VCBE Case of the Month

Piggy, the Guinea pig, and the large bladder stone
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Piggy is a 4-year-old male Guinea Pig who was brought to the Veterinary Center because his owners were concerned he had blood in his droppings. Piggy was on a good diet of mostly timothy pellets and hay, with the occasional carrot, parsley, and watermelon treat. Piggy was not receiving a vitamin C supplement. However, within the past day, Piggy had been eating less. On physical exam, the doctors noted that Piggy was dehydrated, lethargic, quiet, and exhibited pain when his belly was palpated, especially in the region of his bladder. His bladder felt very firm; however, he was able to urinate in small amounts. From the possible blood in the droppings and the palpably firm, uncomfortable bladder, the doctors were concerned about potential bladder stones and recommended taking x-rays.

The x-rays showed a round stone in the region of the urinary bladder, with no other obvious abnormalities. The doctors explained to Piggy’s owners that surgery was needed to remove the stone; however, as Piggy was dehydrated and hadn’t eaten much for the past day but was still able to pass some urine (indicating he was not obstructed - a potentially life threatening emergency), the doctors decided it was better to stabilize him overnight and perform the surgery the next day. Piggy was given fluids under his skin to help hydrate him, an injection of a pain medication, an injection of vitamin C (which is essential in Guinea pigs, since they don’t make vitamin C on their own), and was syringe fed a critical care formula.

Piggy did well overnight. The doctors performed blood work the next morning which showed that Piggy was still slightly dehydrated but had normal organ function and was okay for anesthesia.

Piggy was sedated, given another injection of pain medication, and placed under general anesthesia. He was given more fluids under his skin, and his temperature, heart rhythm and rate, and respiratory rate were closely monitored by the technicians. The doctors made a small skin incision over Piggy’s urinary bladder and then felt the bladder, itself. The bladder wall was extremely thickened, most likely from chronic inflammation. Moist sterile gauze sponges were placed around the bladder to prevent leakage of urine back into the abdomen. A small incision was made in the bladder wall, and the urine inside the bladder was drained. The urine was very dark in color and contained sand-like particles. A 0.5cm wide bladder stone was removed (a large stone for a Guinea pig!). The bladder was flushed out with warm saline to remove all of the gritty material, until the fluid was a clear, light yellow color. Both the bladder and then the skin were sutured closed. An x-ray was taken post-operatively to confirm that there were no visible stones left behind. Piggy was given more fluids under his skin and placed in a warm incubator for recovery.

Piggy recovered well from anesthesia and was hospitalized overnight on fluid therapy, pain medication, anti-inflammatory medication and syringe feeding. By the following morning, Piggy had passed normal urine and stool and seemed much more comfortable. Even though Piggy just had surgery, he was not as painful when his abdomen was palpated, since the stone had been removed, and hewas even eating well on his own.

The doctors sent Piggy home with a syringe feeding formula, in case he didn’t eat at home, and an oral anti-inflammatory medication to keep him comfortable. Piggy was also started on a medication called potassium citrate, which changes the pH of the urine to help prevent future bladder stone formation, as well as a daily vitamin C supplement. His owners were instructed to keep him quiet while he was healing.
Piggy returned to the hospital for a recheck exam 1 week later. He was urinating normally, and his owners thought he seemed much happier than before surgery. The doctors gave the okay for Piggy to go back to normal activity, and since then, Piggy has been doing well!

The stone was submitted to a laboratory for analysis; there was no infection present, and the stone was determined to be 100% calcium carbonate. Calcium carbonate stones are the typical bladder stones Guinea pigs get. Guinea pigs are prone to developing calcium-based bladder stones. The best way to prevent these stones from forming is to provide a low calcium diet and plenty of water to drink. When Guinea pigs are young and growing, they need extra calcium to form growing bones, so they should eat some alfalfa (either as hay or pellets) which contains a higher level of calcium than timothy hay. However, once Guinea pigs are adults and are no longer growing, they no longer need this higher level of calcium in their food, so they should be switched to timothy hay and timothy-based pellets. High levels of calcium in an adult Guinea pig’s diet can lead to calcium precipitating out into a sand-like material in the urine and eventually to having this sand-like material stick together into stones. Vegetables high in calcium (such as parsley, spinach, and kale) should be avoided in adult Guinea pigs. Unfortunately, bladder stones sometimes develop even in Guinea pigs on the best diets. There may be some genetic component to the formation of these stones, as well. Signs in a Guinea pig that may indicate that a bladder stone has formed include lethargy, decreased appetite, bloody urine, straining to urinate, or pain on urination. Guinea pigs require supplemental vitamin C not only to prevent the development of a scurvy-like condition that leads to arthritis, painful joints, and poor teeth, but also to help keep the pH of the urine low to try to deter the formation of bladder stones. Fortunately, for Piggy, he has had no further recurrence of stones, thus far.


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