Chicken with swollen red abdomen

One of my chickens (cuckoo maran) has a swollen red abdomen, and I am trying to figure out possible causes/cures. I can always cull her as my last resort, but I am hoping I could save her. She is a little less than a year old. She's always been quiet, and I've been worried about her for a while, but I have seen no obvious signs of any health issues, so I thought it was just her personality. I couple of days ago I noticed that her entire backside was covered in thick poop. I washed her off and realized that her abdomen was red and swollen. She didn't show other signs of distress, and I discovered the problem, when she was pecking at some scratch with other chickens. My first thought is, of course, that she is egg bound, or something having to do with an egg, possibly broken egg inside. I felt with my finger, yet was not able to feel either an egg or any traces of egg shell. To be honest, I am not even sure what I am trying to feel for, but other than soft tissue, I can't feel anything. I've been giving her an antibiotic for a couple of days, hoping that it would stop any possible infection and let her body expel anything she needs to expel. However, she has been getting worse, she doesn't seem to poop at all, a bit of yellow and white liquid may come out but no regular poop. She is still walking, and other than not eating much now and her abdomen getting bigger and redder, she still doesn't show any appearance of being sick. She tried to make a nest and sit in it for a while this morning, but nothing came out. I am not sure how many days she has not laid, I have close to 40 chickens, so it's hard to keep an eye on all of them, but since I discovered her problem and isolated her (2 days now), she has not laid anything, and it doesn't look like she's pooped at all. Is there any way I could help her or is my only option at this point to cull her? How much longer can I keep watching and waiting/giving antibiotic? I am not in a hurry to kill her, yet I do not want her to suffer. I'll appreciate any input!

Could you post a picture of her backside? She could have one of several things going on. Vent gleet, a fungal or bacterial infection of the digestive tract, similar to a yeast infection, can cause smelly diarrhea and a red area around the vent. There have been some threads on here about a large red swollen area under the vent that can be common. Some of the guesses about those have been possible hernias, cysts, cancer, and teratoma, but I haven't seen many answers. Do you think that her bottom has been pecked? I would be concerned about her not passing droppings. Is she eating and drinking?

Here are some pics if you can make any sense of them. You can barely see the vent, it's almost stretched to being invisible because of her swollen belly. I took one picture upright and 2 with her lying on her side. Where she is lying on the side you can see the stretched line of her vent. I see some blue spots that look like bruises. Not sure where those come from. I do not think her vent was pecked. They roam freely and have a lot of space to get away if they want to. The greasy look is because of the vaseline that I've used to get into her vent. The yellow stuff is what comes out of her vent if I stick my finger in there, looks like could be a yolk, but she does not poop on her own. She drinks, and she eats less and less with every passing day, I guess because of the pressure buildup inside. She doesn't have red spots, just the skin on her belly looks red and inflamed from the pressure inside, not the usual pale chicken skin, and the abdomen is enlarged and very soft.

I wonder if she could have ascites or fluid in her belly that can happen with internal layers, heart failure, or liver disease. This usually looks full and tight in pictures that I have seen. Since you have seen yolk-like material come from the vent, internal laying might be a cause. There are quite a few threads here on the subject if you go to the top of this page in the search box, and enter "ascites." Scroll down to the second thread "Ascites, in desperate need of help" and look at post #4.

Okay, here is that thread: https://www.backyardchickens.com/t/853726/ascites-in-desperate-need-of-some-help-and-guidance

This picture shows a hen with ascites (notice the tight abdomen and vent to the right) with an 18 gauge needle draining fluid from the belly to help relieve pain, pressure, and labored breathing. This may or may not be your hen's problem, but something to think about.

Thanks Eggcessive! Would this prevent her from pooping? Her belly feels soft and squishy, not hard and tight. If it is internal egg laying, and she is all stopped up, is there a way to help her? I was hoping that her body would be expelling poop/egg yolk, whatever she has there. When I get my finger in the vent all the way I can feel another pulsating orifice that is very tight. If I try to probe and push with my finger further I feel warm liquid squirting from there around my finger, yet, it doesn't come out through her vent for some reason, so I can't even see what it looks like. It's really weird, like some constipation.

Do you have any molasses? Or castor oil? A half a teaspoonful of either of those would stimulate her to pass some droppings. Or you could try lubricating her vent with some oil or mineral oil. Inside of the vent is the cloaca, where the reproductive tract joins with the large intestine. I would try to get her to drink some water with electrolytes, so that she doesn't become dehydrated. Offer her some chopped egg or tuna, along with her usual feed. They usually like feed mixed with water to make it soupy.

I may need to go shopping, I don't have any of those things. I gave her some olive oil this morning, and used Preparation H to lubricate her vent. It doesn't look like she had any droppings overnight, yet, when I got my finger in there, some poop did come out, and it looked a bit closer to normal droppings, just more liquid. Her swelling is just as bad as before. I gave her some water with electrolytes and a bit of Nutridrenture. She did nibble on some fresh Mozzarella cheese, but nothing like my other chicken who is also in a sick bay due to rooster inflicted back injuries, who gobbled that cheese down in a blink. I still hope she will recover and I'll continue trying to help her unless she deteriorates to the point where I'll see that she is really suffering. It's hard to tell with chickens, it seems like they are able to tolerate tremendous amounts of pain. The chicken with back injuries had almost half of the skin on her back removed, yet, I only noticed that by accident, by a dirty brown stain on her feathers. During her entire ordeal, she never showed any signs of being uncomfortable, except when I was working on her, trying to fix her up, her appetite never dropped, and she still kept laying eggs.