I thought Ascites but now maybe cancer?

[FathertoFeathers]

@FathertoFeathers , I'm very sorry to hear your bird is having problems.
Is the mass protruding out of the skin, or is the mass inferior to the skin?
Is the mass hard, soft- like memory foam, or firm?
Where exactly is the mass located?

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Unfortunately, as @Miss Lydia mentioned without the diagnostic tests at a veterinary office (exp, radiographs, (FNA) Fine needle aspiration, surgery, etc) determining the exact cause of her problem is unlikely to happen, and any suggestion of what the problem might be is merely a guess and not a proper diagnosis.

Ascites is characterized by fluid-up, so if during your palpation the area did not feel similar to liquid/ when centesis was performed no fluids were extracted it is likely you're dealing with something much firmer. If the mass is firm but palpable/squishy I would gather you may be dealing with something such as salpingitis which is a reproductive disorder that creates caseous-material-shaped eggs that are later expelled into the abdominal cavity. If the area feels hard, you may be dealing with a tumor or an egg that wasn't expelled properly.

Speaking generally, I believe most birds with such a reproductive disorder will cease laying, but speaking from experience, I've had a bird who suffered from salpingitis and laid up until she passed.

A little bit below the cloaca and interior to the skin. It’s hard but you can tell that it’s some sort of fleshy object.

 

[FathertoFeathers]

I don't know if mine was still laying or not, since she lived with three other female ducks. My suspicion is that she wasn't but I really can't say. If the OP's duck is still laying, it seems to me that that might be a positive sign....unless it's a very, very small partially-formed egg that's stuck in such a way that other eggs can still pass through?

She still lays her full size normal eggs. While we used to get a egg every other day now I’m lucky if we get one a week