Oligospermia is defined as a low sperm count or low sperm count in the ejaculate. It is not usually reversible, although it always depends on the patient's case. The first thing to consider is whether the cause is congenital or acquired. If it is congenital, for example, an undescended testicle at birth is reversible as long as descent is achieved in the first years of life. If the cause is acquired, e.g. a varicocele, a better semen analysis is feasible after removal of the testicular varicose vein. Regardless of whether the sperm reduction is congenital or acquired, it is important to define the cause. The decrease in the number of spermatozoa can have a pre-testicular, testicular or post-testicular origin.
As a pre-testicular origin we find gonadal dysgenesis or alterations in the reversible hormonal stimulus. Metabolic alterations, as well as alcohol or stress, can also be considered as an origin of pre-testicular sperm reduction. In terms of testicular origin, we would find all those affecting the testicle; from agenesis to all types of congenital dysgenesis. Other processes such as hydroceles, varicoceles, etc. will depend to a large extent on testicular normalisation according to the time of action on spermatogenesis.
Post testicular causes include all defects of the vas deferens, whether surgical such as sectioning or kinking, and inflammatory causes such as urethritis. In general, any incidence in the normal evolution of the ejaculate such as, for example, trans-urethral prostate resection.