Answer by Dr. Jennifer Graham of Angell Animal Medical Center's Avian and Exotic Medicine Service:
There can be several causes of lower back pain in guinea pigs including, but not limited to, arthritis, degenerative joint disease, intervertebral disk disease, vitamin C deficiency, trauma, inflammation, vascular incident, infection, and certain cancers. Additionally, urinary tract stones are very common in guinea pigs. These causes may appear as generalized pain or localized lower back pain, so it is possible that your guinea pig could have a separate problem manifesting as lower back pain.
It would be helpful to take radiographs (X-rays) if these have not been taken as well as baseline blood tests. We have had some cases where advanced imaging (CT and/or scintigraphy for example) have helped determine the cause of skeletal abnormalities in exotic patients.
Osteodystrophy is a genetically-linked disease that has been reported to cause substantial pain in Satin and Satin cross guinea pigs so it is also important to know the type of guinea pig you own. Radiographs are also usually helpful with diagnosing this disease.
More potent medications can be used to help alleviate pain however it is very important to determine the actual cause of the problem to formulate the best plan for pain relief. Some of these medications have side effects so determining that the guinea pig is otherwise healthy is important (this may require blood tests or a urinalysis).
It is also important to make sure that your guinea pig is eating a high quality Timothy-based (avoid alfalfa) pellet, free choice Timothy/grass hay, fresh vegetables, adequate vitamin C supplementation (35-50mg per guinea pig per day), and clean water at all times.
I am available to consult with your veterinarian or you can make an appointment through Angell Animal Medical Center’s Avian and Exotic Medicine Service by calling (617) 522-7282 or visiting www.angell.org/avianandexotic.