What is Douglas's bag?

He Douglas bag Or rectum sac is an extension of the peritoneum and is previously attached to the uterus and posterior fornix of the vagina and subsequently to the rectum in the female. The term was derived from the Scottish anatomist James Douglas, who conducted studies focused on female anatomy.

This bag is of great clinical importance. The floor of this structure is only 5.5 cm from the anus. When performing a rectal or vaginal examination, any abnormality can be easily felt.

What is Douglas's bag?

Being the most dependent part, pus, blood, or ascitic fluids tend to accumulate there; These fluids can be drained or samples can be collected from The fornix Posterior portion of the vagina.

The peritoneum descends from the anterior abdominal wall to the upper surface of the urinary bladder. It then moves directly over the anterior surface of the uterus. From there it moves downwards and covers the upper part of the posterior surface of the vagina, where it forms the anterior wall together with the Douglas sac (1).

Function in uterus

Eight ligaments hold the uterus in its normal position by anchoring it to the pelvic cavity. Some of these ligaments are actually extensions of the parietal peritoneum in different directions:

  • The posterior ligament or Douglas sac.
  • The two broad ligaments are double folds of the peritoneum that form a kind of partition through the pelvic cavity. The uterus is suspended through these two folds.
  • The two uterosacral ligaments are extensions of the peritoneum from the posterior surface of the putero to the sacrum, one on each side of the rectum.
  • The anterior ligament is the fold of the peritoneum formed by the extension of the peritoneum on the anterior surface of the uterus to the posterior surface of the bladder. This fold is located anteriorly and forms the vesicouterine sac, which is less deep than the Douglas sac.
  • The two round ligaments are fibromuscular cords that extend from the upper and outer corners of the uterus through the inguinal canals and terminate in the labia majora (2).

Associated Pathologies

1- Pelvic Inflammatory Disease

Pelvic Inflammatory Disease is an infection in the female reproductive organs. This is one of the most serious complications of sexually transmitted diseases in women.

It can lead to irreversible damage to the uterus, ovaries, fallopian tubes, and other parts of the female reproductive system. It is also known as the leading cause of infertility in women.

Pelvic Inflammatory Disease occurs when the disease-causing organisms travel from the cervix to the upper genital tract. Symptoms usually are pain in the lower abdomen along with back pain.

In order to diagnose the cause doctors usually order cervical sweeps and also a collection of fluids from the Douglas sac. The disease is usually treated with antibiotics and the fluids begin to be absorbed over time (3).

2- Ovarian tube abscess

A pouch of pus during an infection of the fallopian tubes and ovaries is known as an ovarian abscess. These can develop in women who have a Pelvic Inflammatory Disease. The fluids generated by this infection tend to be collected in the Douglas sac.

These abscesses are diagnosed with physical exams or ultrasound. Treatment is usually with antibiotics, but if the infection persists, the abscess needs to be drained. Drainage is performed with a long needle that cuts the abscess during a laparoscopy or laparotomy. Occasionally the entire infected trunk has to be removed surgically (4).

3- Mohida hydatid

Hydatidiform moles are a rare mass or growth within the uterus at the beginning of gestation. This is a result of too much tissue production that should become the placenta. In these cases there are inflammatory processes with fluids that can be observed in the Douglas sac.

A pelvic exam may show signs similar to a normal pregnancy. The size of the uterus may be abnormal and there may be no heartbeat from the expectant baby. Vaginal bleeding may occur. In these cases, dilatation and curettage are recommended to treat the hydatidiform mole (5).

4- Ectopic Pregnancy

This type of pregnancy occurs when the fertilized egg is implanted in the fallopian tubes or somewhere else in the abdomen. In these cases the pregnancy can not continue and emergency treatment is required. Symptoms include mild vaginal bleeding and pelvic pain.

The women most at risk for this type of pregnancy are those who have presented Pelvic Inflammatory Diseases in the past, with implications in the Douglas sac. If left untreated, this abnormality can lead to rupture of the fallopian tubes with severe internal bleeding (6).

5- Endometriosis

Endometriosis is an abnormality in which the endometrium, which is the tissue that normally lines the inside of the uterus, begins to grow outside the uterus. This tissue that is not in place, also bleeds when the woman menstruates and some of that blood can be collected in Douglas's sac.

This can lead to a secondary complication known as dyspaneuria, in which it is painful for a woman to have sex (7).

6- Peritonitis

Peritonitis is an inflammation of the peritoneum and is usually caused by bacterial or fungal infection. If left untreated, the infection can quickly spread to the blood and other organs causing systemic failure of all organs and death. This disease causes an excessive fluid that can be collected in the Douglas sac (8).

7- Cyst rupture in the ovary

Cysts in the ovaries are sacs filled with fluids inside or on the surface of the ovaries. Many cysts go unnoticed, but others may break apart causing serious complications. The fluid product of the rupture accumulates in the Douglas sac (9).


  1. PR ASHALATHA, G DEEPA. Textbook of Anatomy & Physiology for Nurses. S.l. : JP Medical Ltd, 2012.
  2. Patton, Kevin T. Anatomy and Physiology. S.l. : Elsevier Health Sciences, 2015.
  3. WebMD. Your Guide to Pelvic Inflammatory Disease (PID). [Online] [Quoted on: January 2, 2017.] Taken from webmd.com.
  4. -. Pelvic Inflammatory Disease: Tube-Ovarian Abscess - Topic Overview. [Online] [Quoted on: January 2, 2017.] Taken from webmd.com.
  5. Mediline Plus. Hydatidiform mole. [Online] [Quoted on: January 2, 2017.] Taken from medlineplus.gov.
  6. WebMD. What to Know About Ectopic Pregnancy. [Online] [Quoted on: January 2, 2017.] Taken from webmd.com.
  7. Mayo Clinic. Endometriosis. [Online] [Quoted on: January 2, 2017.] Taken from mayoclinic.org.
  8. WebMD. Peritonitis. [Online] [Quoted on: January 2, 2017.] Taken from webmd.com.
  9. Mayo Clinic. Ovarian cysts. [Online] [Quoted on: January 2, 2017.] Taken from mayoclinic.org.

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