The analysis of plasma urea is usually given as blood urea nitrogen (BUN). The conventional unit (mg/dl) can be converted into the SI unit (mmol/l) by the conversion factor 0.357. Levels can be decreased if the urea cycle is impaired either primarily or secondarily. However, this parameter is an indicator of renal function if elevated rather than an indicator of the urea cycle if decreased. Therefore, there is no important role for BUN in patients with hyperammonaemia.
