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Renal Tubular Acidosis in Dogs

Renal tubular acidosis (RTA) is a rare syndrome, characterized by an excess of acids in the dog's blood. This is due to the kidney's inability to excrete sufficient acid through the urine. Dogs with RTA will also have abnormal levels of potassium in the blood. This condition occurs as a part of the metabolic process, by which food is transformed into energy. And although RTA is seen in both cats and dogs, it rarely occurs in cats. If you would like to learn more about how this disease affects cats, please visit <a target=">this page in the PetMD health library.

Symptoms and Types

Some common symptoms which may be observed include:

• Fever
• Panting
• Lethargy
• Dehydration
• Weight loss
• Muscle weakness
• Lack of appetite (anorexia)
• Bloody urine (hematuria)
• Excessive thirst (polydipsia)
• Frequent urination (polyuria)
• Difficulty urinating (due to bladder stones)

There are two primary RTA types: type 1 RTA (or distal), involves reduced hydrogen ion secretion in the kidney, and type 2 RTA (or proximal), which is characterized by the inability to excrete acid into the urine. Abnormal metabolic processing of bicarbonates is referred to as metabolic acidosis, and is marked by abnormally high levels of acids in the blood, and abnormally low levels of acids in the urine.

Type 2 proximal renal tubular acidosis has been documented in dogs in association with Fanconi syndrome, a genetically recessive disease of the kidneys in which the kidneys are unable to reabsorb phosphate, glucose, and amino acids, spilling them into the urine. This activity causes an imbalance of acids in the blood, leading to renal tubular acidosis. 

Causes

Some of the common underlying causes of RTA include infection of the kidney and ureter(s), and feline hepatic lipidosis, a type of liver disease. However, there are times when the RTA is idiopathic.

Diagnosis

Your veterinarian will perform a complete physical exam on your dog, including a blood chemical profile, a complete blood count, a urinalysis and an electrolyte panel. Your veterinarian will use the results of the blood work to rule out, or confirm an underlying systemic disease. You will need to provide a thorough history of your dog's health leading up to the onset of symptoms.

The results from a blood gases analysis, along with the results of the electrolyte panel, should indicate a normal anion gap (sum of the cations minus the anions in the plasma) with metabolic acidosis, indicating that the alkaline urine is abnormal. This is a key diagnostic feature of type 1 RTA.