Delayed imaging in routine CT examinations of the abdomen and pelvis: is it worth the additional cost of radiation and time?
OBJECTIVE
The purpose of this study was to retrospectively assess the potential benefits of delayed phase imaging series in routine CT scans of the abdomen and pelvis.


METHODS
Routine contrast-enhanced abdominopelvic CT scans of 1000 consecutively examined patients (912 men, 88 women; average age, 60 years; range, 22-94 years) were retrospectively evaluated, and the added benefits of the delayed phase series through the abdomen were recorded for each examination. Examinations performed for indications requiring multiphasic imaging were excluded. Images were reviewed by two fellowship-trained abdominal radiologists, who were blinded to official CT reports. All examinations were performed between July 2008 and February 2010 at a single institution. Radiation doses for both the portal venous and delayed phases, when available, were analyzed to assess the effect of the delayed phase on overall radiation exposure.


RESULTS
Forty-two patients (4.2%) had findings that were further characterized or were observed only in the delayed phase. Most were incidental findings that could have been confirmed at noninvasive follow-up imaging, such as sonography or unenhanced CT or MRI. The most common findings were liver hemangioma (n = 12), adrenal adenoma (n = 12), and parapelvic renal cysts (n = 6). The most important finding was detection of a renal mass in one patient (0.1%). The mass was seen only on the delayed phase images but was difficult to appreciate in the portal venous phase. In the other 958 patients (95.8%), delayed imaging was of no benefit. In addition, use of the delayed phase resulted in a mean 59.5% increase in effective radiation dose.


CONCLUSIONS
An additional delayed phase through the abdomen in routine contrast-enhanced CT examinations of the abdomen and pelvis is of low yield, particularly if reliable follow-up imaging to further elucidate uncertain findings is available.
1 All authors: Departments of Radiology, University of California, San Diego, Medical Center, and San Diego VA Healthcare System, 3350 La Jolla Village Dr, San Diego, CA 92161.
Michael G
MG
Chan
Fiona Hughes
FH
Cassidy
Michael P
MP
Andre
Pauline
P
Chu
Lejla
L
Aganovic
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D005260:Female; D006801:Humans; D033162:Incidental Findings; D007472:Iohexol; D008297:Male; D008875:Middle Aged; D010388:Pelvis / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D011860:Radiography, Abdominal / Q000009:adverse effects / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000009:adverse effects / Q000706:statistics & numerical data*; D014283:Triiodobenzoic Acids
D003287:Contrast Media; D014283:Triiodobenzoic Acids; D007472:Iohexol; C044834:iodixanol