Standardized CT KUB Protocols for Nephrolithiasis: A Retrospective Analysis of Radiation Exposure and Cranial Extent Guidelines

Background and aim Non-contrast computed tomography of kidneys, ureters, and bladder (CT KUB) is the gold standard radiological imaging for nephrolithiasis. It significantly contributes to the total radiation exposure of a population. This is well known to be linked to increased cancer risk over time and as such should be minimized in line with Ionising Radiation (Medical Exposure) Regulations (IR{ME}R). Previous works have explored a number of avenues to reduce the total radiation exposure such as the cranial extent of the scan; however, at present, there are no formalized guidelines. This study aimed to compare the cranial extent of local CT KUB imaging with previously established thresholds and assess whether total radiation can be reduced through local intervention. Results In the first cycle, a total of 102 non-contrast CT KUB scans were included. Of these, 51% (n=52) commenced from the superior border of the T10-T12 vertebral levels, 48% (n=49) commenced above the T10 vertebral level, and only 1% (n=1) started below the T12 vertebral level. In the second cycle, a total of 105 non-contrast CT KUB scans were assessed. Of these, 21.9% (n=23) commenced above the T10 vertebral level, and 75.2% (n=79) commenced from the superior border of T10-T12 vertebrae. A further 2.9% (n=3) commenced below T12 vertebral level. The findings of this study demonstrate that starting the upper extent of the CT KUB at the T10 vertebral level showed a reduction in radiation dose in millisievert (mSv) delivered to patients while maintaining adequate diagnostic utility. Conclusion Limiting the cranial extent of CT KUB imaging to T10 has consistently captured the upper pole of both kidneys across different patient cohorts, including ours, thus making it an effective way of limiting radiation exposure without sacrificing diagnostic accuracy. In order to achieve robust evidence-based guidelines, further studies would be beneficial.