###Human: What causes swelling of testes? ###Assistant: Hello. You are suffering from bilateral epididymo-orchitis (infection of the testis). You need to rule out any obstruction in your urine tract which might cause this. Do you have any difficulty in passing urine? Or any problem with urine flow? Get done with uroflowmery test which will rule out any urinary obstruction. If everything is fine then it is spontaneous and will resolve on its own.