Symmetric Bilateral Aberrant Obturator Artery. A Case Report/ Arteria Obturatriz Aberrante Simetrica Bilateral. Reporte de un Caso.
Obturator artery is one of the parietal extrapelvic branches of the internal iliac artery, which runs along the lateral wall of the pelvis and passes through the obturator foramen to reach and irrigate the medial region thigh muscles and the hip joint. It's origin is variable, usually emerging near the umbilical artery (Moore, 2010). One variation of the obturator artery is aberrant obturator artery (AOA), which is originated from the external iliac artery or the inferior epigastric artery, arching above and behind the superior pubic ramus, descends towards the obturator foramen, completely replacing the irrigation provided by the obturator artery (Baena et al., 2015). The name of this vessel is precisely due to its origin and anomalous course (Darmanis et al., 2007). In the retropubic region it is also possible to find the corona mortis artery, which corresponds to a branch that usually originates from the external iliac artery or inferior epigastric artery, coexists with the obturator artery and anastomoses with it, forming an arc around the superior pubic ramus (Berberoglu, et al., 2001; Smith et al., 2009;. Rusu et al., 2010; Sakthivelavan et al., 2010). Such vascular variant acquires its name (crown of death) product of vital risk to which the person is exposed after accidental injury, which leads to a large bleeding, difficult to manage (Smith et al.; Stavropoulou-Deli & Anagnostopoulou, 2013; Baena et al.).
According to Rusu et al., there is no consensus regarding the terminology for these variant vessels emerging from the system of the external iliac artery, since authors as Mahato (2009) refer to the AOA as corona mortis artery in the absence of the obturator artery. The truth is that these two forms of variation pose a risk in surgical procedures involving the inferior part of the anterior abdominal wall, because vessels run above and behind the superior pubic ramus (Baena et al.).
In this article the case of a symmetrical AOA is described, found in both hemipelvises of a male cadaver from the morphology laboratory of the Universidad de Talca (Chile). The bilateral symmetry of these vessels is very rare and its incidence is unknown in our country.
The purpose of this report was to describe the morphological and morphometric characteristics of this variation, its relations and clinical and surgical importance.
During a routine dissection of the pelvis in a male cadaver that belongs to the morphology laboratory of the Universidad de Talca, the presence of a bilateral vascular variation was found. The obturator region and the back face of the pubis were carefully dissected, and identified the elements passing through the obturator foramen.
The obturator artery presented an aberrant origin and course in both hemipelvises, originating from the inferior epigastric artery. In the left hemipelvis (Fig. 1), its length was 36.41 mm and the diameter at the origin was 2.77 mm, whereas in the right hemipelvis (Fig. 2), its length was 36.93 mm and the diameter at the origin was 2.8 mm. Both vessels formed an arc around the superior pubic ramus, and going back to it reaching the obturator foramen. Right AOA was found to 49.23 mm from pubic symphysis and 6.29 mm from the arc of the lacunar ligament; left AOA, to 47.24 mm from pubic symphysis and 5.11 mm from the arc of the lacunar ligament.
According to Pick et al. (1942), the AOA has been the most studied retropubic vessel, because of its responsibility towards injury during the repair of femoral hernias. Several studies report its incidence from the inferior epigastric artery by 8 %, 14.81 %, 22 % and 27.34 %, respectively (Mahato; Sarikcioglu et al., 2003; Lau & Lee, 2003; Pick et al.). The great variability of these incidents may be due to regional differences in the development of the vascular system, difficulties in dissecting the collapsed vessels on the cadavers and the limitations caused by the size of these vessels (Okcu et al., 2004). In surgery, the presence of an abnormal arc around the superior pubic ramus is lower than in anatomical dissections (Darmanis et al.), possibly due to vascular spasm product traumatic laceration, which makes it difficult to identify (Okcu et al.).
Lau & Lee justify the presence of the AOA, stating that the occlusion of the obturator artery secondary to any cause, such as atherosclerosis or deep vein thrombosis, can lead to the development of collateral circulation and the subsequent formation of aberrant obturator vessels. However, as stated by Darmanis et al., last theory seems to ignore the probably obvious finding that the occluded vessels and their branches would still be present, although as fibrous bands, which are not evident in this case. Pai et al. (2009) tried to give it an embryological explanation for the presence of the AOA, indicating that the arterial patterns of limbs are based on an unusual selection of trajectory from a primary capillary plexus, in which the most suitable passage expands while others retract and disappear, thus establishing the final pattern. Before the obturator artery appears as a separate vessel from pelvic vascular system, blood flow dedicated to this area makes an unusual choice from the source trajectory and instead originate from the internal iliac artery as usually occurs, it arises from the inferior epigastric artery.
The length of aberrant obturator artery in this report is lower than the average indicated by Baena et al. (49 [+ or -] 8.73 mm), while its diameter was smaller than the case described by Darmanis et al. (4.7 mm), but similar to the reported by Baena et al. (3 mm). The distance between the pubic symphysis and aberrant obturator vessels in this case is comparable to the findings of Sarikcioglu et al., (39.79 [+ or -] 11.42 mm) and Berberoglu, et al. (Between 33.2 and 52.7 mm), while the distance between the arc of the lacunar ligament and aberrant vessels was less than described by Sarikcioglu et al. (12.18 [+ or -] 3.55 mm). These differences may be due to demographic and ethnic characteristics of the studied cadavers.
The distance between the pubic symphysis and the AOA has significance for surgeons during an anterior boarding to the acetabulum, as may be encountered with that vessel between 40 and 96 mm lateral to the pubic symphysis, although this potential danger should not compromise the surgical decision to operate through the ilioinguinal approach for fear of excessive bleeding, since it does not appear to be a significant clinical risk (Darmanis et al.).
The distance between the AOA and the arc of the lacunar ligament is relevant because it indicates the risk of injury to these vessels during surgery of the femoral hernia (Sakthivelavan et al.). When the lacunar ligament is opened, this branch vessel that passes behind it, above Cooper's ligament, could be damaged product of the staples or tacks placed on Cooper's ligament, leading to potentially fatal bleeding (Sabuncuoglu et al., 2015). The unexpected presence of the AOA can become a problem for the orthopaedic surgeon, urologist, gynecologist and general surgeon, any of which can perform surgical procedures in this area (Skandalakis et al., 2000). However, in clinical practice the incidence of excessive bleeding of these variant vessels is extremely low (Darmanis et al.). Smith et al., describe the case of a patient with a lesion in an aberrant obturator artery originating from the inferior epigastric artery, the result of a fracture of the superior pubic ramus and isquiopubic ramus.
In all clinical studies and reports it is evident that these retropubic anastomotic vessels are paramount for surgeons who deal with pelvic and acetabular trauma (Darmanis et al.). Such vessels cross the superior pubic ramus in a relatively vertical direction and, therefore, are susceptible to injury during dissection of the preperitoneal space. The entire section of the AOA, which can occur during pelvic surgery, could lead to a dangerous bleeding and difficult hemostasis, especially when the divided vessel retracts through the obturator foramen (Lau & Lee).
According to Pai et al., the advantage of the presence of the AOA is that in case of internal iliac artery and its collateral ligation in patients undergoing pelvic surgery and in cases of internal iliac artery obstruction due to any cause, the AOA and its branches would be preserved, especially the branch to the femoral head.
The fact that the AOA crosses the posterior face of the superior pubic ramus, exposes it to pelvic trauma and multiple surgical procedures performed at this level. A good knowledge of the retropubic vascular anatomy is essential before surgical approach to this region.
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Aladino Cerda Alarcon
Universidad de Talca
Departamento de Ciencias Basicas Biomedicas
Avenida Lircay s/n Oficina No 1
Aladino Cerda *,**
* Unidad de Morfologia, Departamento de Ciencias Basicas Biomedicas, Facultad de Ciencias de la Salud, Universidad de Talca, Talca, Chile.
** Programa de Magister en Ciencias, mencion Morfologia, Facultad de Ciencias de la Salud, Universidad de La Frontera, Temuco, Chile.
Caption: Fig. 1. Origin of the aberrant obturator artery from the inferior epigastric artery in the left hemipelvis. PS = pubic symphysis; EIA = epigastric inferior artery; SPR = superior pubic ramus; AOA = aberrant obturator artery; EIA = external iliac artery; EIV = external iliac vein; ON = obturator nerve; OV = obturator vein.
Caption: Fig. 2. Origin of the aberrant obturator artery from the inferior epigastric artery in the right hemipelvis. PS= pubic symphysis; EIA = epigastric inferior artery; SPR = superior pubic ramus; AOA = aberrant obturator artery; EIA = external iliac artery; EIV = external iliac vein; ON = obturator nerve; OV = obturator vein.