Hidden pain in the left side of the scrotum should be alerted to the occurrence of certain diseases, such as varicocele, epididymitis, scrotal inflammation, and so on, and should be promptly consulted to find out the cause of the disease. 1. Varicose veins of the spermatic cord: it refers to blood stagnation in the spermatic cord’s trailing vascular plexus due to various reasons, resulting in localized venous tortuosity, elongation and expansion. Most patients do not have obvious symptoms, but in serious cases, the affected side of the scrotum may be enlarged, accompanied by vague pain. 2. Epididymitis: Epididymitis is a non-specific infection of the male reproductive system, mainly caused by pathogenic bacteria such as E. coli and staphylococcus. Mostly seen in young and middle-aged men, it mainly manifests as localized pain in the scrotum on the affected side, which may radiate to the groin and lower abdomen on the same side, accompanied by swelling and discomfort, and may even affect the activities. 3. Scrotal inflammation: the left side of the scrotum hidden pain may also be caused by scrotal inflammation, the common causative organisms for the staphylococcus aureus, pseudomonas aeruginosa and so on. Patients can initially appear at the scrotum skin redness, swelling, itching, with the development of the disease, scrotal pain, rash, blisters and other manifestations. There may be other reasons for the vague pain in the left scrotum, and it is recommended to actively seek medical treatment under the guidance of a professional physician.