The accuracy of USG KUB region for detection of urinary tract calculus in comparison to NCCT - A retrospective analysis

Objective: To evaluate the accuracy of ultrasonography (USG) in detecting the urinary tract stone (Urolithiasis) using non-contrast computed tomography (NCCT) as the gold standard. In addition, we correlated the accuracy of sonography with stone size. Patients and methods: We retrospectively identified a total of 368 patients at our institution with a diagnosis of urinary tract stone, who underwent USG followed by non-contrast computed tomography (NCCT). The stone size (maximum diameter) and stone location were collected in USG and data validated by NCCT. Data of the stone size in USG were classified into four groups (0–4, 4.1–6, 6.1–10, and >10 mm) and then compared with NCCT data. Results: A total of 368 USG and CT examinations met the inclusion criteria. Overall, the sensitivity of USG was 72.6%. Among all patients, NCCT detected 552 stones, while USG could identify 426 (77.2%) stones. Detection rate of mid and distal ureteral stone was lower than that at other locations. The detection rate increased with the stone size. About 73% concordance was obtained for the stone size measured by USG and NCCT. Factors such as the stone size, amount of hydronephrosis, and body weight affected the detection rate of the urinary tract stone using USG. Conclusion: No significant difference in measuring the size of urinary stones using USG and CT in most of cases. However, USG may slightly overestimate stones in some cases, USG has limited imaging modality in detecting urinary tract stone, especially in the case of smaller stone size, obese patient, and low grade of hydronephrosis with uretric calculi