Usually, a semen sample is considered normal, when its volume is more than 1.5 ml. However, there are samples with a very small volume – 0.3 or 0.5 ml. These samples do not contain any spermatozoa, that is, they are azoospermic samples. An obstruction in the male reproductive system can be the cause of azoospermia. The measurement of fructose, is a routine way to detect an obstruction in the male reproductive system.
Fructose comes from the seminal vesicles, which are small sacs that produce the fluid that makes up 60-70% of the ejaculate volume. In cases where the obstruction is in the ejaculatory ducts the fluid produced by the seminal vesicles cannot go through. Then the amount of fructose in the semen sample will be zero and this is indicative of obstruction.