Comparision between Low-Dose CT and Ultrasound in Diagnosis of Renal and Uretral Stones in Adults

Abstract
Background: Non-contrast computed tomography of the kidneys, ureters, and bladder (CT KUB) is the examination of decision for renal colic when compared to ultrasonography; be that as it may, radiation presentation can be a worry.
Aim of Study: Comparison between low dose CT and ultrasound in diagnosis of renal and uretral stones in adults.
Patients and Methods: This prospective study was con-ducted on fifty Egyptian adults meeting the inclusion criteria of hading flank pain, suspected to have urinary tract calculi and recruited from Urology Department of Tanta University to Radiology Department at Tanta University Hospitals. All patients were applied to careful history taken, clinical and laboratory examination then underwent imaging studies which include renal ultrasound examination and MDCT-KUB using low dose protocol. Each depicted stone was documented whether it is renal or uretric. All the stones were also defined as single or multiple, unilateral or bilateral and the maximum diameter of them. In case of upper urinary tract calculi reliable secondary signs of obstructing calculi were demonstrated. These include hydronephrosis, hydroureter, ipsilateral renal enlargement and ureter rim sign. The findings were confirmed by comparing to the previous standard CT scans that were done and detected in the medical records for 20 patients, uretroscopy in 12 patients, percutenous nephro lithotomy in 8 patients, medical treatment and more follow-up for 10 patients. The sensitivity, specificity and size accuracy of US was determined using low dose CT as the standard.
Results: Low dose CT showed number of renal and ureteral stones more than ultrasound with statistical significant p-value <0.001 with overall stones detected by ultrasound is 43 stones (5 ureteral and 38 renal) while low dose CT showed 96 stones (40 ureteral and 56 renal). The ultrasound missed 12 stones with 80% with mean size 4mm at uretrovesical junction and 10 stones with 83.8% with mean size 6mm at upper third of ureter. The ultrasound missed 100% of the ureteral stones in middle or distal ureter due to abdominal gases. The ultrasound overestimate the size in size group [4 to 1 0mm] by 3.3mm with statistically significant p-value detected. The ultrasound sensitivity, specificity, accuracy for renal stones detection were 67.8%, 100% and 81.2% respectively when compared to low dose ct and the ultrasound sensitivity, specificity, accuracy for ureteral stones detection were 6.90%, 100% and 43.75% respectively when compared to low dose.
Conclusion: Low dose CT shows up as preferred imaging modality for uorolithiasis over ultrasound because of its high sensitivity and accuracy in identifying renal and ureteral stones.