What is the normal value of residual urine volume in bladder?

Residual urine volume refers to the amount of urine left in the bladder after urination. Normal residual urine volume should be about 0 to 10 ml. If residual urine volume is greater than 20 ml, it can be called residual urine volume. The cause is considered to be bladder detrusor contraction dysfunction or urinary tract obstruction.