Independent usefulness of flow phase 99 mTc-red blood cell scintigraphy in predicting the results of angiography in acute gastrointestinal bleeding.

Objective:: In acute gastrointestinal bleeding, despite positive dynamic phase ⁹⁹ mTc-red blood cell scintigraphy, invasive catheter angiography (CA) is frequently negative. In this study, we investigated the value of flow phase scintigraphy in predicting extravasation on CA.
Methods:: Institutional review board approval with a waiver of informed consent was obtained for this retrospective study. A total of 173 scintigraphy procedures performed in 145 patients with GIB between January 2013 and August 2014 were analysed. Scintigraphy had two phases: flow (1 image/s for 1 min) followed by dynamic (1 image/30 s for 1 h). Patients who underwent CA within 24 hours of positive scintigraphy were assessed. Each scintigraphy phase was randomly and independently reviewed by two nuclear medicine physicians blinded to the outcomes of the other phase and of CA.
Results:: A total of 42 patients (29%) had positive scintigraphy. Of these patients, 29 underwent CA, and extravasation was seen in 6 (21%). In all, dynamic phase scintigraphy was positive. 13 of the 29 patients also had positive flow phase scintigraphy. The sensitivity, specificity, positive-predictive value, and negative-predictive value of flow phase scintigraphy for extravasation on CA were 100, 70, 46, and 100%, respectively. Specificity and positive predictive value were higher when CA was performed within 4 hours of positive flow phase scintigraphy.
Conclusions:: Negative flow phase scintigraphy can identify patients who will not benefit from CA despite positive dynamic phase scintigraphy. The likelihood of extravasation on CA is higher when performed soon after positive flow phase scintigraphy.
Advances in Knowledge:: Negative flow phase scintigraphy identifies patients who will not benefit from invasive catheter angiography despite positive results on subsequent dynamic phase scintigraphy. Increasing the delay between positive red blood cell scintigraphy and catheter angiography progressively reduces the likelihood of identifying extravasation, which is required to target embolization.