One testicle larger than the other. what can be causing this?

?hydrocele or testis: Larger side might have a hydrocele, tumor or cyst. Smaller testicle might have been previously corrected undescended testis, munps in past or presence of a large varicocele. Testes can grow at different rates during puberty ; smaller one may or may not catch up in time ; both testes can otherwise be normal. Thus although not normal maybe ok. Scrotal ultrasound would clarify.