Effective Radiation Exposure in Evaluation and Follow-up of Patients with Urolithiasis

Objective: To quantify the effective radiation dose associated with the evaluation and follow-up of patients with urolithiasis.

Methods: Retrospective review was performed for consecutive patients presenting to a tertiary stone clinic with acute stone episodes between November 2007 and December 2008, and had at least 2 years of follow-up. Number and modality of imaging studies were collected. Effective radiation exposure (ERE) doses were calculated from the dose length product values reported with each computed tomography (CT) scan.

Results: There were 72 males and 32 females with a mean age of 49 years (range 21-78). Patients underwent an average 1.8 (range 0-5) and 0.7 (range 0-2) plain radiographs, 0.82 (range 0-4) and 0.15 (range 0-2) CTs, 0.09 (range 0-1) and 0.03 (range 0-1) intravenous urograms, and 0.3 (range 0-1) and 0.6 (range 0-2) ultrasounds (US) during the first and second years, respectively (all P<.05). The average calculated ERE dose per CT scan was 23.16 mSv (range 4.94-72.77). The calculated mean ERE dose per patient significantly decreased from 29.29 mSv (range 1.7-77.27) in the first year to 8.04 mSv (range 1.4-24.72) in the second year (P<.01). This was because of significantly fewer CT scans and significantly more US imaging during the second year (P<.05). Although 18 (17.3%) patients exceeded 50 mSv during the first year, none exceeded this threshold during the second year. The mean ERE dose did not correlate with stone location, patient age, and sex.

Conclusion: The calculated mean ERE dose significantly decreased during the second year of follow-up in patients with urolithiasis because of significantly higher use of US.