Urine Scald: A Symptom of a Greater Problem
University of Miami Biology Department
House Rabbit Society of Miami
A rabbit suffering from urinary tract problems may experience loss of fur in the genital region and hindquarters. The baldness and red, irritated skin are caused by "urine scald," and it can happen to any bunny whose urine soaks into the fur around her vent and is in constant contact with her delicate skin.
There are many possible reasons for a rabbit to dribble urine and/or sit in urine, and the only way to know for sure is have your rabbit completely examined by a veterinarian experienced in rabbit medicine.
Some possible causes of urinary incontinence (and hence, urine scald) to consider are the following.
Bladder sludge
All rabbits normally excrete excess calcium and oxalate salts via the urinary tract, and the residue of normal urine will often appear "chalky." However, when excessive amounts of calcium/oxalate salts precipitate in the urinary tract, they sometimes manifest as a thick, curry-colored "sludge" that sometimes has a consistency as thick as toothpaste. This can be very painful in the bladder and when it is passed, and sludge buildup can cause urine leakage and incontinence.
Although some vets suggest reducing dietary intake of calcium to help control this problem, we have not found any correlation between dietary intake of calcium and severity of sludge. Rather, this seems to be a metabolic problem suffered by a few individual rabbits, and may be an endocrine problem, rather than a dietary one.
Treatment for bladder sludge may include bladder flushes (in severe cases), or simply helping the bunny flush the bladder by administering subcutaneous fluids and a small dose of diazepam (Valium) to help relax the bladder sphincters. Your vet will know best how to treat your rabbit's particular problem, if this is what it turns out to be.
Bladder stone (urolith)
Diagnosed via radiography, a bladder stone is a mass of calcium and/or oxalate salts that has precipitated into a solid mass. Like sludge, a urolith can cause urinary incontinence and dribbling. Unfortunately, the only viable treatment at this time is surgical removal.
Bacteria can infect the urinary tract (kidneys and/or bladder), just as they can many other organ systems. The best way to diagnose this particular ailment is via cystocentesis: inserting a sterile needle into the bladder and extracting a sterile sample into a syringe. This is then sent to a laboratory for Culture and Sensitivity Testing. This will reveal (1) what species of bacteria is causing the infection and (2) which rabbit-save antibiotics (with good urinary tract penetration) will kill them.
Unfortunately, urinary tract infections are sometimes caused by "fastidious anaerobes": bacteria that die upon the slightest exposure to oxygen. If this is the case, then the culture and sensitivity test will come back negative. However, your vet may be able to determine if a UTI is likely by examining the urine under the microscope for signs of blood and white blood cells in the urine. If there is a good chance that your bunny has a UTI, even if the culture comes back negative, your vet might wish to put her on a course of antibiotics such as chloramphenicol, which is effective against many anaerobes and also concentrates well in the urinary tract. Your vet is the best person to advise you on the proper course of action in case of a UTI.
Arthritis of the spine or pelvis
Arthritis of the spine or pelvis can result in the rabbit's inability to posture correctly for urination. This can cause urine to collect in the fur and soak into it, causing urine scald.
Arthritis can be diagnosed via radiography, and can often be helped tremendously with non-steroidal anti-inflammatory drugs such as carprofen (Rimadyl) or flunixin meglumine (Banamine).
Rear limb/pelvic paresis
Paresis is defined as a weakness without total loss of movement in a particular area of the body. This problem is not uncommon in older rabbits, and some even lose the use of their hind legs. The problem may be caused by arthritis, disc degeneration or other skeletal problems. Some vets suspect that a central nervous system/renal system parasite known as Encephalitozoon cuniculi might be responsible for this condition, but there is still no conclusive clinical evidence to support this contention.
Some people have reported excellent improvement of paresis with acupuncture and massage, whereas others have seen improvement with short-term use of anti-inflammatory drugs (e.g. corticosteroids, which should not be used long term). This also helps with urinary tract continence.
E. cuniculi is being experimentally treated with any one of several related drugs (albendazole, fenbendazole, oxibendazole, etc.), and although some individuals have reported improvement in the condition after using these drugs, there are still no studies to show conclusively that such treatments are effective.
Unspayed female rabbits have a very high risk of developing uterine cancer, and a large tumor can sometimes interfere with normal urination. All female rabbits should be spayed for their health and longevity.
Our vets have noted that removal of the cancerous uterus (via spay operation) usually solves the problem, and they have not noted a high degree of metastasis (spreading) in this type of cancer, once the uterus is removed. Spaying is the best treatment option for this problem.
Incontinence due to hormone imbalance
Because rabbit spaying is a relatively recent notion, data are not yet complete on the long-term effects of early spay. In at least one case, incontinence believed to have been due to hormonal imbalance was successfully treated with DES, a synthetic estrogen.
While your veterinarian is performing diagnostic tests to determine the reason for your rabbit's urine scald, your job will be to keep her comfortable, clean and dry. You can do this by giving her regular "butt baths" when she is soiled (follow the link for instructions), and by administering analgesia (e.g., Banamine) as per your veterinarian's instructions.
The Color of Urine
Healthy rabbits excrete excess calcium salts via the renal system, and this can give the urine a chalky or opaque appearance. The urine will often dry to a white, chalky residue. Unless the residue is thick, pasty, and the color of mustard powder, this is normal, and should not be considered "sludge."
Normal rabbit urine is usually pale yellow in color, but upon exposure to the atmosphere, compounds in the urine may oxidize to darker yellow, orange, red, or even dark brown. This isn't unusual, and--by itself--is not necessarily a sign of a health problem. Blood in the urine, unless it is from a hemorraghing uterus or very serious problem, is usually not readily visible to the naked eye. Test strips are available at most pharmacies that will tell you whether there is blood in the urine or not, but your vet is the best judge of whether your bunny's urine is normal.
Urine that is very dark immediately when it emerges may indicate that the bunny is dehydrated, and should receive more water, either by mouth or--in more serious cases--via administration of subcutaneous Lactated Ringer Solution.