Urinary stone size: comparison of abdominal plain radiography and noncontrast CT measurements

BACKGROUND AND PURPOSE: To compare urinary stone size as measured by abdominal plain radiography (AXR) with stone size as measured by noncontrast three-dimensional spiral CT in patients with acute renal colic. PATIENTS AND METHODS: Patients presenting to the emergency room of a single institution with urinary stones that were visible on both AXR and noncontrast spiral CT were identified. Two radiologists blinded to the clinical outcomes separately and randomly reviewed all films and measured maximum longitudinal (craniocaudal) and transverse (anteroposterior) stone diameters. The two-tailed paired Student's t-test was used to compare the sizes of each stone on AXR and CT. RESULTS: Over a 1-year period, 22 patients were identified with a total of 31 urinary stones visible on both AXR and CT. Nineteen stones were located in the kidney, three in the midureter, and nine in the distal ureter. The mean stone size by AXR was 6.1 mm (range 2-13 mm; SD +/- 1.95) in the longitudinal axis and 5.3 mm (range 2-11 mm; SD +/- 1.50) in the transverse axis. The mean stone size by CT was 6.9 mm (range 3-12 mm; SD +/- 1.95) in the longitudinal axis and 6.1 mm (range 2-11 mm; SD +/- 1.50) in the transverse. The differences between AXR and CT measurements did not attain significance in either the longitudinal (p = 0.67) or the transverse (p = 0.25) axis. CONCLUSIONS: A CT scan provides estimates of stone size that are consistently greater than those of AXR in both the longitudinal and transverse axes. However, for stones between 2 and 13 mm in maximum diameter, these differences do not attain significance. In patients with a history of radiopaque stones in this size range, therefore, AXR may provide useful size data for clinical decision-making without concern about significant disparities between the two modalities. As AXRs are more expeditiously obtained, incur less direct costs, and expose patients to significantly lower doses of radiation than CT scans, they remain a useful adjunctive study in the work-up of nephrolithiasis.     

Comparison of helical computerized tomography and plain radiography for estimating urinary stone size

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

Correlation of ureteral stone measurements by CT and plain film radiography: utility of the KUB

BACKGROUND AND PURPOSE: The practice of utilizing helical CT to evaluate patients suspected of renal colic is increasing. Little is known about the accuracy of CT in estimating stone size or the utility of an accompanying plain abdominal radiograph (KUB film). The purpose of our study was to compare ureteral stone size estimation by helical CT and plain film and determine whether a KUB film provides additional information useful in patient management. PATIENTS AND METHODS: Thirty consecutive patients (17 male, 13 female) having both a helical CT and a KUB study for evaluation of renal colic secondary to ureteral calculi comprised the study population. Calculus number, location, and dimensions were determined from these images. Stone dimensions were measured using electronic calipers on a picture archiving and communications system. Information found by KUB and CT was compared, and both sets of stone measurements were correlated with patient outcome. RESULTS: The mean maximal stone transverse diameter and length were similar on CT and plain film: 5.8 mm v 5.8 mm and 9.5 mm v 8.9 mm, respectively (P = 0.57 and 0.29, respectively). The mean anteroposterior stone diameter on CT of 6.8 mm was statistically greater than the transverse diameter as measured by both CT and KUB, which were 5.8 mm and 5.8 mm (P = 0.0002 and 0.0007, respectively). Eleven patients spontaneously passed their stones, while 19 patients required intervention. Patient outcome, as predicted by transverse stone width, was similar for CT and KUB data. CONCLUSIONS: The management of patients with ureteral calculi relies on estimated stone size and the stone's potential for spontaneous passage. Stone dimensions estimated by CT are similar to the size determined by plain film radiography. Although plain film radiography does not provide information on stone dimensions beyond that obtained with CT, it does reveal precise stone location and radiolucency, data helpful in following and treating patients.     

螺旋CT判定尿结石成分的体外研究

目的:探讨非增强螺旋CT检查对判断尿结石成分的可能性。方法:以改良Mauer法定分析30例尿结石样本的化学成分;在120 kV/140 mA、5 mm层厚下体外测定各类尿结石样本的CT值,比较各类尿结石成分CT值的差异。结果:纯尿结石的CT值由高到低依次为草酸钙(1890±100)Hu、磷酸钙(1382±74)Hu、胱氨酸(1089±22)Hu、磷酸镁铵(674±37)Hu和尿酸(148±88)Hu,纯尿结石成分之间CT值的差异有统计学意义(P<0.05);混和尿结石的CT值均在相应纯尿结石成分的CT值之间。结论:根据CT值可以初步判断尿结石的主要成分,预示着CT检查对于尿结石的诊断、治疗及预防复发有一定的实用价值;非增强螺旋CT是否可以判断体内各类尿结石的成分,还有待进一步研究。     

Determination of the chemical composition of urinary calculi by noncontrast spiral computerized tomography

Various techniques for noncontrast spiral computerized tomography (NCCT) were utilized for the determination of the Hounsefield unit (HU) values of various types of urinary calculi with the aim of determining the best technique for distinguishing various stones compositions. A total of 130 urinary stones, obtained from patients who underwent open surgery, were scanned with a multidetector row scanner using 1.25 mm collimation at two energy levels of 100 and 120 kV at 240 mA. Two post-scanning protocols were used for the HU value assignment, tissue and bone windows, for both kV values. In both protocols, three transverse planes were defined in each stone, one near the top, one in the middle, and one near the bottom. Three regions of interest (ROI) were obtained in each plane. The absolute HU value was determined by three methods: the mean of the nine ROI, the mean of the central three ROI, and the central ROI in the middle plane. Determination of the stones composition was performed using the absolute HU value measured at 120 kV, the dual CT values (HU values at 100 kV–HU values at 120 kV), and HU values/stone volume ratio (HU density). All stones were analyzed by x-ray diffraction to determine their chemical composition. After the exclusion of groups with few calculi, 47 pure stones [25 uric acid (UA), 15 calcium oxalate monohydrate (COM), seven struvite], and 60 mixed stones [15 COM 60–90%+hydroxyl apatite (HA), 14 COM 40–90%+UA, 21 UA+COM <40%, ten mixed struvite+COM+hydroxyl apatite] were included in the statistical analysis. From the least to the most dense, the pure stone types were UA, struvite, COM. Mixed UA+COM<40% calculi were less dense but insignificantly different from pure UA, while when the COM ratio was 40% their density became higher than and significantly different from pure UA, and less than but not significantly differentiated from pure COM. Mixed COM+HA were the most dense stones. Using the absolute HU values at 120 kV and HU density, we could distinguish, with statistical significance, all pure types from each other, pure UA from all mixed calculi except UA+COM <40%, pure COM from mixed UA+COM <40%, and pure struvite from all mixed stones except mixed struvite stones. Dual CT values were not as good as absolute HU values and HU density in the determination of stone composition. These results demonstrate that absolute HU values and HU density derived from CT scanning using a small collimation size could uncover statistically significant differences among all pure and most of the mixed urinary stones. This permits more accuracy in the prediction of stone composition. Moreover, this technique permits diagnostic conclusions on the basis of single CT evaluation.     

Determination of stone composition by noncontrast spiral computed tomography in the clinical setting

OBJECTIVES: Several investigators have evaluated noncontrast computed tomography (NCCT) in predicting stone composition in vitro. We assessed NCCT in predicting stone composition in patients presenting to our emergency room with flank pain and stone disease. METHODS: One hundred twenty-nine patients presenting to our university hospital with flank pain underwent renal colic protocol NCCT scans at the request of the emergency room physicians. A General Electric, high-speed advantage CT scanner was used at 120 kV, 200 mA, and 1.4:1 pitch, with collimation varying between 3 and 5 mm. Ninety-nine patients with predominantly (greater than 50%) calcium oxalate or uric acid composition after either stone passage or stone removal were identified. Each scan was analyzed by one of two radiologists, who determined the predominant attenuation for each stone. Stones once passed or retrieved were analyzed by Urocor Laboratories. The attenuation and attenuation/size ratio (peak attenuation/size in millimeters) were compared with the results of the stone analysis. RESULTS: Eighty-two calculi predominantly composed of calcium oxalate and 17 calculi predominantly composed of uric acid were identified in 99 patients. The calculi ranged in size from 1 to 28 mm. A significant difference (P = 0.017, unpaired t test) was found between the Hounsfield measurement of uric acid calculi (mean 344 +/- 152 HU) and the Hounsfield measurement of calcium oxalate calculi (mean 652 +/- 490 HU). If only the Hounsfield units from stones 4 mm or larger were compared, the data were even more compelling (P = 0.002). However, using an attenuation/size ratio cutoff of greater than 80, the negative predictive value was 99% that a stone would be predominantly calcium oxalate. CONCLUSIONS: Using peak attenuation measurements and the attenuation/size ratio of urinary calculi from NCCT, we were able to differentiate between uric acid and calcium oxalate stones.     

A comparison between an in vitro ureteroscopic stone size estimation and the stone size measurement with the help of a scale on stone baskets

Introduction

Endoscopic treatment of ureter stones and renal calculi relies on the surgeon’s estimation of the stone size for both lithotripsy and removal of stones or stone fragments. We therefore compared precision and reliability of the endoscopic estimation of stone size by the surgeon with measurements on a scale on a stone basket.

Materials and methods

Two surgeons (one high experienced and one low experienced) first estimated, then measured the size of 12 stones differing in size and color using different stone baskets (2.5, 3.0, 4.0 Ch) each via a semirigid renoscope in an artificial ureter under water repeatedly on two different days. All together, we had 288 measurements and 288 estimations.

Results

On the whole, the accuracy of the estimation diminished with bigger stones. There is an increasing underestimation with increasing stone size. Factors, which significantly influence the estimation, are the operating surgeon, the color of the stone, the time sequence, and the size of the closed basket, which was held beside the stone. The accuracy of the measurement of the stone baskets is not as good as the estimation. The small 2.5-Ch basket is the most accurate in measuring big stones (>6 mm), the 3.5 Ch in intermediate stones (3–6 mm), the big basket (4.0 Ch) in small stones (<3 mm).

Conclusion

This first attempt at validation of a scale on stone baskets shows different results for each basket which could be systematically improved. Until now, the estimation of the surgeons is better than the measurement, but it is also influenced by factors like the surgeon or the color of the stone.

     

螺旋CT仿真内窥镜技术对膀胱肿瘤的诊断价值

目的：探讨螺旋CT仿真内窥镜（CTVE）的成像技术及其对膀胱肿瘤的诊断价值。方法：应用螺旋CT对35例膀胱肿瘤患者进行膀胱容积扫描,所得数据在工作站利用软件进行后处理,形成CTVE影像,并用“Fly THrough”软件从多角度观察膀胱,所有患者均行纤维膀胱镜检查及手术治疗,并将术中所见及病理检查结果作为最后诊断标准。结果：所有患者均取得了高质量的CTVE图像,除1例（肿瘤直径＜0．5cm)漏诊外,其余患者均得到了明确诊断,并与手术或病理检查结果符合,其中2例位于膀胱前壁近前列腺部的肿瘤,纤维膀胱镜检查未能发现,而CTVE则明确显示。结论：CTVE对膀胱肿瘤是一种较可靠的非侵入性检查手段,具有一定的优越性,可作为泌尿系统常规检查方法的有益补充。     

Spectrum of stone composition: structural analysis of 1050 upper urinary tract calculi from northern India

BACKGROUND: The purpose of the present paper was to study the spectrum of stone composition of upper urinary tract calculi by X-ray diffraction crystallography technique, in patients managed at All India Institute of Medical Sciences. METHODS: Between 30 April 1998 and 31 March 2003, a total of 1050 urinary calculi (900 renal, 150 ureteric) were analyzed. The stone fragments were collected after extracorporeal shock-wave lithotripsy, or retrieval by endoscopic (percutaneous nephrolithotomy, ureterorenoscopy), laparoscopic and various open surgical procedures. The structural analysis of the stones was done using X-ray diffraction crystallography. RESULTS: Four types of primary and three secondary X-ray diffraction patterns were obtained. The primary patterns were as follows. Pattern A, well organized crystalline structure; pattern B, moderately organized crystalline structure; pattern C, poorly organized crystalline structure; pattern D, very poorly organized crystalline structure. The three secondary patterns mainly highlighted the mixed variety of stones. These patterns were further analyzed and compared with standard X-ray diffraction (powder) photographs. Of the 1050 stones analyzed, 977 (93.04%) were calcium oxalate stones, out of which 80% were calcium oxalate monohydrate (COM) and 20% were calcium oxalate dihydrate (COD). Fifteen were struvite (1.42%) and 19 were apatite (1.80%). Ten were uric acid stones (0.95%) and the remaining 29 (2.76%) were mixed stones (COM + COD and calcium oxalate + uric acid, calcium oxalate + calcium phosphate, and calcium phosphate + magnesium ammonium phosphate). A total of 89.98% of staghorn stones were made of oxalates (COM/+COD) and only 4.02% were struvite. CONCLUSION: Urinary stone disease in the Indian population is different from that in Western countries, with a larger percentage of patients having calcium oxalate stones, predominantly COM. Also, the majority of staghorn stones (89.98%) were made of oxalates.     

Clinical characteristics of ureteral calculi detected by nonenhanced computerized tomography after unclear results of plain radiography and ultrasonography

PURPOSE: Prospective non-enhanced computerized tomography (CT) was performed for patients presenting with renal colic and showing negative or equivocal results on plain x-ray of the kidneys, ureters and bladder (KUB) as well as ultrasonography (US) to evaluate the usefulness of plain CT. We also evaluated the clinical characteristics of urinary calculi detected under such conditions. MATERIALS AND METHODS: Between January 2000 and June 2002, 560 patients presented with acute unilateral renal colic. Of these patients 238 negative or equivocal for ureteral calculus on KUB and US underwent non-enhanced CT. The diagnostic value of plain CT in patients with negative or equivocal KUB and US was determined, and results and other clinical findings were compared. Clinical characteristics of ureteral stones detected by plain CT were compared with those of stones diagnosed by KUB and US. RESULTS: By plain CT 143 (60.1%) and 6 (2.5%) cases of pain were determined to have been caused by ureteral stones and other pathogeneses, respectively. No definitive diagnosis was obtained in 89 (37.4%). Stone size detected by plain CT was significantly smaller than controls (3.77 vs 6.37 mm, p <0.0001) and tended to be located in the middle or lower ureter (76.2% or 109 of 143 vs 52.2% or 168 of 322, p <0.0001). Symptoms spontaneously improved in 137 (95.8%) after conservative therapy while 6 underwent intervention, a rate significantly lower (p <0.0001) than controls (32.9% or 106 of 322). CONCLUSIONS: Non-enhanced CT is a useful modality for diagnosis of patients presenting with acute renal colic but whose results are negative or equivocal on KUB and US. Excretory urography is rarely needed because stones undetected on KUB and US tend to be small and in the middle or lower ureter, and spontaneous passage is expected.     

Comparison of spiral CT scan and arteriography for evaluation of renal and visceral arteries

Renal and visceral artery images obtained concurrently with spiral CT and conventional arteriography were compared for 32 patients. Indications for imaging were occlusive disease (n=12), aneurysmal disease (n=9), and renal or visceral artery disease (n=11). Conventional arteriography enabled visualization of 64 renal arteries and 15 accessory renal arteries. Lateral aortograms obtained in 15 patients enabled visualization of 14 superior mesenteric (SMA) and 14 celiac arteries. Spiral CT enabled visualization of 60 renal arteries, 12 accessory renal arteries, 27 SMAs, and 22 celiac arteries. Calcification or a disparity in timing of contrast material injection and scanning prevented visualization of the celiac artery in 10 patients and the SMA in four patients. With conventional arteriography as the standard for comparison, spiral CT had a sensitivity of 67% and a specificity of 95% for depiction of at least 75% stenosis in the main renal artery. By means of the Pearson correlation coefficient, significant correlation (p < 0.001) was confirmed between spiral CT and arteriography for evaluation of stenosis of the main renal artery, SMA, and celiac artery. This early experience suggests that spiral CT may be useful in evaluation of renal and visceral arteries and their relationship to aortic disease.Presented at the Twentieth Annual Meeting of the Peripheral Vascular Surgery Society, New Orleans, La., June 10, 1995.     

螺旋CT三维重建技术在鹿角形肾结石经皮肾镜取石术中的应用价值

目的 评价螺旋CT三维重建技术在经皮肾镜取石术(PCNL)治疗鹿角形肾结石中的应用价值. 方法 鹿角形肾结石87例104侧.采用16排螺旋CT平扫,容积成像技术进行结石三维重建,根据重建结果设定穿刺目标肾盏,初步判断建立多通道的必要性,并计算结石体积.患者均接受B超引导下24 F PCNL,记录穿刺通道位置、数目以及其他手术技术参数,收集结石并测量结石体积,KUB判断有无结石残留. 结果术中实际穿刺肾盏与术前根据CT三维重建结果设计的目标肾盏选择完全一致,建立多通道数目与术前预测符合率为91.5%(43/47);一期手术结石取净率87.5%,二期或多期手术后取净率91.7%;清除结石体积平均(16.34±13.79)cm3,术前CT三维重建估算结石体积平均为(19.35±19.24)cm3,两者之间相关性分析r=0.993,P=0.000. 结论 螺旋CT三维重建技术可形象直观地显示鹿角形肾结石的立体结构,指导术前穿刺通道的选择,并可以准确计量结石体积.     

Renal tumor size: comparison between computed tomography and surgical measurements

OBJECTIVE: We studied the agreement between renal tumor size as assessed on computed tomography (CT) before surgery and that measured during histopathological examination on the radical nephrectomy specimen. METHODS: We retrospectively analyzed the records of 100 consecutive patients treated with radical nephrectomy for a renal tumor. The tumor size was determined in all patients by the largest diameter shown within the month before surgery on contrast-enhanced CT and as measured postoperatively by the pathologist. A possible influence of the clinical and pathological parameters was assessed in a multivariate analysis. RESULTS: CT estimate and surgical measurement of tumor size were highly correlated (r = 0.9; p<0.001). Median (range) tumor size was 70.0 mm (13-180) and 60.0 mm (10-180) as measured, respectively, on CT and in the specimen, with a significant difference (p = 0.005). Multiple regression did not reveal any significant influence of tumor side, location, type, nuclear grade as well as patient gender, body mass index and radiological center (p>0.3 in all cases). The extent of difference between CT and surgical measurements was significantly influenced by the surgical size of the tumor (p = 0.03): the smaller the tumor, the more the CT overestimated the tumor size. If nephron-sparing surgery had been planned for tumors equal to or less than 40 mm, 24 patients would have been selected following the CT estimate, while 27 patients would have met this criterion on the surgical measurement. CONCLUSION: Renal tumors were statistically smaller than the estimate from CT, although this was not systematically the case. This should be kept in mind when issuing recommendations on the optimal cutoff size value under which nephron-sparing surgery is considered equivalent to radical nephrectomy.