Medical expert of the article
New publications
The reasons for the increase and decrease in ammonia in the blood
Last reviewed: 20.11.2021
All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
Determination of the concentration of ammonia in the blood in liver diseases is assigned the role of an indicator of liver shunting (that is, a substance that normally comes from the intestine into the portal vein system and into the liver). In pathological conditions, with the development of venous collaterals, ammonia enters the system of general blood flow, bypassing the liver, and becomes, thus, an indicator of portal blood loss.
In addition to shunt hyperammonemia, enzymatic hyperammonemia is also observed. The latter develops when the systems involved in the conversion of ammonia (enzymes of the urea formation cycle) are disrupted. Basically, these disorders are registered in children and adolescents and are observed much less frequently by shunt. There are congenital and acquired enzymopathies leading to hyperammonemia. Congenital hyperlysinemia (defect of lysine dehydrogenase), propionic acidemia (defect of carboxylic acid of propionic acid), methylmalonium acidemia (defect of methylmalonyl mutase) and ornithmia (defect of ornithine ketoacid transaminase) belong to the congenital. Acquired fermentopathies include Reye's syndrome, in which there is especially high hyperammonemia (3-5 times higher than normal).
Increase in the concentration of ammonia of blood serum naturally occurs with cirrhosis of the liver. With cirrhosis of the liver without encephalopathy, the concentration of ammonia in the blood usually increases by no more than 25-50% compared with the upper limit of the norm, and with the development of encephalopathy - by 50-100%.
Often an increase in the concentration of ammonia is noted in viral hepatitis. Expressed hyperamonia in these patients occurs with the development of acute liver failure, which is explained by the development of massive necrosis of the liver. Synthesis of urea from ammonia is disrupted if more than 80% of the parenchyma of the liver is damaged. An increase in the ammonia content in the blood is also observed in liver cancer, chronic active hepatitis, fatty degeneration, taking certain medications (barbiturates, narcotic analgesics, furosemide, etc.).