Overview of Anuria (Lack of Urination) in Dogs
Anuria is defined as complete suppression of urine production by the kidneys. In a normal healthy animal, the kidney produces one to two ml of urine per kilogram of body weight every hour. If the kidney produces less than 1 ml/kg/hr, the pet is considered oliguric, which means there is little urine produced. If no urine is produced, anuria is diagnosed.
Anuria is most often associated with acute kidney failure. Urinary obstruction, such as due to a bladder stone, does result in inability to pass urine but does NOT result in the kidney being unable to produce urine. This is an important distinction between anuria and urinary obstruction. Both are treated very differently.
Acute kidney failure has many known causes such as high blood calcium, antifreeze, various drugs, dehydration, bleeding, Addison’s disease, congestive heart failure, anesthesia, blood clots and infections. All of these can result in anuria.
Pets with anuria are usually quite ill. Straining to urinate is not part of anuria. That symptom is more likely to be associated with urinary obstruction. Pets with anuria do not have any urine produced and therefore do not feel the urge to void urine.
Anuria is a serious and potentially fatal symptom of acute kidney failure. Emergency treatment is necessary in order to give the pet any chance of recovery. Pets with anuria have a poor prognosis and many do not recover.
What to Watch For
Diagnosis of Canine Anuria
Physical examination can help lead your veterinarian to a suspicion of anuria. The pet is usually depressed and dehydrated. Abdominal palpation will reveal an empty bladder. The kidneys may be swollen and painful.
Anuria is diagnosed when there is no urine production. Finding the cause of the acute kidney failure may be difficult. In order to diagnose the cause of the acute kidney failure, blood tests, radiographs (x-rays), ultrasound, specialized blood tests or biopsy may be necessary.
In order to confirm the lack of urine production, an indwelling urinary catheter may be placed and urine production monitored. When no urine is produced, anuria is diagnosed and treatment is immediately instituted.
Treatment of Canine Anuria
Before treatment, an accurate weight is obtained and a urinary catheter is placed to accurately measure urine production and to help guide treatment.
Your veterinarian will administer intravenous fluids using extreme care; the fluid rate must be carefully monitored since it is quite easy to overhydrate an anuric pet. A pet that is unable to produce urine cannot handle high fluid rates that are normally used in dehydrated animals. If the kidneys are unable to process the intravenous fluids, these fluids will accumulate in body tissues, resulting in body swelling and weight gain.
In addition to intravenous fluids, there are several drugs that are used to stimulate urine production. These drugs use different methods to affect the kidney and urine production.
Mannitol is slowly administered intravenously. If it is going to be effective, urine should be produced within 15 to 30 minutes. If no urine is produced in that time, repeated doses of mannitol can be given every 15 minutes until a maximum dose is reached. If no urine is produced, even after the maximum dose has been given, another drug is chosen to stimulate urination.
After administration of furosemide, urine should be produced within 30 to 60 minutes. If no urine is produce, double the original dose is given. If still no urine is produced, a dose three times the original dose can be given. If still no urine production after another 30 to 60 minutes, another drug is chosen to try to stimulate urine production.
It has been found that a combination of furosemide and dopamine works better than each drug given separately. Once anuria has been confirmed, dopamine is started as a constant drip and furosemide, low dose, is given intravenously, every hour. If no urine is produced within six hours, the prognosis for recovery is grave.
If drugs are not effective in stimulating urine production, dialysis must be considered. Unfortunately, dialysis for pets is not as readily available as in human medicine. There are few places in the United States that have the necessary equipment. Dialysis must begin immediately, as soon as the drugs have been determined not to be effective. This means that dialysis is not commonly performed.
If urine is not produced within six hours of instituting medications and fluids, recovery is nearly impossible. Euthanasia must be considered at that time.
Additional treatment to treat the underlying cause of the acute kidney failure may also be given. Unfortunately, if urine production does not occur, the underlying cause and appropriate treatment are not very important since pets do not survive very long after their kidneys completely stop functioning.