Renal Failure: When Kidneys Give Up

As the body ages, organs begin to show the strain of time. Kidneys are frequently the first major organs to lose enough function for illness to develop. This is true in rabbits, as it is in many other species. Kidneys are abdominal organs that filter toxins out of the blood, help maintain calcium and water balance, and produce a hormone that stimulates red blood cell production in the bone marrow. Substances filtered out by the kidneys, along with any excess water, are expelled during urination. Kidneys are essential to survival, and with total loss of kidney function (renal failure), the body can live a few days at most.

The signs of kidney disease in an aging bunny include increased thirst and urination in the early stages (vets call this “PUPD” for polyuria/polydipsia, which just means increased urination/increased thirst). This happens when more than 75% of the kidneys are not working, because the kidneys can’t pull enough water out of the urine. As more water is lost in urination, the body takes in more water through drinking. (This also happens in other diseases, like diabetes, and some endocrine disorders.) Litterbox habits can decline at this stage.

With long-term kidney disease, the patient begins to feel tired and ill. Appetite decreases, because toxins begin to build up in the blood, causing nausea and often weight loss. Anemia (decreased red blood cells) develops because the diseased kidneys are not producing enough hormone to stimulate the bone marrow. Being anemic makes the patient tired, because fewer red blood cells are carrying oxygen to the body.

Tests that a vet may run include a urinalysis, bloodwork, and X-rays. A urinalysis gives very useful information about kidney function. In early kidney disease, increased water content in the urine is the first sign of a problem. Try to bring a clean urine sample to your vet, if you notice increased thirst and urination. (Try scrubbing out a litterbox and rinsing it well, then see if your bunny will pee in it without the litter.) X-rays can show if there are stones in the kidneys. Bloodwork should be monitored regularly in any older pet, and especially in rabbits being treated for kidney disease. As kidney disease progresses, creatinine and blood urea nitrogen (BUN), which are toxins the kidneys are supposed to filter out, build up in the blood. Phosphorus also increases and contributes to nausea, and along with calcium, to mineralization.

The main goal of treating kidney disease is to increase quality of life for as long as possible. First, the treatable is addressed – antibiotics for infections, surgery or dietary therapy, along with pain management, for stones. The mainstay of therapy is fluids given under the skin (subcutaneous), which you can learn to do at home. This helps the kidneys flush out toxins. Rechecking levels of creatinine, BUN, and phosphorus helps your vet see if treatment is working. Always remember that whether your bunny is feeling well or not is the only real “test” result that matters. Depending on how severe the anemia is, your vet may also give injections of erythropoietin. These are very expensive and don’t always work. Other species are treated with a low protein diet, because BUN comes from breaking down protein in the diet (but because our rabbit friends aren’t carnivores, this diet doesn’t apply). Pepcid can help reduce some of the gastrointestinal upset that can develop.

As a last resort, hemodialysis and kidney transplants are options for some pets. In hemodialysis, the pet is hooked up to a machine that pulls out blood and rinses it of the accumulating toxins. However, most rabbits are too small for the machine which is designed for humans. It is very expensive and only available locally at Tufts. Transplants have not been done in pet rabbits, and the low survival rate, difficult recovery period, and ethical issues surrounding the donor rabbit, who gives up a kidney, can’t be minimized.

The causes of chronic kidney disease are not known. Some people think that long-term infections in any part of the body spill bacteria into the blood, and that these bacteria end up in the kidneys (as well as other organs) and cause small amounts of damage over a long time. In addition, any event that lowers blood pressure below a critical point, such as severe illness and sometimes anesthesia, can injure the kidneys when blood flow is too low. Kidney stones or infections, and long-term exposure to toxins will cause damage too. Kidneys may also fail suddenly at any age from some toxins (e.g., overdose of drugs like Advil [ibuprofen], some poisonous plants, antifreeze) and infectious diseases. However, acute kidney failure like this is rare in house rabbits.

The key to managing kidney disease is catching it early before the bunny is very sick. Some pets can live with treatment for over a year. However, as with most chronic diseases, quality of life is everything, and only your bunny can tell you when it’s time to let go.