Bladder stones (cystic calculi) are easily recognized in rabbits. Calciuria, the accumulation of calcium "sand" in the urinary tract of rabbits, is recognized with increasing frequency. This syndrome is related to the consumption of excessive dietary calcium.

Absorption of calcium in rabbits is unique because there is almost complete intestinal absorption of all dietary calcium. Humans and most mammals can only absorb a portion of all the calcium consumed; the rest passes undigested through the intestines. Excess absorbed calcium is then excreted in the urine in rabbits. The percent of calcium excreted through the urine in rabbits 20 to 30 times greater than other mammals. Because of this unique feature, blood calcium levels in rabbits may be much higher than other mammals without any associated symptoms. This elevation in blood calcium may be the earliest indicator of excessive dietary calcium and impending urinary calcium deposits.

Because so much calcium is excreted through the kidneys and urine, this becomes a site for the precipitation of excess calcium. The urine may appear thick and cloudy. In some rabbits, the calcium sand forms a precipitate; the rabbit eliminates the clear "supernatant," the clear part on top once the calcium sand settles to the bottom of the bladder, allowing the crystals to remain in the bladder. This can lead to chronic irritation of the bladder, urine retention, bladder infection, and in severe cases, distention of the bladder leading to complete loss of muscle tone and overflow incontinence, which is uncontrolled dribbling occurring only because the bladder is too full to hold anymore urine. The calcium forms stones anywhere along the urinary tract, but it occurs most commonly in the bladder. Calcium in the kidneys can be much more serious. Stones or crystals can plug the urethra and prevent your rabbit from urinating.

Urinary tract infection occurs when there are bacteria in the urine. In rabbits, the opening of the rectum is just above the opening of the penis or vulva under the tail. Feces can come in contact with this opening, and may contribute to infections. Another possible cause for infection is calciuria, as the 'sand' can abrade or scrape the bladder like sandpaper, leaving it raw and more susceptible to infection by bacteria.

Stones or infection in the kidneys themselves can cause temporary or permanent damage to the kidneys. In the bladder, the greatest risk is that of obstruction, a stone or 'plug' of sand becoming lodged in the urethra, which is the passageway from the bladder out the body. This would prevent passing of any urine, and can be fatal in as little as 24 hours.

Excessive thirst and urination are common signs of urinary disorders. Unfortunately, there are a variety of other illnesses that can mimic these signs, making diagnosis difficult. Some of these include:

Similar signs that occur from diabetes, which is uncommon in rabbits but can cause excessive thirst and urination

Hotter weather causes rabbits to drink more.

In females, infection or cancer of the uterus can also cause similar signs. Blood in the urine and straining may occur.

Kidney disease can also cause increased thirst and increased urination.

Behavior problems can also lead to inappropriate urination.

Any illness that causes discomfort can have a similar appearance, as many of these symptoms are general signs of any disease causing your rabbit to not eat or act lethargic.