Although important for the conduct of myomectomy, the distribution of arterial blood vessels on a myoma has not been well studied. In fact, to date, there is no consensus on the optimal direction of myomectomy incision. Thompson and Rock,1 in the book on operative gynecology, advocated vertical incision to avoid the vascular areas of the uterus and broad ligament laterally. Indeed, most gynecologic surgeons use vertical myomectomy incision.2–4 Others have proposed a horizontal incision, believing that such an incision causes less disruption of the arcuate vessels, which run horizontally (Igarashi M. Value of myomectomy in the treatment of infertility [letter]. Fertil Steril 1993;59:1331–2.).5 It seems that this contention is based on anatomy of blood vessels in the normal uterus. The purpose of our study was to evaluate the location and course of arterial blood vessels surrounding the myoma.
MATERIALS AND METHODS
We examined the medical records and results of ultrasonography and magnetic resonance imaging (MRI) including contrast-enhanced MR angiography in 60 consecutive women who underwent uterine artery embolization at the McGill University Health Center between November 2005 and April 2007. The study was granted an exemption from the McGill University Institutional Review Board.
Following our standard procedure, before uterine artery embolization, angiograms of the infrarenal abdominal aorta, both internal iliac arteries, and both uterine arteries were performed using a transfemoral approach. Superselective catheterization of both uterine arteries was performed using 5-F (1.67 mm) end-hole catheters.
All MR and angiographic images were assessed using a digital picture archiving and communication system workstation. The volumes of the dominant fibroid were measured by using the formula of a prolate ellipsoid (length × width × height × 0.523). Records of pelvic examination, ultrasonography, and MRI determined whether the dominant myoma was anterior, posterior, or fundal. We included both intramural and subserous myomas. When the dominant myoma was pedunculated or submucous, it was excluded.
Major arterial branches were defined as vessels coursing on the surface of the myoma equal to or exceeding the diameter of the 5-F catheter (1.67 mm). The first author (F.D.) counted the number of arterial blood vessels encircling the myoma. Each artery was graded as coursing with angles of 0–30 degrees, 30–60 degrees, and 60–90 degrees from the axial plane. The angle was between the course of blood vessel as visualized in the coronal plane relative to the axial plane. For example, an angle of 90 degrees points to the head, 0 degrees parallel to the floor, if the patient is standing. We also evaluated whether the vessels crossed the imaginary vertical midline of the myoma.
Data were analyzed using χ2 test for proportion and Kruskal-Wallis test for three independent samples. A P value of less than .05 was required to reject the null hypothesis.
Of 60 patients with uterine fibroids, we encountered 592 arterial blood vessels surrounding the myoma. The vessels could be seen encircling the surface of the myoma (Fig. 1). The dominant myoma was located on anterior (n:30), posterior (n:17), and fundal part of the uterus (n:13). The patient’s age, volume and mean diameter of the dominant myoma, and the number of arterial blood vessels among the three myoma-location groups were comparable (Table 1). In the anterior and posterior myoma groups, there were significantly more blood vessels in the 30–60 degree group than the other two groups (Table 2). However, these differences were not seen in fundal myomas.
Using angiography, we studied the course of these arteries in detail. The results show that arterial blood vessels run mostly diagonally on the surface of anterior and posterior myomas. No predominant pattern was seen in those with fundal myomas. Unlike those in a normal uterus, new arteries are developed in the myoma and they do not follow the course of normal uterine blood vessels. Our findings indicate that regardless of the direction of the myomectomy incision, arterial blood vessels on myoma surface could be injured.
To evaluate whether there were fewer blood vessels on the midline of the myoma, we evaluated whether the vessels crossed the imaginary vertical midline of the myoma. We found that approximately 40% of the vessels crossed the midline, suggesting that midline vertical incision would not avoid injuring the vessels.
Our study has a few limitations. Because veins are rarely visualized by arteriography, we cannot comment on the venous pattern on the myoma. However, evaluation of arteries is more important than that of venous blood vessels. At surgery, arterial bleeding is more brisk and leads to a greater amount of blood loss than does venous bleeding. In addition, in the coronal plane, imaging as described in this study does not allow determination of whether the vessel has an anterior or posterior angulation. In any event, angulation would not affect the effect of an incision on the vessels.
Based on our findings, the type of uterine incision should not affect the amount blood loss and should therefore depend mainly on the surgeon’s preference. However, other measures to reduce blood loss should be taken. They involve occluding the infundibulopelvic ligament and the uterine vessels, oxytocin infusion, and intramyometrial vasopressin injection.6–10 Although rare, the use of vasopressin could be associated with cardiac arrhythmia and pulmonary edema.11 Myomectomy could be performed by laparoscopy or laparotomy. Two randomized studies showed that laparoscopic myomectomy is associated with significantly less reduction in hemoglobin level than that by laparotomy.12,13
We conclude that arterial blood vessels travel mostly diagonally on the surface of anterior and posterior myomas. There was no predominant pattern in the course of the arteries on fundal myomas. These findings suggest that regardless of the direction of the myomectomy incision, arterial blood vessels on myoma surface could be injured.
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