The pouch of Douglas is the lowest area of the peritoneal cavity in women. It is a small extension of the peritoneal cavity which lies between the uterus and the rectum. This structure is named after Dr. James Douglas, a Scottish physician who worked in the 18th century and was especially interested in this area of the anatomy. Several other anatomical features are named for Dr. Douglas, recognizing his contributions to the understanding of human anatomy.
Terms such as “rectouterine pouch” and “cul de sac” are sometimes used to refer to the pouch of Douglas. The structure is long and narrow, open at the top and closed at the bottom. Because of its position at the bottom of the peritoneal cavity, it can serve as a drainage point for fluids in the cavity. This can lead to medical problems; malignant growths may spread to the pouch of Douglas, and women can experience discomfort if the pouch of Douglas fills with fluid, pus, and other materials.
Due to concerns about the fact that the pouch of Douglas can act as a collection point for materials in the peritoneal cavity, a doctor may recommend examination of the area if a woman has a medical issue which involves the peritoneal cavity. The examination can be used to determine whether or not the pouch of Douglas has become involved, and to identify emerging complications which could threaten reproductive health, such as infections which could penetrate the uterine wall.
In a procedure known as peritoneal dialysis which is sometimes used to treat kidney failure, the peritoneal cavity is regularly bathed with a dialysate solution which may be introduced through the pouch of Douglas in women. In this case, a catheter is placed into the structure and is used as a semi-permanent port to introduce dialysate fluid and to allow for drainage of the fluid.
In a procedure known as culdoscopy, an endoscope is introduced to the pouch of Douglas through the vagina for the purpose of examining the interior. This may be done for the purpose of preparing for a procedure such as a fluid drainage, or to look for signs of abnormalities which could be involved in a medical diagnosis. The structure can also be visualized with a medical imaging study such as an MRI scan if a doctor suspects that a woman has endometriosis, adhesions, or other abnormalities inside the pouch of Douglas.