Diagnostic accuracy of single-, tri-, and four-phasic CT urography and radiation dose assessment: a systematic review and meta-analysis

Abstract

Computed tomography urography (CTU) is widely used for evaluating urinary tract disorders, but the optimal number of acquisition phases remains uncertain because additional phases increase radiation exposure. This study aimed to evaluate the diagnostic accuracy of single-, tri-, and four-phase CT urography and to synthesize available evidence on radiation dose characteristics and dose-reduction strategies. A systematic review and meta-analysis were conducted in accordance with PRISMA 2020 guidelines and registered in PROSPERO. PubMed, Scopus, Embase, Web of Science, and CINAHL were searched for studies published between January 2000 and July 2026. From 2,247 identified records, 38 studies (26 diagnostic accuracy and 12 radiation dose studies) met the inclusion criteria. Diagnostic accuracy was pooled using a bivariate random-effects model, with phase-wise subgroup analyses where feasible. Radiation dose metrics (CTDI vol and dose–length product) were synthesized using random-effects models. Study quality was assessed using QUADAS-2 for diagnostic accuracy studies and the Joanna Briggs Institute checklist for radiation dose studies. For urothelial carcinoma, pooled sensitivity and specificity were 0.88 and 0.93, respectively. Compared with single-phase CTU (specificity 0.87), specificity increased to 0.95 for both tri-phase and four-phase CTU, while sensitivity remained high across protocols. For renal cell carcinoma, pooled sensitivity and specificity were 0.90 and 0.97, respectively; however, phase-wise comparisons were not feasible because of the limited number of eligible studies. Tri-phase CTU demonstrated a pooled CTDI vol of approximately 9 mGy, with reported values ranging from 5 to 16 mGy across studies. Low-dose strategies, including phase reduction, low tube voltage, and advanced reconstruction techniques, achieved radiation dose reductions of 20–72% while maintaining diagnostic performance. CT urography provides high diagnostic accuracy across urinary tract pathologies. For urothelial carcinoma, tri-phase CTU provides the most favorable balance between diagnostic performance and radiation exposure. In contrast, single-phase CTU may be appropriate for patients with microscopic haematuria and a low pre-test probability of urothelial malignancy, whereas four-phase CTU may be reserved for patients with a high pre-test probability of urothelial carcinoma or equivocal findings requiring further characterization. Indication-based protocol selection and dose-optimization strategies should be adopted to minimize radiation exposure while maintaining diagnostic quality. The review was developed and recorded in accordance with the PRISMA guidelines and has been registered with PROSPERO (CRD420251163062).