E1355. Modifications to CT Urography Protocol and Detection of Uroepithelial Malignancy: Quality Assurance and Comparative Study
  1. Aaron Marks; University of New Mexico Health Sciences
  2. William Thompson; University of New Mexico Health Sciences
  3. Masoud Shiehmorteza; University of New Mexico Health Sciences
Studies have identified that the addition of a nephrographic/venous phase at 100 seconds through the abdomen and pelvis combined with CT excretory phase increases detection of uroepithelial lesions (UELs) particularly within the bladder and mid/distal ureters. A before-and-after comparative study analysis was conducted to assess changes made to the single-bolus CT (computed tomography) urogram protocol. The aim of this study was to compare detection rates of UELs defined by malignancy of any type or grade within the upper urinary tract and bladder and to assess differences in scan time and radiation dose.

Materials and Methods:
Single-bolus CT urogram parameter changes included: abdomen and pelvis acquisition during venous phase (100 seconds), previously only through the abdomen, and an abdomen only noncontrast enhanced acquisition, where previously was abdomen and pelvis. No changes were made to the 10 minute excretory phase of the abdomen and pelvis. CT urogram studies 3 months before and after the changes were reviewed with the following analyzed: scan time (seconds), radiation dose (mGy*cm), number of positive and negative scans by CT urography and number of cases confirmed at tissue biopsy and/or cystoscopic/ureteroscopic findings. Statistical differences were determined using a two sample T-test with equal variances not assumed.

A total of 59 and 70 CT urography examinations were reviewed before and after intervention, respectively. Of these, 8 and 13 examinations were identified as positive CT examinations (i.e. focal bladder or upper urinary tract irregularity), respectively. The mean difference in scan time increased by 75.41 seconds (95% CI: 23.60 - 127.23, p = 0.005), however, radiation dose was not significantly changed with an average DLP of 2080 mGy*cm (p= 0.846). The sensitivity was unchanged at 50%. The specificity decreased to 81% from 92%. The PPV decreased to 27% from 57% and the NPV increased to 92% from 90%. The overall accuracy decreased, 77% from 85%.

These preliminary data demonstrate that the inclusion of the pelvis on venous phase and exclusion on the noncontrast enhanced phase did not significantly increase radiation dose to the patient. However, scan time did significantly increase possibly related to time required to adjust to protocol changes and changes in routine workflow. Detection rates of UELs yielded mixed results. NPV of the examination increased slightly, although at the expense of decreased specificity. The addition of a venous/nephrographic phase through the pelvis was initially thought to decrease reliance of the excretory phase in identifying a filling defect and increase detection of more sessile lesions. However, this increased detection of other benign enhancing foci such as scar formation, treatment changes and polypoid cystitis. A low PPV (53%) of CT urography for the detection of urothelial carcinoma has been reported, potentially suggesting an inherent drawback of the examination itself. Continued observation and increase in sample size will be required.