Uremia or uraemia (see spelling differences) is a term used to loosely describe the illness accompanying kidney failure (also called renal failure), in particular the nitrogenous waste products associated with the failure of this organ. This is not to be confused with uricemia, or hyperuricemia, a build up of uric acid in the blood.
In kidney failure, urea and other waste products, which are normally excreted into the urine, are retained in the blood. Early symptoms include anorexia and lethargy, and late symptoms can include decreased mental acuity and coma. Other symptoms include fatigue, nausea, vomiting, cold, bone pain, itch, shortness of breath, and seizures. It is usually diagnosed in kidney dialysis patients when the glomerular filtration rate, a measure of kidney function, is below 50% of normal.
Azotemia is another word that refers to high levels of urea, but is used primarily when the abnormality can be measured chemically but is not yet so severe as to produce symptoms. Uremia can also result in uremic pericarditis. There are many dysfunctions caused by uremia affecting many systems of the body, such as blood (lower levels of erythropoietin), sex (lower levels of testosterone/estrogen), and bones (osteoporosis and metastatic calcifications). Uremia can also cause decreased peripheral conversion of T4 to T3, producing a functionally hypothyroid state.