Aging Bunny, Aging Bladder

by Gil Stanzione, DVM

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Everyone wants their bunnies to live to an old age and to stay as healthy as possible for as long as possible. As rabbits age, many begin to develop specific clinical conditions that need to be addressed. Some of the most common clinical problems we see in aging bunnies involve their urinary tract and may be related to improper diet and inadequate exercise.

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Bladder stones (“uroliths”) and sludge
Rabbits are often fed free-choice alfalfa pellets or alfalfa hay which are high in calcium. Calcium absorption in the intestinal tract of rabbits is much higher than in other species and does not depend on vitamin D, so high-calcium diets may lead to increased blood calcium concentrations. Most mammals only excrete a small amount of calcium in their urine. In rabbits, however, urinary excretion of calcium is much higher, and can range from 45% to 75%. This calcium load in the urinary tract can, in some rabbits, lead to the production of thick, sandy urine (hypercalciuria, commonly called “bladder sludge” ) or even small stones (“uroliths”) in the urinary tract. A sludgy bladder may palpate like a wet bag of sand. Even a rabbit who always produces clear normal-looking urine may have a sediment precipitation that is undetected until a clinical exam is done.

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How do we diagnose urinary tract problems in aging bunnies?
In addition to a thorough clinical exam with manual palpation of the bladder, urinalysis and urine culture/sensitivity tests are usually the first steps in identifying problems in your older bunny’s urinary tract. These procedures can help diagnose the presence of bacterial infection (which often accompanies bladder stones or sludge) and determine the composition of suspected uroliths or sludge (rabbits usually form calcium carbonate crystals, but they may also form calcium oxalate, ammonium phosphate, or monohydrate crystals). Your bunny’s vet can suggest specific techniques for obtaining free-catch samples of urine from rabbits at home, or s/he can obtain a sterile sample in the veterinary office. Abdominal ultrasound and/or radiographs (xrays) will help confirm a diagnosis, demonstrating mineral opacity within the urinary tract consistent with calcium sand or stone (urolith) formation.

What can can be done to help with urinary tract problems?
In rabbits, early stages of hypercalciuria can often be satisfactorily managed by increasing the amount of fluid a bunny gets. The most efficient way to do this is usually by administering subcutaneous fluids (“diuresis”), although encouraging a bunny to drink more can also help. You can flavor the bunny’s water with a small amount (a few drops) of fruit juice, as long as you change the water frequently to prevent bacterial growth in the sweetened fluid. Manual bladder expression can often help eliminate accumulated crystalline debris. Owners can learn to give subcutaneous fluids at home, and even to gently express their bunny’s bladder, as instructed by their veterinarian. Potassium citrate is sometimes administered to help reduce some kinds of crystalline accumulations.

Limiting the alfalfa-based pellets in the diet and avoiding or discontinuing mineral supplementation can reduce the amount of calcium excreted in the urine. Providing good-quality grass hay, leafy greens, and fresh vegetables will ensure adequate vitamin intake without creating calcium excess. And providing plenty of exercise can help to keep the bladder healthy as well. When the bunny moves, the bladder contents also move (picture shaking up a bottle of sandy water to distribute the sand throughout the water), and this can help a bunny to excrete excess calcium more easily and efficiently.

Since rabbits are herbivores and have alkaline urine, urinary acidifiers are not effective in dissolving the calcium uroliths. Therefore, in advanced cases where bladder stones have already formed, surgical removal of the uroliths is typically the treatment of choice. The surgery is straightforward, and recovery is usually quick and without complications.