Split-Bolus CT Urography Combined With Renal CT Angiography: Evaluation of Image Quality, Radiation Dose, and Clinical Feasibility

OBJECTIVE: To evaluate a clinically applicable split-bolus computed tomography urography (CTU) protocol combined with renal computed tomography angiography (CTA) by comparing image quality, radiation dose, and contrast medium volume with conventional multiphasic CTU. METHODS: Patients with suspected urinary tract disease were prospectively enrolled and allocated to a modified split-bolus CTU plus renal CTA protocol (group A) or conventional CTU (group B). Group A underwent unenhanced CT, bolus-triggered renal arterial-phase CT, and a delayed comprehensive phase after a second contrast injection. Group B underwent conventional 4-phase CTU. A retrospective cohort of renal CTAs (group C) was included to compare the image quality of renal arteries. Objective CT attenuation, subjective image quality, dose-length product (DLP), effective dose (ED), and contrast medium volume were analyzed. RESULTS: Among 153 prospective participants (group A, n=77; group B, n=76), visualization of the urinary collecting system did not differ significantly between groups A and B in CT attenuation or subjective scores (all P>0.05). Arterial attenuation and renal artery image quality were significantly higher in group A than in group B (all P<0.001), whereas subjective renal artery scores did not differ significantly between groups A and C (P=0.324). Compared with group B, group A reduced DLP and ED by 29.9% and contrast medium volume by 14.4% (all P<0.001). CONCLUSIONS: The split-bolus CTU protocol, combined with renal CTA, may provide a feasible imaging option for selected patients requiring both urinary tract and renal arterial assessment, with reduced radiation exposure and contrast medium use, without compromising urinary tract image quality.