Radiation exposure – what is the optimal imaging modality in the follow-up of patients with urinary tract calculi?
Reviewed by Hamid Abboudi

Cumulative radiation dose is an important consideration in the nephrolithiasis patient population. Exposure to ionising radiation is known to be harmful and is associated with an increased risk of malignancy. Understanding radiation doses is necessary to make informed decisions regarding imaging techniques in these patients and for counselling patients about the relative risks from radiation exposure. This single institution study compared the effective radiation doses (EDs) associated with four imaging modalities for the follow-up of patients with urolithiasis, including: (1) stone protocol non-contrast computed tomography (NCCT), (2) kidney, ureter, and bladder radiography (KUB), (3) intravenous urography (IVU), and (4) digital tomosynthesis (DT). Validated simulation based software and an anthropomorphic male phantom with high sensitivity metal oxide semiconductor field effect transistor dosimetors were used to measure organ radiation doses. DT was associated with the least radiation exposure (0.83mSv). The EDs for a stone protocol NCCT, KUB and IVU were 3.04mSv, 1.63mSV and 3.93mSv, respectively. The need to decrease radiation exposure in recurrent stone formers is a challenge, in particular for young recurrent stone formers who are at increased risk of developing malignancy. DT has shown promise as a safe investigation modality for long-term follow-up; however questions remain regarding its sensitivity and specificity in particular for ureteric stones. Further studies and consensus are required to determine the clinical role of DT in such patients. It is likely that CT will remain the gold standard for surgical planning given its superior sensitivity and specificity, while DT’s role may be limited to annual surveillance of stone formers replacing the traditional KUB radiograph.

Radiation exposure in the follow-up of patients with urolithiasis comparing digital tomosynthesis, non-contrast CT, standard KUB and IVU.
Astroza GM, Neisius A, Wang AJ, et al.
JOURNAL OF ENDOUROLOGY
2013;27(10):1187-91.