What is Ovarian remnant syndrome (ORS)
Ovarian remnant syndrome (ORS) is an uncommon problem, but one that seems to be increasing in incidence and one that is important to diagnose and treat properly, as well as prevent.
Patients with ovarian remnants tend to have a history of extensive adhesive disease and/or severe endometriosis including ovarian endometrioma. Surgery therefore is technically challenging, usually requiring complete ureterolysis, careful adhesiolysis (often enterolysis), and excision of much of the pelvic sidewall peritoneum with extirpation of the remnant and endometriosis. High ligation of the ovarian vasculature also often is required.
This complexity and the consequent risk of intraoperative injury to the bowel, bladder, and ureters requires careful preoperative preparation. When an ovarian remnant is suspected, it may be important to have other surgeons – such as gynaecologic oncologists, urologists, colorectal surgeons, or general surgeons – either present or on standby during the surgical intervention. In expert hands, surgical intervention has been shown to resolve or improve pain in the majority of patients, with no recurrence of the syndrome.
How do we diagnose ORS
Patients with ORS have had previous oophorectomies with incomplete removal of ovarian tissue. Pelvic pain, either cyclical or most commonly chronic, is a common symptom. Other symptoms can include dyspareunia, dysuria and other urinary symptoms, and bowel symptoms. Ovarian remnants may have an expanding cystic structure – oftentimes secondary to endometriosis – that causes mass-like effects leading to pain and inflammation and to symptoms such as low back pain, constipation, and even urinary retention.
Laboratory assessment of serum follicle-stimulating hormone (FSH) and oestradiol can be helpful, but the absence of such premenopausal values should not rule out the possibility of an ovarian remnant.
ORS often involves a pelvic mass, and preoperative imaging is important in this regard. A pelvic mass was identified in 93%, 92%, and 78% of those who were imaged presurgically with ultrasonography, computed tomography, and magnetic resonance imaging, respectively.1 As with laboratory testing, however, a negative result does not rule out the presence of an ovarian remnant.
The differential diagnosis includes supernumerary ovary (a rare gynaecologic congenital anomaly) and residual ovary syndrome (a condition in which an ovary is intentionally or unintentionally left in place during a hysterectomy, as well as often an intended bilateral oophorectomy, and later causes pain). The latter occurs when surgical anatomy is poor, and the surgery is consequently very difficult.
Surgical principles and approach
Previously, laparotomy was believed to be the best approach for minimizing intraoperative complications and achieving the extensive dissections necessary for effective treatment of ORS. In recent years, conventional laparoscopy and robot-assisted laparoscopy have been shown to be just as safe and effective provided that the same surgical principles – extensive retroperitoneal dissections and ureterolysis – are applied.
Good outcomes can be achieved with less blood loss, shorter operating room time, and less time in the hospital. The better visualization with greater magnification afforded by a minimally invasive approach offers a distinct advantage for such complex dissections.
A remnant of ovarian tissue can be located anywhere along the pelvic sidewall, which makes the surgical protocol largely individualized and based on the suspected location of the remnant.
Still, there are certain standard components of any surgical approach to ORS: The retroperitoneum should be entered at the level of the pelvic brim and the ureter must be clearly identified; usually, a partial or complete ureterolysis is necessary. Then, a window into the broad ligament inferior to the infundibulopelvic (IP) ligament is created, or the peritoneum of the broad ligament is removed, in order to completely isolate both the IP ligament and the ureter.
Once the ovarian remnant is isolated, a wide excision at least 2 cm from all ovarian tissue is performed. This wide surgical clearance is critical to prevent recurrence.
These standard components form the crux of the most basic and straightforward surgery for ORS. In some cases, more extensive dissections such as a cystectomy or even a bowel resection might be necessary. Ligation of the IP ligament as high because its connection to the aortic bifurcation also may be necessary – depending, again, on the location of the ovarian remnant.
The risk of intraoperative injury to the bowel, bladder, and ureters is not insignificant, but with careful planning and the involvement of other surgeons in the most complex cases, these risks can be minimized.
For patients who have a significant surgical history and do not want more surgery, pharmacologic therapy, such as leuprolide (Lupron) or danazol, is an option for ORS. It’s important to note, however, that no studies have been done to demonstrate that medical therapy is a curative option. In addition, one must consider the small risk that remnants may harbour or develop malignancy.
Malignancy has been reported in ovarian remnant tissue. While the risk is believed to be very small it is generally recommended that surgeons send frozen sections of suspected ovarian tissue to pathology. Frozen-section diagnosis of ovarian tissue is about 95% accurate.
Preventing ovarian remnants
Oophorectomy is a common procedure performed by gynaecologic surgeons. While routine, it is imperative that it be performed correctly to prevent ovarian remnants from occurring. When performing a laparoscopic or robot-assisted laparoscopic oophorectomy, it is important to optimize visualization of the ovary and the IP ligament, and to account for the significant magnification provided by laparoscopic cameras.
Surgeons must make sure all adhesions are completely cleared in order to optimally transect the IP ligament. Furthermore, wide excision around ovarian tissue is critical. Accessory ovarian tissue has been found up to 1.4 cm away from the ovary itself, which is why we recommend that surgeons excise at least 2-3 cm away from the IP in order to safely ensure complete removal of ovarian tissue.