MP36-13: Radiation and Cost are Reduced Utilizing Ultra-Low-Dose Limited Renal CT for Nephrolithiasis Surveillance as Compared to Standard Non-Contrast CT, KUB, and US

Scott Quarrier, Perry Pickhardt, Benjamin Weigman, Viswanathan Aravind, Stephen Nakada

Introduction: The AUA guidelines suggest periodic follow-up of potentially symptomatic stones using renal imaging. We previously presented the results of a pilot series for the CT limited renal protocol scan (Planz, 2019). We now present our two-year experience utilizing ultra-low-dose (ULD) limited renal CT ($1135) as an alternative option to standard low-dose (SLD) non-contrast CT ($2363, more radiation), KUB ($294, more radiation, low sensitivity and specificity) and US ($1141, low specificity).

Methods: ULD entered our clinical practice for the surveillance of patients with kidney stones starting in 2017 after completion of previously reported validation study. ULD was performed by adjusting kV, slice thickness, noise index and limiting imaging field to the renal bed. Patients with a single ULD were included in the study.

Results: Patients (N=123) underwent ULD (Figure 1). There were 114 patients who had a prior SLD that was utilized for comparison, 25 patients had more than one ULD during this two-year period. The mean effective dose was 4.1 mSv for the ULD compared to 13.4 mSv for the SLD (p<0.01). When we evaluated the number of all-cause diagnostic studies during a 15 year period, these patients underwent 7.8±7.4 SLD (range 2 to 70); 8.0±8.3 KUBs (range 0 to 45); and 3.4±3.8 USs (range 0 to 23). One ULD was converted to SLD at time of imaging due to new hydronephrosis seen on ULD.

Conclusions: Using ULD compared to SLD, KUB and US led to reduced radiation dose and cost. ULD is an excellent alternative to SLD, KUB and US for surveillance of patients with recurrent renal stones. Source of

Funding: none