What is the most likely reason for having an abnormally high blood urea level? liver dysfunction kidney dysfunction protein intake twice the rda protein intake one-tenth the rda hyperstimulation of the immune system ?

The correct answer is "kidney dysfunction".

Physiologically, urea is filtered in the glomerulus in the kidneys. The urea in the blood is further secreted through out the renal tubules but more urea being reabsorbed than secreted. This results to 40% of the filtered urea present in the final urine. In the event of kidney dysfunction, there is destruction of the glomerulus or necrosis of the tubules. Therefore, urea is not efficiently filtered and excreted which will lead to high blood urea levels.