Pouch of Douglas
Peritoneal reflections of the female pelvis: pouch of Douglas, vesicouterine and rectovesical pouches
Pelvic peritoneum drapes over the bladder, uterus and rectum like a sheet, leaving two pouches in women and one in men. The rectouterine pouch of Douglas is the lowest point of the female peritoneal cavity, so blood, pus, ascites and tumour collect there and can be reached through the posterior vaginal fornix. These reflections also decide how the bladder is handled at caesarean section and hysterectomy.
Course of the peritoneum in the female pelvis
- From the anterior abdominal wall it passes onto the superior surface of the bladder, then reflects onto the uterus at the level of the isthmus (internal os), forming the vesicouterine pouch.
- It covers the front and back of the uterine body and fundus (perimetrium), then runs down the back of the supravaginal cervix onto the posterior vaginal fornix (upper 1–2 cm of the posterior vaginal wall).
- It then reflects onto the rectum, forming the rectouterine pouch (pouch of Douglas).
- Rectal covering: upper third front and sides, middle third front only, lower third none (below the pouch).
- Laterally the sheet over the uterus extends to the pelvic walls as the broad ligament.
The pouches compared
| Pouch | Sex | Between | Notes |
|---|---|---|---|
| Vesicouterine | Female | Bladder and uterus | Shallow, usually empty; reflection is loose over the lower segment |
| Rectouterine (Douglas) | Female | Uterus, cervix and posterior fornix in front; rectum behind | Deepest point of the female peritoneal cavity |
| Rectovesical | Male | Bladder (and seminal vesicles) and rectum | Male equivalent of Douglas; deepest point in men |
- Sides of the pouch of Douglas: crescentic rectouterine (uterosacral) folds, raised by the uterosacral ligaments.
- The retropubic space in front of the bladder and the pelvirectal spaces are extraperitoneal, not pouches.
Why the pouch of Douglas matters
- It is the most dependent part of the peritoneal cavity in an upright woman, and the lowest pelvic space in a supine one. In the supine patient, the hepatorenal pouch (Morison) is the lowest point of the upper abdomen.
- Haemoperitoneum from a ruptured ectopic pregnancy or ruptured corpus luteum collects here first; transvaginal ultrasound shows fluid behind the uterus.
- Culdocentesis: a needle through the posterior fornix enters the pouch directly to sample blood or pus.
- Pelvic abscess after appendicitis, PID or peritonitis collects here: swinging fever, mucus diarrhoea and tenesmus from rectal irritation, and a boggy tender mass in front of the rectum. It can be drained through the rectum or posterior fornix.
Other disease in the pouch
- Transcoelomic metastases (for example signet-ring gastric carcinoma) form a hard shelf in front of the rectum (Blumer shelf); ovarian deposits may coexist.
- Endometriosis: nodules on the uterosacral folds and obliteration of the pouch (fixed retroverted uterus, deep dyspareunia).
- Enterocele: a hernia of the pouch containing small bowel between vagina and rectum, bulging the upper posterior vaginal wall, common after hysterectomy.
- Ovaries and tubes may prolapse into the pouch, so an ovary felt there can cause pain on deep intercourse.
Surgery and the reflections
- Lower segment caesarean section: the loose uterovesical fold is incised transversely and the bladder pushed down before the uterus is opened. In obstructed labour the bladder is drawn up over the lower segment and can be cut if this step is missed.
- Vaginal hysterectomy: a cut through the posterior fornix enters the pouch of Douglas almost at once, because peritoneum reaches the fornix. An anterior cut meets the bladder first, which must be dissected off before the vesicouterine pouch is opened; skipping this injures the bladder.
- At hysterectomy the vault is closed and the uterosacral ligaments attached to it to reduce enterocele.
Peritoneal fluid flow and ovarian cancer
- Pelvic fluid passes up the right paracolic gutter to the right subphrenic space and is absorbed by diaphragmatic lymphatics; the left gutter is limited above by the phrenicocolic ligament.
- At ovarian cancer staging, the undersurface of the right hemidiaphragm is inspected and biopsied along with peritoneal washings, omentum and pelvic peritoneum.
- Fowler (semi-upright) position after peritonitis lets pus collect in the pelvis, where it is easier to drain than under the diaphragm.
Remember Peritoneum reaches the posterior fornix but not the anterior one: the posterior fornix is the doorway to the pouch of Douglas.
Exam trap The pouch of Douglas is the deepest part of the female peritoneal cavity; the vesicouterine pouch is shallow.
Exam trap The retropubic space is outside the peritoneum; the male counterpart of the pouch of Douglas is the rectovesical pouch.
Test yourself on this topic
5 of the 11 questions in our bank on this topic. Choose an answer to see why every option is right or wrong.
At vaginal hysterectomy, a cut through the posterior vaginal fornix enters the peritoneal cavity almost at once, but an anterior cut first meets the bladder and must be dissected further before peritoneum is reached. What explains this difference?
Answer: Peritoneum covers the posterior fornix only
Posteriorly, the peritoneum of the rectouterine pouch covers the back of the uterus and cervix and extends down onto the upper part of the posterior vaginal wall, so the posterior fornix is separated from the pouch only by the vaginal wall and peritoneum. Anteriorly, the peritoneum is reflected onto the bladder at the level of the isthmus, so the supravaginal cervix and anterior fornix are in contact with the bladder and are not covered by peritoneum. This also explains why culdocentesis is done through the posterior fornix.
Peritoneal coverage
- Back: peritoneum reaches the posterior fornix
- Front: reflects onto bladder at the isthmus
- Anterior cervix touches the bladder
- Posterior colpotomy enters the pouch quickly
Remember Peritoneum goes lower behind the uterus than in front.
Exam trap Opening the anterior fornix without dissecting off the bladder risks a bladder injury.
Why the other options are wrong
- The bladder lies behind the cervix The bladder lies in front of the cervix.
- The posterior fornix is shorter The posterior fornix is the deepest fornix.
- The anterior fornix lies below the pelvic floor Both fornices lie above the pelvic floor.
- The rectum lies in front of the vagina The rectum lies behind the vagina.
Ten days after treatment for a perforated appendix, a 24-year-old woman has a swinging fever, frequent loose stools with mucus and rectal tenesmus. Rectal examination reveals a tender, boggy mass in front of the rectum. What best explains her bowel symptoms?
Answer: Pus in the rectouterine pouch irritating the rectum
After peritonitis, pus gravitates to the most dependent part of the peritoneal cavity, the rectouterine pouch in women. A pelvic abscess there lies directly against the front of the rectum, which it irritates, causing frequent mucus-containing stools and tenesmus, and it can be felt as a boggy tender mass on rectal or vaginal examination. Swinging fever is typical of an undrained collection. Such abscesses may drain spontaneously into the rectum or be drained through the rectum or posterior fornix.
Pelvic abscess
- Pus collects in pouch of Douglas
- Swinging fever
- Rectal irritation: mucus, tenesmus
- Boggy mass on rectal examination
Remember Diarrhoea with fever after peritonitis: feel the pelvis.
Exam trap Do not dismiss mucus diarrhoea after peritonitis as antibiotic-related without examining the pelvis.
Why the other options are wrong
- Clostridioides difficile colitis from antibiotics Possible after antibiotics but would not produce a mass in front of the rectum.
- Ischaemic colitis of the sigmoid Unlikely in a young woman and would not cause a pelvic mass.
- Infective gastroenteritis Would not cause a tender mass felt rectally.
- Ulcerative proctitis Would not produce a boggy extrarectal mass with swinging fever.
At a lower segment caesarean section, the surgeon incises a loose transverse fold of peritoneum over the front of the uterus and pushes the bladder downward before opening the uterus. Which peritoneal reflection is incised?
Answer: Uterovesical fold
The peritoneum covering the front of the uterine body is reflected forward onto the upper surface of the bladder at about the level of the isthmus, forming the shallow vesicouterine pouch. Over the lower segment the peritoneum is loosely attached, so it can be incised transversely as the uterovesical fold and stripped down with the bladder. This keeps the bladder away from the uterine incision and allows the peritoneum to cover the repair later if needed.
Uterovesical fold
- Peritoneum from uterus to bladder
- At the level of the isthmus
- Loose over the lower segment
- Incised to push bladder down
Remember Open the fold, drop the bladder, then cut the uterus.
Exam trap The bladder is pulled up in obstructed labour and can be cut if this step is skipped.
Why the other options are wrong
- Rectouterine fold Lies behind the uterus, at the side of the pouch of Douglas.
- Broad ligament Lies at the sides of the uterus, not in front.
- Median umbilical fold Covers the urachus in the anterior abdominal wall.
- Lateral umbilical fold Covers the inferior epigastric vessels.
During staging laparotomy for ovarian carcinoma, the surgeon inspects and biopsies not only the pelvis and omentum but also a particular upper abdominal surface, because peritoneal fluid from the pelvis circulates there preferentially. Which surface is it?
Answer: Undersurface of the right hemidiaphragm
Peritoneal fluid circulates from the pelvis mainly up the right paracolic gutter, which is wider and not blocked by the phrenicocolic ligament, towards the right subphrenic and hepatorenal spaces. Diaphragmatic movements and lymphatic uptake through the right hemidiaphragm drive this flow. Ovarian cancer cells therefore commonly seed the undersurface of the right hemidiaphragm, which is inspected and sampled at staging. The left paracolic gutter is limited above by the phrenicocolic ligament.
Peritoneal fluid flow
- Pelvis to right paracolic gutter
- Up to right subphrenic space
- Absorbed by diaphragmatic lymphatics
- Inspect right hemidiaphragm at staging
Remember Pelvic fluid travels up the right side.
Exam trap The left gutter does not lead freely to the left subphrenic space.
Why the other options are wrong
- Undersurface of the left hemidiaphragm Flow on the left is limited by the phrenicocolic ligament.
- Lesser sac behind the stomach Reached only through the epiploic foramen; not the main path.
- Root of the small bowel mesentery Receives some deposits but is not the preferential site of flow.
- Left paracolic gutter Its upward route is blocked by the phrenicocolic ligament.
In a man, which space is the most dependent part of the peritoneal cavity when standing, corresponding to the pouch of Douglas in a woman?
Answer: Rectovesical pouch
In the male pelvis the peritoneum passes from the upper surface of the bladder back onto the front of the rectum, forming the rectovesical pouch. It is the lowest point of the peritoneal cavity when upright, so blood or pus collects there, and a pelvic abscess can be felt and drained through the rectum. In females the uterus lies between bladder and rectum, creating the vesicouterine pouch in front and the deeper rectouterine pouch (of Douglas) behind.
Pelvic peritoneal pouches
- Male: rectovesical pouch
- Female: vesicouterine (front)
- Female: rectouterine (back, deepest)
- Pelvic abscess drained via rectum or vagina
Remember Men have one pouch; women have two.
Exam trap The retropubic space is outside the peritoneal cavity.
Why the other options are wrong
- Vesicouterine pouch Present only in females, and shallow.
- Hepatorenal pouch The lowest part of the upper abdomen when supine, not the pelvis.
- Retropubic space Extraperitoneal fat in front of the bladder.
- Pararectal fossa Lateral recesses beside the rectum, not the deepest point.
Where this sits in the CPSP syllabus
- Obstetrics & Gynaecology, Paper 2: Pelvis, pelvic floor and perineum, Peritoneal reflections, pouch of Douglas and rectovesical pouch