Mild left-sided varicocele is usually harmless, while severe varicocele may cause pain and lead to infertility. 1. Mild varicocele: Most patients with mild varicocele do not have obvious discomfort and are not easy to be found, usually discovered during a physical examination. It can be treated without any special treatment, and regular rechecking of ultrasound is enough. 2. Severe varicocele: Severe varicocele may lead to swelling and pain in the testicles, especially after strenuous exercise. Some patients may also suffer from decreased sperm quality and testicular atrophy, leading to male infertility. Overall, patients with varicocele need to go to the hospital in time for examination, and according to the degree of the condition, targeted treatment under the guidance of the doctor.