What is going on with my Hen? Large, swollen, red under vent. *Graphic photo*

[RainForestBird]

My Easter Egger had something similar to this-looked exactly like it. I brought her into the house to bathe her in a warm tub and she passed the egg (no shell) on the floor as I walked in holding her. The red swollen part seemed to retract inside of her with the passing of the egg and after that she's been fine and lays an egg for me almost every day, its been two years.