High renal urea indicates impaired kidney function, which can be caused by pre-renal factors or renal factors, or post-renal factors, which can cause kidney function impairment. Pre-renal factors, such as insufficient blood volume, can lead to inadequate perfusion of the kidneys, which can cause renal impairment and lead to elevated urea. In the case of renal factors, such as chronic nephritis and other renal diseases, it can lead to elevated urea, causing damage to kidney function and even uremia in severe cases. Post-renal factors are obstructive diseases, such as ureteral stones, kidney stones or hydronephrosis caused by lower urinary tract obstruction, which can lead to post-renal renal impairment, resulting in urea elevation.