Ovarian drilling is a surgical technique of puncturing the membranes surrounding the ovary with a laser beam or a surgical needle using minimally invasive laparoscopic procedures. It differs from ovarian wedge resection, because resection involves the cutting of tissue. Ovarian drilling is often preferred to wedge resection because cutting in to the ovary can cause adhesions which may complicate postoperative outcomes.

Anovulation (absence of ovulation) is a major cause of female infertility, and polycystic ovary syndrome (PCOS) is the leading cause of anovulation. While undergoing drug-induced ovulation, women with PCOS usually have a satisfactory response recruiting follicles, but some are unable to recruit follicles or often produce an excessive number of follicles, which can result in ovarian hyper-stimulation syndrome and/or multiple pregnancy. Surgical laparoscopy with ovarian drilling may prevent or reduce the need for drug-induced ovulation.

This procedure probably reduces the need for clinical induction of ovulation, or facilitates its use. The procedure can be performed with admission in "day hospitals", with very little surgical trauma compared to the initial laparotomy technique. Laparoscopic drilling is a minimally invasive surgery in which the ovaries are treated with small perforations using heat or laser. The mechanism by which partial destruction results in ovarian follicular development and ovulation is unknown. Despite the contribution of hormonal changes caused by the procedure, such as the reduction of serum androgens, it is not clear whether this is the basis of the ovulation restoration mechanism. The most plausible theory involves the sharp drop in intraovarian androgens (and perhaps estrogens) resulting in an increase in the secretion of follicle-stimulating hormone (FSH) and an intra-follicular environment more conducive to normal follicular maturation and ovulation.

Many forms of ovarian drilling are described, including electrocautery or laser use. All of these share a common goal, which is creating focal areas of damage in the ovarian cortex. There is no evidence that one method consistently produces results superior to another. Nevertheless, the use of laser therapy has become less popular. The method most commonly used worldwide at the moment is monopolar needle or hook due to ease of installation and the wide availability of the necessary equipment.

The procedure

Standardization of the surgical techniques is lacking. Reproductive outcomes are comparable with laser and diathermy. Electrocautery, using an insulated unipolar needle electrode with a non-insulated distal end measuring 1-2 cm, is the most commonly used method, although few authors have reported similar ovulation and pregnancy rates with bipolar energy.

The number of punctures is empirically chosen depending on the ovarian size. In the original procedure, 3-8 diathermy punctures (each of 3 mm diameter and 2-4 mm depth) per ovary were applied, using power setting of 200-300 W for 2-4 s. Most surgeons perform four punctures per ovary, each for 4 s at 40 W (rule of 4), delivering 640 J of energy per ovary (the lowest effective dose recommended). Nevertheless, clinical response is dose-dependent, with higher ovulation and pregnancy rates observed by increasing dose of thermal energy up to 600 J/ovary, irrespective of ovarian volume. Conversely, adjusting thermal dose based on ovarian volume (60 J/cc) has better reproductive outcomes with similar postoperative adhesion rates than fixed dose of 600 J/ovary. Despite lack of convincing evidence and significant reduction in operative time, most gynecologists still perform bilateral over unilateral drilling.

Different modifications of the classic needle electrode technique such as laparoscopic ovarian multi-needle intervention, ovarian drilling using a monopolar hook electrode, ovarian drilling using the harmonic scalpel and office microlaparoscopic ovarian drilling are proposed. Various transvaginal methods such as transvaginal hydrolaparoscopy (fertiloscopy) and transvaginal sonography - guided ovarian interstitial laser treatment are also developed. However, larger prospective studies are needed to validate the use, safety, efficacy and long-term effects of these alternate techniques.

Ovarian drilling and ovarian wedge resection are performed to reduce the amount of androgen (male sex hormones) producing tissue in women with polycystic ovarian syndrome (PCOS). For PCOS patients, laparoscopic ovarian surgery is considered a second-line or third-line therapy for ovulatory dysfunction associated with PCOS; specifically, as an alternative to gonadotropins. All recommend its use in highly selected cases, particularly in those with hypersecretion of luteinizing hormone (LH), normal body mass index, those needing laparoscopic assessment of the pelvis or who live too far away from the hospital for the intensive monitoring required during gonadotropin therapy. 

Despite its theoretical advantages, ovarian drilling is not superior to clomiphene citrate (CC), neither as a first line therapy for ovulation induction nor for CC-failure or prior to in vitro fertilization (IVF). This implies that ovarian drilling is a valid, but not the sole option for CC-resistant PCOS. The evidence for improvement in biochemical hyperandrogenism translating into comparable improvement in clinical hyperandrogenism is not clear; hence ovarian drilling should not be offered for non-fertility indications like amelioration of acne or hirsutism or for regularization of menstrual cycles.

Due to significant reduction in OHSS in women undergoing ovarian drilling, this surgical treatment may be considered as a useful technique in the management of patients who have previously developed ovarian hyperstimulation syndrome (OHSS).

Laparoscopic surgery is generally safe and that the higher incidence of complications with advanced procedures conforms to the principle that the risks of surgery are proportional to its extent and complexity. 

Despite being minimally invasive, LOD results in postoperative adhesions due to bleeding from the ovarian surface or premature contact between the ovary and the bowel after cauterization; although at a lower rate when compared to ovarian wedge resection by laparotomy. Adhesion rates ranged from 0 to 100%, involving higher risks with laser, probably owing to lesser thermal penetration (2-4 mm) by the cone-shaped lesions of laser drilling compared with cylinder-shaped lesions (8 mm) of monopolar electrocoagulation. Most studies reported mild to moderate adhesions which do not seem to affect pregnancy rates after LOD. Adhesion prevention strategies like liberal peritoneal lavage, application of adhesion barriers like intercede and performance of adhesiolysis at early second-look laparoscopy, are not effective in preventing de novo adhesions or in improving pregnancy rates. Ovary should be raised before application of energy and saline washed after the procedure to decrease the temperature thereby reducing the risk of injury.

Another potential risk is premature ovarian failure, especially if the ovarian blood supply is damaged inadvertently or if large number of punctures are made, leading to excessive destruction of ovarian follicular pool or production of anti-ovarian antibodies. When applied correctly, it does not appear to compromise the ovarian reserve.

Ovarian drilling often results in either resumption of spontaneous ovulations or ovulations after adjuvant treatment with clomiphene or FSH. This procedure is also effective in terms of pregnancy and live birth rates, but without the risks of ovarian hyperstimulation syndrome and multiple pregnancies. It improves ovarian responsiveness to successive ovulation induction agents. Its favorable reproductive and endocrinal effects are sustained long.
Serum luteinizing hormone and testosterone levels were normalized following LOD, while their levels remained unchanged over long-term follow-up. LOD can reduce the risk of cancellation of the assisted reproduction techniques (ART) treatment cycle.

Ovarian drilling can restore ovulation in some but not all PCOS women. On an average, 20-30% of anovulatory PCOS women fail to respond to LOD; possibly due to inadequate destruction of ovarian stroma or inherent resistance of the ovaries. The rationality of increasing the number of punctures or thermal energy applied to improve response at the expense of increased risks of adhesions and premature ovarian failure (POF) is yet to be proved. The clinical and endocrine response to LOD is governed by a dose-response relationship. LOD alone is usually effective in <50% of women. In such cases, addition of clomiphene citrate and recombinant FSH (rFSH) may be considered after 3 and 6 months respectively. LOD also improves the sensitivity of the ovaries towards subsequent CC and FSH, especially in those who are less hyperandrogenic and less insulin-resistant.

Most of the changes in the ovarian reserve markers observed after LOD could be interpreted as normalization of ovarian function rather than a reduction of ovarian reserve. Adhesion formation related to pregnancy outcome is an important aspect of LOD. LOD causes abdomino-pelvic adhesions which results in further impairment in the reproductive performance of women with PCOS. This is based on a reportedly different amount and severity of adhesions seen in second look laparoscopy and leads to the obvious conclusion that surgery is not the choice which exposes women potentially to severe morbidity. This clinical approach should be challenged as, in these patients; good pregnancy outcomes are obtainable with safe, effective and inexpensive surgical technique that can last for prolonged period of time.

Laparoscopic ovarian drilling failure is defined as failure to ovulate within 6-8 weeks, recurrence of anovulatory status after an initial response or failure to conceive despite regular ovulation for 12 months. Since LOD improves responsiveness of the polycystic ovaries to subsequent ovulation induction agents, reintroduction of drug treatments (first CC and then gonadotrophins) and possibly IVF can be considered in those do not spontaneously become pregnant within 6 months after LOD once ovulation has been re-established or after 3 months when ovulation has not been detected.

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