Teenager with a catheter that infuses but does not draw back

Line study of a fibrin sheath on a central venous catheter
Image from a line study (above) with the catheter filled with contrast shows a mild dilation in the diameter of the distal catheter, suggesting the contrast is inside a sheath encasing the distal catheter. When contrast is injected through the catheter (below), a sheath is seen to flip off the tip of the catheter to the left.

The diagnosis was fibrin sheath of the catheter tip.