The left side of the testicle is a little bit vague and painful, which is mostly seen in varicocele and chronic epididymitis. The incidence of varicocele is higher on the left side than on the right side because the left spermatic vein converges into the left renal vein at a right angle, which needs to overcome the effect of gravity and makes the blood flow back relatively difficult, so it is more likely to cause blood stagnation. Therefore, once varicocele occurs, most patients are uncomfortable on the left side, manifesting as a feeling of scrotal swelling and vague pain in the scrotum. Chronic epididymitis mostly occurs when acute epididymitis is not completely cured and turns into chronic epididymitis. Epididymitis may also cause a vague pain. Varicocele can be treated by medication and surgery. Since varicocele can cause a decrease in sperm quality in addition to the symptoms of scrotal discomfort, it should be taken seriously. Chronic epididymitis causing vague pain in the testicles usually requires sufficient amount and course of antibiotic treatment, in addition to the usual attention to reduce the sedentary time and drink a lot of water can also help relieve the symptoms. To sum up, the vague pain on the left side of the testicle is often caused by varicocele or chronic epididymitis, so it is important to pay attention to a clear diagnosis in the treatment, and it is recommended to pay attention to it and treat it in a timely manner.