Anuria is defined as a total urine output of less than 100 ml in 24 hours or less than 17 ml per hour.There are many causes of anuria, which are classified as pre-renal factors, renal factors and post-renal obstruction. Pre-renal factors include shock, heart failure, dehydration, and other conditions with reduced effective blood volume, all of which can lead to insufficient glomerular filtration and anuria. Renal factors, including a variety of substantial renal lesions, are commonly seen clinically in glomerulopathy and nephrotic syndrome. Post-renal factors, which are the result of post-renal obstruction. Because of urethral stricture, stone, tumor compression causing urinary obstruction and difficulty in urination, resulting in urinary retention, bilateral hydronephrosis, causing excessive postrenal pressure, resulting in postrenal renal insufficiency or renal failure, which will eventually lead to anuria.