A large or small epididymis may be caused by diseases such as orchitis, epididymitis and varicocele. 1. Orchitis: usually due to bacterial, viral, chlamydial, mycoplasma and other pathogenic infections. Acute non-specific orchitis patients often appear on one side of the scrotum contents of the rapid enlargement of the situation, and may also be accompanied by pain, and the affected side of the testicles become larger, harder. 2. Epididymitis: usually caused by bacterial infection, urinary reflux, sexually transmitted infections, tuberculosis and other conditions, but also with trauma, bad sex, urinary tract infection and other factors. Generally, acute epididymitis patients often appear on one side of the scrotum rapid swelling, may also appear erythema, and may also appear scrotal enlargement and pain, activity restriction and so on. 3. Varicocele: the cause and pathogenesis are still unclear, mostly considered to be related to venous valve insufficiency, venous return obstacle, etc., while standing for a long time, combined with retroperitoneal tumors, etc. can induce varicocele. Patients are usually asymptomatic, but if the condition is serious, the scrotum on the affected side may be enlarged, and may be accompanied by swelling and hidden pain. Other diseases, such as tumors, may also lead to a large or small epididymis, and it is recommended that the patient consult a doctor in time to find out the cause of the disease, and under the guidance of the doctor reasonable treatment.