Understanding Allen-Masters syndrome and Allen-Masters windows (peritoneal pockets)

A cute little tree dwelling creature holds its tummy with a crushingly sad expression on its face.

An Allen-Masters window, also known as peritoneal pocket, is a pocket or fold in the peritoneum – the thin membrane that lines the abdominal cavity.

These pockets can trap endometrial cells that make their way into the peritoneal cavity during menstruation or grow there. Peritoneal pockets are associated with endometriosis​1,2​, when the endometrial cells attach to the peritoneum, causing pain and bleeding every menstrual cycle.  

Peritoneal pockets may also be called retraction pockets, and leading theories for their formation include peritoneal irritation or endometrial lesions, which cause scarring and retraction. A retraction/peritoneal pocket may already exist, and endometriosis grows on this surface.​3​

Treatment for peritoneal pockets

Removing the peritoneal lining from the Allen-Masters pocket during endometriosis laparoscopic surgery is often recommended.

Peritoneal pockets and fertility

These pockets are not thought to impact fertility, but it’s unclear if endometriosis lesions on the surface of the peritoneum are a cause of infertility (rather than the pockets themselves). The general advice is to treat endometriosis separately from infertility.

What is Allen-Masters syndrome?​4​

Allen-Masters syndrome is a condition characterised by ongoing pelvic pain, painful sex (dyspareunia) and menstrual irregularities and disturbances.

Allen-Masters syndrome is caused by lacerations of the broad ligament in the pelvis, thought to be acquired during childbirth. Damage to these muscles/ligaments enables the cervix and/or uterus to move abnormally.​4​

Allen-Masters syndrome should not be confused with Allen-Masters windows or peritoneal windows, which are different conditions associated with endometriosis.

What is the peritoneum?

The peritoneum is the tissue that lines the abdominal cavity, typically smooth and glistening in appearance. Therefore, any imperfections on the surface are visible and presumed to be acquired.

Allen and Masters described these imperfections as a clinical syndrome where the uterine support structures were damaged (lacerated), causing defects in the broad and/or uterosacral ligaments. These defects can result in pelvic pain and may be found during laparoscopic investigation.

It has been suggested that these imperfections may be related to endometriosis since, in one study, 25 cases of pelvic peritoneal defects were documented in 635 diagnostic laparoscopies performed to investigate pelvic pain, and none of them were good candidates for Allen-Masters syndrome.

Sixty-eight per cent, however, had associated endometriosis, suggesting a causal relationship with endometriosis.

Getting help for peritoneal pockets

If you’ve been told you have peritoneal pockets, the best person to continue talking to is your doctor to establish the most appropriate pathway for you.

For holistic support and treatments for endometriosis, My Vagina’s endometriosis expert naturopath, Simone Jeffries, can help – schedule a consultation.


  1. 1.
    Carranco RC, Zomer MT, Berg CF, Smith AV, Koninckx P, Kondo W. Peritoneal Retraction Pocket Defects and Their Important Relationship with Pelvic Pain and Endometriosis. Journal of Minimally Invasive Gynecology. Published online February 2021:168-169. doi:10.1016/j.jmig.2020.05.020
  2. 2.
    Chatman DL. Pelvic peritoneal defects and endometriosis: Allen-Masters syndrome revisited. Fertility and Sterility. Published online December 1981:751-756. doi:10.1016/s0015-0282(16)45921-2
  3. 3.
    Stuparich MA, Lee TTM. Peritoneal Pockets: Tips for Complete Excision. Journal of Minimally Invasive Gynecology. Published online November 2017:S106. doi:10.1016/j.jmig.2017.08.233
  4. 4.
    Glezerman M. Teh Allen Masters syndrome revisited. Successful treatment by laparoscopy. Intl J Gynecology & Obste. Published online August 1984:325-330. doi:10.1016/0020-7292(84)90092-4
  5. 5.
    Ventolini G, Neiger R. Allen-Masters Syndrome Detected at the Time of a Cesarean Delivery: A Case Report and a Review of the Literature. Journal of Gynecologic Surgery. Published online September 2007:117-120. doi:10.1089/gyn.2007.b-02277-1

Jessica Lloyd - Vulvovaginal Specialist Naturopathic Practitioner, BHSc(N)

Jessica is a degree-qualified naturopath (BHSc) specialising in vulvovaginal health and disease, based in Melbourne, Australia.

Jessica is the owner and lead naturopath of My Vagina, and is a member of the:

  • International Society for the Study of Vulvovaginal Disease (ISSVD)
  • International Society for the Study of Women's Sexual Health (ISSWSH)
  • National Vulvodynia Association (NVA) Australia
  • New Zealand Vulvovaginal Society (ANZVS)
  • Australian Traditional Medicine Society (ATMS)