Sarica et al.(36) in his evaluation for stone impaction parameters demonstrated a statistically significant correlation between UWT, degree of hydronephrosis and serum ESR values. Evaluation of serum CRP and ESR values could let to predict the UWT, a parameter which is closely related with the degree of stone impaction.Also Sarica et al. in another study (37) found that the diameter of the ureteric wall (UWT) at the impacted stone site was found to be highly predictive and strongly recommend to make this very simple, practical but highly reliable calculation in all such cases before making treatment selection between SWL and URS. This will enable us to identify cases that will be more likely benefit from ureteroscopic lithotripsy instead of time consuming repeated SWL sessions as well as other additional procedures. He also found that a cut-off value of 3.55 mm was highly predictive where cases with a value beyond this calculation required additional procedures for a completely stone-free status.In this study it is found that ureteric wall thickness UWT at the site of impacted stone is an important independant predictor for success of ESWL, and a value of less than 3.25 mm has significant success rate about 90.3% in stones less than 10mm.In stones more than 10 mm it is found that UWT has minimal not significant effect on stone fragmentation outcome and on number of ESWL sessions as in table (6).28In hospitals equipped with ESWL there is a controversy whether applying ESWL shortly after the onset of renal colic could help resolving this issue. Interestingly enough, although ESWL is widely considered as one of the treatments of choice of ureteral stones, its use as an immediate therapeutic tool in an ER setting has not yet deserved much attention.Tligui M et al (38) found that Non-deferred ESWL for acute renal colic secondary to obstructing ureteral stones has a satisfactory success rate and very low morbidity.Ghalayini (39) in his study found that Emergency ESWL for obstructing ureteral stones has a satisfactory success rate and very low morbidity.Tombal et al. in 2005 (40) reported the results of the first randomized trial addressing the role of emergency ESWL in 100 patients requiring hospitalization for the management of renal colic. This study showed that Emergency ESWL increased the proportion of patients stone-free (SF) after 48 and proportion of patients discharged from the hospital at 72 hours by respectively 40% and 25% when the stone was located proximally and > 5 mm, and they advocated that it should be strongly recommended in these cases. In contrast, when the stone is located distally from the crossing of the iliac artery, ESWL only slightly increased stone free rate by 5% .Their study demonstrated that emergency ESWL is a valuable therapeutic option to improve elimination of ureteral stones and shorten duration of hospital stay, when proven that the stone is located proximally to the iliac vessels.In this study it is found that doing ESWL within 24 hours from the first attack of pain felt by the patient and confirmed diagnosis of ureteral stone, this will limit the degree of inflammation and impaction and has great role in increasing stone free rates and the number of ESWL sessions especially for stones less than 10 mm.In stone size more than 10 mm it is found than there is still effect of the time on the stone free rate and number of ESWL sessions but has no statistical significance .29Our study has some certain limitations; first, we could not completely control for the subjectivity of the radiologists when they determined the radiodensity of the stones based on KUB. We tried to diminish it. Two radiologists evaluated the radiodensity independently. In cases of disagreement, another radiologist made the final decision, which we abided by. Secondly, the number of cases was limited to derive a new scoring system depending on the parameters evaluated; this was due the strict inclusion criteria of the study for the selection of patients. we believe that our preliminary data and the highly predictive value of “ureteral wall thickness” will contribute to the existing literature to a certain extent.Conclusions# Stone density on plain x-ray is correlated with HU density on non-contrast CT scan.# Stone with a density greater than that of the 12th rib had a relatively higher risk of ESWL failure than did stone with a lower density.# Radiological findings on the preoperative KUB may be helpful for predicting ESWL outcomes.# Ureteral wall thickness as a secondary characteristic of Non-contrast CT scan is an important predictor of ESWL outcome for ureteric stones less than 1cm.# Ureteral wall thickness is correlated to the degree of inflammation and impaction of ureteral stone.# Early intervention using ESWL within <24 hours from first attack of pain is important predictor for ESWL SuccessRecommendation:# Regular and precise calculation of these studied parameters will enable us to lower the treatment cost but most importantly limit the negative effects of prolonged treatment interval, repeated SWL sessions and additional procedures on the QOL of the treated patients.