Optimising Urinary Tract CT Scans for Renal Colic: Enhancing Efficiency and Reducing Radiation

In a locally performed audit, we found that the majority of computed tomography (CT) scans of the urinary tract performed for suspected renal colic did not meet the overscan criteria in line with national guidelines. We aimed to reduce unnecessary radiation in a local radiology department by designing a suspected renal colic radiology pathway.  Methods: We designed a retrospective, observational, single-centre study performed at Basildon & Thurrock University Hospital (BTUH), Basildon, United Kingdom. Using the department's Picture Archiving and Communication System (PACS), this study reviewed 101 chronological CT scans of the urinary tract in two separate audit cycles between January and August 2025 that had been requested to investigate suspected renal colic, assessing whether they met criteria for overscan as per national standards. Our interventions included a vetting note offering a recommendation for the upper border of the scan (T11 vertebra), included for all CT urinary tracts requested for suspected renal colic. We also designed a poster for radiographers, highlighting the expected borders of the CT scan. The data were anonymised, and demographical information was collected. We calculated the overscan percentage by recording the number of total and overscan axial slices. Dose length product (DLP) data was obtained to quantify excess radiation exposure.  Results: In our initial audit cycle, we found that only 36% (18/50) of CT scans reviewed met criteria for overscan. Mean DLP overscan was calculated at 28.21 mGy·cm with extrapolated overscan radiation dosage measured at 0.423 mSv. Following the interventions, a further 51 scans were audited, revealing improved results; 70.6% (36/51) of CT scans reviewed met criteria for <10% overscan. Mean DLP overscan improved to 16.21 mGy·cm, and extrapolated overscan radiation dosage markedly improved to 0.243 mSv. Only 28% (14/50) of scans had correct positioning at the T11 vertebra level pre-intervention, improving to 56.9% (29/51) post-intervention. Compliance with the accepted standard increased by 96.1%. Average overscan decreased by 29.2%, and average excess radiation exposure decreased by 42.6%.

Our interventions resulted in adherence to the accepted standard doubling over a four-month period. Average ionising radiation exposure has been significantly reduced, which reduces the risk of carcinogenesis. Both interventions carried out in this study are low fidelity and are readily reproducible on a national scale. This study encourages radiology departments to audit radiation exposure from CT scans of the urinary tract for suspected renal colic, according to national standards. Future work should focus on multi-centre implementation to validate generalisability, assess long-term sustainability of behaviour change, and quantify the cumulative dose savings at a population level.