Similar linings. Indirect inguinal hernias and hydroceles are both lined by a membrane originating from the peritoneum. The communication usually closes at or shortly after birth, once the ipsilateral testis has reached the base of scrotum. This membrane becomes the tunica vaginalis. It is a hernia if the neck permits, bowel or omentum to enter. Communicating hydroceles have narrow necks, permitting fluid in+out.
Not usually. While hernia are probably more common than hydroceles, and they certainly can occur at the same time, they are usually separate entities that don't occur together. If they are there together, they can be treated together, and may require coordinating both a general surgeon and urologist, .