There is significant anatomic variation between individuals in the branching pattern of the internal iliac vessels. There is no constant order in which branches divide from the parent vessel; some branches may arise as common trunks or may spring from other branches rather than from the internal iliac. Occasionally, a branch may arise from another vessel entirely (e.g., the obturator artery may arise from the external iliac or inferior epigastric artery). This variation may be found in the branches of other major vessels; the ovarian arteries are reported to arise from the renal arteries or as a common trunk from the front of the aorta on occasion. The inferior gluteal artery may originate from the posterior or the anterior branch of the internal iliac (hypogastric) artery. Patterns of blood ﬂow may be asymmetric from side to side, and structures supplied by anastomoses of different vessels may show variation from person to person in the proportion of vascular support provided by the vessels involved (16). The pelvic surgeon must be prepared for deviations from “textbook” vascular patterns.
3.
The pelvic vasculature is a high-volume, high-ﬂow system with enormous expansive capabilities throughout reproductive life. Blood ﬂow through the uterine arteries increases to about 500 mL per min in late pregnancy. In nonpregnant women, certain conditions, such as uterine fibroids or malignant neoplasms, may be associated with neovascularization and hypertrophy of existing vessels and a corresponding increase in pelvic blood ﬂow. Understanding the volume and ﬂow characteristics of the pelvic vasculature in different clinical situations will enable the surgeon to anticipate problems and take appropriate preoperative and intraoperative measures (including blood and blood product availability) to prevent or manage hemorrhage.
4.
The pelvic vasculature is supplied with an extensive network of collateral connections that provides a rich anastomotic communication between different major vessel systems (Fig. 5.6). This degree of redundancy is important to ensure adequate supply of oxygen and nutrients in the event of major trauma or other vascular compromise. Hypogastric artery ligation continues to be used as a strategy for management of massive pelvic hemorrhage when other measures have failed. Bilateral hypogastric artery ligation, particularly when combined with ovarian artery ligation, dramatically reduces pulse pressure in the pelvis, converting ﬂow characteristics from that of an arterial system to a venous system and allowing use of collateral channels of circulation to continue blood supply to pelvic structures. The significance of collateral blood ﬂow is demonstrated by reports of successful pregnancies occurring after bilateral ligation of both hypogastric and ovarian arteries (17). Table 5.3 lists the collateral channels of circulation in the pelvis.