Large skull bump filled with blood no pus no recent trauma

More than a week after a car accident, from which our Lisa emerged ostensibly unscathed, her eye swelled up but no retinal redness. Then she developed a large bump over the eye on the skull,msensitive to the touch. We had it cut open under anesthesia,mand there was no pus, only blood. Size of a small fist, female hunting labrador 30% smaller than normal labradors. Vet could notndiagnose. Never seen it before.mwhat could it be?

Hello - that sounds very unusual.  I immediately wondered about a haematoma, which is a collection of blood forming under the skin, often a result of trauma.   I hear you that the vet could not offer a firm diagnosis, but what did they say?  What are the possibilities and are there tests they can do to rule some of them out?  Is the eye still swollen?  In veterinary medicine we often see things that we have never seen before and this is okay, providing that we have an appropriate course of action as to what to do next and at what point to intervene.  It sounds as though some more communication with your vet, to establish their plan and course of action, may prove reassuring for you. (I assume here that it is the skin around the outside of the eye that was swollen like a black eye for example?)  

If the globe of the eye itself is enlarged, this can be an emergency.  In the case of a lump, sampling and testing may be a possibility for example.

Sometimes clotting problems can present as unexpected bruising;  other times there has simply been trauma that was not observed.

I hope that some of these thoughts help; please do let us know how you get on!