Differential diagnosis of free fluid in cul de sac (pouch of Douglas)
The cul-de-sac, also known as pouch of Douglas or rectouterine pouch, is an extension of postero-inferior reflection of peritoneal fold between uterus (anteriorly) and rectum (posteriorly), and is being the most inferior aspect of the peritoneal cavity it is the earliest location for free fluid to accumulate.
Evidence of fluid within the cul-de-sac is a common finding, and the underlying cause can be thought of either physiological or pathological.
- ruptured follicle
- retrograde menstruation
- increase ovarian permeability due to oestrogen influence
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