Kidney failure in rats

The kidneys are vital organs (most of us and our rats have two) within our bodies, which perform three major tasks:

  1. cleaning waste products from the blood and maintaining fluid balance by excreting excess fluid,
  2. filtering the blood by keeping some (useful) compounds and excreting others,
  3. helping to regulate blood pressure and the production of red blood cells by secreting a hormone called erythropoieitin.

Kidney failure is thought to be the third most common cause of death in pet rats after respiratory disease and tumours.

The kidney tissue is composed of millions of tiny filters called glomeruli. Happily we all have many more than we need to maintain our health (this is why it is possible to live a normal life, oblivious to the fact that we only have one kidney and what makes live donor transplants possible for humans). Blood is filtered in huge volumes each day to remove waste products and excess water from the body, so maintaining the balance of fluid and electrolytes ('salts' such as sodium and potassium). Over time the filtering efficiency is reduced as the glomeruli get damaged or clogged by wear and tear, infection, diseases (such as polycystic kidney disease) and nutritional imbalance. In rats the main nutritional influence is feeding a high protein diet, although orange skin oil (found in whole oranges, juices/products made from whole oranges and dried peel) also has an impact. Kidney disease does have a genetic influence.

It is not until over 75% of the kidney's filters are clogged and damaged that levels of toxic waste products begin to increase in the body. Blood tests can be performed on rats that will conclusively determine kidney failure by measuring these toxins. Normal levels of urea and creatinine in a rat are 12-20 mg/decilitre and 0.3-0.4 mg/decilitre respectively. However, other symptoms may point the finger fairly conclusively at renal failure.

Symptoms of kidney disease in rats may include:

  • increased drinking
  • increased urination (both in an effort to flush toxins from the body using the few remaining filters available)
  • weight loss
  • loss of appetite
  • anaemia (often seen in very pale ears and toes)
  • high blood pressure (obviously this can't be recorded in rats under normal circumstances, but in laboratory studies most rats with kidney failure are found to have high blood pressure)
  • low blood calcium and high blood phosphorus leading to softened bones
  • hard and irregular kidneys on palpation.

Treatment in humans would be dialysis and transplantation, which are not available to our rats. All treatment should be considered supportive rather than curative, but can significantly increase the rat's comfort and slow disease progression.

Always have fresh water available in quantity. They are using this to flush out toxins with their few remaining filters.

If rats with kidney disease become stressed or sick in other ways they can deteriorate very quickly. Administering subcutaneous (under the skin) or intra-peritoneal fluids (vet) and diuretics can help to get their metabolic balance restored.

Aim to decrease the work the kidneys have to do with alterations in diet:

  • Reduce protein to 8-10%.
  • Use a diet based on soya protein, which has been shown to slow progression.
  • Decrease dietary phosphorus by eliminating high phosphorus foods such as yoghurt, milk, sardines, spinach, corn, nuts, bran, cheese, oatmeal, sweet potato.
  • Increase or supplement B vitamins, which have been shown to improve anaemia.
  • Supplement/feed omega 3 and 6 fatty acids, which have been shown to slow progression.
  • Feed flax seed or flax oil, which has been shown to slow progression.
  • Consider antacids as these help to remove excess phosphorus.
  • Feed low salt diet. This may help to reduce high blood pressure, which is known to accelerate progression of the disease.
  • Supplement with high dose vitamin E (talk to vet) as this may help to reduce blood pressure also, and has few toxic effects in high doses (these include increased blood clotting times, nausea, diarrhoea and reduced blood sugar).
  • Be careful to avoid non-steroidal anti-inflammatory medication, such as aspirin, ibuprofen and metacam.
  • Avoid any antibiotics that are toxic to the kidneys.

Specific diet and quantities of different foods are further discussed here.