Michael Galen Chan MD, Presenter: Nothing to Disclose

Pauline Chu MD, Abstract Co-Author: Nothing to Disclose

Fiona Hughes Cassidy MD, Abstract Co-Author: Nothing to Disclose

Lejla Aganovic MD, Abstract Co-Author: Nothing to Disclose

While delayed imaging helps to assess for contrast excretion and certainly plays a role in specific situations such as trauma, the value of adding a delayed scan through the kidneys on routine contrast-enhanced CT scans of the abdomen and pelvis is unclear. This study aims to weigh the clinical benefits of routine delayed scanning against the risks of radiation and added time.

Consecutive, contrast enhanced abdominal and pelvic CT scans performed over two months were analyzed by a fellowship trained radiologist. Scans obtained for indications requiring delayed or multiphasic imaging were excluded. Standard protocol included imaging through the abdomen and pelvis at 70 seconds after contrast administration followed by imaging of the kidneys after 3 minutes. Unclear abnormalities on the initial phase were recorded, and the added benefit of delayed imaging was noted. These findings were subcategorized based on whether the delayed imaging helped make a definitive diagnosis and whether the findings changed clinical management.

In all, 236 patients were included (average age 60 years, 91% male, 49% hospitalized or emergency patients). Fifteen patients (6.4%) had unclear findings on the initial phase that were clarified on delayed scans. One patient had a lesion with falsely reassuring features on delayed scan, resulting in a missed malignancy. All other patients could have been re-assessed with non-invasive imaging (non-contrast CT or ultrasound) with no detriment to the patient. Three patients showed no contrast excretion, one likely technically related while the others were patients in the intensive care unit for unrelated reasons.

Adding a delayed phase to routine CT scans of the abdomen and pelvis yielded little benefit in our preliminary series. Few patients had clinical management changed by findings on delayed scans, and most could have been re-examined on a non-emergent basis. Three cases of non-excretion were identified; none had clinical management affected. Given the increased radiation dose by approximately 50% and the added time per scan, the benefit of delayed imaging does not appear to be cost effective and could likely be eliminated without adverse effects.

Routine delayed imaging through the kidneys in routine CT studies yields little clinical benefit, particularly in light of the increased radiation to the patient and time cost.

Chan, M, Chu, P, Hughes Cassidy, F, Aganovic, L, Delayed Imaging on Routine CT Examinations of the Abdomen and Pelvis: Is It Worth the Additional Cost of Radiation and Time?.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9004735.html