What is the difference between azotemia and uremia?

Will is a 68-year-old male with a history of hypertension. Eight months ago, he started regular dialysis therapy for ESRD. Before that, his physician was closely monitoring his condition because he had polyuria and nocturia. Soon it became difficult to manage his hypertension. He also lost his appetite, became weak, easily fatigued, and had edema around his ankles. Will debated with his physician about starting dialysis, but she insisted, before the signs and symptoms of uremia increased, the treatment was absolutely necessary.