Pouch of Douglas: The Facts
The term was derived and named after Scottish anatomist, James Douglas, who conducted studies regarding the female body. Among its other terms include rectouterine pouch, rectouterine excavation, Ehrhardt-Cole recess, cul-de-sac, and cavum Douglasi. 
The Pouch of Douglas is an area of the peritoneal cavity located between the rectum and the uterus’ posterior wall. It is a long and narrow structure located at the lower portion of the peritoneal cavity. Being open at its superior end and closed at its inferior, it functions in draining the fluids from the cavity. [1, 2]
An illustration showing the pouch of douglas and its location in the pelvic cavity.
What’s Inside the Pouch? : Physiologic and Pathologic States of the Pouch of Douglas
Being located in the farthest location of the abdominopelvic cavity among women, the Pouch of Douglas is at risk for accumulation of pus and fluids. It has inclinations for spread of tumor, ascites, and endometriosis. Thus, one should be able to know and delineate if the findings seen at the retrouterine pouch is of physiologic or pathologic importance. [3, 4]
Fluid in the Pouch of Douglas
Presence of minimal fluid within the retrouterine pouch does not have much of a significance. During a normal menstrual cycle, a small volume of fluid may be found collected within the pouch. This fluid dissipates spontaneously, and is of normal physiology. 
Fluids beyond normal range and of higher volume may indicate the following pathologic conditions:
Ruptured Ovarian Cyst
Fluid contained in the cul de sac may have originated from a ruptured ovarian cyst. There may have been an ovarian cyst, a small fluid filled sac, present inside the pouch. This cyst may have eventually ruptured, causing the fluid accumulation within the cul de sac. It is commonly associated with sudden abdominal pain and heavy menstrual flow, and may require surgery for removal. [6,7]
This is caused by intra-abdominal abscess or a collection of pus resulting to inflammation of the peritoneum. The manifestation of which includes abdominal tenderness, worse when touched or moved. It may have evolved spontaneously from a bacterial infection (Primary peritonitis), from a perforation within the abdomen (Secondary Peritonitis), or caused by a recurring infection (Tertiary Peritonitis). 
Seen as a soft, bulged swelling of the Pouch of Douglas, pelvic abscess is usually caused by pelvic inflammatory diseases. In this condition, pus accumulation is seen originating from the previous genital tract infection. This is usually managed by antibiotics and drainage. 
Endometriosis is a condition wherein the endometrial tissue normally within the uterus is inadvertedly found amongst organs and areas outside of the uterus. When found along the Pouch of Douglas, this condition is characterized by dyspareunia, pain experienced during sexual intercourse. 
Severe cases of endometriosis are presented with an obliteration of the Pouch of Douglas, along with classic findings of chocolate cysts upon laparoscopy. Other manifestations of which include dysmenorrheal, pelvic pain, and heavy menstrual blood flow. 
Treatment modalities of this condition may range from the use of hormones, progesterones and oral contraceptive pills, to operative procedures, such as hysterectomy, if there is persistence of heavy and painful periods of menstruation. [10, 11, 12]
An image showing endometriosis, with endometrial tissues found outside the uterus.
Diagnostic and Treatment Modalities Involving the Pouch of Douglas
Procedures, both for assessing and managing certain conditions, may involve the Pouch of Douglas.
This is a method by which an endoscope is inserted through the vagina and placed in the Pouch of Douglas to further internally examine the pelvic cavity. It is usually done prior to fluid drainage. 
An image showing the culdoscopy procedure.
Used to manage kidney failure, peritoneal dialysis is done by inserting a catheter into the Pouch of Douglas. In this procedure, the peritoneal cavity is infused with the dialysate solution. The catheter placed within the cul de sac serves as a port to bring in the dialysate fluid and a conduit for drainage. [2,4]
An image depicting the role of Pouch of Douglas in performing peritoneal dialysis.
Pouch of Douglas: More than Just a Pelvic Pouch
The Pouch of Douglas, may be a pelvic organ, with its location at the pelvic region, and its function related to that of the other organs of the pelvis, but, it also has relations to the digestive and even renal systems. It can be associated with intra abdominal abscess and peritonitis, and may even be helpful in managing kidney failure thru its involvement in peritoneal dialysis. Hence, it is more than just a pelvic pouch, more than just a sac for collecting fluid in the pelvis.
- Drake, R. et al. (2010) Gray’s Anatomy for Students. Churchill Livingstone. P 460.
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