was rated subjectively and objectively and was correlated with patient size expressed as body cross-sectional area at the level of acquisition by using Spearman correlation coefficients. One calcified concrement in the distal ureter of an obese patient was mistakenly interpreted as mixed calcified and uric acid. One struvite calculus was falsely interpreted as cystine. All other uric acid, cystine, and calcium-containing calculi were correctly identified by using dual-energy CT. The mean radiation dose was 2.7 mSv. The average image quality was rated as acceptable, with a decrease in image quality in larger patients. Low-dose unenhanced dual-source dual-energy CT can help differentiate between calcified, uric acid, and cystine calculi at a radiation dose comparable to that of conventional intravenous pyelography. Because of decreased image quality in obese patients, only nonobese patients should be examined with this protocol.

The feasibility of using microwave-induced thermoacoustic tomography for detection and evaluation of renal calculi

Imaging of renal calculi is important for patients who suffered a urinary calculus prior to treatment. The available imaging techniques include plain x-ray, ultrasound scan, intravenous urogram, computed tomography, etc. However, the visualization of a uric acid calculus (radiolucent calculi) is difficult and often impossible by the above imaging methods. In this paper, a new detection method based on microwave-induced thermoacoustic tomography was developed to detect the renal calculi. Thermoacoustic images of calcium oxalate and uric acid calculus were compared with their x-ray images. The microwave absorption differences among the calcium oxalate calculus, uric acid calculus and normal kidney tissue could be evaluated by the amplitude of the thermoacoustic signals. The calculi hidden in the swine kidney were clearly imaged with excellent contrast and resolution in the three orthogonal thermoacoustic images. The results indicate that thermoacoustic imaging may be developed as a complementary method for detecting renal calculi, and its low cost and effective feature shows high potential for clinical applications.

Limitations to Ultrasound in the Detection and Measurement of Urinary Tract Calculi

To evaluate differences in stone measurement using computed tomography (CT) and ultrasound (US). Axial unenhanced helical CT is the reference-standard imaging modality for the assessment of urinary tract calculi; however, US is also commonly used. Differences in stone measurement using these techniques are poorly described and contributors to measurement error remain unknown. All patients at our institution undergoing both abdominal CT and renal US less than 1 month apart since June 2004 were reviewed. Solitary renal calculi were identified on both CT and US in all cases. We identified 71 calculi in 60 patients. Compared with CT, US overestimated stone size, an effect that was more pronounced with smaller calculi. The mean stone measurement on CT was 7.4 +/- 4.4 mm and on US it was 9.2 +/- 4.5 mm (P = .018). For stones </=5 mm, US measurements were a mean of 1.9 +/- 1.2 mm greater than CT (P <.001). US and CT measurements were discordant for 60% of stones </=5 mm. Discordance was associated with US measurement of skin-to-stone distance (P = .018), but not body mass index (P = .189) or location within the urinary tract (P = .161). Review of the literature revealed that US has a pooled sensitivity and specificity of 45% and 94%, respectively, for the detection of ureteric calculi and 45% and 88%, respectively, for renal calculi. US overestimates stone size in urolithiasis, a finding that may have implications for stone management. Discordance in stone measurement varies with size and is greatest in stones </=5 mm. US measurement of skin-stone-distance is an important determinant of error in US measurement of renal calculi.

Effect of Reduced Radiation CT Protocols on the Detection of Renal Calculi

To determine the effect of reduced radiation (tube charge, measured as milliamperes per second) protocols on the sensitivity and specificity of multidetector computed tomography (CT) in the detection of renal calculi. This Health Insurance Portability and Accountability Act-compliant human cadaveric study was approved by the Department of Anatomic Pathology with strict adherence to the university policy for handling donor specimens. Three to five renal stones (range, 2.0-4.0 mm) were randomly placed in 14 human cadaveric kidneys and scanned with a 16-detector CT scanner at 100, 60, and 30 mAs while maintaining other imaging parameters as constant. Following acquisition, images were reviewed independently by two radiologists who were blinded to the location and presence of renal calculi. Interobserver agreement was measured with kappa statistics. The McNemar test was used to compare the sensitivity and specificity between different radiation settings for each reader. Specificity for both readers ranged from 105 (0.95; 95% confidence interval [CI]: 0.90, 0.99) to 109 (0.99; 95% CI: 0.95, 1.0) of 110 without significant differences between 30 and 60 mAs to the standard 100 mAs (P = .500 to >.999). Sensitivity ranged from 42 (0.74; 95% CI: 0.60, 0.84) to 48 (0.84; 95% CI: 0.72, 0.93) of 57, also without significant differences (P = .070 to >.999). When renal calculi detection rates were analyzed by size, 3.0-4.0-mm stones were detected well at all tube charge settings, ranging from 86%-90% (n = 21 for 3.0-mm stones) to 95%-100% (n = 19 for 4.0-mm stones). However, 2.0-mm stones were poorly detected at all tube charge settings (29%-59%; 5-10 of 17). Overall interobserver agreement for stone detection was excellent, with kappa = 0.862. Decreasing the tube charge from 100 to 30 mAs resulted in similar detection of renal stones while reducing patient radiation exposure by as much as 70%. Multidetector CT scanning parameters should be tailored to minimize radiation exposure to the patients while helping detect clinically significant renal stones.

Impact of dose reduction on CT detection of urolithiasis

Patients undergoing CT for the evaluation of stone disease are likely to receive high levels of radiation over time. Although the results from small studies using simulation software suggest that using a reduced radiation dose has little effect on calculi detection, larger prospective randomized studies are required to produce clinically applicable results.

Detection of Urinary Stones at Reduced Radiation Exposure: A Phantom Study Comparing Computed Radiography and a Low-Dose Digital Radiography Linear Slit Scanning System

In this experimental study we assessed the diagnostic performance of digital linear slit scanning radiography compared with computed radiography (CR) for the detection of urinary calculi in an anthropomorphic phantom imitating patients weighing approximately 58-88 kg. Compared with CR, linear slit scanning radiography is superior for the detection of urinary stones and may be used for pretreatment localization and follow-up at a lower patient exposure.

Color Doppler Twinkling Artifact and Clinical Use

The color Doppler twinkling artifact manifests as a rapidly changing mixture of red and blue colors behind a strongly reflecting structure. Spectral Doppler analysis of the twinkling artifact does not yield a flow spectrum. It is important to recognize this artifact because it may lead to misdiagnosis of vascular flow within a tissue. Additionally, the artifact may be considered a sonographic sign in the detection of calcifications and calculi. In this article, we review the history of the interesting phenomenon and its clinical use, as well as our personal experiences of the artifact.