Hypokalaemia and hepatic encephalopathy in the dog: the mechanism
9-year-old female Labrador with advanced chronic hepatitis and ascites, treated with increasing doses of furosemide. Over the last few days she has become disorientated, head-presses and hypersalivates. There are no signs of gastrointestinal bleeding.
| Parameter | Result | Reference |
|---|---|---|
| Potassium | 2.8 mEq/L | 3.8–5.4 |
| Venous pH | 7.50 | 7.35–7.45 |
| Bicarbonate | 29 mmol/L | 18–24 |
| Ammonia | 210 µmol/L | < 60 |
| Albumin | 1.9 g/dL | 2.6–4.0 |
Why does hypokalaemia contribute to this dog's encephalopathy?
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A. It directly inhibits urea cycle enzymes in hepatocytes
This is not the main mechanism: the problem is not direct inhibition of the urea cycle but increased renal ammonia production and greater passage into the brain.
B. It increases renal ammoniagenesis, and alkalosis favours NH₃ entry
Correct. In hypokalaemia, K⁺ leaves cells and H⁺ enters: intracellular acidosis in proximal tubular cells stimulates renal ammonia production, which enters the circulation. The accompanying metabolic alkalosis shifts the NH₄⁺/NH₃ equilibrium towards uncharged NH₃, which crosses the blood–brain barrier.
C. It reduces glomerular filtration so the kidney stops excreting ammonia
The kidney does not eliminate ammonia mainly by filtration; it actually produces it, and hypokalaemia increases that production and the fraction returned to the blood.
D. It stimulates intestinal production of endogenous benzodiazepines
Benzodiazepine-like substances may play a role in hepatic encephalopathy, but they have no direct link to hypokalaemia.
lightbulb Key takeaway
In a dog with liver disease and encephalopathy, correct hypokalaemia and alkalosis and avoid excessive diuresis: spironolactone is the mainstay diuretic for ascites, and furosemide is used with caution. Also look for other triggers: gastrointestinal bleeding, infection, dehydration and constipation.
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Updated: November 1, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.