Hidden pain in the left egg may be caused by acute epididymitis, orchitis, testicular trauma and torsion, testicular tumor and other reasons. 1. Acute epididymitis: this is a non-specific infection of the male reproductive system, which can lead to swelling and discomfort of the left egg, local pain and other symptoms, and even affect the action, which can be diagnosed by ultrasound and blood test. If there is abscess, you can seek medical treatment to drain the pus to relieve pain symptoms and avoid testicular necrosis. 2. Testiculitis: vague pain in the left side of the balls may be caused by testicular inflammation, which will result in testicular pain, scrotal swelling and so on. 3. Testicular trauma and torsion: if the left testicle is traumatized or torsion occurs, it may also lead to vague pain, and you need to consult a doctor in time for examination. 4. Testicular tumor: it can be manifested as increased testicular volume and hidden pain, it is necessary to use ultrasound or CT for differential diagnosis. Hidden pain on the left side of the balls may be caused by a variety of reasons, so you need to consult a doctor in time to avoid delaying the treatment, and the use of medication should follow the doctor’s instructions.