A condition resulting from the formation of calculi in the urinary tract.
Calcium from diet (or sometimes leached from bones due to a deficiency) can build up in the urinary tract, which will first cause a gritty sludge to form, and then hard stones. A guinea pig usually needs to have a genetic predisposition toward bladder stones. A pig who exhibits symptoms of sludge/stones needs to have adjustments in his/her diet to manage the amount of calcium consumed. Often, the condition will progress and surgery will be required to remove the urolith (stone).
Guinea pigs tend to have a slightly opaque urine. However, if the urine is milky, gritty, or leaves gritty residue after it dries, it often indicates that there is too much calcium in your pig's diet. Minerals will bond together to form stones if left untreated. Pink or bloody urine indicates that sludge or stones are present. Guinea pigs will generally rear up and show signs of pain while passing urine or feces. In severe cases, the guinea pig may not be able to pass urine. Generally, an x-ray or abdominal ultrasound will be used to confirm a bladder stone. Symptoms of bladder stones are the same as a urinary tract infection (UTI); your veterinarian will take x-rays to rule out bladder stones before prescribing antibiotics to treat a UTI.
Mineral buildup causes inflammation and pain. In boars, it often cakes around the penis, and needs to be removed (gently!) with a lubricating oil. In sows, some gentle massage of the urethral opening with a lubricant can be enough to ease very small stones (excellent article by Peter Gurney below). Larger stones can be treated with medication, but often a stone will need to be surgically removed. Postoperative pigs will need preventive care to ward off a reoccurence of buildup.
For guinea pigs who have a predisposition for bladder sludge/stones, dietary changes are recommended. Alfalfa, for instance, has a high calcium content, so a switch to Timothy or grass hay and pellets is essential. Antibiotics and pain medications may be prescribed by your veterinarian. Flushing large amounts of water (via syringe-feeding) through the system can help sludge and smaller stones move through; cranberry juice is an excellent urinary tract cleaner, as it helps break up the stone and control bacteria.
Calcium is needed in your guinea pig's diet. The trick is the same for humans: everything in moderation. Pellets and hay, of course, are staples, and hay should be available to pigs AT ALL TIMES. Some tips for vegetables and fruits follow, but the key is to use common sense when it comes to your pig's diet.
Popular vegetables that are high in calcium content, and thus should not be fed every day: dark leafy greens such as spinach, collards, kale, and mustard greens, dandelion greens, and parsley. Lower calcium-content vegetables include red and green bell peppers, carrots, and cucumber. Romaine, Boston, and bibb lettuces, a popular diet staple for guinea pigs, are in the moderate-level zone for calcium.
As for fruits: Raisins, oranges, and blackberries have a fairly high calcium level. However, fruits, due to a higher sugar content, would not be a main staple in a guinea pig's diet, so the risk is lower than with vegetables. Fruits that are particularly low in calcium include peaches, blueberries, and bananas. Cranberries, which are EXCELLENT for cleaning out the urinary tract, are low in calcium as well!
A very nice table of calcium content for vegetables and fruits is available on GuineaLynx.
Emma (1994-1999) was very asymptomatic with her bladder stone. She never exhibited the usual signs of pain while urinating, and her urine was never bloody. Our veterinarian suggested that Emma had a "bouyant" stone that was never irritating to her. One day in 1999 I was taking photos of Emma, and I noticed that she was rearing up repeatedly, trying to pee. She started squeaking in pain; I immediately took her to an emergency vet, where a large bladder stone was found lodged firmly in her urethra.
Since Emma was already an elder piggy, we opted to not have the surgery for her, and she was euthanized. I regret the decision, but we were concerned with her recovery and post-op quality of life.
Gwinnie (2003-2008), on the other hand, had classic symptoms of a bladder stone. One day we noticed blood in the pen, and watched the pigs for signs of pain during urination. Gwinnie would rear up and squeak while urinating, so we took her to the vet. A bladder stone was detected; Gwinnie was scheduled for immediate surgery. The surgery was successful, but another stone reappeared two months later! Our veterinarion explained that stones can be aggressive in some pigs. We put Gwinnie on antibiotics and pain medication, but died before we could schedule the surgery.
Two different pigs, two very different stones. While diet is often considered the culprit with stones, a secondary cause is genetic predisposition to mineral buildup in the body. Ironically, too little calcium in the diet can cause stones when the guinea pig's body makes up for lack of calcium by leaching it from the bones! Some calcium is needed in your guinea
pig's diet, but calcium-rich foods, such as alfalfa, must be fed sparingly
to avoid getting a surplus of calcium in your guinea pig's system. In my herd, alfalfa is an occasional treat; we rely on Timothy-based pellets, as well as Timothy and grass hay.
has an excellent page on stones and treatments in the Medical Guide.
Guinea Pig Compendium has an article on general ailments, including bladder stones and sludge.
Urolithiasis in Cavia Porcellus presents bladder stone diagnosis and treatment of 20 guinea pigs.
Gurney Guinea Pig Pages has excellent advice on guinea pig care,
including this passage on kidneys and stones:
...More often than not, when a sow has [a bladder stone] the stone will travel down the urethral tube when it is very small and be flushed out. However, it can sometimes lodge near the opening where it will grow as more mineral crystals are flushed around it in the urine.
If the sow is seen to strain a little more than she was wont to do, lifting herself high on her back legs as she crouches and sometimes squeaking in pain, when she is passing urine, palpate just above the opening of the urethra. You can sometimes detect a very small stone, and even see part of it, chalky white in the opening. At this early stage, with the help of some K.Y. jelly as a lubricant, it can be gently expressed out. Once these stones get to about the size of a small pea then surgery may be required. This is a relatively easy procedure, even if the stone has become much larger.
If upon first examination there is no stone, rub your finger around the urethral opening to try and find out if the urine is at all gritty. If it is then this as an early warning that trouble could be brewing and anti lithic drugs or herbs should be considered.
The reason stones are more of a problem for boars is because when they are very small they do not pass down the urethra as easily as those that form in a sow's bladder. Consequently those that stay and grow in the bladder are much harder to remove surgically.
Sometimes, when the penis is extruded, the whole of the shaft is coated with what appears to be the kind of lime scale that is found on the inside of a kettle. There are several drugs that can be used to break these stones down, but they are not always successful. The success rate of veterinary surgeons who specialise in small animal surgery, in removing these stones is usually very good, but the big problem is how to stop these stones reoccurring.
The only sure way to prevent the stones reoccurring is to get the stone that was removed analysed to find out the main substance it is made of. If it appears that it got there via the diet, then a change in diet may help. However there is a theory that the calcium oxalate ones, and these are what most of those found in guinea pigs are formed of, could actually be caused by a lack of calcium in the diet! The theory goes that calcium is needed in the filtering process of the kidneys and if there is not enough in the diet it will come from the bones.
What I am trying to say is that preventing reoccurrence of stones is not an easy matter for there are so many factors to be considered, and what will work on one animal will prove negative on another.