What radiation exposure can a patient expect during a single stone episode?

There is increasing concern about the risks of radiation exposure with the advent of new, more complex imaging modalities. For example, computed tomography (CT), with its obvious advantages, is being more commonly used in the investigation of acute flank pain. The likely radiation exposure a patient can expect during a single complete urinary stone episode was studied.

The hospital records of 60 consecutive unselected patients who had become or were rendered stone-free were studied. The effective radiation doses in milliSieverts (mSV) associated with diagnostic imaging modalities such as intravenous urogram studies and CT scans were calculated for St. George's Hospital. By combining these with the published effective doses for interventional examinations, the total effective dose over an entire stone episode was derived.

There were a total of 60 patients with 68 stones (15 renal, 9 in the upper, 12 in the middle, and 32 in the lower ureter), with a median stone burden of 4 mm. Thirty-two patients had procedures performed, including extracorporeal shockwave lithotripsy SWL. Total effective doses ranged from 1.18 to 37.66 mSv (median 5.3 mSv; 95% CI of the median 4.13, 7.61). Renal and proximal ureteral stones resulted in the highest radiation exposures.

In this study the median radiation dose per stone episode was calculated at 5.3 mSv, with higher doses in those with renal stones and those who required CT scans and other interventions. Monitoring and reduction of radiation exposure is advised for all patients presenting with urolithiasis.