Weird black spot on swelling on rear end

[Snicketysnoksnaksnik]

Hello! I noticed that one of my hens are drowsy so I checked on her and realised she was covered in poo. After I clean her I noticed a black spot which wouldn’t wash away. Underneath this spot she seemed to be a bit swollen. Her poo tends to be very wet.

Besides being drowsy she’s managed to fill up her crop everyday (I’ve checked that it empties overnight) and take dust baths by herself. She’s lost some weight and now when she is picked up you can feel bone. She eats fine though, she’s free ranged so she finds her own food and in the afternoon I give her some fruit. She also drinks water normally. She’s around 4 years old. She moves around with the flock and I don’t know if I should separate her

I’ve asked other people and they’ve suggested that she might of had an egg crack in her. I don’t quite know how to help her out nor what I should do

 

[MysteryChicken]

Looks like she's been getting pecked at. She also looked a bit chunky.

 

[MysteryChicken]

I'd keep the area cleaned, & moist. Cleaning it every day, & applying some Triple Antibiotic ointment(Non pain Relieving), to it every day until it heals up.

 

[Snicketysnoksnaksnik]

Looks like she's been getting pecked at. She also looked a bit chunky.

She is a fairly fat hen but she has lost a bit of weight and I can now feel bone when I pick her up (forgot to mention, let me edit the post).
Odd thing is that she was never really pecked, she was one of my first hens (around 4 years old) and was never bullied. She tends to peck others and only one hen pecks her but they are always far away from each other

 

[MysteryChicken]

She is a fairly fat hen but she has lost a bit of weight and I can now feel bone when I pick her up (forgot to mention, let me edit the post).
Odd thing is that she was never really pecked, she was one of my first hens (around 4 years old) and was never bullied. She tends to peck others and only one hen pecks her but they are always far away from each other

I'd figure out what time this picking is going on. Most likely when they're roosting, is probably when it's happening. Even the head hen will lose her place in the pecking order.

 

[Snicketysnoksnaksnik]

I'd figure out what time this picking is going on. Most likely when they're roosting, is probably when it's happening. Even the head hen will lose her place in the pecking order.

She does get pecked a bit on the roosts but so she sleeps on the second lowest roost and the other hens are 3 roosts up. I’m worried that she will fall off the roosts during the night so I moved her to a crate with some dried leaves and hay (changed daily). She seems happier in the crate then on the roosts

 

[MysteryChicken]

She does get pecked a bit on the roosts but so she sleeps on the second lowest roost and the other hens are 3 roosts up. I’m worried that she will fall off the roosts during the night so I moved her to a crate with some dried leaves and hay (changed daily). She seems happier in the crate then on the roosts

Are you planning to let her out after her wound heals?

 

[Snicketysnoksnaksnik]

Are you planning to let her out after her wound heals?

I put her in a cage at 6am, it has shelter, fresh water, food and a corner with nesting material. Although sometimes she’s a bit lonely so I let her out for a couple hours.
Right now she’s sun bathing with the other chickens, the only one which pecks her is with her own small flock

 

[Eggcessive]

Her lower belly looks very full and enlarged as though she might have ascites. Tumors or liver disease from egg yolk peritonitis, as well as heart disease can cause ascites. The wound under her vent looks like pecking, but in warm weather, flystrike (maggot infestation) can occur there. I would try to make sure there are no maggots. Chlorhexidene 2% spray or Vetericyn can be used to clean the wound twice daily followed by plain Neosporin or Triple Antibiotic Ointment.

 

[Wyorp Rock]

Can you get a photo of her vent?

The black almost looks like dried on cecal poop, but it may be a large scab.
I would apply an ointment or oil to the black portion, especially around the edges. See if it starts to work loose over time revealing healthy skin. I don't think I would pick it off, but it may lift over the course of several days if you apply the ointment/oil daily.

I agree, the abdomen looks like it's full.

For me, if a hen is able to move about, still roost, isn't getting pinned down and picked on by the others, then I leave them with the flock. I let her decide about her roosting place. Sometimes once they start having reproductive issues, they start roosting lower and lower until they are unable to roost, then they choose a comfy corner. Once they start sleeping in a corner, then I make sure they have adequate clean bedding for overnight.