I do through the clinic I sometimes volunteer at and my own pigs too. What do you need to know?
A large cyst can affect the gut as it grows and cause issues like you have experienced.
I believe
@GPTV may have experience too.
I have Ellie who was about 6.5+ yrs at the time. She kept suffering reoccurring urinary tract infections with blood &sometimes heavy bleeding when she pooped.
None of the other classic signs such as -hair loss, crusty nipples &dominant behavior.
my vet told me my only option was to spay- but she wouldn't do a spay on such an old piggy! Due to general anaesthetic risks etc.
It was determined it was an ovarian cyst by a non intrusive,reasonably cheap ultrasound scan.
Ellie was fully conscious throughout&I was fascinated watching all the movement &bits n pieces at work!
A walnut sized lump was found.
So I suggested after research (mainly on here) could the (hcg)chorulon hormone injections be tried?
The vet researched it a bit &spoke to the drug manufacturer to find out dosage etc whilst I was there.
Its actually a cattle licensed drug. But a signing of a disclaimer/permission solved that.
The drugs were ordered&came 2-3days later. 1injection into the leg muscle (&lots of wheeking! DIVA PIG!) &some cucumber.
Then 7-10days later a repeat of the process.
Touchwood ellie has had no bleeding since &that was about March 2014 now I think.
The jabs were £20 ish each I think maybe less &there was a possibility of having a 3rd but the vet didnt in the end.
Consultation fee,metacam painkiller for a few days if needed &ultrasound so not even expensive considering. But well worth it
The cyst didnt seem to shrink but the bleeding has stopped.
Make sure she has a painkiller if needed, apparently ovarian cysts are very painful in humans. Might make her more comfortable.
Ellies 2 consultations,jabs, ultrasound &metacam came to no more than £60 at the time.
Although my vet isn't an exotics specialist &doesn't charge steep prices.
the vet locator (at the top of page) may have a few recommended piggy savvy vets near you ,
https://www.theguineapigforum.co.uk/pages/guinea-pig-vet-locator/
@biscandmatt had dealings with ovarian cysts so might come up with some other ideas for you. Xx
Ellie has just had a second batch of two injections as she was puffing up & the cysts seemed to have started grown again, she is now over 7 1/2yrs old & although steadily losing weight she is still happy munching away & enjoying life
I know others have had no joy with these but in my case it worked wonders &I would definitely try again.
Good luck with your furball baby &let us know how you get on.
Heres my original thread of Ellies link, have a look through a lot of members had some great advice on it
https://theguineapigforum.co.uk/threads/ellie-ovarian-cyst-maybe-stones-suggestions-please.112412/
Speedy recovery from Ellie, Grace & I.xx