Concordance of diagnostic tests, ultrasound of urinary tract versus non-contrast CT in urolithiasis in a four-level center in Bogotá, Colombia

Objective: In the approach and diagnosis of urinary stone disease, computed tomography (CT)-scan with a focus on the urinary tract is the gold standard. However, renal ultrasonography may be more cost-effective and faster in some settings. Renal ultrasonography has been considered as an alternative in the emergency protocols of some institutions and studies. The objective of this research is to make a study of diagnostic concordance between urinary tract ultrasound and non-contrast CT in a fourth-level center in Bogotá. Method: Retrospectively, a base is developed with a sample of all the patients who were taken to non-contrast CT and renal ultrasound at the same time for a clinical course suggestive of stone disease. All patients between the period January 2011 and December 2015 with both tests were selected. Data were collected from each of the official reports. A Cohen’s Kappa test was performed to evaluate the diagnostic concordance between the variables used. Results: A sample of 269 patients who underwent simultaneous non-contrast CT and renal ultrasound was collected. Diagnosis of lithiasis was 80.3% CT-KUB versus 44.03% US kappa = 0.29. The kappa value for the size of the largest stone diagnosed between the two images was 0.458. For the location of the largest stone diagnosed between the two images, it was 0.54. For obstruction and degree of obstruction, the kappa correlation value between images was 0.42. Finally, for the number of stones, the kappa correlation value was 0.37. Conclusion: Non-contrast CT should be the imaging of choice considering its diagnostic values.