An Audit of Unnecessary Over-radiation in Renal Colic Diagnosis
BAUS ePoster online library. Simson N. Jun 26, 2018; 217793
Mr. Nick Simson
Mr. Nick Simson
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CT KUB (kidney, ureter and bladder) is critical in the diagnosis, acute management and follow up for patients with renal- or uro-lithiasis1. The British Association of Urological Surgeons (BAUS) guidelines dictate that it is the gold standard investigation in patients presenting acutely with suspected renal colic2.
However, as imaging techniques involving ionising radiation become more common, it is important that these tests are used appropriately to avoid unwarranted exposure, decrease cumulative exposure1 and avoid potential cancer risks3.
In this case, the area of the body scanned should be limited to the region needed to diagnose renal- or uro-lithiasis4 (i.e. from the upper limit of the highest kidney to the lower limit of the bladder). Imaging beyond this point, would be unnecessary and contribute to higher radiation doses.
The Royal College of Radiologists make the following recommendations with regards to CT KUB scan length5.
1) Excess scan length above the upper pole of the highest kidney should not exceed 10% of total length of scan
2) The accepted practice is to image from the superior border of the kidneys (T10-T12) to the symphysis pubis6.
3) A local standard should be agreed within each department, and adopted
The aims of this audit were as follows;
- To assess practice within our department according to the recommendations laid out by the Royal College of Radiologists.
- To demonstrate that there is no additional benefit of overscanning, in terms of providing alternative diagnoses or incidental findings.
- To identify shortcomings in initial audit, establish local guidelines for CT KUB, and initiate educational intervention to improve outcomes for subsequent re-audit and in the future.

Retrospective analysis of 100 consecutive CT KUB scans ordered for suspected renal colic was conducted between 1st November and 1st December 2016, and following intervention subsequent analysis of 100 consecutive patients between 1st June and 1st July 2017.
Data collected included: patient demographics; indication for scan; the percentage of the total scan that exists above the upper limit of the highest kidney; the highest vertebral level identified; the lowest anatomical landmark identified, and the presence of any incidental pathology present on the scan (with particular attention to pathology outside of the 'ideal limit' previously described). Paediatric patients and patients who underwent CT KUB for any other reason than suspected acute renal colic were excluded.
Unpaired t-tests were used to identify statistical significance between groups.

Results: Initial Audit 2016 (Group 1)
Excess Scan Length: [Target = 100% of scans <10% overscan]
- 19% of patients had <10% overscan, 67% had 10-20% overscan, 13% had 20-30% overscan, and 1% had >30% overscan (mean value 14.1% overscan)
Anatomical Landmarks: [Target = 100% of scans start between T10-T12 vertebral levels and end at the pubic symphysis]
- 6% of scans started at the level of T12, 54% of scans started between T10 and T12, 46% started above T10
- 2% of scans ended at the pubic symphysis, 50% ended between the pubic symphysis and the level of the lesser trochanter of the femur, 48% ended below the level of the lesser trochanter of the femur
- 1% of scans started at or below T10 and ended at the pubic symphysis (99% of scans were either too cranial or too caudal)
- No incidental findings of clinical significance were identified.

Recommendations and Interventions
After initial audit, a joint meeting between urology and radiology departments was organised to present the data and discuss the findings. Subsequently, a local guideline was established as follows. 'For CT KUB scans for suspected renal and ureteric colic, the radiographer should aim to scan from the upper limit of the highest kidney to the pubic symphysis' (though clearly there may be exceptional circumstances.
Several teaching sessions to radiography colleagues were organised and delivered in order to disseminate the new guidelines, as well as posters placed in CT technician rooms outlining the new guidelines.

Results: Re-Audit 2017 (Group 2)
Excess Scan Length
- 58% of patients had <10% overscan (19% Group 1), 34% had 10-20% overscan, 8% had 20-30%, 0% had >30%. (Mean value = 10.6%, (14.1% Group 1, p<0.0001)
Anatomical Landmarks
- 30% of scans started at the level of T12, 49% started between T10 and T12, 11% started above T10
- 33% of scans ended at the pubic symphysis, 23% ended between the pubic symphysis and lesser trochanter, 44% ended below the level of the lesser trochanter
- 47% of scans started between T10 and ended at the pubic symphysis, 53% of scans were either too cranial or caudal, (99% Group 1, P<0.05)
There were no incidental findings above the kidney or below the pubic symphysis.


Although the exact nature of the relationship between radiation exposure in the form of CT imaging and future morbidity requires further investigation3, it is a great concern to health professionals and patients.
As a result it is now common place to have protocols to limit radiation exposure in situ. At the time of initial audit, there was no local protocol in place to limit radiation exposure to patients undergoing CT KUB stone protocol for diagnosis of renal colic, including a guide on scan length.
As a result, our initial audit revealed that we were over-radiating between 81-99% of our patients unnecessarily with no diagnostic benefit. Evaluation of the data showed that scanning beyond the required 'ideal limits' did not detect additional pathology in the liver, lung, bowel and imaged bones.
Even if additional incidental pathology was picked up, we feel this would not justify exposing our patients to a higher level of radiation. We also consider it to be poorly practiced medicine.
After a concerted effort to establish local guidance in conjunction with radiology colleagues, and disseminate information to the radiography department, we re-audited our practice. We were pleased to note significantly improved results with regards to percentage overscan and the upper and lower anatomical landmark limits of the scan. We demonstrated statistically significant improvement for both parameters.
There remains room for improvement, however, we feel that we have made a significant impact to patients as a result of this project. We aim to continue to re-audit this aspect of urological investigation annually and hope to continue the improvements that have been made.
By initiating clear guidelines with regards to CT KUB scan length at our centre, we have made significant improvements in reducing unnecessary over-radiation of our patients. We encourage hospitals nationally to audit their practice, and have suggested simple measures to reduce irradiation of patients without negative impact on outcomes.
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