The urea cycle is a process that occurs in liver cells, where the body breaks down ammonia, a waste product from protein digestion, into urea, which is then excreted by the kidneys. Urea Cycle Disorders (UCDs) are genetic disorders that occur when one of the six enzymes involved in this process is defective, causing the body to be unable to eliminate ammonia. Accumulation of ammonia in the body is toxic and without proper treatment can lead to brain damage. UCDs often manifest in the early days to weeks of life with lethargy, sleepiness, and sometimes vomiting or respiratory distress. Certain forms of UCDs are milder and may present during later childhood with symptoms like nausea, confusion, fatigue, and even drowsiness.
These disorders are diagnosed through tests aimed at detecting high ammonia levels in the blood, combined with specialized urine tests that identify breakdown products in the body that could indicate the source of the disorder.
A liver biopsy might be required for confirmation, but genetic testing can also provide a diagnosis in some cases.
Since UCDs interfere with the metabolism of protein, the dietary intake of protein is restricted in children affected by these disorders. This is done in consultation with a nutrition and dietetics specialist to balance the essential needs of growth and proper functioning with potentially toxic factors for the body. Some children might need specific protein supplements that their bodies are unable to synthesize. Some may also require medication to aid in the removal of ammonia from the body.
Liver transplantation is an option for those suffering from severe diseases that cannot be controlled through the aforementioned approaches.