Mysterious swelling/filling up (mares)

[viola]

I wonder if someone has any experience of this: mare has one tit that sort of swells/fills up. Looks and feels 'solid' when up but you can prod it, touch it, squeeze it etc She shows no pain and no bother. Swelling sometimes reduces compeletely after work. Sometimes seems to travel up the belly.
Vet is puzzled and said never seen anything like it before and investigation is ongoing.
There is no fluid coming out, nothing; mare has only just turned 4 years old and has never been in foal (and is not now).
It doesn't seem to bother her in the slightest but surely cannot be anything good...
Any ideas

 

[Little_Mare]

My mare gets this, same as yours: never been in foal, shows no pain/discomfort and it comes and goes - I've always put it down to time of the month/hormonal changes - much like us human ladies!!!

I've also wondered if it was fly-bite related but I'm always pretty careful to get under there with the spray but you know those pesky flies...

 

[viola]

Interesting! It's not coming and going with relation to the time with her though - it's there all the time at least since I met her in July, it just gets bigger or smaller but always looks slightly filled (even in the best sort of stage). If it happened to me to such extent due to hormones I would freak out

I am pretty sure it's not a bite related swelling as it wouldn't just come and go as it does.

 

[Little_Mare]

Hmmm, that is strange, especially as its always on one side - my girl tends to get it more on one side but does get it on both... Also she's quite "curvy" (she's a welsh section C) so I suppose she's naturally quite fleshy down there on both sides...

 

[viola]

Yes, only one side. The other side is as normal as they come and she's not that fleshy there at all.