appendix of testis appendix of 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. appendix of testisthe right testis, exposed by laying open the tunica vaginalis (appendix of testis is labeled at right)detailsprecursormüllerian ductidentifierslatinappendix testista98a09.3.02.010ta23612fma19846 19846, 19846anatomical terminology scrotal ultrasonography of an 85-year-old man with hydrocele, making the appendix of the testicle clearly distinctive as a 4 mm outpouching at upper left in image. doppler shows some blood flow. clinical significance torsion the appendix of testis can, occasionally, undergo torsion (i.e. become twisted), causing acute one-sided testicular pain and may require surgical excision to achieve relief. one third of patients present with a palpable "blue dot" discoloration on the scrotum. this is nearly diagnostic of this condition. if clinical suspicion is high for the serious differential diagnosis of testicular torsion, a surgical exploration of the scrotum is warranted. torsion of the appendix of testis occurs at ages 0–15 years, with a mean at 10 years, which is similar to that of testicular torsion.