AZOTEMIA refers to increase in blood urea nitrogen & creatinine levels.it is related to reduced GFR.it can also b due to extra-renal disorders.PRERENAL AZOTEMIA occurs when there is hypoperfusion of kidneys(which leads to reduced GFR).there is no parenchymal damage.POST RENAL AZOTEMIA can result when urine flow is obstructed below the level of kidney.WHEN AZOTEMIA PROGRESSES TO SYSTEMIC & BIOCHEMICAL ABNORMALITIES & CLINICAL MANIFESTATIONS,IT IS TERMED UREMIA.