The role of contrast-enhanced computed tomography to detect renal stones

Purpose To investigate the detectability of renal stones in corticomedullary and nephrographic phases on contrast-enhanced computed tomography (CT). Methods All consecutive patients between January 2012 and February 2016 undergoing CT of the kidneys according to our department’s standard four-phase protocol and having at least one stone in the NC-phase (NCP) were included. Fifty patients with altogether 136 stones were eligible. Two radiologists in consensus evaluated the NCP from each examination and documented the number, location, and size of stones. Three abdominal radiologists blinded to the findings of the NCP reviewed independently the corticomedullary and nephrographic phases on two different occasions. They reported the number and location of stones in each kidney. For the inter-observer agreement the intra-class correlation coefficient (ICC) was estimated. The detection rate of renal stones was calculated for the three radiologists and compared between the two contrast-enhanced phases and the results were analyzed with concern to the size of the stones. Results The ICC was 0.86. There was no statistically significant difference between corticomedullary and nephrographic phases ( p = 0.94). The detection rate for stones measuring 3–5 mm was 82–88% and 98% for stones ≥ 6 mm. Conclusion The detectability of renal stones ≥ 6 mm on contrast-enhanced CT is extremely high. This means that stones with a higher risk of not passing spontaneously can be safely diagnosed.