Endometriosis occurs when endometrial tissue is detected outside of the uterus. The prevalence of endometriosis depends on the diagnostic method, but ranges between 25 and 40 % of women [ 1 ]. The relationship of endometriosis to infertility is not always clear-cut. A review of 32 studies by Eskenazi showed that up to 78 % of infertile women had endometriosis [ 2 ]. Similarly, D'Hooghe et al. pooled 13 studies, demonstrating that up to 50 % of previously fertile women had proven endometriosis [ 3 ]. An endometrioma is formed following the invagination of endometriotic deposits on the ovarian cortex, eventually forming what is commonly described as 'chocolate' cysts [ 4 ]. Ovarian endometriomas are found in 17-44 % of women with endometriosis [ 5 , 6 ]. Although the ovaries are the commonest site of endometriomas, there are numerous reports of extra-gonadal chocolate cysts in distant locations like the umbilicus [ 7 , 8 ], brain [ 9 ], liver and other sites [ 10 , 11 ]. These extra-gonadal lesions do not, however, have direct effects on infertility.