You're speaking to Dr. Michael Salkin. Welcome to JustAnswer. I'm currently typing up my reply.
No, an on-call vet isn't usually necessary for anything of that nature. Dogs don't suffer from piles/hemorrhoids but do experience rectal prolapse and anal swelling secondary to diarrhea/straining or perhaps anal sac gland impaction/infection. Can you upload a photo(s) of this to our conversation? You can use the paperclip icon in the toolbar above your message box (if you can see that icon) or you can use an external app such as dropbox.com/ I can be more accurate for you if I can see what you're seeing.
Thank you! This appears to be a perianal adenoma (benign glandular growth) but if it truly arose peracutely (suddenly) it would represent anal hyperplasia (benign swelling) associated with straining to defecate (tenesmus). How old is she, please? An adenoma isn't expected in the young dog.
We can forget about an adenoma! This represents anal hyperplasia usually addressed by correcting diarrhea if present and applying a steroid-containing ointment every few hours to that area. Her vet has potent ointments of that nature. You can apply over the counter hydrocortisone creams until she's attended to by her vet. Please continue our conversation if you wish.
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Thank you for your kind accept. I appreciate it.