Left testicular pain and numbness in the left thigh may be caused by epididymitis, prostatitis or varicocele. 1. Epididymitis: when bacterial infection occurs in the epididymis, it often causes epididymitis, and the inflammation of the local tissues may spread to the testicles, and some patients may experience pain in the left testicle, and if the peripheral nerve tissue is damaged, a numbness in the left thigh may occur. 2. Prostatitis: acute or chronic inflammation of the prostate gland may lead to congestion and hypertrophy of the prostate tissue, which may sometimes compress the vas deferens and indirectly cause left testicular pain, and when the scope of local inflammation is large, the symptom of numbness in the left thigh will also occur. 3. Varicocele: If the blood in the veins of the spermatic cord does not flow well, it will usually lead to varicocele and cause bruising around the testicles, which will also cause left testicular pain and numbness in the left thigh. The causes of left testicular pain and numbness of the left thigh are more reasons, need to be carried out in a timely manner for the lower abdomen ultrasound and other imaging tests to clarify the diagnosis, usually pay attention to a light diet and avoid prolonged sedentary activities, but also diligently urinate to maintain pubic hygiene, if the abnormal symptoms continue to aggravate, we should seek medical treatment as soon as possible.