Can a superficial clot cause a tributary to stick out of the leg?

Possible.: Vessels seem to stand out when they are full of blood. This could be due to a large variety of factors - one of these could be a clot, but generally this does not affect small vessels - it is only seen with large blood clots which should produce a variety of other symptoms. Small vessels that seem to stick out are much more likely just due to their superficial location, gravity and local factors.