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.     

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

OBJECTIVE: The objective of this study was to assess the diagnostic value of attenuation measurements of the kidney on unenhanced helical CT in patients with obstructive ureterolithiasis. MATERIALS AND METHODS: Consecutive unenhanced helical CT scans of patients referred for acute unilateral renal colic were retrospectively reviewed. Patients with CT evidence of other urinary system diseases were excluded. Included scans (n = 145) were assessed for ureteral stone and secondary signs of obstruction such as unilateral collecting system or ureteral dilatation, perinephric stranding, and periureteral edema. Renal attenuation in Hounsfield units was measured in the upper, middle, and lower portions of the parenchyma, and a mean value was determined for each kidney. RESULTS: Ureteral stones were present in 76 patients. Renal attenuation on the side with lithiasis was lower than on the opposite kidney: 27.2 +/- 3.9 H vs 32.6 +/- 3.4 H (p < 0.001). Attenuation differences between kidneys were higher for patients with ureterolithiasis: 5.4 +/- 3.2 H (range, -3.3 to 13.0 H) versus 1.2 +/- 1.0 H (range, 0-4.7 H) (p < 0.001). An attenuation difference between kidneys greater than or equal to 5.0 H had 61% sensitivity, 100% specificity, 100% positive predictive value, 69% negative predictive value, and 79% accuracy for diagnosis of ureteral lithiasis. CONCLUSION: Attenuation difference between kidneys greater than or equal to 5.0 H was a valuable sign and had diagnostic performance similar to other secondary signs of obstructive ureterolithiasis. Furthermore, attenuation difference had the advantage of being an objective, measurement-based indicator.     

Relationship between duration of pain and secondary signs of obstruction of the urinary tract on unenhanced helical CT.

OBJECTIVE: The objective of this study was to investigate the relationship between duration of flank pain and the frequency of secondary signs of ureteral obstruction on unenhanced helical CT. SUBJECTS AND METHODS: The duration of flank pain was prospectively determined in 227 consecutive patients diagnosed with acute ureterolithiasis on unenhanced helical CT. These CT studies were evaluated for the presence or absence of perinephric stranding, ureteral dilatation, perinephric fluid, collecting system dilatation, periureteral stranding, and nephromegaly. The frequency of each sign was determined as a function of the duration of pain. RESULTS: The frequency of moderate or severe perinephric stranding increased from 5% at 1--2 hr to 51% at 7--8 hr (p < 0.001); ureteral dilatation increased from 84% at 1--2 hr to 97% at more than 8 hr (p < 0.03); moderate or severe perinephric fluid increased from 0% at 1--2 hr to 22% at 3--4 hr (p < 0.03); collecting system dilatation increased from 68% at 1--2 hr to 89% at 7-8 hr (p < 0.03); periureteral stranding increased from 35% at 1--2 hr to 76% at 7--8 hr (p < 0.004); and nephromegaly increased from 40% at 1--2 hr to 54% at 7--8 hr (p < 0.36). CONCLUSION: All CT secondary signs of ureteral obstruction except nephromegaly showed a significant increase in frequency as duration of flank pain increased. This observation may explain why the CT studies of some patients with acute ureterolithiasis show negative findings for some or all CT secondary signs of obstruction. Therefore, knowledge of the duration of pain is important when interpreting unenhanced CT studies in patients with acute ureterolithiasis.     

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.     

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

PURPOSE: To compare the efficacy of low-dose and standard-dose computed tomography (CT) for the diagnosis of ureteral stones. MATERIAL AND METHODS: Unenhanced helical CT was performed with both a standard dose (260 mAs, pitch 1.5) and a low dose (50 mAs, pitch 1.5) in 121 patients suspected of having acute renal colic. The two studies were prospectively and independently interpreted for the presence and location of ureteral stones, abnormalities unrelated to stone disease, identification of secondary signs, i.e. hydronephrosis and perinephric stranding, and tissue rim sign. The standard-dose CT images were interpreted by one reviewer and the low-dose CT images independently by two reviewers unaware of the standard-dose CT findings. The findings of the standard and low-dose CT scans were compared with the exact McNemar test. Interobserver agreements were assessed with kappa analysis. The effective radiation doses resulting from two different protocols were calculated by means of commercially available software to which the Monte-Carlo phantom model was given. RESULTS: The sensitivity, specificity, and accuracy of standard-dose CT for detecting ureteral stones were 99%, 93%, and 98%, respectively, whereas for the two reviewers the sensitivity of low-dose CT was 93% and 95%, specificity 86%, and accuracy 92% and 94%. We found no significant differences between standard-dose and low-dose CT in the sensitivity and specificity for diagnosing ureter stones (P >0.05 for both). However, the sensitivity of low-dose CT for detection of 19 stones less than or equal to 2 mm in diameter was 79% and 68%, respectively, for the two reviewers. Low-dose CT was comparable to standard-dose CT in visualizing hydronephrosis and the tissue rim sign. Perinephric stranding was far less clear on low-dose CT. Low-dose CT had the same diagnostic performance as standard-dose CT in diagnosing alternative diseases. Interobserver agreement between the two low-dose CT reviewers in the diagnosis of ureter stones and alternative diseases, the identification of secondary signs, and tissue rim sign were high, with kappa values ranging from 0.769 to 0.968. On standard-dose CT scans, the calculated mean effective radiation dose was 7.30 mSv for males and 10.00 mSv for females. On low-dose CT scans, the calculated mean effective radiation dose was 1.40 mSv for males and 1.97 mSv for females. CONCLUSION: Compared with standard scans using 260 mAs, low-dose unenhanced helical CT using a reduced tube current of 50 mAs results in a concomitant decrease in the radiation dose of 81%. Although low-dose CT was limited in its ability to depict small-sized calculi less than or equal to 2 mm, it is still comparable to standard-dose CT for the diagnosis of ureter stones and alternative disease.     

输尿管恶性肿瘤的影像学诊断

目的：探讨输尿管恶性肿瘤的影像学表现，提高对该病的诊断水平。方法：选择过去5年经手术和病理证实的12例输尿管恶性肿瘤患者，回顾性分析其静脉尿路造影、US、CT和MRI表现，并与手术及病理结果进行对照。结果：CT与MRI准确地检出了所有12例肿瘤，对其向周围组织的浸润范围和腹腔淋巴结肿大也作了正确的判断。静脉尿路造影仅显示3例输尿管狭窄或梗阻，6例患侧尿路未见显影或显影不佳。尽管US检出了所有12例肿瘤所致的尿路积水，但仅2例诊断为输尿管肿瘤，4例提示输尿管狭窄。结论：CT和MRI对诊断输尿管恶性肿瘤有很高的敏感性，并能对其准确分期。尿路造影和US对肿瘤所致的输尿管狭窄和梗阻有一定的诊断价值，但通常不能直接显示肿瘤及其向周围组织的浸润。     

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.     

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.     

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.     

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.     

CT对输尿管结石的诊断价值及其对临床治疗的导向作用（附54例分析）

目的探讨疑诊输尿管结石的急性肾绞痛病人的CT表现、CT诊断价值及其对临床治疗的指导作用。方法54例患均未口服对比剂直接CT平扫,5例平扫后静注泛影葡胺造影剂60ml,延迟10～15分钟增强扫描。2例盆腔感兴趣区域HRCT扫描。对每一例病人观察记录输尿管结石的部位、大小、有无继发CT征象。结果45例CT平扫显示输尿管内高密度结石影;5例未见阳性结石影像,仅有继发CT征象;肾盂结石、肾实质结石各1例;2例盆腔静脉结石。结石位于输尿管近端8例,中段4例,远段12例,输尿管膀胱交界处21例。37例有肾盂积水表现,36例有输尿管积水、35例有肾周水肿或肾周软组织影。输尿管周围水肿29例。结石直径大小为2～35mm,其中小于4mm17例,4～6mm20例,大于6mm8例。结论输尿管结石CT诊断,除直接显示高密度输尿管结石及其部位和大小外,还可显示输尿管结石的继发CT征象,而且对临床治疗方案的制定起指导作用。     

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.     

Helical CT in renal transplantation: normal findings and early and late complications.

Over a 5-year period, 346 helical computed tomographic (CT) studies were performed in renal transplant recipients. Helical CT proved useful in this context by depicting parenchymal, perirenal, renal sinus, pyeloureteral, and vascular complications in great detail. CT often delineates fluid collections and their anatomic relationship to adjacent structures better than ultrasonography (US), particularly in obese patients. CT-guided puncture and drainage can be performed in cases in which US is deemed inadequate. CT angiography can depict arterial diseases such as stenosis, thrombosis, arteriovenous fistulas, aneurysms, and pseudoaneurysms in the graft artery and in the recipient iliac arterial system, thereby obviating conventional angiography in some cases. Helical CT with three-dimensional image reformatting allows accurate imaging of the entire course of ureteral and periureteral diseases (eg, hydronephrosis, ureteral leak and stricture, pyeloureteral obstruction). CT can be used in the confirmation and staging of malignancies of the renal parenchyma and urothelium. It is also helpful in evaluating associated disease in the native kidneys, acute and chronic rejection, graft embolization, and end-stage disease. Although US and nuclear medicine examination are the imaging modalities of choice in renal transplantation, helical CT is a valuable alternative when these techniques are inconclusive.     

The role of renal scintigraphy and unenhanced helical computerized tomography in patients with ureterolithiasis

Unenhanced helical computerized tomography (UHCT) has recently evolved as an accurate imaging modality for determination of the presence or absence of ureterolithiasis in patients with acute flank pain. Functional renal scintigraphy is considered the gold standard for urinary tract obstruction. The objective of this study was to correlate the secondary signs of urinary obstruction on UHCT with findings of functional renal scintigraphy. UHCT was performed in 30 patients admitted to the emergency room with acute flank pain. All patients had a calcified urinary stone identified on UHCT. The location of each urinary stone was classified as ureteral or in the ureterovesical junction. The presence of secondary CT signs of ureteral obstruction was determined for each patient. After oral or intravenous hydration, a technetium-99m diethylene triamine penta-acetic acid renal scan was performed in all patients within 12 h of the CT scan. Follow-up delayed scintigraphic images were obtained at 2 h and 24 h in patients with evidence of ureteral obstruction. The sensitivity, specificity and predictive values of each possible combination of CT findings were determined by comparison with the scintigraphic results. The distal ureter was the most common location for a calculus on UHCT, followed in frequency by the ureterovesical junction, proximal ureter and mid-ureter. The renograms showed high-grade, unilateral obstruction in 12 patients, indeterminate scans in five patients and normal renograms in 13 patients. The sensitivities and specificities of individual CT findings ranged from 50% to 75% and from 8% to 69%, respectively. Perinephric stranding gave the highest positive predictive value (PPV) for obstruction (69% including indeterminate renograms). None of the individual CT findings showed a statistically significant correlation with scintigraphic findings. A combination of one or two positive CT findings had a PPV of only 25% for obstruction. A combination of three or four positive CT findings gave a PPV of 70% for obstruction. Our preliminary study shows that secondary CT signs of ureterolithiasis correlate poorly with the scintigraphic findings and that they do not permit evaluation of the functional status of obstructed kidneys. Even a combination of the most frequent CT findings has a low predictive value, i.e. does not allow a decision to be made as to the most suitable treatment. Therefore, renal scintigraphy should be performed in conjunction with UHCT in all patients with ureteral calculi. Received 21 October and in revised form 14 December 1999     

Sensitivity of CT scout radiography and abdominal radiography for revealing ureteral calculi on helical CT: implications for radiologic follow-up

OBJECTIVE: We compared the sensitivity of CT scout radiography with that of abdominal radiography in revealing ureteral calculi on unenhanced helical CT. MATERIALS AND METHODS: Over a 6-month period, patients presenting to the emergency department with acute flank pain were examined with standard abdominal radiography and unenhanced helical CT, which included CT scout radiography. In 60 patients in whom a diagnosis of ureteral calculus was made, CT scout radiographs and abdominal radiographs were examined by two interpreters who assessed whether stones could be visualized. All CT scout radiographs were viewed on a workstation using optimized window settings. RESULTS: CT scout radiography and abdominal radiography revealed 28 (47%) and 36 (60%) of 60 ureteral calculi, respectively. All ureteral calculi that appeared on CT scout radiography also appeared on abdominal radiography. However, eight calculi that were visible on abdominal radiography were not visible on CT scout radiography. CT scout radiography and abdominal radiography revealed 28% and 46% of 39 calculi less than or equal to 3 mm in diameter, respectively. For 21 calculi larger than 3 mm, the sensitivity of CT scout radiography and abdominal radiography was 81% and 86%, respectively. CONCLUSION: Abdominal radiography is more sensitive than CT scout radiography in revealing ureteral calculi; however, some calculi revealed on unenhanced helical CT cannot be seen on either abdominal radiography or CT scout radiography. Ureteral calculi not visible on either study can only be followed, when necessary, with unenhanced helical CT.     

The role of renal scintigraphy and unenhanced helical computerized tomography in patients with ureterolithiasis

Unenhanced helical computerized tomography (UHCT) has recently evolved as an accurate imaging modality for determination of the presence or absence of ureterolithiasis in patients with acute flank pain. Functional renal scintigraphy is considered the gold standard for urinary tract obstruction. The objective of this study was to correlate the secondary signs of urinary obstruction on UHCT with findings of functional renal scintigraphy. UHCT was performed in 30 patients admitted to the emergency room with acute flank pain. All patients had a calcified urinary stone identified on UHCT. The location of each urinary stone was classified as ureteral or in the ureterovesical junction. The presence of secondary CT signs of ureteral obstruction was determined for each patient. After oral or intravenous hydration, a technetium-99m diethylene triamine penta-acetic acid renal scan was performed in all patients within 12 h of the CT scan. Follow-up delayed scintigraphic images were obtained at 2 h and 24 h in patients with evidence of ureteral obstruction. The sensitivity, specificity and predictive values of each possible combination of CT findings were determined by comparison with the scintigraphic results. The distal ureter was the most common location for a calculus on UHCT, followed in frequency by the ureterovesical junction, proximal ureter and mid-ureter. The renograms showed high-grade, unilateral obstruction in 12 patients, indeterminate scans in five patients and normal renograms in 13 patients. The sensitivities and specificities of individual CT findings ranged from 50% to 75% and from 8% to 69%, respectively. Perinephric stranding gave the highest positive predictive value (PPV) for obstruction (69% including indeterminate renograms). None of the individual CT findings showed a statistically significant correlation with scintigraphic findings. A combination of one or two positive CT findings had a PPV of only 25% for obstruction. A combination of three or four positive CT findings gave a PPV of 70% for obstruction. Our preliminary study shows that secondary CT signs of ureterolithiasis correlate poorly with the scintigraphic findings and that they do not permit evaluation of the functional status of obstructed kidneys. Even a combination of the most frequent CT findings has a low predictive value, i.e. does not allow a decision to be made as to the most suitable treatment. Therefore, renal scintigraphy should be performed in conjunction with UHCT in all patients with ureteral calculi.     

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.     

Assessment of the clinical utility of the rim and comet-tail signs in differentiating ureteral stones from phleboliths.

OBJECTIVE: This study was designed to assess interobserver variability in identifying the rim and comet-tail signs and to determine the clinical utility of these signs in determining whether or not the calcifications with which they are associated represent ureteral calculi. MATERIALS AND METHODS: Two radiologists and a radiology resident, unaware of the final diagnosis, reviewed preselected helical CT images from renal stone examinations in patients with 65 indeterminate pelvic calcifications. Assessment of calcifications for rim or comet-tail signs was performed independently of an assessment for the following five secondary signs of urinary tract obstruction: caliectasis, pelviectasis, ureterectasis, perinephric stranding, and renal enlargement. Agreement in identifying rim and comet-tail signs was assessed by obtaining kappa statistics. The utility the of rim or comet-tail signs in determining whether ureterolithiasis was present in patients in whom perinephric stranding and ureterectasis were present or absent was determined. The frequency with which one or more of each of the five assessed secondary signs was identified ipsilateral to a calcification having rim or comet-tail signs was also tabulated. RESULTS: Kappa values for interobserver agreement ranged from 0.49 to 0.73. In only one patient was a rim sign detected in the absence of ureterectasis and perinephric stranding. Reviewers identified at least three of the five assessed secondary signs ipsilateral to calcifications showing a rim sign in all but one patient (by each radiologist) and four patients (by the resident). When three or more secondary signs of obstruction were seen ipsilateral to a calcification having a comet-tail sign, in all but one instance, this was because the calcification was a ureteral calculus or because there was a separate ipsilateral ureteral calculus. CONCLUSION: In many instances, observers did not agree about whether the rim and comet-tail signs were present. The rim sign was observed in the absence of any secondary signs of urinary tract obstruction in only one (1.5%) of the 65 patients in our series (95% confidence interval, 0-5.3%). The comet-tail sign, when accompanied by secondary signs of obstruction, should indicate that an ipsilateral ureteral stone is present and not the reverse.     

Ureterolithiasis: classical and atypical findings on unenhanced helical computed tomography

Evaluation of patients with acute flank pain using helical computed tomography (CT) is a well-accepted, rapid, and safe procedure in the emergency setting. Various primary and secondary signs are described in the literature for evaluation of these patients. Our purpose is to demonstrate both the classical findings associated with ureteral calculi on unenhanced helical CT and atypical findings and potential pitfalls. We also provide readers with a systematic approach to interpreting unenhanced helical CT scans performed for acute flank pain. Electronic Publication     

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.