Peter Gurney found that barely water is beneficial for guinea pigs with urinary problems. You take 2.5 cups of water and had 1/2 cup pearl barley, which is the old-fashioned pearl barley that your grandmother made. You can find usually find it in the store in the section where rice is sold. Bring the water to a boil, then lower the heat and let it simmer until the barley is soft. Then, you pour the water into a clean coffee cup and let it cool to room temperature. There should be at least half a cup. If not, then add some water to the barley, stir it well, and add it to the cup. The water should be cloudy. When the water has cooled to room temperature, then use a 1 ml syringe (no needle), hand-feed the water to your guinea pig. She should have at least 5 ml. Most guinea pigs like barely water, so give her as much as she wants. Do this 2 - 3 times a day.
Barley water helps reduce inflammation in the kidney, bladder, and urethra.
Also, if your veterinarian did an ultra-sound, go back and get an x-ray. Bladder stones are hard, but they are difficult to see if they are small.
GET RID OF THE POTASSIUM CITRATE! Guinea pigs can SODIUM CITRATE! Potassium has fatal interactions with certain medications, particularly trimethylprin sulfa. For a bladder infection, your guinea pig should be receiving 0.2 ml metacam every day (0.1 ml in the morning and 0.1 ml in the evening). You can increase that to 0.15 ml if she is still in pain. The best antibiotic for urinary tract infections is doxycyline or enrofloxacin (batril).
You can give your guinea pig some apricot nectar or cranberry juice.
Finally, why is the urine sample being sent off? A veterinarian should be able to spin it down and examine it under a microscope. The vet can also take the pH using litmus paper to determine if urine is too alkalyne.
That said, if your guinea pig has had these problems for 2 years and now she is in pain, then you need to consider putting her to sleep. I know it's hard, but guinea pigs can't choose to end their suffering, so we have to do it for them. I've maintained a collection of longhair guinea pigs for 20 years. During that time, there's been a few whose quality of life went downhill, despite best efforts. It's always correct to consult your veterinarian when a guinea pigs is sick or doing poorly. Most of them will recover and live a happy life. But a guinea pig who is repeatedly sick or in pain needs to be put to sleep. There can be an underlying cause that you simply can't see in an x-ray. Unless you're willing to spend the very expensive cost for an MRI, it could be impossible to determine the root cause. And even then, it might not be curable. It's never easy to make the decision to put a beloved guinea pig to sleep, but sometimes, it's what is best.
In closing, try the barley water, stop the potassium citrate, and up the metacam if the current dosage you're giving doesn't relieve all the pain. Metacam is well-tolerated by guinea pigs and increasing the dose by 0.5 ml twice a day is very safe. You should also try to keep her clean, so make sure her the bedding in her habitat is clean and dry.
