LAUSR

Slow contrast injection through a catheter can differentiate between a catheter tip thrombus (irregularity of the contrast jet as it exits the catheter) and a catheter that is resting against a vessel wall (asymmetric or oblique flow of contrast away from the catheter tip). Neither of these signs was observed in this case. The presence of a fibrin sheath is identified as initial pooling of contrast at the catheter tip in the early phase of the injection followed by tracking of contrast medium back along the length of the catheter on later images. A circumferential but incomplete fibrin sheath will cause the classic subtle sign of narrowing of the contrast jet as it exits the catheter with fanning out of contrast more distally [1]. The presence of a fibrin sheath is often misinterpreted as extravasation due to catheter fracture. In this case, both contrast studies were reported as suspicious for line breakage; however, no fracture in the line was identified on inspection of the catheter after removal. Despite a lack of clear evidence for a fibrin sheath on imaging studies, this was the most likely diagnosis in this case.