Diabetes insipidus occurs as the result of a hormonal dysfunction, in which the water-metabolism of the affected dog is disrupted. Excessive thirst and urination are often the predominant symptoms.
There are two variants of this disease, the so called "renal type" and the "central type". In case of both types, the kidney increasingly discharges water. A risk exists when the dog does not compensate the loss of water by sufficient drinking. Dehydration (drying up with symptoms such as dry oral mucosa with little pasty spittle, weak pulse up to breakdowns) will result. Diabetes insipidus is a rather rare disease whereas neither one age class nor one breed is increasingly affected. The central type is primarily present, in some little cases the renal variant. The skin symptoms of diabetes insipidus are considerably increased drinking and increased urine discharge. The animal also needs to urinate at night. Frequently, due to strong desire to urinate "accidents" happen. In severe cases, the dog may lose much weight or dehydrate which is characterized by indications such as drying-out of the oral mucosa with viscous little spittle, weak pulse up to breakdowns. In addition, the increased water discharge provokes light and transparent looking urine which furthermore has a less strong smell than the urine of a healthy dog.
Usually, only a fraction of the urine which is at first generated in the kidney is then discharged. The bigger part of the contained water, as well as certain vital substances and salts are regained and remain in the body. That process is called re-absorption which among others is controlled by the hormone ADH, which particularly controls the water content of the urine, or its concentration. Diabetes insipidus is caused by a lack of ADH or the reduced capability of the nerves to react to that hormone. Depending on the cause, two types of diabetes insipidus are distinguished. In case of the central variant of diabetes insipidus, the gland of the brain region is impaired which produces and releases the hormone ADH. Causes of this dysfunction may be traumata (injuries) or tumors within this area (brain area), a genetic defect but also infections and the so called autoimmune disease, where the immune system destroys the cells that produce the ADH. Additionally, drugs (the active ingredient Phenytoin is applied for epilepsy or heart rhythm disturbances) may impede the ADH production and thus be activator of the disease. The renal type (renal = "pertaining to kidney") of the disease is caused by a genetic defect by means of which the kidneys may not react to the controlling hormone. Often, this type is caused by a basic disease (Morbus Cushing or liver disease). In both cases increasingly water is discharged with the urine. The body loses one of its most important mechanisms, to control and regulate the water balance.
The diagnosis is quite comprehensive since there is a variety of diseases which cause increased drinking and increased urine discharge. In addition to a clinical examination with blood and urine count, some functional tests are appropriate for making the diagnosis. In case of the central diabetes insipidus, the patient is given a synthetically generated ADH substitute (Desmopressin) for the therapy. In case of the renal variant, the causing disease is primarily to be treated, unless the defect is caused genetically. In such cases or for the alleviation of the symptoms, the dog should be given a special diet. Additionally, certain drugs can be applied for the alleviation of the symptoms.
In case you notice any of the symptoms indicated before with your dog, you should consult a veterinarian at next opportunity. If your animal suffers from diabetes insipidus, the development of the dog should be checked more frequently by a veterinarian than in normal cases. As the veterinarian will possibly require a urine sample of your dog for diagnostic reasons, it makes sense to collect a urine sample prior to the consultation.