Left side scrotal pain in a 5-year-old child may be caused by epididymitis, varicocele, orchitis and other diseases, or it may be caused by other diseases such as trauma. 1. Epididymitis: the cause of epididymitis is not single, mainly caused by bacterial infection. The main symptoms of the patient are pain in the epididymis area, enlargement of the epididymis, scrotal pain, etc., and most of them occur unilaterally, so the 5-year-old child with epididymitis in the left testicle will have pain in the left scrotum. 2. Varicocele: the etiology of varicocele is not yet clear, and it is considered to be caused by congenital factors or increased venous pressure. Patients will have symptoms such as hidden pain, enlargement and swelling of the scrotum on the affected side, so a 5-year-old child with varicocele on the left side will have scrotal pain on the left side. 3. Testiculitis: Testiculitis is mostly caused by bacterial, viral and other pathogenic infections, patients will have testicular pain, swelling and other manifestations, the pain can radiate to the scrotum. Therefore, 5-year-old children will have left scrotal pain. 4. Other: 5-year-old children with genital trauma, prostatitis, genital herpes and other diseases can also lead to the performance of the left scrotum pain. When a 5-year-old child develops symptoms of left scrotal pain, he or she should go to the hospital in time and follow the doctor’s instructions for treatment.