Late one evening at the Animal Care Center, a 7 year old male guinea pig presented for lethargy, loss of appetite, and not acting like himself. According to his owners, this behavior had been going on for approximately 2 days. On physical exam, the guinea pig was laterally recumbent, meaning he was unable to sit up and was laying on his side. He was very weak and on palpation of his abdomen a very firm mass was able to be felt. The mass was approximately the size of a golf ball and felt like a very full bladder. A very small needle was inserted into the bladder for a cystocentesis and about 30 milliliters of dark urine was removed. During the procedure it was noted that there was a small, hard object about the size of a BB pellet within the urethra. It was suspected to be a urolith or bladder stone that had passed into the urethra.
The findings were discussed with the guinea pig’s owner and a radiograph (x-ray) was performed to confirm our suspicions. Sure enough, a small stone could be seen in the distal urethra. The stone had almost passed out of the urethra but became lodged where the urethra narrows. Now, combined with local inflammation and tissue swelling the urine flow was completely blocked and the poor guinea pig could not urinate. Fortunately, the stone was almost out before it had caused the obstruction and was able to be retrieved with a very small hemostat.
The guinea pig was rehydrated with some fluids under the skin, given antibiotics, and pain medication. Once the stone was removed and the fluids were in place the guinea pig began to stand on his own and by the end of treatment was looking remarkably better.
Guinea pigs naturally have a high content of the mineral calcium carbonate in their urine. This phenomenon is also present in horses. Usually this will not cause a problem, but when the diet causes the urine to be a higher pH than it should be the stones are able to form in the bladder. It may be unknown to the owner that the guinea pig is suffering from bladder stones until one enters the urethra and either is passed without any problems or it becomes lodged in the urethra causing an emergent situation.
A complete diet including pellets, mixed fruits and vegetables, grass and alfalfa hay is important in guinea pigs. Alfalfa hay is high in calcium and too much in the diet can increase the calcium content in the urine. Timothy hay has a lower content of calcium and should be mixed in to reduce the amount of calcium intake. A balanced calcium and phosphorous is important in a guinea pig’s diet and a ratio of Ca:P of 1.2-2.0:1.0 is acceptable. Hydration is also important to reduce the risk of urinary stones. Making sure your guinea pig has access to fresh, clean water at all times to encourage adequate water consumption. For a full list of other diet recommendations and Ca:P ratios of many vegetables visit www.guinealynx.com. As always, if you are concerned about your guinea pig visit your veterinarian because early diagnosis can prevent a life threatening situation.