Kidney disease (also referred to in medical terminology as renal disease) is common in many small mammals. Diet and husbandry can play a major role in preventing certain kidney diseases.
What are the common causes of renal disease in small pets?
Kidney stones (uroliths) made of calcium oxalate can cause kidney disease in chinchillas. The cause is presumed to be nutritional: moldy food, vitamin B6 deficiency, or a diet with too many plants high in oxalic acid (e.g., kale, mustard greens, and spinach).
Guinea pigs commonly develop a condition termed 'chronic interstitial nephritis,' which is a long-term inflammation of the kidney. Kidney disease may also be caused by diabetes mellitus and spread of infection from pododermatitis due to the bacteria Staphylococcus.
Guinea pigs are also susceptible to a parasite, Klossiella cobayae, which lives in the kidney, but rarely seems to cause disease.
Similar to guinea pigs, gerbils are prone to developing chronic interstitial nephritis as they age.
The most common kidney disease in older rats and mice is termed, 'chronic progressive nephrosis' (CPN). The kidneys become enlarged and the urine contains large amounts of protein. Feeding diets low in protein and restricting calories help to reduce the possibility and progression of CPN.
Rats may develop several different types of tumors of the kidney, and often both kidneys are affected.
Like mice and rats, hamsters can develop CPN. They are also prone to a condition called 'amyloidosis,' in which a certain protein is deposited in the kidney and causes loss of function.
Rabbits may develop several different types of renal disease.
Rabbits are prone to developing uroliths, especially if they have limited exercise, are fed pellets and alfalfa free-choice, have been over-supplemented with vitamins or minerals, or are obese. Rabbits with uroliths have the typical signs of kidney disease but may also have difficulty urinating, blood in the urine, and may show pain through a hunched posture and grinding of their teeth. A urinary obstruction is a medical emergency and the rabbit should be seen by a veterinarian immediately.
Kidney failure can occur in rabbits, and be due to many causes including:
Infections including pyelonephritis, an inflammation of the kidney, often due to a bacterial infection
High blood calcium levels, often due to poor diet
Calcification of the kidney, resulting from excessive levels of vitamin D
Fatty degeneration in overweight rabbits
Cancer, especially lymphosarcoma
Rabbits with chronic renal failure often develop anemia.
Encephalitozoon cuniculi is a parasite that is transmitted through the urine, is ingested, and moves from the intestines to the kidneys, brain, and other organs. It most commonly causes neurological signs such as a head tilt or paralysis, but it can also cause chronic renal disease. There is a blood test for antibodies to E. cuniculi that can determine whether a rabbit has been exposed. Unfortunately, a positive test is not diagnostic since many (up to 80%) of rabbits may test positive for this parasite. There is no specific treatment for infection with E. cuniculi. In addition to supportive care, corticosteroids may be given to reduce inflammation.
Some drugs, especially certain antibiotics such as gentamicin, can cause renal toxicity in rabbits, with the typical signs of kidney disease.
Renal cysts are an inherited condition in rabbits, but usually do not cause illness.
What are the signs of renal disease in small pets?
The most common signs of renal disease include:
- Depression and lethargy
- Increased drinking and urination
- Difficult or painful urination if an obstruction (e.g., a kidney stones) is present
- Loss of weight and appetite
- Urine scalding in rabbits
In acute disease, such as a toxicity, the signs occur suddenly and can be very severe. In chronic kidney disease, the onset may be very slow and the signs fairly non-specific, i.e., the animal is "just not doing well." Whether the disease is acute or chronic is typically related to the cause.
How is kidney disease diagnosed?
A diagnosis of renal disease is based upon the results of the physical examination, a complete medical history, a complete blood count, blood chemistry tests (including electrolytes, total protein, albumin, blood urea nitrogen, and creatinine), and a urinalysis. Radiographs (x-rays) can be very helpful, and endoscopy, ultrasound, and sometimes a kidney biopsy may also be needed.
How is kidney disease treated?
General treatment includes fluid therapy, nutritional support, and possibly providing supplemental heat. The fluid therapy may need to be continued for the life of the animal. Periodic blood testing may be necessary to monitor the response to treatment and adjust it accordingly. Since bacterial infections can be a common cause of renal disease, or can occur secondarily, antibiotics are often included in the treatment regimen. The underlying cause of the renal disease needs to be treated, as well. Surgery is often necessary to remove uroliths. Dietary and husbandry changes are often necessary.