AUDIT OF CT KIDNEY URETER AND BLADDER (CT KUB): AN EFFORT TO MINIMIZE UNNECESSARY RADIATION EXPOSURE

Abstract

Background: Computed tomography of the kidneys, ureters and bladder (CT KUB) is performed for renal colic chiefly in younger patients hence, radiation dose should be minimized as much as possible without compromising diagnostic adequacy. One way of doing it is via reducing scan field.

First audit standard: Local departmental policy is to scan from the diaphragm to the symphysis pubis.

Objective: To determine the upper limit of CT KUB scans in terms of vertebral level, at which kidneys are fully imaged.

Target: 100% of the CT KUB scans should be commenced within two vertebral levels above the superior border of the kidney.

Material and Methods: 100 consecutive CT KUB scans were reviewed retrospectively. Parameters assessed were; Vertebral level at which scan was commenced, vertebral level at which kidneys were fully imaged and patient dose.

Results of first audit: 100% of kidneys fully imaged at T10. This was then taken as standard for subsequent audit. Only 34% scans were commenced within set standard. Mean dose=998 mGycm².

Second audit standard: All CT KUB scans to be commenced from T10 vertebral body or diaphragm whichever is lowest.

Results of second audit: Six months later, 100 consecutive CT KUB scans were reviewed prospectively. T10 remained as highest vertebral level at which kidneys are imaged fully. 95% scans were commenced within set standard. Mean dose reduced to 897 mGycm².

Conclusion:CT KUB scans should be commenced from T10 vertebral body to decrease patient dose without altering quality; and mean dose values of this audit can provide our National Reference Level (NRL) for CT KUB studies.