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High Levels of Blood Nitrogen in Cats

4 min read

Azotemia and Uremia in Cats


An excess level of nitrogen-based substances compounds such as urea, creatinine, and other body waste compounds in the blood is defined as azotemia. It can be caused by higher than normal production of nitrogen-containing substances (with high protein diet or gastrointestinal bleeding), improper filtration in the kidneys (kidney disease), or reabsorption of urine back to bloodstream.


Uremia, meanwhile, also leads to an accumulation of waste products in the blood, but is due to improper excretion of the waste products through the urine because of abnormal kidney function.


Symptoms and Types


  • Weakness
  • Fatigue
  • Vomiting
  • Diarrhea
  • Depression
  • Dehydration
  • Constipation
  • Weight loss (cachexia)
  • Loss of appetite (anorexia)
  • Bad breath (halitosis)
  • Muscle wasting
  • Hypothermia
  • Poor haircoat
  • Unnatural lack of color in the skin
  • A minute red or purple spot on the surface of the skin as the result of tiny hemorrhages of blood vessels in the skin (petechiae)
  • The escape of blood from ruptured blood vessels into the surrounding tissue to form a purple or black-and-blue spot on the skin (ecchymoses)




  • Low blood volume or blood pressure
  • Infections
  • Fever
  • Trauma (e.g., burns)
  • Corticosteroid toxicity
  • High protein diet
  • Gastrointestinal bleeding
  • Acute or chronic kidney disease
  • Urinary obstruction




You will need to give a thorough history of your cat’s health, including the onset and nature of the symptoms, to your veterinarian. He or she will then perform a complete physical examination, as well as a biochemistry profile, urinalysis, and complete blood count (CBC). The CBC results may confirm nonregenerative anemia, which is common in cats with chronic kidney disease and failure. Hemoconcentration may also occur in some cats with azotemia, whereby the blood thickens due to a decrease of fluid content.


Along with identifying abnormally high concentrations of urea, creatinine, and other nitrogen-based compounds in the blood, a biochemistry test may reveal high levels of potassium in the blood (hyperkalemia). The urinalysis, meanwhile, may reveal changes in urine specific gravity (a urinalysis parameter commonly used in the evaluation of kidney function) and abnormally high concentrations of protein in the urine.


Abdominal X-rays and ultrasound are two other valuable tools often used by veterinarians to diagnose azotemia and uremia. They can help in determining the presence of urinary obstructions and the size and structure of the kidneys -- smaller kidneys are commonly found in cats with chronic kidney disease, while larger kidneys are associated with acute kidney failure or obstruction.


In some cats, a kidney tissue sample will be collected to confirm the diagnosis of kidney disease and also to eliminate the possibility of other acute or chronic kidney diseases that may be present.




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