To the Editor:
I read with interest the article by Hendriks et al. (1) and I would like to express certain considerations. Since polycystic ovary syndrome (PCOS) ovaries in humans have different endocrinologic and morphologic properties, the normal bovine ovary model for the evaluation of the amount of damage at different energy modalities seems inadequate. The PCOS ovaries in human are mostly bigger (volume difference), contain several subcortical antral follicles (morphologic difference), are usually anovulatory (functional difference) and secrete more androgen than the non-PCOS counterparts (endocrinologic difference). The suggested ovarian reserve marker reduction after laparoscopic ovarian drilling (LOD) could be interpreted either as a harmful effect or requirement of the procedure (2).
During laparoscopy, the surgeon starts drilling on the protuberant areas of ovarian surface. The decision on the number of punctures is commonly made by the operator subjectively according to the size and appearance of the ovaries during the operation. The follicular fluid spurt is commonly observed as the monopolar energy activated needle tips are inserted on the ovarian surface. This observation suggests that the tissue destruction is generally created on the cystic component of the ovary. Hendriks et al. applied and demonstrated the procedure on the solid tissue component of the normal bovine ovaries (1).
The shape of the area of destruction on the ovarian surface should be different between monopolar and bipolar techniques, which should be circular and ovoid in shape, respectively. Calculation of the volume of a circular-based cylindrical volume and ovoid-based cylindrical volume should be different. If the same formula is used in the estimation of the damaged tissue volume during the LOD procedure, one may use the short axis or long axis of the ovoid base which may cause underestimation or overestimation.
The authors suggested that the whitening around the charred area was excluded in the estimation of the extent of damage caused by the technique. It is well known that monopolar energy modality creates wider tissue damage around the visible coagulation field (beyond the whitening). When the visible and invisible tissue damage are both taken into consideration, the extent of tissue destruction would be wider using the monopolar energy than the bipolar. Furthermore, the laser energy beam has very limited penetration property. This issue has the potential to change the conclusion remarks of the paper.
The bipolar cautery possibly creates wider surface area destruction than the monopolar, since two closely approximated electrodes are used. The tissue destruction on the ovarian surface by the laser could be even wider. The less the laser beam is focused on a point, the more surface ovarian tissue destruction is expected. Those surface damages possibly cause different amounts of postoperative adhesion formations, and it is reported that women who conceived following the surgery were treated with diathermy rather than laser (3).
In conclusion, the bovine ovary model in elucidating and investigating the damage inflicted by the use of different techniques has several short-comings to represent the current application of LOD on the infertile women with PCOS.
Murat Api, MD, PhD
Haseki Education and Research Hospital
1. Hendriks ML, van der Valk P, Lambalk CB, Broeckaert MA, Homburg R, Hompes PG. Extensive tissue damage of bovine ovaries after bipolar ovarian drilling compared to monopolar electrocoagulation or carbon dioxide laser. Fertil Steril. 2008 Dec 17. [Epub ahead of print]
2. Api M. Is ovarian reserve diminished after laparoscopic ovarian drilling? Gynecological Endocrinology, Month 2008; 00(0): 1–7 [ahead of print ISSN 0951-3590 print/ISSN 1473-0766 online ª 2008 Informa Healthcare USA, Inc. DOI: 10.1080/09513590802585605]
3. Li TC, Saravelos H, Chow MS, Chisabingo R, Cooke ID. Factors affecting the outcome of laparoscopic ovarian drilling for polycystic ovarian syndrome in women with anovulatory infertility. Br J Obstet Gynaecol. 1998;105(3):338-44.
Published online in Fertility and Sterility doi: 10.1016/j.fertnstert.2009.03.006
The Authors Respond:
We thank Dr. Api for the comments on our paper. We disagree, however, over some statements made. Using a bovine ovary model instead of human ovaries is not ideal, but bovine ovaries do have a very high resemblance to human PCOS ovaries, as the size and cellular morphology approximately match. We have stated in the article that direct interpolation of the bovine results to the human clinical situation cannot be done, but the results provide a good indication of the amount of expected tissue damage and the differences between the techniques. The aim of our study was to show the differences in tissue destruction between the three most frequently used ovarian drilling techniques. This study was not set up to provide an answer for the best ovarian drilling procedure.
From a theoretical perspective, one could expect ovoid shaped tissue damage using the bipolar electrocoagulation. In our experience, bipolar electrocoagulation resulted in cylinder- shaped destruction, which is clearly seen in Figure 2e. Therefore we used the formula of a cylinder to calculate the tissue damage. To make sure the visible tissue damage was comparable to the microscopic cellular damage, the sliced ovaries were assessed under a light microscope (see section Materials and Methods). Macroscopic damage was found comparable to the cellular damage and therefore the macroscopic affected area was used as a marker for tissue destruction.
We agree that reduction of the ovarian reserve after ovarian drilling is a requirement of the procedure, but too much ovarian destruction is not desirable as it could lead to problems in the long-term fertility prognosis and reduce the age of onset of menopause. It is therefore essential to realize the destructive effect of the various ovarian drilling procedures, and this paper is the first to show the substantial differences between the techniques.
Marja-Liisa Hendriks, MD
Cornelis B. Lambalk, MD, PhD
Roy Homburg, MD, PhD
Peter G.A. Hompes, MD, PhD
Division of Reproductive Medicine
Department of Obstetrics and Gynaecology
VU University Medical Center
Amsterdam, The Netherlands
Published online in Fertility and Sterility doi: 10.1016/j.fertnstert.2009.03.007