Appendix testis

The appendix testis (or hydatid of Morgagni) is a vestigial remnant of the Müllerian duct, present on the upper pole of the testis and attached to the tunica vaginalis. It is present about 90% of the time.

Clinical significance
Although it has no physiological function, it can be medically significant in that it can, rarely, undergo torsion (i.e. become twisted), causing acute one-sided testicular pain and requiring surgical excision to achieve relief. 1/3 of patients present with a palpable "blue dot" discoloration on the scrotum. This is nearly diagnostic of this condition. Although if clinical suspicion is high for testicular torsion, a surgical exploration of the scrotum is warranted.

Occasionally a torsion of the hydatid of Morgagni can produce symptoms mimicking those created by a testicular torsion; a torsion of the hydatid, however, does not lead to any impairment of testicular function.