In Chronic Kidney Disease, the body’s internal pH balance becomes increasingly unstable. The kidneys are responsible for excreting acids and regenerating Bicarbonate, the body’s primary buffer. When they fail, the cat's blood becomes too acidic, a condition called Metabolic Acidosis.
The "Internal Burn" Mechanism
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Acid Buildup: Every day, the body produces acids as a byproduct of protein metabolism. Healthy kidneys neutralize these acids.
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The Buffer Loss: In CKD, the kidneys can no longer produce enough bicarbonate to neutralize the rising acid.
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The Result: The blood pH drops. While the change is tiny, it has a massive impact on the cat’s cellular health. It essentially feels like a permanent, low-grade flu or a "heavy" feeling in the body.
Why Acidosis is Dangerous
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Muscle Wasting: Acidosis triggers the body to break down its own muscle tissue to release glutamine (an amino acid that helps the kidneys excrete acid). This is a major reason why CKD cats lose their "thigh muscles" and become very thin.
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Bone Loss: To buffer the acid, the body pulls minerals (like calcium) out of the bones, contributing to the bone-weakening cycle of renal disease.
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Worsening Kidney Damage: High acidity in the kidneys themselves accelerates the scarring (fibrosis) of the remaining healthy tissue.
Symptoms of Acidosis
The symptoms are often subtle and overlap with general uremia:
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Poor appetite or "picky" eating.
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Rapid or shallow breathing (the body tries to "breathe out" the acid as $CO_2$).
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Lethargy and weakness.
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Weight loss despite eating.
Measuring Bicarbonate (TCO2)
On a standard blood panel, vets look at Total CO2 (TCO2) as a proxy for bicarbonate.
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Target Range: Most vets want to see TCO2 levels between 16 and 24 mmol/L.
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The "Grey Zone": If the TCO2 drops below 15, the cat is in a state of clinical acidosis and needs intervention.
Management
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Renal Diets: Most prescription kidney diets are "alkalizing," meaning they are formulated to help keep the blood pH in a more neutral range.
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Bicarbonate Supplementation: If diet alone isn't enough, your vet may prescribe oral Sodium Bicarbonate (baking soda in capsule form) or Potassium Citrate.
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The Balancing Act: Supplements must be dosed carefully. If you give too much, the blood can become too alkaline, and the sodium in sodium bicarbonate can sometimes be a concern for cats with high blood pressure.
The Link to Potassium
Acidosis and Potassium are closely linked. When the blood is too acidic, potassium shifts out of the cells and into the blood. This can mask a true potassium deficiency. Once the acidosis is corrected, the potassium levels may "drop," requiring the vet to adjust both supplements simultaneously.
Disclaimer: This content is for educational purposes only and does not constitute veterinary medical advice. Always consult with your primary care veterinarian or a veterinary internal medicine specialist regarding your cat’s specific condition.