Ovarian remnant syndrome

INTRODUCTION — Ovarian remnant syndrome (ORS) is defined as the presence of ovarian tissue in a patient who has had previous oophorectomy; this must be confirmed histologically after remnant ovarian tissue is obtained at the time of surgical exploration [1,2]. ORS was first described in 1970 in a report of a study in felines in which ovarian specimens left in the abdominal cavity were able to reimplant and become functional, even after devascularization [3].

ORS is associated with pelvic pain or pelvic mass after oophorectomy. Though infrequent, this condition presents a challenge to the clinician in its diagnosis and treatment.

The epidemiology, diagnosis, and management of ORS are reviewed here. The technique for oophorectomy is discussed separately. (See "Oophorectomy and ovarian cystectomy".)

DEFINITION — Historically, the definition of ORS included only patients with histologically confirmed ovarian tissue after bilateral oophorectomy.

The definition has since been broadened to include patients with a history of unilateral oophorectomy with ovarian tissue remaining ipsilateral to the side of excision [4,5].

ORS is a different entity than "residual ovary syndrome," also referred to as a retained ovary, in which an ovary is intentionally left in place during surgery and subsequently causes pelvic pain [6,7]. It is also different from supernumerary ovary syndrome, which involves the development of extra ovaries during embryogenesis [8].

Ovarian tissue may be present due to ectopic implantation of excised ovarian tissue. There are rare reports of patients who developed endometriosis or ovarian carcinoma at laparoscopic port sites after oophorectomy, particularly when the ovarian specimen was cut into pieces [9-11]. During laparoscopic procedures, the implantation of a tiny piece of ovarian tissue might occur during the extraction of the specimen through the trocar site, which does not allow us to define this occurrence as remnant ovary, but rather as port site ectopic tissue or port site metastasis [9,12].

RISK OF ENDOMETRIOSIS OR OVARIAN CANCER — Patients with ORS may be affected by endometriosis or ovarian cancer. Thus, post-oophorectomy presentation consistent with either of these conditions requires evaluation. These two issues are related, since endometriosis is a risk factor for some histologic types of ovarian carcinoma. (See "Epithelial carcinoma of the ovary, fallopian tube, and peritoneum: Incidence and risk factors", section on 'Endometriosis'.)

ORS with pelvic pain is often associated with endometriosis. Remnant ovarian tissue may contain endometriotic implants, or hormonal stimulation from functional ovarian tissue may stimulate endometriotic implants at other sites [13]. Endometriosis in an ovarian remnant typically presents with pelvic pain, which may be cyclic. (See "Endometriosis: Clinical features, evaluation, and diagnosis", section on 'Presenting symptoms'.)

The presence of malignancy in remnant ovarian tissue has been described in patients with a history of bilateral oophorectomy [14-19]. In one series, 2 of 20 patients with ORS were reported to have ovarian adenocarcinoma [15], and a case of ovarian endometrioid carcinoma was noted in a patient 10 years after initial oophorectomy [16]. Ovarian endometriosis was also present in the majority of the reported cases of ovarian carcinoma in ORS patients [16].

There is no evidence that patients with ORS are at an increased risk of ovarian cancer compared with the general population; the risk for each patient is based upon individual risk factors (table 1).

Patients with a malignancy in an ovarian remnant typically present with either pelvic pain, which is often associated with endometriosis (a risk factor for some histologic types of ovarian carcinoma) and may be an early symptom of ovarian cancer (table 2), or with a pelvic mass. Patients should be evaluated for ovarian cancer following oophorectomy as appropriate based upon risk factors, symptoms, and imaging findings. (See "Epithelial carcinoma of the ovary, fallopian tube, and peritoneum: Incidence and risk factors", section on 'Endometriosis' and "Approach to the patient with an adnexal mass", section on 'Assessing the risk of malignancy'.)

Differentiating a malignancy in an ovarian remnant from peritoneal carcinoma is discussed below. (See 'Differential diagnosis' below.)

INCIDENCE — The incidence of ORS is difficult to determine [3,14]. The available data are limited to case reports or to retrospective case series [1,3-5,9,14-16,20-29].

The best available data are from a cohort study describing the frequency and outcome of laparoscopy in patients with chronic pelvic pain and/or pelvic mass who were later found to have ovarian remnants. In 119 patients with persistent cyclic or chronic pelvic pain after total hysterectomy and bilateral salpingo-oophorectomy who then underwent operative laparoscopy, an ovarian remnant was present in 26 (22 percent); during one to eight years of follow-up, one additional patient was found to have an ovarian remnant [30]. However, this was a small study and the cohort represents only symptomatic participants.

ETIOLOGY AND RISK FACTORS — Surgical factors that contribute to incomplete removal of the ovarian tissue at the time of oophorectomy increase the risk of ORS [31]. These include factors that limit surgical exposure of the ovary or compromise surgical technique:

●Pelvic adhesions – They limit visualization of the ovary and may also cause it to adhere to surrounding tissues

●Anatomic variations

●Intraoperative bleeding

●Poor surgical technique – This may include failure to achieve adequate exposure or restore adequate anatomy, or imprecise choice of incision site used to remove the ovary

Ovarian remnants are commonly encased in adhesions due to the preexisting conditions and prior surgeries [32]. Indeed, in the majority of the cases reported since 2007, endometriosis was the most common indication for the initial oophorectomy in patients who were subsequently diagnosed with ORS [4,9,15,16,27].

Factors and conditions that predispose to pelvic adhesions include: previous pelvic or abdominal surgery, endometriosis, pelvic inflammatory disease, ruptured appendix, and inflammatory bowel disease. Endometriosis increases the risk for functional ovarian tissue being embedded into adjacent structures (eg, pelvic peritoneum), making complete excision challenging [33].

Incomplete removal of the ovarian tissue may also occur due to anatomic variations, such as patients in whom there is a retroperitoneal location of ovarian tissue or the sigmoid colon is attached at the pelvic brim overlying the infundibulopelvic ligament [5,34,35]; the left side has been reported to be the side most affected by ORS [5]. This is likely because on the left side the sigmoid colon is frequently attached at the pelvic brim overlying the infundibulopelvic ligament, which may impede visualization and excision of the ovary.

PREVENTION — The most important approach to prevention of ORS is meticulous surgical technique at the time of oophorectomy, with adequate exposure, visualization, and margins around ovarian tissue. Based on the possibility of microscopic ovarian tissue, in our practice we achieve a ≥2 cm margin along the infundibulopelvic ligament from the grossly visible margin of the ovary.

In terms of surgical technique, if the ovarian pedicle is clamped or stapled too close to the ovary, there may be ovarian tissue that is not excised [15,31]. In some cases, this may be because the grossly visible border of ovarian tissue is misleading.

In a novel study, ovarian specimens were examined microscopically after oophorectomy, and in 8 of 58 ovaries, ovarian stroma was noted to extend into the infundibulopelvic ligament, beyond the grossly visible margin of the ovary (most were in the range of 0.2 to 0.8 cm; 1.4 cm in one ovary) [36]. This finding requires further study. It is uncertain whether the ovarian tissue identified was functional or had malignant potential.

Based upon these results, a 2 cm margin would be necessary to ensure complete excision of the ovary.

In our practice, we use the following approach to different types of procedures:

●Laparotomy or conventional or robotic laparoscopy – We enter the retroperitoneum at the level of the pelvic brim and isolate the infundibulopelvic ligament (IP) after clearly identifying the ureter. A window is made in the posterior leaf of the broad ligament immediately inferior to the IP and superior to the ureter. The IP can then be clamped, cut, and suture ligated or sealed and divided with a vessel-sealing device at least 2 cm proximal to the grossly visible ovarian margin. When the adnexa is involved with adhesions to the pelvic sidewall or underlying ureter, we mobilize and lateralize the ureter completely in order to avoid leaving behind any ovarian tissue.

●Vaginal approach – When adnexectomy is intended at the time of the vaginal hysterectomy, we use the round ligament technique (figure 1) to remove the entire adnexa. That is, after the hysterectomy is performed, the utero-ovarian ligament is grasped gently in order to identify the round ligament, which is then transected with electrosurgery. Transection of the round ligament results in skeletonization of the IP, releases the adnexa from the pelvic side wall, and allows for safe placement of the Heaney clamp at least 2 cm proximal to the grossly visible ovarian margin.

CLINICAL PRESENTATION — Patients with ORS most commonly present with pelvic pain. Less frequently, it presents as a pelvic mass or the absence of menopausal symptoms after oophorectomy [20,37]. Other possible symptoms are consistent with endometriosis, including dyspareunia, urinary symptoms, or bowel symptoms [20]. It is likely that some patients are asymptomatic, but the rate of this is unknown since the incidence of ORS is uncertain. (See 'Incidence' above and "Endometriosis: Clinical features, evaluation, and diagnosis", section on 'Clinical features'.)

In terms of timing of presentation, most cases present with symptoms within the first five years of the oophorectomy, although there are reports of ORS presenting in patients 20 years after the initial surgery [15].

Some examples of clinical case scenarios that warrant further evaluation for ORS include:

●A 38-year-old patient underwent abdominal hysterectomy and bilateral salpingo-oophorectomy (BSO) for severe endometriosis and now presents with right lower quadrant pain. Pelvic examination reveals tenderness on the right aspect of the vaginal cuff. Imaging confirms the presence of a 3 cm cystic mass. A serum follicle stimulating hormone level is in the premenopausal range.

●A 69-year-old patient underwent hysterectomy and right salpingo-oophorectomy and presents five years later with right-sided tenderness. Imaging reveals a 6 cm complex mass in the right adnexal region.

●A 40-year-old premenopausal patient with estrogen receptor-positive breast cancer with metastasis to the liver underwent BSO and is on single therapy anastrozole [38]. Repeat positron emission tomography scan six months later reveals progression of the liver lesion and a new right adnexal mass.

Pelvic pain — Pelvic pain is the most common symptom of ORS and can present in a variety of ways [4,9,15,16,27,28]. In the largest cohort of patients (n = 186) who were surgically treated for ORS, presenting symptoms included: chronic pelvic pain (84 percent), dyspareunia (26 percent), cyclic pelvic pain (9 percent), dysuria (7 percent), and tenesmus (6 percent) [29].

In premenopausal patients, the mechanism of pelvic pain may be hormonal stimulation of endometriotic implants by remnant ovarian tissue. Other causes of pelvic pain in patients with ORS and previous endometriosis may include infiltration of nerves, or even local inflammatory processes [13,18,28].

In patients with or without endometriosis, pain may be caused by the expansion of a cystic structure with pressure on adjacent structures or in a confined, scarred tissue that does not allow for the natural expansion of ovarian follicles as occurs in the normal ovary.

Pelvic mass — ORS may present as a pelvic mass, which may be accompanied by pain or be asymptomatic. This may be noted on pelvic examination or imaging. In a series of 186 patients, 57 percent had a pelvic mass [29]. A pelvic mass may result in low back pain, constipation, or urinary retention. The mass may represent ovarian tissue that has developed a physiologic cyst, endometrioma, or other neoplasm.

Symptoms of persistent ovarian function — In premenopausal patients, ovarian remnant tissue may continue to be functional. Thus, the absence of typical menopausal symptoms after bilateral oophorectomy should raise clinical suspicion of ORS. The series of 186 patients cited above showed that 37 percent of patients did not exhibit menopausal symptoms such as vaginal dryness, hot flushes, and vasomotor symptoms despite the absence of estrogen replacement therapy immediately after BSO [29]. In addition, these patients may continue to have menstrual symptoms, including molimina, uterine cramping, or cyclic vaginal bleeding (if the uterus is in place).

However, in premenopausal patients in whom unilateral oophorectomy is performed, pain symptoms alone often trigger the suspicion for ORS [4].

In patients with breast cancer, progression of cancer may raise suspicion of ORS. Two case reports described progression of metastatic breast cancer disease and persistent premenopausal serum estradiol levels due to ORS in patients with hormone receptor positive breast cancer and previous prophylactic bilateral oophorectomy [38,39].

DIAGNOSTIC EVALUATION — An evaluation is prompted by a clinical suspicion of ORS in a patient who has undergone oophorectomy. Key findings in the evaluation are suggestive symptoms, the presence of a pelvic mass, and, in those who have undergone bilateral salpingo-oophorectomy, a serum follicle stimulating hormone and estradiol level consistent with persistent ovarian function [14].

History — The medical history should be elicited, including symptoms associated with ORS (see 'Clinical presentation' above). The history should include questions about pelvic pain before and after oophorectomy and associated diagnoses (eg, endometriosis). Risk factors for ovarian cancer should be assessed (table 1). (See "Chronic pelvic pain in nonpregnant adult females: Causes" and "Epithelial carcinoma of the ovary, fallopian tube, and peritoneum: Incidence and risk factors", section on 'Probable risk factors'.)

A history of oophorectomy is required, by definition, to make the diagnosis. The indication for oophorectomy should be obtained and the detailed procedure and pathology notes reviewed, if possible. Salient parts of the history include risk factors for poor surgical visualization, including prior abdominal or pelvic surgery and endometriosis.

The patient’s menopausal status at time of bilateral oophorectomy should be determined. Patients who may have functional remnant ovarian tissue (based on age younger than upper range of normal for menopause) should be asked about symptoms indicating persistent ovarian function (molimina symptoms, cyclic vaginal bleeding, absence of menopausal symptoms). (See "Clinical manifestations and diagnosis of menopause".)

Physical examination — A complete pelvic examination should be performed. Focal areas of pelvic tenderness should be noted. If a pelvic mass is present, the size, mobility, and location should be documented. The key points of the examination are the same as for the examination of patients with pelvic pain or a pelvic mass. (See "Approach to the patient with an adnexal mass", section on 'Diagnostic evaluation' and "Chronic pelvic pain in adult females: Evaluation", section on 'Physical examination'.)

Laboratory evaluation — For patients with a history of bilateral oophorectomy, serum follicle stimulating hormone and estradiol levels consistent with persistent ovarian function support an initial clinical diagnosis of ORS and thus provide an indication for surgical exploration.

In a patient with a history of unilateral oophorectomy, laboratory evaluation is not helpful.

The goal of laboratory testing for ORS following bilateral oophorectomy is to test for any evidence of ovarian activity, rather than to confirm postmenopausal status. Hormone levels that are consistent with persistent ovarian function include [29] (see "Clinical manifestations and diagnosis of menopause", section on 'Posthysterectomy or endometrial ablation'):

●Serum follicle-stimulating hormone (FSH) <30 UI/dL

and/or

●Serum estradiol >20 pg/mL

On the other hand, the finding of menopausal levels of these hormones does not exclude the diagnosis, since ovarian function may have ceased in the residual ovarian tissue [31]. Pathologically confirmed ovarian remnant tissue has been noted in patients with menopausal hormone levels.

In addition, test results at a single point in time may be misleading. Often, patients with ORS have fluctuating levels of estradiol and FSH. In some months, the patients have an elevated FSH and low estradiol, consistent with the perimenopausal or postmenopausal state, alternating in other months with a low FSH and high estradiol consistent with follicular activity.

For patients on estrogen replacement therapy, serum measurements do not reflect remnant ovarian function. Estrogen replacement therapy should be discontinued for at least 10 days in these patients prior to testing.

In a series of 186 patients, 63 and 69 percent of patients with ORS had premenopausal levels of estradiol and FSH, respectively. Similarly, in a study of 30 patients, 71 and 59 percent had premenopausal levels of estradiol and FSH, respectively [4].

Imaging studies — If ORS is suspected, pelvic imaging should be performed to evaluate for a pelvic mass. Alternatively, ORS may present as an asymptomatic pelvic mass on imaging performed for another indication.

Pelvic ultrasound is the imaging study of choice to evaluate for a pelvic mass (image 1). It is less expensive than computed tomography (CT) (image 2) or magnetic resonance imaging (MRI) and provides high resolution images of the pelvis.

In the largest series (n = 186), a complex pelvic mass corresponding to ORS was identified in 93, 92, and 78 percent of patients by ultrasound, CT, and MRI, respectively [29]. Similarly, in another study, 90 percent of the adnexal masses were detected by pelvic ultrasound [4]. In the imaging methods, the mass may appear on the side of the previous salpingo-oophorectomy and most commonly contains debris-filled cysts [4]. If the ultrasound is negative or indeterminate, we order magnetic resonance imaging to try to characterize an adnexal mass.

Clomiphene provocation — Administration of clomiphene citrate (50 mg twice daily for 10 days) has been suggested as an adjunct to the preoperative diagnosis of the remnant ovary [21]. In patients with suspected ORS who present with pain and negative imaging, provocation with clomiphene citrate may demonstrate the presence of a cystic mass on repeat imaging (image 3). Stimulation of ovarian tissue may also allow for easier identification and removal at the time of surgery. In one study, provocation with clomiphene citrate was helpful in identifying the remnant tissue in three of four patients [15]. A negative provocation test, however, does not exclude the diagnosis of ORS, because some anovulatory patients may fail to respond to the medication. In our practice, we only perform the clomiphene citrate test when there is a clinical suspicion of ORS and imaging is negative for any masses.

Surgical exploration — Surgical exploration and biopsy of possible ovarian tissue is required for the definitive diagnosis of ORS, and treatment by excision of the remnant ovarian tissue may be performed during the same procedure (picture 1). The ovarian remnant is frequently located on the pelvic sidewall peritoneum near the angle of the vaginal vault and may be encased in dense and fibrotic scar tissue [29]. Frozen section is often helpful to confirm the diagnosis and especially if malignancy is suspected. (See 'Surgical technique' below.)

DIAGNOSIS — ORS is a diagnosis limited to patients with a history of oophorectomy, unilateral or bilateral. ORS is a histologic diagnosis, made based upon pathologic confirmation of remnant ovarian tissue obtained at the time of surgical exploration. For patients who are not candidates for surgery, a clinical diagnosis can be made based on the symptoms and upon a finding of premenopausal follicle-stimulating hormone and estradiol levels following bilateral oophorectomy and/or imaging findings consistent with the presence of remnant ovarian tissue.

DIFFERENTIAL DIAGNOSIS — The differential diagnosis of ORS includes other conditions that present with pelvic pain or a pelvic mass in patients with a history of oophorectomy.

There are many etiologies of pelvic pain, and the patient's prior history helps to guide the differential diagnosis. In patients with pelvic pain prior to oophorectomy, it is difficult to distinguish persistent or recurrent pain from ORS from other etiologies. In patients with prior endometriosis, the pain from ORS may, in fact, be due to endometriotic implants. In patients with endometriosis with pelvic pain alone after oophorectomy, standard medical treatment should be given. If a pelvic mass is present, ORS should be considered as part of the differential diagnosis, and the surgical exploration is typically performed to diagnose and treat the etiology of the pain.

For patients with a new onset of pelvic pain after oophorectomy, postoperative complications should be investigated (eg, urinary tract or bowel injury, infection, abscess, hematoma, retained surgical material or instrument, adhesions). If these are not present, the likelihood of ORS versus other etiologies will depend upon whether the symptoms and findings are suggestive of ORS (ie, pelvic mass, findings consistent with continued ovarian function). The evaluation of acute and chronic pelvic pain are discussed separately. (See "Acute pelvic pain in nonpregnant adult females: Evaluation" and "Chronic pelvic pain in adult females: Evaluation".)

Patients with a pelvic mass should be evaluated for potential malignancy. An ovarian remnant malignancy is often located in close association with the pelvic peritoneum and may resemble peritoneal carcinoma. Carcinoma in an ovarian remnant and peritoneal cancer both include malignant tissues consistent with ovarian carcinoma in the absence of an obvious ovary. However, in contrast to peritoneal carcinoma, an early stage malignancy in an ovarian remnant is unifocal and metastatic disease is not present [18,27].

MANAGEMENT — Surgical incision is the mainstay of treatment of ORS. Pharmacologic therapy for patients who refuse or are not candidates for surgical treatment consists of hormonal therapy to suppress ovarian function.

Indications for treatment — Treatment is indicated for patients with suspected ORS who are symptomatic, have a pelvic mass, or require or desire complete removal of ovarian tissue to decrease risk of ovarian cancer (eg, BRCA mutation carriers).

Choice of treatment method — For patients with ORS with pelvic pain, we suggest surgical excision rather than pharmacologic therapy. Pharmacologic therapy is a reasonable option only for patients with suspected ORS who have pelvic pain and have no pelvic mass, and who are not candidates for or who refuse surgery. Patients treated with pharmacologic therapy should be counseled about the limited data supporting the efficacy of this approach, the lack of a histologic diagnosis, and the risk of ovarian cancer in the remnant tissue. We recommend against use of radiation therapy for ORS.

●Surgical therapy – Patients with ORS with a pelvic mass require appropriate evaluation for an adnexal mass, typically surgical exploration and excision. (See "Approach to the patient with an adnexal mass", section on 'Management'.)

ORS is a rare condition, and there are no randomized trials or other comparative studies regarding choice of therapy [40]. Surgical excision of all residual ovarian tissue is the gold standard treatment. Based on the limited available data, it appears to be effective for treating pelvic pain associated with ORS. Importantly, it also allows for a histologic evaluation to confirm the diagnosis and surgical exploration to exclude malignancy, particularly in patients with a pelvic mass.

In the largest retrospective case series (n = 186) of patients who underwent surgery for treatment of ORS, 90 percent had marked improvement in or complete resolution of pain symptoms at an average of 1.2 years after surgery [29]. Similarly, in two other series, 17 of 20 [15] and 26 of 28 patients [4] treated surgically had improvement or resolution of pain symptoms after surgery. A lower success rate was reported in a retrospective series that measured pain scores (no objective measure was used in other studies) and found 10 of 20 ORS patients treated surgically showed improvement (defined as a decrease in pain scores of ≥30 percent) [41]. Of note, this study also evaluated associated factors and found that patients with ORS and endometriosis were significantly less likely to achieve this level of pain relief than those with ORS alone.

A disadvantage of surgery is the risk of complications, which is higher than in most gynecologic surgery for benign indications because extensive dissection is often required to identify and excise remnant ovarian tissue. In the series of 186 patients, 10 patients had an enterotomy or colotomy (three were performed intentionally so the surgeon could ensure complete excision of ovarian tissue), three had cystotomy, and one had ureteral injury. Twenty-two patients received a blood transfusion, and three required a return to the operating room within 30 days postoperatively [29].

●Pharmacologic therapy – There are few data regarding use of pharmacologic therapy alone for ORS [28]. In one study, symptomatic improvement was seen in 3 of 6 patients treated with contraceptive agents, 11 of 17 of those treated with gonadotropin-releasing hormone agonists, and 4 of 7 patients treated with danazol therapy [29]. However, these patients all subsequently had surgical treatment as part of a surgical case series; there are no data in this study and no other larger series about patients treated with hormonal therapy who did not require surgery.

Postoperative pharmacologic therapy is an option for patients with ORS and endometriosis, if pain is persistent after surgery. This management is the same as for other patients with persistent pain after surgical treatment of endometriosis. (See "Endometriosis: Surgical management of pelvic pain", section on 'Postoperative care'.)

●Other

•Ovarian artery embolization – Treatment with ovarian artery embolization has been described. In one case report of a patient with persistent ORS-related pelvic pain, ovarian artery embolization resulted in marked improvement of pelvic pain and a decrease in ovarian remnant tissue volume [40].

•We recommend against radiation therapy as there are few reports of its use, efficacy, and safety [31]. In one such series, all three patients treated with radiation therapy alone had resolution of symptoms [3]. However, the risks of radiation outweigh the potential benefits. Risks include injury or fibrosis of surrounding tissues and the potential for malignant transformation of ovarian remnant tissue [15,16,31].

Surgical technique — The surgical removal of remnant ovarian tissue may be performed by laparotomy or conventional or robot-assisted laparoscopy. The minimally invasive approach is utilized more frequently in an attempt to decrease the morbidity associated with laparotomy [4,15,16,27,28].

In the majority of cases, surgery is technically challenging and often requires more extensive dissection (ureterolysis, peritonectomy) and resection (segmental cystectomy, vaginectomy, and the bowel) [1,31]. In one series, adhesiolysis was performed in 90 percent of patients, ureterolysis in 93 percent, isolation of the uterine artery in 67 percent, and bowel resection in 10 percent [4].

The surgical approach for ORS traditionally emphasizes identification of the ovarian vessels with high repeat ligation at the level of the aortic bifurcation, lateralization and mobilization of the ureter, and complete peritonectomy for removal of the remnant ovarian tissue (picture 2) [1,31]. A video illustrating this technique is available elsewhere [42]. Following this technique, one series reported recurrent ORS in only 1 of 186 patients [29]. In another series, the majority of patients underwent retroperitoneal dissection (97 percent), but the authors advised that, to limit complications, complete ureterolysis, high re-ligation of the ovarian vessels, and complete peritonectomy should be performed only when necessary to completely excise the remnant ovarian tissue [4]. Further comparative studies with long-term follow-up would be helpful in determining the effects of the extent or radicality of surgical dissection on patient outcomes and recurrence of the condition.

In patients with severe adhesions in whom no ovarian tissue is grossly visible, we perform the same procedure (high ligation of the ovarian vessels and peritonectomy). If no ovarian tissue was identified with imaging, preoperative clomiphene provocation is an option to aid visualization of ovarian tissue at surgery. (See 'Clomiphene provocation' above.)

ORS is commonly associated with endometriosis; thus, preoperative imaging methods to evaluate for deep endometriosis may be useful, particularly if the patient has bowel or bladder symptoms [43]. Because of the extensive dissection and more radical procedures often required in these cases, careful planning and involvement of other surgeons, such as colorectal or urologic surgeons, may greatly benefit the patient. (See "Endometriosis of the bladder and ureter" and "Endometriosis: Clinical manifestations and diagnosis of rectovaginal or bowel disease", section on 'Approach to imaging'.)

Pharmacologic therapy — Pharmacologic options for treatment of ORS include medications that suppress ovulation. The medications and rationale for the choice of therapy is the same as for endometriosis. As an example, a retrospective series of three cases of patients with ORS and ureteral obstruction who were not candidates for surgery reported successful treatment with leuprolide acetate in two patients and danazol in the third [44]. (See "Endometriosis: Treatment of pelvic pain", section on 'Medical treatment options'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Gynecologic surgery".)

SUMMARY AND RECOMMENDATIONS

●Definition – Ovarian remnant syndrome (ORS) is defined as the presence of ovarian tissue in a patient who has had previous oophorectomy; this must be confirmed histologically after remnant ovarian tissue is obtained at the time of surgical exploration (picture 1). After unilateral oophorectomy, it is the presence of ovarian tissue on the side ipsilateral to the excision. (See 'Definition' above.)

●Etiology – Surgical factors that contribute to incomplete removal of the ovarian tissue at the time of oophorectomy increase the risk of ORS. These include factors that limit surgical exposure of the ovary or compromise surgical technique (eg, adhesions, distorted anatomy). (See 'Etiology and risk factors' above.)

●Prevention – The most important approach to prevention of ORS is meticulous surgical technique at the time of oophorectomy. As microscopic ovarian tissue may be present, in our practice, we achieve a ≥2 cm margin along the infundibulopelvic ligament from the grossly visible margin of the ovary to prevent ORS (figure 1). (See 'Prevention' above.)

●Clinical presentation – Patients with ORS most commonly present with pelvic pain and, less frequently, with an asymptomatic pelvic mass or the absence of menopausal symptoms after oophorectomy. (See 'Clinical presentation' above.)

●Diagnostic evaluation – In addition to a history and physical examination, diagnostic evaluation includes laboratories for follicle-stimulating and estradiol levels and imaging (typically with pelvic ultrasound). In patients with negative imaging, provocation with clomiphene citrate may demonstrate the presence of a cystic mass on repeat imaging (image 3). (See 'Diagnostic evaluation' above.)

●Diagnosis – ORS is a histologic diagnosis, based on confirmation of remnant ovarian tissue obtained at the time of surgical exploration in a patient with a prior oophorectomy. For patients who are not candidates for surgery, a clinical diagnosis can be made based upon a finding of premenopausal follicle-stimulating and estradiol levels following bilateral oophorectomy; however, the finding of menopausal levels of these hormones does not exclude the diagnosis. (See 'Diagnosis' above.)

●Management

•For patients with ORS with pelvic pain, we suggest surgical excision rather than pharmacologic therapy (Grade 2C). Pharmacologic therapy is a reasonable option for symptomatic patients with suspected ORS who have no pelvic mass and who are not candidates for surgery or refuse surgery. Patients treated with pharmacologic therapy should be counseled about the limited data on efficacy, the lack of a histologic diagnosis, and the risk of ovarian cancer in the remnant tissue. We recommend against use of radiation therapy for ORS (Grade 1C). (See 'Choice of treatment method' above.)

•Patients with ORS with a pelvic mass require appropriate evaluation for malignancy, typically surgical exploration and excision. (See 'Choice of treatment method' above.)