1Urolithiasis previous ureteric stone disease increases the probability of

1Urolithiasis is a common disease with a peak incidence around the third to fourth decade of life .The lifetime risk of urolithiasis in the general population is 13% in men and 7% in women and prevalence is increasing. Known risk factors that can contribute to the development of ureteric stones include socioeconomic status, environmental factors, genetic predisposition and certain metabolic disorders (Coe 1992). History of previous ureteric stone disease increases the probability of a second stone forming within five to seven years to approximately 50% (Stamatelou 2003). The most common symptom of ureteric stones is pain, often in the form of colic, which is caused by irritation of submucosal nerve fibers triggered by movement of stones which results in spasm, dilatation, peristalsis and obstruction. Ureteric stones are usually formed in the renal collecting system and progress downward into the ureter. Stones tend to lodge at three narrowing in the ureter: the pelviureteric junction, over the iliac vessels, and at the ureteric meatus. (1)Urinary lithiasis can cause a greater or lesser degree of obstruction, depending on the size of the calculus, location, urothelial edema and the degree of impaction, requiring instrumental treatment, sometimes as an urgent procedure. Optimal treatment for ureteral calculi remains controversial. Treatment options vary and include expectant management, passage of ureteral stent, extracorporeal shockwave lithotripsy (ESWL), ureteroscopy with basket extraction or intracorporeal lithotripsy and open ureterolithotomy. (2,3) However, a conservative approach is often complicated by recurrent flank pain, multiple visits to the emergency room (ER), absence from work and an increased risk of serious complications, such as obstruction, infection and silent loss of renal function (4). There is a significant risk of long-term renal impairment if patients have unrelieved obstruction for more than 4 weeks regardless of symptoms and stone size 4. ESWL can be the first choice for moderately sized, uncomplicated ureteric stones (3, 5, 6). It is a simple, robust and safe procedure and is usually recommended for stones resistant to medical treatment in absence of absolute indication of ureteral drainage (5).2However, all urinary stones are not easily fragmented by ESWL, and the success rate of ESWL depends on multiple factors, such as stone size, location, and composition (7) Auxiliary procedures, which are used in cases of ESWL failure to clear stones, are costly and time consuming. Therefore, it would be useful to be able to predict which stones will be successfully fragmented by ESWL.Several studies have investigated how to predict the success of ESWL treatment with radiological tools, such as non-contrast computed tomography (NCCT) and plain x-ray (kidney-ureter-bladder, KUB). Recently, many studies have attempted to correlate the radiographic findings on NCCT with ESWL treatment success. Most studies have shown that the consistency, size, shape, location, and attenuation value of urinary calculi measured in Hounsfield unit (HU) density on NCCT and body mass index may be predictors of ESWL success, as determined by the stone-free (SF) rate (8,9). However, NCCT has some disadvantages, diagnosis with NCCT is costly, and this procedure exposes patients to more radiation than does plain x-ray. To avoid these disadvantages, Excretory Urogram or KUB x-ray has been used as an alternative; however, the accuracy of these methods is not as good as that of NCCT (10). Few studies have analyzed KUB and NCCT findings together for predicting ESWL outcomes. The aim of this study was to determine whether radiological findings on NCCT and KUB can predict the outcome of ESWL for ureteral stones.