Several theories have been proposed to explain the harmful effect of varicoceles on sperm quality, including the possible effects of pressure, oxygen deprivation, heat injury, and toxins.
Despite considerable research, none of the theories has been proved unquestionably, although an elevated heat effect caused by impaired circulation appears to be the most reproducible defect. Supporting this hypothesis is the fact that a varicocele created in an experimental animal led to poor sperm function with elevated intratesticular temperature. Regardless of the mechanism of action, a varicocele is indisputably a significant factor in decreasing testicular function and in reducing semen quality in a large percentage of men who seek infertility treatment.
Although unproved, a varicocele may represent a progressive lesion that can have detrimental effects on testicular function. An untreated varicocele, especially when large, may cause long-term deterioration in sperm production and even testosterone production. If an infertile male has bilateral varicoceles, both are repaired to improve sperm quality.
A patient with a varicocele is usually asymptomatic and often seeks an evaluation for infertility after failed attempts at conception. He may also report scrotal pain or heaviness. Careful physical examination remains the primary method of varicocele detection. An obvious varicocele is often described as feeling like a bag of worms. Scrotal examination for varicocele should be a facet of the standard urologic physical examination because of the potential for varicoceles to cause significant testicular damage. The presence of a varicocele does not mean that surgical correction is a necessity.
In men with a varicocele, the presence of an initially abnormal semen quality may be a risk factor for future deterioration of semen quality. In a prospective study of men with a mean follow-up of 5 years, among men with an abnormal semen analysis at presentation, the quality of semen degenerated in 28 subjects (87.5%); however, but among men with initially normal semen quality, only 6 patients (20%) had degenerated quality during follow-up.