Urolithiasis, the formation of stones in the urinary tract, is a common problem in guinea pigs, mostly seen in males and females over two years old.
Stones often form in the bladder or urethra, but can also appear in the kidneys, ureters or vagina. They usually consist of calcium carbonate, calcium oxalate, or magnesium ammonium phosphate.
Although it is not entirely clear why guinea pigs are affected, there seems to be a relation to a diet high in pellets and low in good quality hay and vegetables, which causes high levels of calcium in the urine. Risk factors include low water intake, over-supplementation of vitamins or minerals, inadequate cage hygiene, urinary tract infections, lack of exercise, obesity and urine retention.
Symptoms depend on the size and location of stones. They include a hunched posture, blood in urine, crying or straining when urinating, unwillingness to move, reduced appetite, teeth grinding, weight loss, and lethargy.
If stones get stuck and obstruct the urethra, making it impossible to urinate, this is an emergency and needs to be seen by a vet as soon as possible.
Your vet will make a diagnosis via analysis of the urine, x-rays, abdominal ultrasound, and possibly a blood test. Most cases require surgical intervention. Depending on the patient’s condition, an operation can carry a relatively high risk and post-surgical complications might occur. Unfortunately, medical treatment alone has not proven successful, but pain relief, fluid therapy and antibiotics are crucial in recovery.
Once recovered, the main focus lies on diet to prevent new uroliths. Don’t over-supplement minerals and vitamins, but removing them carries its own risks — a lack of calcium or vitamin D can lead to metabolic bone disease, and scurvy is caused by a vitamin C deficiency.
Alfalfa-based pellets and hay are rich in calcium, and oxalate levels are high in vitamin C and in foods such as spinach, kale, parsley and celery. Feed a balanced diet, with lots of fibre from timothy, oat or grass hays, vegetables, and fewer pellets. Remove mineral blocks. Rabbits and guinea pigs drink 60 per cent more water from a bowl than a bottle.
Other factors, such as daily cleaning of the cage, lots of space and a stimulating environment, should not be neglected.
By Juliane Dreher, Vet