The proportion of computed tomography kidneys, ureters and bladder (CTKUB) scans that comply with scan extent protocol in an emergency department: a clinical audit and dose ramification study.

Introduction: To assess computed tomography kidneys, ureters and bladder (CTKUB) scan extent protocol compliance and associated doses in the Emergency Department (ED) of an Australian tertiary hospital.

Methods: A retrospective clinical audit of 150 consecutive ED CTKUB cases was completed. For each patient, scan extent compliance at the superior (kidneys) and inferior (pubic symphysis) borders, in reference to the protocol was recorded. Compliance and non-compliance (over-/under-scanning) was identified, described (superior/inferior), quantified (via IMPAX measurements) and recorded via a purpose-built audit tool. In addition, a PBU40 phantom was scanned to assess the percentage of dose (DLP) increase per centimetre of over-scanning to contextualise results.

Results: A notable non-compliance with department protocol was noted. Eight cases (5.3%) demonstrated overall CT scan extent compliance. The remaining 142 cases (94.7%) demonstrated some form of non-compliance; superiorly, inferiorly or both. Analysing the 150 superior and 150 inferior data points independently, the most common non-compliance was over-scanning at the kidneys by 4 cm to5 cm (19 cases, ~10% extra DLP) beyond tolerance and over-scanning inferiorly at the pubic symphysis by 1 cm to 2 cm (29 cases, ~6.4% extra DLP). Estimated dose increases of up to 35% to 45% were found when clinical audit results were simulated using a PBU40.

Conclusions: Over-scanning is a predominant occurrence in CTKUB scans in this department. Reasons for over-scanning weren't investigated. It's anticipated this audit will lead to greater awareness of scan extent compliance and dose ramifications of non-compliance. The usage of more easily identified anatomical landmarks and a follow-up audit is suggested.