Spider naevi are telangiectases that consist of a large arteriole from which radiate numerous small vessels that resemble, in the mind's eye, spider's legs. They are found in the distribution of the superior vena cava i.e. on the arms, neck, and chest wall.
They vary in size from barely visible to more than half a centimetre in diameter. Occasionally, they bleed profusely.
Pressure applied with a pointed object to the central arteriole causes blanching of the whole lesion. Pressure applied through a transparent glass object may illustrate pulsatile blood flow.
The finding of more than two spider naevi is abnormal.
Why they occur only in the upper part of the body is uncertain.
Last reviewed 01/2018