Most Common Site of Endometriosis
The ovaries are the most common site of endometriosis overall, followed by the anterior and posterior cul-de-sac, posterior broad ligaments, and uterosacral ligaments. 1, 2
Anatomic Distribution by Location
Pelvic Sites (Most Common)
The typical distribution of endometriotic lesions in decreasing order of frequency includes:
- Ovaries - the single most frequently affected site 1, 2
- Anterior and posterior cul-de-sac (pouch of Douglas) - second most common location 1, 2
- Posterior broad ligaments and uterosacral ligaments - frequently involved in deep infiltrating disease 1, 3
- Uterus, fallopian tubes, and round ligaments - less commonly affected 1
Bowel Involvement (Most Common Extrapelvic Site)
When endometriosis involves the gastrointestinal tract, the distribution follows a specific pattern:
- Anterior wall of the rectosigmoid colon - the most common bowel location 4, 3, 5
- Sigmoid colon - second most common bowel site 4, 3, 5
- Cecum and ileocecal valve - third in frequency 4, 3, 5
- Appendix and small bowel - least common bowel locations 4, 3, 5
Clinical Significance of Location
Deep Infiltrating Disease
The depth of endometriotic lesions correlates directly with pain severity, unlike superficial peritoneal implants. 3, 6
- Deep infiltrating endometriosis in the posterior cul-de-sac and uterosacral ligaments is strongly associated with severe pelvic pain 3
- Superficial peritoneal lesions show little correlation with pain symptoms 6
- In patients with unilateral endometriomas, the lateral compartment (ovarian fossa) shows dense adhesions in approximately 60% of cases 7
Laterality Patterns
- Left-sided ovarian endometriomas occur more frequently (54.8%) than right-sided (45.2%) 7
- The posterior cul-de-sac becomes obliterated in approximately 51% of patients with unilateral endometriomas 7
Important Clinical Pitfalls
Do not assume that the absence of ovarian involvement excludes significant endometriosis - deep infiltrating disease can cause severe symptoms even without ovarian cysts 3, 6
Recognize that extrapelvic sites, while rare, can occur - including umbilicus and diaphragm, though these represent uncommon manifestations 2, 8
Understand that imaging has limited sensitivity for superficial peritoneal disease - all imaging modalities poorly detect superficial implants despite their presence 6