الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Uolithiasis is a commonest disease facing the urological clinic. The prevalence of urinary stones has progressively increased in the industrialized nations, and a similar trend is being observed in developing countries due to changing social and economic conditions. In addition, many patients will be affected by multiple stones throughout their lifetime. Many methods used to diagnose urinary stones, among which MDCT remain the gold standard in diagnosis of urinary calculi & considered most accurate method for detection of calculi in the urinary tract. Its new advances allow the acquisition of isotropic volume data, with respect to post processing algorithms and imaging workstations that allow multiplanar and three-dimensional evaluation of these isotropic data sets, which give the chance for radiologists to meet the greater expectations of urologists in the assessment of stone disease. Identification of the number, size, and location of calculi and determination of the presence of hydronephrosis (i.e., obstruction) are routinely made with multidetector CT. Concerning to KUB, there is limitation in visualization of urinary stones depending on their composition with a cutoff point Hounsfield unit on MDCT between the visualized & non visualized stones on KUB which change according to the used equipment while MDCT can visualize these stones regardless their composition. Also MDCT can detect any resulting obstructive effects ranging from mild backpressure changes to marked dilatation &ballooning of the pelvicalyceal system of the kidney or the ureter. Also it easily determine if there are chronic changes resulting from old standing obstruction by stones as chronic pyelonephritis & atrophic changes & this have a significant clinical value in determination the healthy kidney to be started with treatment. MDCT can give ideas about many parameters which are gold standard in treatment an post treatment follow up as stone burden (Size and Number), stone Fragility, Stone Composition through Hounsfield unit, SSD as the efficacy of ESWL drops substantially when SSD exceeds 10 cm and in post treatment evaluation as following urologic intervention to confirm stone-free status, to identify the presence of residual stones, to rule out obstruction in the urinary system and to detect the complications such as perirenal hematoma and urinoma. Regarding to stone size MDCT provide a great advances in determination the accurate size through post-processing including multiplanar reformat (MPR), curved planar reformat (CPR), and thin-slab or thick-slab average intensity projection (AIP), maximum intensity projection (MIP) or volume rendering (VR) 3D images. MPR is the most commonly used post-processing technique which can be used to further characterization of the most urinary tract stones, particularly in the Z-axis (cranio-caudal). When imaging the urinary tract, MPR images in the coronal plane are typically referred, these images can be used to evaluate the exact size of stones, which have high clinical significance in the choice of the appropriate method of treatment. As measuring the axial size only may provide underestimation of the stone size in some cases, which may change the selected method for treatment. While coronal reformatted images provide upgrading of the stone size according to accepted thresholds of treatment: ≤5 mm, 6–9 mm and ≥10 mm.