Hey Shruti hope you are doing good. Well endometriosis is caused by endometrium lining. Which a female body is supposed to shred. There are several reasons for this. Anyone can have this disease. It is a growing concern now a days. As almost every other girl has cyst. If this cyst isnt cured properly. Or the patient fails to follow preventive measures. Then the chances to get endometriosis grow. Pelvic and abdominal pain followed by swelling is the sign that everything is not right. If any girl complains about any such thing. Then you should take her for scanning. An ultrasound can detect the presence of endometriosis signs. Though for verification laparoscopy is required in some cases.