Ovarian Abscess within an Endometrioma: Risk Factors and Management

Abstract

Ovarian endometriosis increases the risk of development of an abscess within the ovary. Tubo-ovarian abscess within an endometrioma occurs when the infected tube serves as a portal of infection and the endometriotic blood serves as a culture medium. Pelvic Inflammatory Disease, Intra uterine contraceptive device (IUCD), ultrasound guided oocyte retrieval in IVF-ET and endometrioma aspiration are possible sources of infection. Primary ovarian abscess without involvement of the fallopian tube, is a rare complication of an underlying endometrioma and may be due to iatrogenic introduction of pathogen during transvaginal surgical procedures. De novo primary ovarian abscess within an endometrioma in the absence of a risk factor is even rarer. Weakened endometriotic cyst wall and hematogenous spread of infection are possible explanations for bacterial implantation. Infected ovarian endometrioma is a surgical emergency and preserving the fertility in a nullipara is a challenge which can be overcome by timely intervention.

1. Introduction

Endometriosis is the development of estrogen-dependent endometrium-like tissue outside the uterine cavity. It primarily involves the pelvis but may be found at extra-pelvic sites too. In the pelvis, the lesions are predominant on the peritoneum, ovaries and rectovaginal septum. Extra pelvic implants can be seen on the bowel, scar of previous surgical incisions and at distant locations like lung parenchyma, cerebellum etc. About 10% of the reproductive aged women are affected by this condition worldwide.

The ectopic endometrial tissue being hormonally active, will undergo shedding during the menstrual phase forming a hematoma. Recurrent bleeding induces a chronic inflammatory reaction with formation of adhesions and adnexal masses. Endometriotic lesions undergo a stepwise phenotypic progression. The earliest lesion is the red vesicular subtype and bleeding stimulates the development of fibrin-mediated adhesions. In the final stage, cicatrization leads to the formation of black powder-burn lesions. Recurrent inflammatory reaction may result in a peritoneal defect referred to as an Allen-Masters window.

Endometriosis is a debilitating condition with a range of painful symptoms that include dysmenorrhea, dyspareunia, dyschezia and dysuria. The most common presenting complaints are persistent pelvic pain and/or infertility. Often, the severity of the condition does not correlate with the severity of the patient’s symptoms leading to a delay in seeking help. Patients may even ignore the condition due to confounding indicators and the condition may only be revealed during infertility evaluation. A mean latency of 6 to 7 years from onset of symptoms to conclusive diagnosis of endometriosis is reported in most studies [1].

1.1 The ASRM classification system

The ASRM (American Society for Reproductive Medicine) classifies endometriosis into four grades using a point system corresponding to the number of lesions and depth of infiltration.

Stage 1: Minimal

Stage 11: Mild

Stage 111: Moderate

Stage 1v: Severe

This grading system most often fails to correlate with the degree of pain or the probability of a successful outcome of infertility treatment in the patient.

To overcome these limitations, The Endometriosis Foundation of America (Endofound) proposed a more descriptive classification system based on the anatomical location and pathophysiology of the lesions.

1.2 The Endofound classification system

1. Category 1: Peritoneal Endometriosis

2. Category 11: Ovarian Endometrioma

3. Category 111: Deep Infiltrating Endometriosis I (DIE I)

4. Category 1v: Deep Infiltrating Endometriosis II (DIE II)

2. Ovarian endometrioma

Ovarian Endometrioma occurs when endometrial stromal and glandular tissue appear in ovaries giving rise to cystic lesions. It is seen in 2–10% of reproductive age women. The incidence almost 50% in women seeking assisted reproductive treatment (ART).

The ectopic endometrial tissue is responsive to proliferative effect of estrogen and undergoes cyclical shedding during menstruation. Bleeding within a closed space leads to formation of ovarian cysts enclosed by an endometrial epithelium. The collected blood is thick and brown resembling chocolate sauce and hence, endometriomas are also referred to as “chocolate cysts”.

3. Etiopathogenesis of endometrioma

The etiopathogenesis of endometriomas remains debatable and several hypotheses have been suggested.

1. Retrograde menstruation through patent fallopian tubes with implantation of endometriotic tissue on ovaries.

2. Invagination of the ovarian cortex and subsequent collection of menstrual debris from bleeding of active endometriotic implants invading the cortex [2].

3. Failed resorption of the entrapped blood within a corpus luteum due to the presence of endometriotic lesions and adhesions on the ovarian cortex [3].

4. Colonization of functional ovarian cysts by endometriotic cells.

5. Coelomic metaplasia of the invaginated ovarian mesothelium forming mesothelial inclusions in the ovarian cortex [4].

4. How do endometriomas reduce fertility?

Ovarian endometrioma is a more severe form of the disease corresponding to ASRM Stage 111 or Stage 1v. About 17–44% of women diagnosed with endometriosis will have an endometrioma. It has a deleterious effect on the fertility of a woman in the following ways:

1. Decreased Ovarian Reserve: It causes destruction of the ovarian cortical tissue with loss of antral follicle quality and quantity.

2. Formation of adhesions: Repeated bleeding induces a chronic inflammatory reaction in the peri-adnexal region with formation of tubo-ovarian masses and adhesions.

3. Altered tubo-ovarian anatomical relationship: The ovaries may be pulled medially behind the uterus due to fibrosis which then appear as “kissing ovaries”.

4. Tubal blockage: The fallopian tubes may be buried inside adhesions with loss of fimbriae. Scarring of the tubes can lead to loss of patency.

5. Etiology of formation of ovarian abscess in endometrioma

Infected endometriotic cysts are rare and very few cases have been reported. This may be due to the following reasons:

• Endometrioma capsule is generally thick, and this may impede the entry of bacteria from the infected fallopian tube.

• Under-reporting of infected endometriomas due to lack of clear pathologic guidelines for diagnosis.

Infected endometrioma was recognized as a serious gynecologic entity for the first time in 1981 when Cecilia, et al. conducted a retrospective analysis of 11 patients with pathologically confirmed infected endometriotic cysts. None of them had any history of long standing Pelvic inflammatory Disease (PID). 10 of the 11 patients had salpingitis suggesting that the fallopian tube was a probable portal of infection. The source of infection could not be established in 1 patient who had ovarian abscess with healthy tubes [5].

Different explanations have been given for the development of an abscess within an endometrioma:

1. Altered menstrual blood collected within an endometrioma acts as a potential culture medium for pathogenic microorganisms. Altered blood within the cyst provides an anaerobic environment favorable for the growth of bacteria.

2. There is an altered immune environment within the endometrioma due to a decreased natural killer (NK) cell cytotoxicity in the peritoneal cavity and peripheral blood of women with endometrioma leading to a compromised local immune system. Resistance to lysis by natural killer (NK) cells and a weakened macrophage function contribute to persistence of ectopic endometrial tissue.

3. Endometriotic cyst walls are more friable than normal ovarian epithelium.

4. Hematogenous and lymphatic spread of infection due to urinary tract infection, appendicitis, diverticulitis, tonsillitis and tuberculosis.

   Associated pelvic inflammatory disease (PID), hydrosalpinx, use of intrauterine contraceptive device (IUCD), bowel infection, transvaginal invasive procedures increase the risk of developing a tubo-ovarian abscess within an endometrioma.

6. Types of ovarian abscess

Ovarian abscess can be:

1. Primary Ovarian Abscess – It is defined as inflammation originating in the ovarian tissue. The fallopian tubes are not involved.

   It may result from disruption of the ovarian capsule, as may occur during ovulation or some surgical intervention, which gives bacteria access to the ovarian stroma.

   This is a rare complication of an underlying endometrioma. It develops as an isolated ovarian lesion without simultaneous tubal infection. It may be of 2 types-

   1. With an associated risk factor

      This can be a complication of invasive procedures like:

      1. Transvaginal Oocyte Retrieval as part of In-vitro fertilization (IVF)

      2. Transvaginal or percutaneous needle aspiration of an Endometrioma.

      3. Surgical intervention like cesarean section, vaginal hysterectomy, use of intrauterine device

      Pathogenic microorganisms are possibly introduced into the ovarian stroma from the vagina during such procedures.

   2. Without any associated risk factor

   De novo primary ovarian abscess within an endometrioma is even more rare and very few cases have been reported. The first case of spontaneous abscess in an endometrioma was reported by Gary H et al. in 1991. The possible source of infection is suggested to be hematogenous or lymphatic spread from the urinary tract or gastrointestinal tract [6].

2. Secondary Ovarian Abscess – It arises in extraovarian locations with simultaneous fallopian tube infection.

   Secondary Ovarian abscess in more common than primary where the infected fallopian tube serves as the portal of infection. It is associated with tubo-ovarian abscess, salpingitis, pelvic inflammatory disease (PID) or complications of gastrointestinal infections like diverticulitis, appendicitis, Crohn’s disease.

   Endometrioma is a risk factor for PID as the cyst provides a favorable site for bacterial proliferation. A distorted anatomy of the ovaries and fallopian tubes, impaired immune system, an increased inflammatory cytokines production and alterations in the vaginal microbiome further increase the risk of PID. A diagnosis of ovarian abscess should always raise the suspicion of an underlying endometrioma.

7. Route of infection

1. Ascending infection via the tubes: The cervical opening has a mucus plug which acts as a barrier and prevents the entry of vaginal microorganisms into the uterus. A breach in this barrier leads to ascending infection via the fallopian tubes into the pelvic cavity.

2. Hematogenous and lymphatic spread

3. Iatrogenic –due to invasive surgical procedures

4. Unknown

8. Risk factors for ovarian abscess

• ASRM Stage 111 and 1v Endometriosis

• Nulliparity

• History of pelvic surgery

• Bacteremia from skin wounds

• Dental treatment

• Congenital genitourinary anomalies

• Compromised immune system.

9. Pathogenesis

Ovarian abscesses are often polymicrobial with a predominance of anaerobic bacteria. The most commonly isolated microorganisms are Streptococcus type B, Escherichia coli, Gardenella vaginalis, Enterococcus sp., Candida albicans, Brucella, Morganella morganii, Enterobius vermicularis, Streptococcus milleri, Peptococcus and Peptostreptococcus. Ascending infection from the vaginal canal of normal commensals like Bacteroides has been suggested after the bacteria was isolated from the pus culture of an infected endometrioma [7].

10. Endometrioma and art

ASRM Stage 111 and 1v are considered risk factors for the development of tubo-ovarian abscess, particularly in nulliparous women [8]. Surgical management of endometriosis is controversial in a woman with subfertility as it may further reduce the ovarian reserve in an already compromised ovary. In-vitro fertilization and embryo transfer (IVF-ET) is considered the first line of management in such patients.

Oocyte retrieval (OR) is a standard IVF procedure following ovarian stimulation in assisted reproductive technology (ART) where the follicles are aspirated with the help of a needle introduced under transvaginal sonographic guidance. Risk of post-puncture pelvic infection is less than 1% but this can dramatically increase in the presence of endometriomas [9]. Endometriosis itself is a risk factor for recurrent pelvic inflammatory disease (PID) [10].

Presence of endometriomas may limit the accessibility of follicles which are behind the cyst. It is advisable to aspirate only the easily accessible follicles without puncturing the endometrioma. Yet, more often, it may be necessary to puncture the cyst to approach the follicles and this increases the risk of development of ovarian abscess in an endometrioma.

11. Clinical presentation

Classically, an ovarian abscess presents as an adnexal mass with acute abdominal-pelvic pain, fever, raised white blood cell count and/or vaginal discharge. An intrauterine or ectopic pregnancy should be ruled out with a urine pregnancy test. Rupture of the abscess may result in life-threatening sepsis with increased morbidity and mortality.

12. Diagnosis

1. Ultrasound: A transvaginal ultrasound provides a relatively easy and accurate diagnosis of endometrioma. Ovarian abscess appears as a complex multilocular mass with internal echoes consistent with inflammatory debris. Thickening of the fallopian tube wall with presence of incomplete septa within, suggests tubal involvement. Fluid will be present in the Pouch of Douglas.

2. Magnetic resonance imaging (MRI) and Computed Tomography (CT) Scans: MRI and CT imaging help in better characterization of the pelvic masses. MRI is comparable to transvaginal ultrasound in diagnosing Ovarian Endometrioma. CT is not preferred due to its high cost and risk of exposure to ionizing radiation.

3. Laparoscopy: Laparoscopy is still considered the gold standard for diagnosis and facilitates the drainage of the abscess.

13. Management of endometrioma and ovarian abscess

It is pertinent to map the size and location of the endometriomas during infertility evaluation with the help of imaging techniques. Laparoscopy helps to determine the magnitude of the disease and its impact on fertility [11]. Surgical excision is a double edged sword and must be discussed in detail with the couple prior to IVF-ET. The decision depends on the age of the patient, her ovarian reserve, severity of the disease and any history of previous pelvic surgery.

Removal of small endometriotic cysts is not recommended. Surgery can have a poor impact on a woman’s fertility by reducing her ovarian reserve. The risk of ovarian failure after bilateral ovarian endometrioma removal is reported to be 2.4% [12]. Risk of recurrence must also be considered. However, surgery is indicated if the endometriomas are large and there is a likelihood of inadvertent puncture with the needle during ovum retrieval as part of IVF-ET.

Laparoscopic surgery is preferred, and three approaches have been proposed in literature:

1. Surgical excision (Cystectomy).

2. Drainage and coagulation of the cyst wall.

3. Drainage and CO2 laser vaporization of the cyst wall.

The route of infection during oocyte retrieval starts in the vagina and hence, antibiotic prophylaxis should always be considered in the presence of an endometrioma irrespective of their size.

Development of an ovarian abscess in an endometrioma is a gynecological and surgical emergency and the woman should be immediately hospitalized for further care. Conservative treatment is generally ineffective in tubo-ovarian abscesses larger than 5 cm in diameter [13]. Failure of conservative treatment and suspected rupture are indications for urgent laparoscopic cystectomy.

Leakage of pus can cause peritonitis, extensive pelvic adhesions and sepsis. Early diagnosis and timely treatment of ovarian abscess is the key to prevent further complications like infertility, ectopic pregnancy and chronic pelvic pain.

After taking care of the hemodynamics, an emergency operative laparoscopy is performed to drain the abscess. Cyst drainage followed by stripping of the cyst wall is the procedure of choice to preserve the ovarian tissue in nulliparous women. Laparoscopic surgery is less invasive as compared to laparotomy with less blood loss, less intraoperative and post-operative complications and a shorter hospital stay. A laparotomy should be considered if the patient is hemodynamically unstable, has extensive pelvic adhesions, generalized peritonitis or if facility for laparoscopy is not available. Care should be taken to preserve the uterus and at least one ovary and one fallopian tube if the patient is keen for future fertility. Irrigate the cavity well and initiate the patient on broad-spectrum antibiotics. Consider intra-operative aerobic and anaerobic cultures. Intra-operative tubal patency test should be avoided when an ovarian abscess is encountered in an endometrioma because of the risk of a flare-up of infection.

14. Histopathology

The pathologic criteria for an infected endometrioma are the presence of both endometrial glands and stroma within an ovarian cyst more than 4 cm in diameter along with frank pus within the cyst on gross examination or micro abscess formation within the cyst wall on histological examination. The cyst wall is lined by a fibrinopurulent exudate with underlying mixed inflammatory cells, including plasma cells.

15. Precautions

1. Every effort should be made to avoid puncturing an endometriotic cyst, if possible.

2. If there is a need to puncture an endometrioma during oocyte retrieval, flush the cavity of the cyst carefully. Consider prophylactic i.v. antibiotics.

16. Conclusions

An underlying endometrioma must be suspected in a young nulliparous woman presenting with an ovarian abscess. A history of transvaginal invasive procedures like oocyte retrieval for IVF and endometrioma aspiration increase the likelihood of development of an abscess in an endometrioma. Ultrasound is an easy and accurate diagnostic modality. Laparoscopic abscess drainage followed by ovarian cystectomy is the procedure of choice. An ovarian abscess is a surgical emergency and a timely intervention can save the future fertility of the patient (Figures 1 and 2).

Figure 1.

Ultrasound picture of adnexal cyst with echogenic fluid.

Figure 2.

Ovarian cyst wall after abscess drainage with endometriotic deposits on uterine fundus and pelvic wall.