Fig. 4
![Fig. 4](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs42155-020-00141-2/MediaObjects/42155_2020_141_Fig4_HTML.png)
While arterial opacification can be avoided by performing an aortogram and defining arterial vascular anatomy, it is difficult to define venous outlines and inadvertent venous opacification can occur. a Shows needle in the left common iliac vein (black arrow) with opacification of the IVC (black asterisk) and even contralateral common iliac vein (white arrow). b The a characteristic triangular blob of contrast for SHNB is seen (white triangle). However the external iliac vein also opacified (black arrow). Needle was repositioned and SHNB performed