Polyuria in Birds
Dr. Barbara Oglesbee
In birds, droppings are composed of three elements, feces, urates and urine. The droppings are stored in the cloaca, the common emptying chamber for the gastrointestinal, urinary and reproductive tract. Feces are produced in the intestinal tract, and are normally green or brown in color. Urine and urates are produced in the kidneys. Normal birds on a diet that has a low water content only produce a very small volume of liquid urine. The majority of the waste from the kidneys will be in the form of semi-solid, white/beige urates. Bacterial infection. Bacteria infections may come from other birds, from an overgrowth of dangerous bacteria on dirty food or water bowls, or spoiled foods. Often, small amounts of potentially dangerous bacteria live in the intestinal tract without causing harm. This population of bacteria can overgrow and cause disease if the bird's immune system is not functioning properly, as may occur during times of stress.
The urates seen in the droppings consist of uric acid, which is the form in which the majority of nitrogenous waste is eliminated. This method is very efficient, since greater amounts of waste can be concentrated in a semi-solid form as compared to a liquid urine. The avian kidney always produces some urine. This urine serves to flush the semi-solid urates out of the kidney and into the cloaca. If a large amount of liquid is ingested, either by drinking or eating foods with a high water content, this liquid is eliminated in the form of urine. Birds often drink excessively with many different diseases, including infections and metabolic diseases, like liver disease and pancreatic disease.
Normally, the kidneys serve to balance the amount of water retained in the body. If the kidneys are damaged, they may loose the ability to form a concentrated urine. Excessive amounts of water can be lost from the body, resulting in polyuria and dehydration.
Since the major method of eliminating waste is via the production of uric acid, birds have not developed the ability to form urine that is as concentrated as mammalian urine. To compensate for this, liquid is reabsorbed by the colon. When urine enters the cloaca, it is moved by peristaltic waves into the colon, where water is absorbed.
Birds with intestinal tract disease often develop intestinal hypermotility. Peristaltic waves (rhythmic contractions of the intestinal tract which serve to push digested food forward) occur at regular controlled intervals in normal birds. In some birds with diarrhea, these waves lack coordination, so that food moves through the intestinal tract too quickly. This results in an increase in frequency of defecation and polyuria since water moved into the colon does not have a chance to be absorbed.
A small amount of urine in the dropping may be normal. For example, switching to a commercial pelleted diet may cause temporary polyuria in some birds, as these birds may initially drink more water. Also, as mentioned above, birds eating a large amount of fruit and vegetables will become temporarily polyuric since these foods contain a higher water content. Similarly, birds may drink excessively following a bath, or if sweet tasting beverages are offered.
It is common for birds to become temporarily polyuric when stressed. This may occur when the environment changes, such as the addition of a new bird, new people in the house, or moving the cage. Most birds are polyuric when taken to a strange place, like a veterinarian's office.
Nesting birds and their offspring are usually slightly polyuric. This is commonly seen before egg laying in female birds. After laying the eggs, however, the droppings should return to normal. Birds that are feeding babies will also be polyuric, since they will drink more water to make a gruel in the crop to feed to the offspring.
There are many causes of polyuria in birds. The cause may be very simple, such as a dietary change, or may be due to a number of complex disease processes. There are many contagious diseases which cause polyuria, so it is important to inform your veterinarian of any potential contact – direct or indirect – with other birds. Possible causes of polyuria in birds include:
An overgrowth of harmful bacteria may also occur when antibiotics are used improperly. Bacteria may cause intestinal disease or move from the intestines directly to the kidneys though a specialized system of veins, call the renal portal system.
Viral infection. Several different avian viruses may cause polyuria, either by causing intestinal disease, or by directly infecting the kidneys.
Neoplasia (cancer). Neoplastic diseases of the kidneys or portions of the brain may cause polyuria.
Toxins. Polyuria is a common symptom of heavy metal toxins (lead and zinc), since these may directly damage the kidneys.
Antibiotic use. Birds may develop polyuria following treatment with antibiotics harmful to the kidneys. These include the aminoglycosides and sulfa drugs. Usually, the polyuria ceases once the drug is discontinued.
Metabolic disorders. These include liver disease and pancreatitis. Most birds with metabolic diseases will have other symptoms in addition to polyuria. The amount of excessive urine in the droppings is small
Diabetes Mellitus. It is common in smaller psittacine birds such as budgerigars and cockatiels, but can be seen in any species. Birds with diabetes drink very large amounts of water and will commonly soak the bottom of the cage with urine.
Dietary deficiencies or excess. Deficiency in vitamin A or excessive consumption of calcium and vitamin D can directly damage the kidneys.
Localized abscesses or infection. Such a uterine infections in female birds, peritonitis, or abscessed air sacs.
Steroid use. Corticosteroids (such as prednisone or dexamethasone) or progesterones.
Diet changes. The polyuria seen with diet changes, such as eating fruits and vegetables, is temporary and normal.
Stress induced. This is usually the result of a change in environment