Sensitivity and value of digital CT scout radiography for detecting ureteral stones in patients with ureterolithiasis diagnosed on unenhanced CT.

OBJECTIVE: When unenhanced CT reveals ureterolithiasis, some patients will require baseline or follow-up conventional radiography to help guide clinical management. We sought to determine the sensitivity of routinely obtained scout radiographs for revealing stones to determine if the scout view can be used in place of baseline conventional radiography. MATERIALS AND METHODS: We retrospectively reviewed the CT scout radiographs in conjunction with axial CT images in a series of 215 consecutive patients in whom CT revealed a single ureteral stone. On the scout radiographs, stones were classified as definitely visible, definitely not visible, or indeterminate. In addition, a phantom was constructed using fragments of kidney stones to evaluate the effect of the digital scout kilovoltage settings on stone visualization. RESULTS: Forty-nine percent of stones were definitely visible on scout radiography, 47% were definitely not visible, and 4% were indeterminate. Four stones larger than 10 mm that were not visible on scout radiography were composed of uric acid (n = 2) or xanthine (n = 2). Scout radiographs of the phantom determined an optimal kilovoltage setting of 80-100 kVp to visualize stones less than 3 mm, whereas stones greater than or equal to 3 mm were visible at all kilovoltage settings. CONCLUSION: In our series, 49% of ureteral stones were visible on the often-overlooked routine CT scout radiograph. Imaging of phantoms showed that stone visualization can be optimized by using the lowest kilovoltage settings. Therefore, the CT scout view can be used as a baseline study in patients requiring follow-up radiography and for planning treatment of patients requiring lithotripsy or other intervention. Finally, large stones not visible on scout radiographs are likely composed of uric acid or xanthine.     

Abdominal radiography after CT reveals urinary calculi: a method to predict usefulness of abdominal radiography on the basis of size and CT attenuation of calculi

OBJECTIVE: The purpose of this study was to determine if the radiographic visibility of urinary tract calculi could be predicted on the basis of CT features. MATERIALS AND METHODS: The images of 26 patients whose urinary tract calculi were revealed on unenhanced helical CT and who also underwent digital abdominal radiography were retrospectively reviewed. CT features studied included size and CT attenuation of the calculi. These CT findings were correlated with the ability to detect the same calculi with radiography. RESULTS: Forty-nine urinary tract calculi were detected with unenhanced helical CT in 26 patients. Twenty-six (53%) calculi were visible on radiography. Most (79%) calculi larger than 5 mm were detectable with radiography (p < 0.01). One (8%) of 13 calculi with CT attenuation below 200 H was detectable on radiographs. Ninety-five percent (21/22) of calculi with CT attenuation exceeding 300 H were visible on radiographs (p < 0.0001). The one remaining calculus was obscured by overlying anatomy. CONCLUSION: Radiographic surveillance of urinary tract calculi detected with CT may not be useful if the calculi have a CT attenuation below 200 H. Most calculi larger than 5 mm and nearly all calculi with a CT attenuation exceeding 300 H can be seen on abdominal radiographs.     

Trends in the use of unenhanced helical CT for acute urinary colic

OBJECTIVE: Unenhanced helical CT for urolithiasis detection is a limited CT examination that was designed specifically for the detection of urolithiasis. The purpose of this study was to repeat a prior study to assess whether clinicians had broadened the indications and changed the yield and findings of unenhanced helical CT. MATERIALS AND METHODS: One hundred consecutive patients with suspected renal colic or flank pain referred for unenhanced helical CT were selected for this study. We reviewed the original radiographic reports for each patient and recorded the presence of ureteral calculi. Other urinary abnormalities and extraurinary lesions were also recorded and compared with the results of the previous study. RESULTS: In this study, 56% of the patients who underwent unenhanced helical CT had symptoms of urinary colic, and 44% of patients had unspecified flank pain, compared with 100% of patients with symptoms of urinary colic 1 year earlier. The sensitivity and specificity of unenhanced helical CT in detecting ureteral calculi were 96% and 99%, respectively. Ureteral calculi were identified in only 28% of the patients versus 49% of patients (p < .01) 1 year earlier. Extraurinary lesions were identified in 45% of the patients versus 16% (p < .01) 1 year before. CONCLUSION: As clinicians developed familiarity with this technique, the indications for performance of unenhanced helical CT were expanded with a consequent reduction in the rate of detection of stone disease and identification of an increased number of extraurinary lesions, which suggests a demand for emergency abdominal CT studies.     

Suspected ureteral colic: primary helical CT versus selective helical CT after unenhanced radiography and sonography.

OBJECTIVE: The purpose of this study was to compare the accuracy of unenhanced helical CT with combined sonography and unenhanced radiography in patients with acute flank pain suggestive of ureteral colic. SUBJECTS AND METHODS: From January 1997 to December 1999, 181 consecutive patients with acute flank pain underwent unenhanced radiography, sonography, and unenhanced helical CT (protocol A). From January 2000 to December 2000, 96 consecutive patients arriving at the emergency department with acute flank pain were alternately submitted either to primary unenhanced helical CT (protocol B, 48 patients) or to unenhanced radiography and sonography with the addition of helical CT in unclear cases (protocol C, 48 patients). RESULTS: When compared with the diagnostic accuracy for ureterolithiasis of the combined sonography and radiography in the same group of subjects (protocol A), CT had a greater sensitivity (92% vs 77%), negative predictive value (87% vs 68%), and overall accuracy (94% vs 83%). Among patients who underwent primary CT (protocol B), we found three false-negatives (all with spontaneous stone passage) and no false-positives. Among patients initially examined with unenhanced radiography and sonography (protocol C), we found one false-positive (leading to patient admission and needless repeated radiographic and sonographic studies) and six false-negatives (all followed by an uncomplicated course and spontaneous passage); CT depicted four of these stones but did not result in change in treatment. Fourteen percent of the patients in protocol C required invasive treatment, but combined sonography and radiography showed stones and hydronephrosis in all these patients. CONCLUSION: Unenhanced CT was the most accurate modality for determining the presence of ureterolithiasis. The combination of abdominal radiography and sonography, however, yielded comparable results with no clinically important misdiagnoses and thus can be used as an alternative when CT resources are limited.     

Value of multislice helical CT scans and maximum-intensity-projection images to improve detection of ureteral stones at abdominal radiography

OBJECTIVE: The purpose of this study was to assess the improvement in the detection of ureteral stones on abdominal radiographs when the stones were viewed on multislice helical CT scans and maximum-intensity-projection (MIP) images. SUBJECTS AND METHODS: The study included 72 patients with renal colic who underwent abdominal radiography and multislice helical CT. For each patient, a frontal MIP image was generated, and the stone, when present, was marked with a cross on the transverse CT scan. The cross appeared automatically on the corresponding MIP image. The CT examination was used as the standard of reference. The presence and location of ureteral stones on the abdominal radiographs were assessed during three interpretation sessions. In the first session, the abdominal radiographs were viewed alone. In the second, they were viewed with the transverse CT scans. In the third, the abdominal radiographs were viewed with the CT scans and the MIP images. RESULTS: Ureteral stones were present in 58 patients. The percentage of stones detected on the abdominal radiographs was 45% when the radiographs were viewed alone, 66% when they were viewed with the CT scans (p = 0.002 vs radiographs alone), and 78% when viewed with the CT scans and MIP images (p = 0.016 vs radiographs with CT scans). CONCLUSION: The sensitivity of stone detection on abdominal radiographs was greatest when the interpreters viewed the radiographs in conjunction with the CT scans and MIP images.     

Nontraumatic acute abdominal pain: unenhanced helical CT compared with three-view acute abdominal series

PURPOSE: To prospectively evaluate and compare the diagnostic accuracy of unenhanced helical computed tomography (CT) for patients with nontraumatic acute abdominal pain with that of traditional abdominal radiography. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained; this study was completed before implementation of the HIPAA. Ninety-one patients (44 men; 47 women; age range, 18-84 years; mean age, 48.5 years) with acute nontraumatic abdominal pain over a 7-month period were referred by the emergency department of one institution. These patients underwent a three-view acute abdominal series (AAS) and unenhanced helical CT. AAS included an upright chest radiograph and upright and supine abdominal radiographs. Unenhanced helical CT images with 5-mm collimation were obtained from the lung bases to the pubic symphysis, without intravenous, oral, or rectal contrast material. AAS and unenhanced helical CT images were each separately and prospectively interpreted by a different experienced radiologist who was blinded to patient history and the images and interpretation of the other examination for each patient. Final diagnosis was established with surgical, pathologic, and clinical follow-up. The sensitivity, specificity, accuracy, positive predictive value, negative predictive value, and positive and negative likelihood ratios were calculated for AAS and unenhanced helical CT. Confidence intervals of 95% were calculated for each value with the standard equation for population proportions. Results of AAS and unenhanced helical CT examinations were compared with chi2 analysis. RESULTS: Among the 91 patients examined, unenhanced helical CT yielded an overall sensitivity, specificity, and accuracy of 96.0%, 95.1%, and 95.6%, respectively. The AAS interpretations yielded an overall sensitivity, specificity, and accuracy of 30.0%, 87.8%, and 56.0%, respectively. The accuracy of unenhanced helical CT was significantly greater than the accuracy of AAS (P < .05). CONCLUSION: AAS is an insensitive technique in the evaluation of nontraumatic acute abdominal pain in adults. Unenhanced helical CT is an accurate technique in the evaluation of adult patients with nontraumatic acute abdominal pain and should be considered as an alternative to radiography as the initial imaging modality.     

Subchondral fractures in osteonecrosis of the femoral head: comparison of radiography,CT, and MR imaging

OBJECTIVE: Our objective was to compare the sensitivity of unenhanced radiography, CT, and MR imaging in revealing subchondral fractures. SUBJECTS AND METHODS: Forty-five subjects with stage I and stage II osteonecrosis of the femoral head were included in the study as part of a multicenter clinical trial to evaluate the effectiveness of recombinant human bone morphogenetic protein as an adjuvant treatment to core decompression. Patients were evaluated with radiography, CT, and MR imaging 6 and 12 months after surgery. RESULTS: At 6 months, 18 fractures were shown on CT scans, but only 12 were detected on radiographs and six, on MR images. At 12 months, 20 subchondral fractures were detected on CT scans, but only 17 were seen on radiographs and 11, on MR images. Compared with CT, MR imaging has a sensitivity and specificity of 38% and 100%, and unenhanced radiography has a sensitivity and specificity of 71% and 97%, respectively. On T2-weighted MR images, the subchondral fractures were visualized as crescentic high-signal-intensity lines, and in all patients, on the corresponding CT scans, the fracture clearly breached the femoral cortex. CONCLUSION: CT reveals more subchondral fractures in osteonecrosis of the femoral head than unenhanced radiography or MR imaging. The high-signal-intensity line seen on T2-weighted MR images appears to represent fluid accumulating in the subchondral fracture, which may indicate a breach in the overlying articular cartilage.     

Evaluation of the sensitivity of scout radiographs on unenhanced helical CT in identifying ureteric calculi: a large UK tertiary referral centre experience

Objective

Unenhanced helical CT for kidney, ureter and bladder (CT KUB) has become the standard investigation for renal colic. This study aims to determine the sensitivity of scout radiographs in detecting ureteric calculi using CT KUB as a standard reference.

Methods

A retrospective review of consecutive patients who presented with acute flank pain and were investigated using CT KUB. 201 patients with positive ureteric calculi were included. Two radiologists independently reviewed the scout radiographs with access to CT KUB images. Each observer recorded the presence or absence of calculi, location, size and mean Hounsfield units of each calculus.

Results

203 ureteric calculi were analysed from 201 patients. The overall sensitivity of scout radiographs for Observer A was 42.3% and for Observer B 52.2%, with an interobserver reliability κ-value of 0.78. The significance of mean Hounsfield units and size between two groups of patients with visible stones and those not visible were tested; the p-value for both variables was <0.0001, which is statistically significant. The study found that calculi in the upper ureter and larger than 4 mm are more likely to be seen on the scout radiograph.

Conclusions

Usage of CT scout radiography should be encouraged and reported routinely in conjunction with CT KUB as a baseline for treatment follow-up.Unenhanced helical CT for kidney, ureter and bladder (CT KUB) has become the standard investigation for renal colic [1,2]. Its superior sensitivity and specificity has led to the demise in popularity of intravenous urogram (IVU) [3-5], although there remain some concerns about radiation dose [6]. At our institution, CT KUB has been the first-line investigation for patients suspected of having acute renal colic since 2006 [7]. Serial plain abdominal radiographs (KUB) however remain useful baseline and follow-up investigations to track the passage of stones unless the calculi are radiographically occult, in which case CT KUB or ultrasound will then be the investigations of choice.Digital CT scout radiographs are produced routinely to assist in positioning patients before axial images are acquired. They are taken from the level of the xiphoid sternum to the level of the pubic symphysis. The scout view is often overlooked and deemed not to be of diagnostic quality. However it has been proposed that careful study of the scout radiograph may identify the calculus and negate the need for a baseline plain abdominal KUB radiograph [8].In our institution, only a small number of patients who had ureteric calculi diagnosed on CT KUB had baseline plain radiographs at the same clinical presentation; the timing of the baseline plain KUB radiographs taken differs depending on varying urologists'' clinical practices. This has posed a real clinical dilemma as the absence of calculi on follow-up plain KUB taken several days after the initial presentation could be due either to the successful passage of calculi or to a radiographically occult stone. As a consequence, repeat CT KUB is occasionally performed in order to clarify the position of the calculi. We postulate that, if scout radiographs have sufficient sensitivity to detect calculi, they can be reported in conjunction with all the CT KUB examinations and patients will have a clear follow-up pathway with either plain KUB or ultrasound at the time of presentation.Although there are several recently published series that evaluate the sensitivity of scout radiographs, the number of patients used was relatively small [8-11]. The primary aim of this study was to determine the sensitivity of CT KUB scout radiographs in detecting ureteric calculi using CT KUB as a standard reference and comparing this against the recently published series. Factors that may affect the sensitivity of detection on scout radiographs will be evaluated. The secondary end point was to assess the sensitivity of plain radiographs in detecting ureteric calculi compared with scout radiographs using CT KUB as the gold standard. The potential saving on the cost of plain radiographs and radiation dose will be discussed.     

64层螺旋CT尿路成像与超声、X线平片诊断输尿管结石的对比研究

目的探讨64层螺旋CT尿路成像（MSCTU）诊断输尿管结石的临床价值。并与超声及平片结果对照分析。方法总结分析62例经MSCTU诊断,并经临床证实的输尿管结石患者的影像资料,并与超声及平片结果对照。结果MSCTU证实62例中双侧结石4例,多发3例,共计69枚结石,超声检出41枚（59．42％）,平片检出13枚（18．84％）。结论MSCTU对输尿管结石,尤其是微小结石的诊断明显优于超声及平片。     

CT and MR imaging of neurocysticercosis

OBJECTIVE: The purpose of this study was to evaluate whether unenhanced helical CT of the abdomen and pelvis, supplemented as necessary with delayed enhanced CT of the pelvis, is sufficient for urologists to treat patients with acute renal colic. MATERIALS AND METHODS: CT scans from 99 patients were analyzed retrospectively for the presence, size, and location of ureteral calculi and the presence and severity of secondary signs of obstruction. Clinical follow-up was analyzed by reviewing charts, directly communicating with patients, and reviewing surgical reports. Clinical information was correlated with CT findings. RESULTS: The findings of 51 CT scans were positive for calculi, and the findings of 48 were negative for calculi. The findings from two CT scans were false-positive, and none of the findings were false-negative. The sensitivity, specificity, and accuracy of helical CT were 100%, 96%, and 98%, respectively. A significant difference in stone size was found between patients who were treated conservatively (3.3 +/- 1.3 mm) and patients who underwent a urologic procedure (7 +/- 6.2 mm) (p < .01) and between patients in whom successful ureteral stent placement was the sole intervention (3.9 +/- 2.8 mm) and patients in whom initial stent placement failed and who then underwent a second urologic procedure (7.4 +/- 3 mm) (p < .05). We found no statistically significant difference between the conservatively and interventionally treated groups with respect to stone location. The presence and severity of secondary signs of obstruction were not significantly different between the two groups. CONCLUSION: Stone size alone was found to correlate with patient treatment. Stone location and the presence and severity of secondary signs of obstruction did not affect patient treatment. Because the degree of obstruction and relative renal function are not relevant to the initial treatment of patients with ureteral stone obstruction, CT is adequate for both diagnosis and treatment.     

Relationship of spontaneous passage of ureteral calculi to stone size and location as revealed by unenhanced helical CT.

OBJECTIVE: Prior studies using radiography have examined the relationship of ureteral stone size and location to the probability of spontaneous passage. Given the improved accuracy and new role of unenhanced CT in the diagnosis of acute ureterolithiasis, we studied the relationship of stone size and location as determined by unenhanced CT to the rate of spontaneous passage. MATERIALS AND METHODS: Over a 29-month period, 850 patients with acute flank pain were evaluated with unenhanced CT. Confirmation of the CT diagnosis was obtained retrospectively for 172 patients with ureteral stones: 115 stones passed spontaneously and 57 required intervention. Stone size was defined as the maximum diameter within the plane of the axial CT section. Stone location was classified as proximal ureter (above the sacroiliac joints), mid ureter (overlying the sacroiliac joints), distal ureter (below the sacroiliac joints), and ureterovesical junction. RESULTS: The spontaneous passage rate for stones 1 mm in diameter was 87%; for stones 2-4 mm, 76%; for stones 5-7 mm, 60%; for stones 7-9 mm, 48%; and for stones larger than 9 mm, 25%. Spontaneous passage rate as a function of stone location was 48% for stones in the proximal ureter, 60% for mid ureteral stones, 75% for distal stones, and 79% for ureterovesical junction stones. CONCLUSION: The rate of spontaneous passage of ureteral stones does vary with stone size and location as determined by CT. These rates are similar to those previously published based on radiography.     

Normal ureter size on unenhanced helical CT

OBJECTIVE: Unenhanced helical CT is the imaging method of choice when evaluating patients with acute flank pain and suspected ureterolithiasis. In addition to directly identifying stones in the lumen of the ureter, CT secondary signs of obstruction such as ureteral dilatation are frequently present and can be helpful in establishing a diagnosis. The purposes of this study were to define ureteral dilatation on unenhanced helical CT and determine the range of normal ureter size. MATERIALS AND METHODS: We retrospectively reviewed the unenhanced helical CT studies of 212 consecutive patients with acute flank pain whose CT scans showed acute ureterolithiasis. The size of the ureter was determined on the asymptomatic side as well as on the obstructed side. Mean ureteral diameter was determined as the largest transverse dimension along the course of the ureter beginning 1-2 cm below the ureteropelvic junction. RESULTS: The mean size of ureters on the asymptomatic side was 1.8 mm with a standard deviation (SD) of 0.9 mm. The mean size of ureters on the obstructed side was 7 mm with an SD of 3.2 mm. In 96% of patients, the ureter diameter on the asymptomatic side was 3 mm or smaller. CONCLUSION: Three millimeters should be considered the upper limit of normal size for nonobstructed ureters on unenhanced helical CT.     

Spiral computerized tomography without perfusion of contrast media as first line investigation in patients with renal colic

INTRODUCTION: We investigated the diagnostic accuracy of unenhanced helical CT in the detection of stones in patients with suspected renal colic from ureteral stones and compared CT findings with the results of plain abdominal film and US. MATERIAL AND METHODS: We reviewed the findings relative to 80 patients (age range 24-75) who came to our observation to the Emergency Department with acute flank pain. All patients had been examined with plain abdominal radiography, US and unenhanced helical CT. RESULTS: While abdominal radiography showed the presence of radiopaque stones in 38 patients only (47.5%), US demonstrated ureter dilatation in 72 patients and detected stones in 36 of them (45%). Helical CT performed best, depicting a stone in 72 patients (90%), with high sensitivity and specificity. Mean stone size was 3 mm, with 7 mm-1 mm range. The biggest stones were seen in 3 cases and the smallest ones in 34. In 8 patients with no signs of stones we found other extraurinary conditions, namely pancreatitis, diverticula, renal cancer. We also found a case of urinary tract infection. CONCLUSIONS: Thanks to its short execution time and accuracy, helical CT makes the examination of choice in patients with acute flank pain due to renal colic. It is also a most valuable tool in the differential diagnosis of other pathological causes of pain such as abdominal or pelvic masses and inflammatory conditions.     

Distinguishing pelvic phleboliths from distal ureteral calculi: thin-slice CT findings

The objective is to evaluate the appearance of phleboliths and distal ureteral stones by determining their roundness and presence of central lucency on thin-slice CT. Seventy-seven patients with pelvic radioopacities at unenhanced CT were selected. Those patients consequently underwent thin-slice CT with 1-mm collimation, a FOV of 10 cm, a pitch of 1:1 and a bone reconstruction algorithm. Three radiologists reviewed all images for roundness and the presence of central radiolucency. No calculi showed central lucency on either imaging technique used. Thin-slice CT revealed central lucency in 60% of phleboliths with 100% specificity. Three of 40 ureteral stones showed round contour. Thin-slice CT revealed a round contour in 97% of phleboliths with 93% specificity. Central lucency is a characteristic finding of pelvic phleboliths on thin-slice CT. This finding can therefore be used in combination with roundness as a problem-solving tool in differentiating phleboliths from distal ureteral stones.     

Acute nontraumatic abdominal pain in adult patients: abdominal radiography compared with CT evaluation

PURPOSE: To compare the diagnostic yield of abdominal radiography with that of computed tomography (CT) in adult patients presenting to the emergency department with nontraumatic abdominal pain. MATERIALS AND METHODS: Records of 1,000 consecutive patients presenting to the emergency department with acute abdominal pain from April to June 1998 were retrospectively reviewed. A total of 871 patients underwent abdominal radiography, and 188 underwent abdominal CT. The report interpretations of the abdominal radiographs and CT scans were divided into normal, nonspecific, and abnormal categories. Final discharge diagnoses were compared with the interpretations of the imaging examination results, and sensitivities and specificities of each modality were calculated and compared. RESULTS: Interpretation of abdominal radiographs was nonspecific in 588 (68%) of 871 patients, normal in 200 (23%), and abnormal in 83 (10%). The highest sensitivity of abdominal radiography was 90% for intraabdominal foreign body and 49% for bowel obstruction. Abdominal radiography had 0% sensitivity for appendicitis, pyelonephritis, pancreatitis, and diverticulitis. Sensitivities of abdominal CT were highest for bowel obstruction and urolithiasis at 75% and 68%, respectively. CONCLUSION: Abdominal radiographs are not sensitive in the evaluation of adult patients presenting to the emergency department with nontraumatic abdominal pain.     

Lung parenchymal injury and its frequency in blunt thoracic trauma: the diagnostic value of chest radiography and thoracic CT

PURPOSE: The aims of this study were to determine the value of chest radiography in diagnosing lung parenchymal injury in patients with thoracic trauma, and to evaluate the frequency of lung parenchymal injury by using thoracic computed tomography (CT). MATERIALS AND METHODS: Between January 2005 and June 2006, we retrospectively evaluated the anteroposterior chest radiographs and thoracic CTs of 60 patients that presented to our emergency department and were hospitalized due to multi-organ trauma. RESULTS: Chest radiography revealed parenchymal injury in 32 of the patients, while thoracic CT confirmed parenchymal injury in only 27 of these 32 patients. Chest radiographs did not reveal any parenchymal injury in 28 of the patients, whereas thoracic CT detected parenchymal injury in 12 of these 28 patients. Thoracic CT results were accepted as the gold standard in the evaluation of patients with chest trauma and showed that the sensitivity, specificity, positive predictive value, and negative predictive value of chest radiography in determining parenchymal injury were 69%, 76%, 84%, and 57%, respectively. In addition, thoracic CT revealed that 65% of the patients with blunt thoracic trauma suffered parenchymal injury. CONCLUSION: The sensitivity of anteroposterior chest radiography in identifying lung parenchymal injury was low, with a high false negative rate; therefore, we think that early evaluation with thoracic CT is extremely helpful in the diagnosis and treatment of patients with thoracic trauma, adding to the cooperative work that exists between radiologists and emergency physicians.     

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.     

Combined magnetic resonance urography and targeted helical CT in patients with renal colic: a new approach to reduce delivered dose

PURPOSE: To determine whether magnetic resonance urography (MRU), obtained before helical computed tomography (CT) in patients with acute renal colic, can help delimit the obstructed area to be subsequently examined by a targeted CT scan, thus reducing the dose of radiation. MATERIALS AND METHODS: Patients (51) with symptoms of acute renal colic underwent MRU and a total urinary tract helical CT. CT images from the 5 cm below the level of ureteral obstruction as demonstrated by MRU were selected out. Combined interpretation of MRU and selected CT images constituted protocol A. Protocol B consisted of the entire unenhanced helical CT of the urinary tract. The two protocols were compared regarding the following points: 1) sensitivity in diagnosing the presence of obstructing urinary stones, and 2) the delivered radiation dose. RESULTS: Protocol A and protocol B had, respectively, 98% and 100% sensitivity in demonstrating ureteral stone as a cause of renal colic. Estimated average dose calculated from phantom study was 0.52 mSv for protocol A and 2.83 mSv for protocol B. Therefore, the effective radiation dose was 5.4 times lower in protocol A compared to protocol B. CONCLUSION: Combined MRU and short helical CT has a high sensitivity in detecting ureteral calculi with a reduced radiation dose.     

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.     

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.