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Reevaluating diagnostic confidence: the impact of delayed excretory phase imaging in CT urography on detecting renal

Negar Firoozeh1, Sung Yoon Park1, Deepashri Basavalingu1

  • 1Department of Radiology, University of Washington, Seattle, USA.

Abdominal Radiology (New York)
|August 11, 2025
PubMed

Insights

The delayed excretory phase in CTU offers limited diagnostic value for hematuria patients, with no significant improvement in detecting most urinary tract abnormalities. Selective use may reduce radiation exposure without compromising overall diagnostic performance.

Area of Science:

  • Radiology
  • Urologic Imaging
  • Diagnostic Imaging

Background:

  • Computed tomography urography (CTU) is crucial for evaluating hematuria.
  • Concerns exist regarding radiation exposure, cost, and the added benefit of the delayed excretory phase in CTU.
  • Assessing the diagnostic utility of this phase is essential for optimizing patient care and resource allocation.

Purpose of the Study:

  • To evaluate the diagnostic value of the delayed excretory phase in CTU for detecting renal and urinary tract abnormalities.
  • To determine the impact of the delayed phase on radiologists' diagnostic confidence in hematuria patients.
  • To inform decisions about the selective use of the delayed phase to balance diagnostic yield and potential risks.

Main Methods:

  • Retrospective cross-sectional study of 489 CTU exams with non-contrast, nephrographic, and delayed phases.
  • Six radiologists independently reviewed exams in two sessions: without and with the delayed phase.
  • Statistical analyses included McNemar's test and mixed-effects logistic regressions to compare detection rates and diagnostic confidence.

Main Results:

  • No significant difference in detecting most abnormalities between sessions; cystic renal masses were more often detected without the delayed phase.
  • Detection of renal and ureteral congenital anomalies increased with the delayed phase, but overall detection and reader performance did not improve.
  • Diagnostic confidence was lower with the delayed phase, particularly for less experienced readers, and specific reader experience influenced anomaly detection.

Conclusions:

  • The delayed excretory phase in CTU provides a modest benefit for detecting congenital anomalies but does not improve the identification of ureteral or bladder lesions.
  • The delayed phase did not enhance overall diagnostic confidence, especially for less experienced radiologists.
  • Selective utilization of the delayed excretory phase in CTU may be considered to minimize radiation exposure without compromising diagnostic accuracy.
Abstract

Keywords:
Computed tomographyHematuriaTechnique

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