What causes pain in one testicle and lower abdominal pain?

Pain in one testicle and lower abdominal pain is generally caused by inflammation or testicular torsion. Epididymitis and prostatitis are relatively common inflammatory conditions, which often occur simultaneously. If prostatitis is not effectively controlled, the inflammation may spread through the vas deferens and spermatic cord to the epididymis and testicles; thus, both conditions could potentially result from prostatitis. Pain may also be caused by testicular torsion, particularly during adolescence, when it typically presents with severe pain.