Non-contrast spiral CT for patients with suspected renal colic

Renal colic, defined as acute flank pain caused by the passage of a ureteral calculus, is a common condition, but the correct diagnosis may not be apparent clinically. For decades, intravenous urography has been the test of choice for evaluating patients with suspected renal colic. Recently, unenhanced (non-contrast) helical CT has been shown to be an accurate and highly effective examination which can be used instead of intravenous urography. In this article, the technique is reviewed in detail, including its advantages and potential pitfalls.     

Low-dose nonenhanced helical CT of renal colic: assessment of ureteric stone detection and measurement of effective dose equivalent

PURPOSE: To evaluate a low-dose, nonenhanced helical computed tomographic (CT) protocol in the detection of ureteric stones and measure the associated effective dose equivalent (H(E)) of radiation. MATERIALS AND METHODS: Sixty patients suspected of having renal colic and referred by emergency department physicians underwent nonenhanced helical CT with 7-mm collimation and a 2:1 pitch and then conventional intravenous urography (IVU). The two studies were prospectively and independently interpreted. The diagnostic accuracy of CT for ureteric stone detection was determined by comparing the scans with the IVU images and with a combination of clinical, surgical, and other imaging findings. The radiation risk from typical CT and IVU examinations (five images) was measured in terms of H(E) and compared with the estimated risk from two previously reported CT protocols. RESULTS: CT correctly depicted 36 of 37 ureteric stones, and one false-positive case was recorded, for a sensitivity of 97%, specificity of 96%, and accuracy of 97%. The H(E) for our CT protocol was determined to be 2.8 mSv, which is about double that for IVU and about 75% and 50% of that for two previously reported CT protocols. CONCLUSION: Our low-dose CT protocol is superior to IVU and clinically adequate for diagnosis of renal colic.     

Low-dose unenhanced multidetector CT of patients with suspected renal colic

OBJECTIVE: This study is designed to assess the intraobserver and interobserver agreements and the diagnostic performances of low-dose unenhanced multidetector CT (MDCT) in patients with suspected renal colic. SUBJECTS AND METHODS: The study included 106 patients who underwent unenhanced MDCT with 4 x 2.5 mm collimation, 120 kVp, 30 mAs, and, if necessary, additional focused acquisitions at 60 or 120 mAs on areas with an equivocal ureteral stone or with significant image noise. The effective radiation dose was computer-simulated with software based on the Monte Carlo model and International Commission on Radiological Protection recommendations. CT scans were archived and independently reviewed by three radiologists during two interpretation sessions on a workstation with three dimensions functions. Intraobserver and interobserver agreements were calculated with the kappa statistics. Accuracy for detection of ureteral stone on low-dose MDCT was calculated by comparison with combined clinical (stone passage), surgical (stone retrieval, extracorporeal shock wave lithotripsy), biologic (urinalysis, urine culture), and other imaging (excretory urography, standard-dose MDCT, follow-up sonography, and abdominal radiography) findings or by evidence for an alternative diagnosis. RESULTS: Ureteral stones were present in 38 (36%) of 106 patients. Thirty-six of 38 ureteral stones were detected by low-dose MDCT. From reviewer to reviewer, the number of true-positive, false-positive, true-negative, and false-negative findings ranged, respectively, from 34 to 36, 1 to 4, 64 to 68, and 2 to 4. The corresponding sensitivity, specificity, and accuracy ranged from 89.5% to 94.7%, from 94.1% to 100%, and from 93.4% to 98.1%, respectively. The intraobserver and interobserver agreements were excellent, with kappa values ranging from 0.87 to 0.98. In 13 patients, an alternative diagnosis explaining the patient's symptoms was proposed by all reviewers using images obtained at 30 mAs. No additional or alternative diagnosis was found at standard dose. At 30 mAs, the mean effective dose was 1.2 mSv in men and 1.9 mSv in women. Additional acquisitions at 60 mAs, all focused on the lower pelvis, were acquired in 20 patients, but the corresponding images were needed by the reviewers for only six of them. The acquisitions at 60 mAs were responsible for an additional mean effective dose of 0.5 in men and 0.8 mSv in women. CONCLUSION: Our study shows that low-dose unenhanced MDCT is appropriate for the diagnosis of ureteral stones, and that it provides excellent intraobserver and interobserver agreements and does not obscure alternative diagnoses.     

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

Purpose

The 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).

Methods

181 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.

Results

The 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.

Conclusions

In 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.

     

Present-day imaging of patients with renal colic

In the past decade alternatives to urography have been proposed for the study of patients with renal colic. In 1992 it was suggested to replace urography with KUB and ultrasonography. In 1993 the combination of KUB and ultrasonography followed by urography in unresolved cases was proposed and, in 1995, it was suggested to replace urography with unenhanced helical CT (UHCT). This article illustrates the contribution of UHCT to the study of patients with renal colic and analyses advantages and shortcomings of the technique compared with other diagnostic approaches. Diagnostics of the patient with renal colic is based on the detection of direct and indirect signs which allow identification of not only the calculus, with a sensitivity of 94–100 % and accuracy of 93–98 % according different authors, but also other signs that can serve to guide patient management and evaluate long-term prognosis. Unenhanced helical CT has the capability to detect extraurinary abnormalities which present with flank pain and mimic renal colic. The examination technique affects the quality of the images and therefore diagnostic accuracy as well as the dose to the patient. With regard to setting parameters, the choice of thickness and table feed should be guided by numerous factors. Multiplanar reconstruction is indicated in the study of the entire ureter course to identify the exact site of the calcification for the urologist to perform an evaluation similar to that obtained by urography. Many authors consider UHCT to be a valuable tool for suggesting the best therapeutic approach. Among these there are also urologists. The evaluation is based on the stone detection, its size and level in the urinary tract. Cost analysis shows that the cost of UHCT is equal to or inferior to the cost of urography. With regard to the dose, different data are reported in the literature. A high pitch (more than 1.5) and a thin collimation (3-mm thickness) are good compromise between quality and dose which can be compared to the dose of normal urography. What is to be done if helical CT is not available? If helical CT is not available, plain film plus ultrasonography should be considered. This approach does not solve all the cases; in unresolved cases urography is indicated. It should also be noted that US has a good sensitivity in detecting other conditions such as biliary lithiasis, acute pancreatitis, acute appendicitis and abdomino-pelvic masses which are responsible for pain that mimics renal colic. In conclusion, IVU should not have any more the priority in investigating the patients with renal colic. Helical CT should be the first choice in imaging a patient with renal colic. If this technique is not available, plain film and ultrasonography should be considered adding urography in unresolved cases.     

Nonenhanced helical CT and US in the emergency evaluation of patients with renal colic: prospective comparison

PURPOSE: To compare nonenhanced helical computed tomography (CT) with ultrasonography (US) for the depiction of urolithiasis. MATERIALS AND METHODS: During 9 months, 45 patients (mean age, 44 years; mean weight, 92.5 kg) prospectively underwent both nonenhanced helical CT (5-mm collimation; pitch of 1.5) and US of the kidneys, ureters, and bladder. US evaluation included a careful search for ureteral calculi. Presence of calculi and obstruction and incidental diagnoses were recorded. Clinical, surgical, and/or imaging follow-up data were obtained in all patients. The McNemar test was used to compare groups. RESULTS: Diagnoses included 23 ureteral calculi and one each of renal cell carcinoma, appendicitis, ureteropelvic junction obstruction, renal subcapsular hematoma, cholelithiasis, medullary calcinosis, and myelolipoma. CT depicted 22 of 23 ureteral calculi (sensitivity, 96%). US depicted 14 of 23 ureteral calculi (sensitivity, 61%). Differences in sensitivity were statistically significant (P: =.02). Specificity for each technique was 100%. When modalities were compared for the detection of any clinically relevant abnormality (eg, unilateral hydronephrosis and/or urolithiasis in patients with an obstructing calculus), sensitivities of US and CT increased to 92% and 100%, respectively. One case of appendicitis was missed at US, whereas medullary calcinosis and myelolipoma were missed at CT. CONCLUSION: Nonenhanced CT has a higher sensitivity for the detection of ureteral calculi compared with US.     

Radiologic investigation of renal colic: unenhanced helical CT compared with excretory urography.

OBJECTIVE: Our aim was to compare unenhanced helical CT and excretory urography in the assessment of patients with renal colic. SUBJECTS AND METHODS: Fifty-three of 70 consecutive patients with acute signs of renal colic were prospectively examined with unenhanced helical CT, which was followed immediately by excretory urography. Two radiologists who were unaware of the findings independently interpreted these examinations to determine the presence or absence of ureteral obstruction. On all CT scans that had positive findings for ureteral stones or obstruction, we looked for secondary signs of obstruction (perinephric or periureteral fat stranding, ureteral wall edema, ureteral dilatation, and blurring of renal sinus fat). RESULTS: A stone was recovered in 45 of the 53 patients, nine before and 36 after imaging. The latter 36 patients had their stones identified on CT, whereas only 24 patients had their stones identified on excretory urography. Eight patients without stone disease had normal ureters on both CT and excretory urography. Of the 45 patients who had stone disease, 26 had ureteral dilatation on both CT and excretory urography, and 36 patients who recovered a stone after CT had secondary signs of obstruction. Of the nine patients who recovered a stone before CT, three had secondary signs of obstruction. Two patients had periureteral fat stranding, ureteral wall edema, and renal sinus fat blurring. One patient had only ureteral wall edema. CONCLUSION: Compared with excretory urography, unenhanced helical CT is better for identifying ureteral stones in patients with acute ureterolithiasis. Secondary CT signs of obstruction, including renal sinus fat blurring, were frequently present even when the stone was eliminated before imaging.     

CT血流灌注参数对于肾动脉狭窄的肾脏血流研究价值

目的:探讨利用CT血流灌注参数研究肾动脉狭窄患者肾脏血流状况.方法:高血压患者34人,分为肾动脉狭窄组(23人)和对照组(11人),通过肾脏电影扫描获得的CT时间密度曲线测量肾脏皮质血流量,分析肾脏皮质血流量与肾动脉狭窄程度的关系.结果:肾动脉狭窄程度 ＜50%、50%～75%、＞75%肾皮质血流量(RBF)分别是 268±47.2ml/100g/min,227±39.2ml/100g/min, 225±88.2ml/100g/min,对照组RBF 345±62ml/100g/min.肾动脉狭窄＞50%的肾皮质血流量与对照组有明显差别(P＜0.05).结论:明显肾动脉狭窄的肾脏皮质RBF下降,CT血流灌注参数可以评估肾动脉狭窄导致的肾脏血流改变.     

Ultrasound detection of differences in density. Explanation of the ureteric jet phenomenon and implications for new ultrasound applications

Flow of urine from the ureter into the bladder can be encountered during routine sonographic examination of the pelvis. The findings include a stream of hyperechogenic foci spurting into the bladder in real time with the production of a frequency shift during Doppler examination. We have demonstrated that visualization of this phenomenon, at least in part, reflects differences in density and associated compressibility changes between urine in the bladder and in the ureter, and need not be dependent upon flow velocity or other previously hypothesized parameters. The clinical utility of these reproducible and measurable phenomena is explored.     

Suspected ureteral colic: plain film and sonography vs unenhanced helical CT. A prospective study in 66 patients

The aim of this study was to compare the sensitivity and specificity of plain abdominal films plus ultrasound, vs nonenhanced CT for the diagnosis of ureteral colic in patients with acute flank pain. During a 4-month period, 66 patients (mean age 48 years) with acute flank pain were prospectively studied by means of plain abdominal film, US, and unenhanced CT. The presence of lithiasis and of obstructive uropathy signs were determined. The plain film was only used as a guide for the US exam. Clinical follow-up of all patients was obtained. Ureteral lithiasis was confirmed in 56 patients. The CT had a greater sensitivity (93 vs 79%) and negative predictive value (71 vs 46%) for the detection of lithiasis. The combination of lithiasis plus obstructive signs showed a sensitivity and a specificity of 100% for CT and of 100 and 90%, respectively, for US. The 11 lithiasis not detected by US were passed spontaneously (10 were <5 mm). Both techniques showed similar extraurinary pathology. Computed tomography is the most accurate technique for the detection of ureteral lithiasis; however, the combination of plain film and US is an alternative to nonenhanced CT with a lower sensitivity and radiation dose that has a good practical value.     

Radiation dose associated with unenhanced CT for suspected renal colic: impact of repetitive studies

OBJECTIVE: The purpose of our study was to assess the dose of ionizing radiation delivered through the use of unenhanced CT for suspected renal colic by determining the incidence of repeated unenhanced CT examinations and the cumulative radiation dose delivered. MATERIALS AND METHODS: All unenhanced CT examinations for suspected renal colic performed at our institution over a 6-year period were included, and patient age, sex, and multiplicity of examinations were determined. For the adult patient, this protocol prescribes a fixed tube current of 200 mA, 140 kVp, and a nominal slice width of 5 mm. The dose-length product (DLP) was estimated for 15 randomly chosen single-detector CT (SDCT) and MDCT adult flank pain examinations using manufacturer's software. The mean DLPs for SDCT and MDCT were computed and converted to effective doses. Total effective doses were calculated for patients who underwent more than three examinations, and values were compared with established standards. RESULTS: A total of 5,564 examinations were performed on 4,562 patients. Of these patients, 2,795 (61%) were women (mean age, 45.5 +/- 16.2 [SD] years) and 1,731 (38%) were men (mean age, 44.7 +/- 16.4 years), with 144 patients (3%) of pediatric age. The mean effective doses for a single study were 6.5 mSv for SDCT and 8.5 mSv for MDCT. A subset of 176 patients (4%) had three or more examinations, with estimated effective doses ranging from 19.5 to 153.7 mSv. All patients with multiple examinations had a known history of nephrolithiasis. CONCLUSION: Patients with a history of nephrolithiasis and flank pain are at increased risk for serial CT with potentially high cumulative effective doses.     

Rupture of renal artery aneurysm into the renal pelvis, clinically mimicking renal colic: diagnosis with multidetector CT

We report on a 60-year-old man, seen at the emergency department because of severe left flank pain. Clinical diagnosis was that of renal colic. Overnight he became haemodynamically unstable and haematuria became massive, so multidetector CT (MDCT) was performed. MDCT with reconstructions can represent complex imaging findings in a more straightforward way compared with transverse images. Rupture of a renal artery aneurysm into the left pelvis was seen on coronal reconstructed CT images. Nephrectomy was performed. Rupture of a renal artery aneurysm into the pelvis is unusual and death is likely if diagnosis and treatment are delayed. The initial clinical presentation may be very similar to renal colic. MDCT allows timely and correct diagnosis of this unusual condition.     

Efficacy of model-based iterative reconstruction technique in non-enhanced CT of the renal tracts for ureteric calculi

The purpose of this study was to assess the efficacy of model-based iterative reconstruction (MBIR), statistical iterative reconstruction (SIR), and filtered back projection (FBP) image reconstruction algorithms in the delineation of ureters and overall image quality on non-enhanced computed tomography of the renal tracts (NECT-KUB). This was a prospective study of 40 adult patients who underwent NECT-KUB for investigation of ureteric colic. Images were reconstructed using FBP, SIR, and MBIR techniques and individually and randomly assessed by two blinded radiologists. Parameters measured were overall image quality, presence of ureteric calculus, presence of hydronephrosis or hydroureters, image quality of each ureteric segment, total length of ureters unable to be visualized, attenuation values of image noise, and retroperitoneal fat content for each patient. There were no diagnostic discrepancies between image reconstruction modalities for urolithiasis. Overall image qualities and for each ureteric segment were superior using MBIR (67.5 % rated as ‘Good to Excellent’ vs. 25 % in SIR and 2.5 % in FBP). The lengths of non-visualized ureteric segments were shortest using MBIR (55.0 % measured ‘less than 5 cm’ vs. ASIR 33.8 % and FBP 10 %). MBIR was able to reduce overall image noise by up to 49.36 % over SIR and 71.02 % over FBP. MBIR technique improves overall image quality and visualization of ureters over FBP and SIR.     

16层螺旋CT对肾结石并发肾盂癌术前诊断的可行性

目的探讨16层螺旋CT对肾结石并发肾盂癌的术前诊断价值。方法回顾性分析经手术病理证实的14例肾结石并发肾盂癌的B超及多层螺旋CT资料,并将二者的诊断与术后病理诊断对比。结果 B超检查术前有6例漏诊并发肾盂癌,检查漏诊率42.8%(6/14);而多层螺旋CT术前13例诊断明确,仅有1例漏诊,检查准确率达92.8%(13/14)。结论与超声相比,16层多层螺旋CT能显著提高肾结石并发肾盂癌的术前诊断准确率,故可作为肾结石并发肾盂癌术前诊断的首选检查方法。