TechniqueSurgical anatomy of the infraumbilical extraperitoneal space
- The transversalis fascia
The most important, and at the same time, most puzzling entity in the infraumbilical space is the transversalis fascia. This fascia has been described as being bilaminal : a superficial sheet and a deep, translucent, usually tough sheet. The transversalis fascia covers the deep aspect of the m tranversus abdominis. Medially, it lies deep to the posterior sheath of the m rectus abdominis. This sheath however ends abruptly distally, at a distance from the pubis constituting the semilunar line of Douglas.
At that level, both layers of transversalis fascia separate on their way to the midline. The most superficial one passes anterior to the rectus muscle and blends with other fascial layers constituting the linea alba1. The deepest layer of transversalis fascia remains deep to the rectus muscle, thus constituting the only posterior fascial reinforcement of the muscle at that level. The rectus muscle inserts on the pubic bone. The posterior layer of the transversalis fascia blends with the periosteum of the pubis and forms Cooperís ligament laterally to the insertion of the rectus muscle. Even more laterally, just where superficial and deep layer of tranversalis fascia separate, the deep layer is pierced from posterior to anterior by the epigastric vessels , immediately cephalad to their origin from the iliac vessels. The epigastric vessels therefore run between the 2 sheets of transversalis fascia, but as they run more cranially and medially in close contact with the lateral end of the rectus muscle, they remain adherent to the posterior layer of transversalis fascia.
- Retziusí space
The peritoneum lies deep to the posterior layer of transversalis fascia and is very adherent to it. Distally, this close contact remains in the area lateral to the epigastrics. Medially, however, the peritoneum reflects on the roof of the bladder and runs sharply dorsally, away from the deep layer of transversalis fascia. The separation of transversalis fascia and peritoneum contains loose fatty tissue allowing for the filling of the bladder. This space is called the retropubic space of Retzius16.
At the line of reflection of the peritoneum on the bladder roof, however, the peritoneum is firmly attached to the bladder by a fibrous expansion running from cranial to caudal in a frontal plane, and enveloping the bladder. This expansion of peritoneum called the umbilico vesical fascia contains the urachus on the midline and the remnants of the umbilical arteries laterally. These three structures forming the umbilical folds run from distal to proximal to the umbilicus where they join after piercing the transversalis fascia from deep to superficial.
In the preperitoneal dissection the correct plane is the space of Retzius5. This means that dissection has to be carried out between the deep layer of transversalis fascia and the umbilico-vesical fascia. The umbilical folds, which are important landmarks in the transperitoneal approach17, are much less important here since dissection has to be performed superficial to the membrane containing them.
Another important feature is that the epigastric vessels must remain covered by the deep layer of transversalis fascia. If the bare vessels are seen, the plane of dissection is too superfical.
- Bogrosí space
Bogrosíspace is situated laterally and cranially to Retziusí space. It represents the retroinguinal preperitoneum, limited anteriorly by the deep layer of transversalis fascia, enveloping the epigastric vessels, medially by the adherent zone of umbilico vesical fascia, transversalis fascia and peritoneum situated just behind the epigastrics, laterally by the pelvis wall and iliacus muscle and inferiorly by the psoas muscle, with medially to it the external iliac vessels and femoral nerve. Cranially, Bogrosíspace is in free continuity with the lumbar retroperitoneum. This continuity explains the inferior expansion of perirenal abcesses appearing in the groin.
If one insufflates Retziusíspace and Bogrosíspace separately, the adherence of fascia behind the epigastric vessels will give to this part of the retroperitoneum the aspect of an hour glass with long axis running cranially and laterally.
Possible pitfalls in preperitoneal dissection
Other than the obvious potential laceration of the iliac vessels or the epigastrics, particular attention has to be drawn to the corona mortis, constituted by recurrent epigastric artery and vein, which run around the pubis joining epigastric vessels and obturator artery and vein. This corona mortis is located just medially to the iliacs. In case of a femoral hernia, the hernia will be just lateral to the recurrent vessels.
While doing balloon dilation, particular care has to be taken so as not to injure the dorsal penile vein, which lies deep to the pubis on the midline and can be injured if one pushes the balloon rod too deep at the beginning of the procedure.
The nerves at potential hazard of being injured are :
- The femoral nerve. Deeply located, lateral to the iliac vessels, it is rarely injured, but electrical damage has been reported.
- The genito femoral nerve. After piercing the psoas muscle from deep to superficial, the nerve lies in close contact with the psoas, but remains deep to its fascia. The genital branch often accompanies the spermatic vessels as they enter the internal inguinal ring. The femoral branch travels to the thigh, posterior to the iliopubic tract.
- The lateral cutaneous nerve of the thigh. This nerve usually runs parallel to the femoral branch of the genito femoral nerve, and is lateral to it. It is also situated under the fascia of the psoas muscle.
- The ilio inguinal nerve. This nerve pierces the anterior abdominal wall from deep to superficial a little cranial to the anterior and superior iliac crest. It can often be seen, and spared, while doing the lateral dissection (Bogrosíspace).
- Patients preparation and preoperative evaluation, anesthesia
All patients undergo anti-thrombotic prophylaxis. They are asked to void on call for the operating room. One shot of I.V. antibiotics is given.
The patient is put in the supine position with the arms fixed along the body. General anesthesia with endotracheal intubation is used. The patient is put in Trendelenburg position. The surgeon first takes place at the left shoulder of the patient , if he is right handed, or at the right shoulder if he is left handed. The surgeon stays in this position for the introduction of both the first and the second trocar. He will eventually switch to the side opposite the hernia for the lateral dissection. The assistant is placed at the opposite side of the surgeon and a scrub-nurse, if available, is placed at the same side as the surgeon, along the patient's trunk. The TV monitor is located at the tableís foot end.