The epididymis and testicles are both part of the male reproductive organs. The epididymis is an accessory gland of the testicle and is located adjacent to it. If epididymitis or orchitis occurs, it is difficult to distinguish between them based on symptoms alone, as both conditions can cause noticeable enlargement and pain of the scrotum, but further examination is required for a definitive diagnosis. During a physical examination, it can be observed that patients with epididymitis have a noticeably enlarged epididymis, while the enlargement of the testicle is not as prominent. Conversely, with orchitis, the testicle is significantly enlarged, while the enlargement of the epididymis is less noticeable. Since these two organs are adjacent, epididymitis often occurs with orchitis, and vice versa. Clarification typically requires examinations such as ultrasonography. However, there are no significant differences in the treatment of these two conditions, so they are often collectively referred to as epididymo-orchitis.