Letter to the Editor RE: Application of Digital Tomosynthesis in the Diagnosis of Urolithiasis: Comparison with MDCT by Liu et al. (J Endourol 2019;34(2):145–150;DOI: 10.1089/end.2019.0327)

Dear Editor:

In this study, ¹ the authors tried to compare digital tomosynthesis (DT) with multidetector computed tomography (MDCT) in diagnosing urolithiasis, in terms of diagnostic accuracy and entrance surface dose (ESD). They came to a conclusion that diagnostic accuracy of DT was as good as MDCT and DT owned a significant lower ESD and diagnosis expense. The purpose of this study is to explore the feasibility of a novel technique in a well-established field. However, a total of 50 patients enrolled, received both DT and MDCT, and are in higher risk of radiation exposure. Furthermore, the fact that not available in patients with radiolucent stone could hardly reflect true diagnostic value of DT.

As for urolithiasis diagnosis, European Association of Urology Guideline has specific recommendations on selection of diagnostic imaging. ² Ultrasonography as primary diagnostic imaging tool is quick and out of radiation, should be first considered. With sensitivity of 96.6% and specificity of 94.9% in detecting urinary stone, noncontrast-enhanced computed tomography (NCCT) is commonly used to confirm stone diagnosis and postoperative reevaluation of some complicated stone. But compared with conventional CT, radiation risk can be reduced by low-dose CT. An intravenous urography is recommended to assess the anatomy of the renal collecting system before stone removal. In the case of complex cases, enhanced CT enables three-dimensional reconstruction of the collecting system. As a branch of fluoroscopy, DT can show anatomic location of radiopaque stone, but with higher exposure of X-ray. DT could not play a accurate role as intravenous pyelography in presenting the real anatomy of collecting system. Direct vision of urinary stone as well as lower radiation exposure would be a great advantage of DT compared with NCCT, but potential radiolucent stone hampers the further application of DT.