1. Sampson's theory of Retrograde menstruation
2. Coelomic metaplasia ( Meyer & Ivanoff)
3. Metastatic theory (Halban et al)
4. Histogenesis by induction
5. Direct implantation
6. Hormonal factors
7. Immunologic factors
8. Genetic factors
9. Vaginal / Cervical atresia

Risk factors of Endometriosis

1. Polymenorrhagia
2. Retroverted Uterus

Sites:

• Abdominal
  • Ovaries
  • Pouch of Douglas
  • Uterosacral ligaments
  • Peritoneum overlying bladder
  • Back of the Uterus
  • Sigmoid Colon
  • Intestinal coils & appendix
• Extraabdominal
  • Umbilicus following an operation
  • Laparotomy scars
  • Tubal stumps following sterilization operation
  • Amputated stump of cervix
  • Scars of vulva & perineum
• Remote
  • Pleura
  • Lungs
  • Deeps tissues of the arms and thighs