Swollen vent? or egg bound?

[Sheac929]

1 year old hen

She's always been perfectly healthy. Last few days has been lethargic and having diarrhea. We noticed today that she has a swollen sack under her vent.
Sorry for gross picture. We have since cleaned her back side with warm water and soap soaks.
Anybody know what it is, or treatments?

 

[Eggcessive]

From the yellow droppings, I would wonder about ascites or salpingitis. How old is she? Has she been laying eggs recently? Have you seen any soft or abnormal egg shells? Is her enlarged lower belly under her vent firm or squishy?

 

[Sheac929]

From the yellow droppings, I would wonder about ascites or salpingitis. How old is she? Has she been laying eggs recently? Have you seen any soft or abnormal egg shells? Is her enlarged lower belly under her vent firm or squishy?

Thank you for replying.
She's 1 year old.
Strong egg layer. Always hard, thick shells. she last laid egg 5 days ago. The swollen part is pretty squishy