Hi Roo,
What Wiebke has said is spot on.
I have had this problem with 2 pigs now and it is such a worry when you first see it.
CONNIE: Connie started to wee an orangey / red wee and squeaking / being in pain when she wee'd in November 2008. Over 5 month, she was backwards and forwards to the vets. During this time, she was on Baytril and Septrin, had 2 x rays, a bladder flush and was opened up. The first x ray showed nothing but the second x ray which was carried out a few months later showed speckles and inflammation of the bladder. With my consent, the vet opened Connie up but found nothing. The vet gave her a bladder flush to clean out her bladder of any grit or sludge but we unfortunately lost Connie a few days later.
ELIZA: Eliza started to pass an orangey / red urine at the beginning of last summer. When it first happened, I was so scared because of what had happened to Connie. I took Eliza to the vets along with a urine sample and the vet found nothing abnormal. She explained that after speaking with a specialist (going back to when Connie had the same wee) guinea pig urine can sometimes be this colour. She advised me to keep an eye on her and to take a sample in in a week or so if it was still the rusty colour. Unlike Connie, Eliza showed no symptoms of discomfort but still had the rusty coloured wee's. A few weeks down the line, the vet detected blood in the urine was Eliza was put on a course of Septrin. Eliza had an x ray just to make sure there wasn't a stone and thankfully there wasn't.
four weeks later and 4 urine samples later, Eliza's urine had gone back to being a clear colour and no blood was found. She was finally taken off the antibiotics at the beginning of September.
Since then, Eliza has had on occasion, an orangery / red wee. From advise from people on here and my vet, it is probably something that will just happen from time to time with Eliza. My vet has told me to only take a urine sample to them if Eliza shows signs of discomfort when urinating and / or the rusty wee continuous for a week or more.
Eliza has had clear wee's now for a good couple of months so I am keeping my fingers crossed.
From reassurance from people on here and my vet, Eliza does NOT have what Connie had and her urine colour is just one of those things. My vet has said that it could even be down to diet. Although Eliza didn't eat anything red or orange before the wee's, my vet explained that it could be something as simple as preservatives or colourings in the dried food
From my experience, I would keep an eye on Fuzzy for now and if the urine continuous or becomes persistent where every pee is the orange / red colour I would take him to the vet just to be on the safe side. If you do take him, I would suggest that you take a urine sample with you so that it can be tested there and then.
Good luck but you probably don't have anything to worry about at this stage.
x