Help, guinea has a baseball like swelling tumor at the rear end

[SFBayArea]

My 2 years old guinea hen developed a large - baseball like swelling tumor at the rear vent.
It is still laying eggs and behaves normally, but this tumor been growing for last three weeeks.
We've tried giving her antibiotics, but every night I need to catch her in the coop it was soooo much stress for her that we've give up on it. I tried isolating her in the cage, but again she was very stressed in the cage.
So my question is kind of two folds:
1. What is this swelling-tumor can be?
2. How to ingeniously give her antibiotics without super stressing her?

Thank you.

 

[nuthatched]

Can you get a picture, please? If it's a tumor, antibiotics won't help her.

 

[OzarkCountryGirl]

Poor girl. I would probably take her to the vet, much to my husband's chagrin (though he should be used to it). I've even taken a wild turkey poult with an injured leg to the vet. Thankfully my vet is not super expensive, though he's a very good vet and very knowledgeable about a wide host of creatures. He also lets me know if the treatment will be more pain and stress than humanely putting it down.

 

[LaFleche]

This looks as if it could be a hernia or a tumor.

Both might soon lead to complete obstruction of her oviduct and/or intestine.

Is she still able to poop normally?

 

[SFBayArea]

This looks as if it could be a hernia or a tumor.

Both might soon lead to complete obstruction of her oviduct and/or intestine.

Is she still able to poop normally?

Sorry, been out of commission, yes, she is still alive, behaves totally normally, poops, and even lays normally and regularly.

 

[The Chick Addict]

@R2elk

 

[The Chick Addict]

@SFBayArea, how is she doing now?

 

[SFBayArea]

@SFBayArea, how is she doing now?

Surprisingly she is not showing any discomfort, she still lays, eats, and do daily strolls around the property with her "boyfriend". However, I do see that it has gotten bigger and I am afraid pretty soon I will have to make an unpleasant decision.

 

[The Chick Addict]

Surprisingly she is not showing any discomfort, she still lays, eats, and do daily strolls around the property with her "boyfriend". However, I do see that it has gotten bigger and I am afraid pretty soon I will have to make an unpleasant decision.

Do you have a vet in your area? I will tag some experts.
@Eggcessive
@Wyorp Rock
@azygous
@aart

 

[Eggcessive]

Does it feel soft, spongy, like fluid, or firm? Can you get a picture of the dark area under her vent?