Identifying & securing the internal iliac and uterine arteries
Demonstrating the common iliac (red sling), ureter (yellow sling) and the anterior division of the internal iliac (loose vicryl tie applied in anticipation of need to ligate during the surgery)
The pelvic viscera are separated from one another and the pelvic sidewalls by eight potential spaces, filled with either fatty or areolar connective tissue. These natural cleavage planes can be expanded surgically to aid relatively bloodless dissection, preserving visualisation of the surgical field and allowing identification of relevant structures.
The pararectal space is bordered by the ureter medially, internal iliac artery laterally, and uterine artery anteriorly. Previous slinging of the ureter guides identification and subsequent development of this space. In doing so using blunt dissection, the internal iliac and uterine arteries can be systematically located. This step is recommended before embarking on dissection in the territory of neo-vascularised tissue in order to gain early vascular control of the pelvis.
Identifying the anterior division internal iliac artery
On identifying the internal iliac artery, it can be isolated and slung using the same technique as for the ureter – but instead slinging with a 1-0 Vicryl (Ethicon, UK) suture rather than vessel loop.
* Additional care must be taken if advancing the Lahey’s from medial to lateral to avoid inadvertent injury of the external iliac vessels during this step.
It is important to appreciate the target as the anterior division of the internal iliac artery, arising 3.5 - 5cm from the origin, accuracy is vital as the posterior division must be spared.
* Inadvertent ligation of the posterior division can precipitate claudication or ischaemia of the lumbosacral trunk.
After slinging, the free ends of the suture are clipped. The anterior division of the internal iliac artery can now be readily identified and tied. If performed unilaterally there is very low risk of adverse sequelae and it can be a very effective form of haemorrhage control. If performed bilaterally, it will reduce the pelvic arterial blood flow by 49% but there is a small theoretical risk of postoperative bladder dysfunction. This small risk must be weighed against the risk of morbidity and mortality in the face of significant haemorrhage as this can definitely be a life saving manoeuvre.
Preparation for stepwise devascularisation of the pelvis
In cases of severe PAS, it is recommended to prepare for step-wise devascularisation of the pelvis in the event of catastrophic haemorrhage – repeating the above steps to also isolate and sling the common iliac artery; and even ensure access to the aorta in selected cases in anticipation of requiring temporary clamping.
The SAC Technique used the Satinksky, Fogarty and De Bakey clamps. These should all be readily available for use should massive haemorrhage ensue at any point.
Ligation of the uterine artery at source
The anterior division of the internal iliac artery will guide a surgeon to locate the uterine artery. Differentiation of this from other branches of the anterior division is made by relation of the vessel to the ureter – characteristically tortuous and coursing superiorly (already slung to aid identification).
The uterine artery is isolated, again using a Lahey’s forcep, and secured at the origin using the Ligasure Impact device (Medtronic, UK).
Ligation of both uterine arteries can reduce the blood flow to the uterus by up to 90%, making subsequent steps of the hysterectomy safer and more controlled.