Laparoscopic anatomy of inguinal canal

Laparoscopic Anatomy of the Inguinal Region

Since laparoscopy has been used in the treatment of patients

with inguinal hernias, new interest has developed in the anatomy of

the inguinal region of the posterior aspect of the abdominal wall.

Anatomists and laparoscopists have published interesting articles on

the surgical anatomy of this region, which they call the laparoscopic

inguinal anatomy (Claude et al, 2000).

The laparoscopic repair of the inguinal hernias is dependent on

a proper understanding of the complex anatomy of the inguinal

region (Colborn and Skandalakis, 1998).

The inguinal ligament, pubic tubercle and lacunar ligament are

not visible laparoscopically, whereas the iliopubic tract and Cooper's

ligament are seen. Exposure of the iliopubic tract, transversus

abdominis and Cooper's ligament provides the anatomical landmarks

for securing the margins of the prosthetic mesh. Identification of the

external iliac, testicular and inferior epigastric vessels and vas is

essential so that injury can be avoided (Cheslyn Curtis and Russell,

1993).

It is essential to recognize the anatomical structures of the

preperitoneal space, as seen through the laparoscope, to be able to

achieve an efficient repair.Three landmarks which are essential to

define which are Cooper's ligtment, the umbilical artery (or its

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Laparoscopic Anatomy

embryological stump) and the epigastric vessels coming from the

iliac arteries and veins (Condon, 1995).

These three structures together with the iliopubic tract define

the inguinal hernia space; lateral to the inferior epigastric artery is the

indirect hernia space, medially to the inferior epigastric vessels and

lateral to the umbilical artery is the triangle of Hasselbach, site of

direct hernia space, and under the iliopubic tract and above the

Cooper's ligament is the femoral hernia space (Katkoudaand

Mouiel, 1993)

The complex three-dimensional relationship of the osseofascial

vascular and visceral components of each region must be positively

identified in order to avoid injury and assure an optimal hernia repair

(Klsin, 1991).

In contrast to the external groin anatomy, the topography and

internal features of the posterior surface of the lower abdominal wall

is an area with which many general surgeons are not familiar (Klein,

1991).

The medial aspect of the inguinal region is angled inferiorly,

consequently inguinal hernia defect lies in an oblique plane relative

to a laparoscope placed in the umbilicus, whether direct or indirect

inguinal hernia. For best visualization through the umbilicus the

Laparoscope should be held towards the horizontal plane. The

inguinal anatomy with the peritoneum intact requires identifying four

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structures; the inferior epigastric vessels, the obliterated umbilical

artery, the spermatic vessels and the vas deferens (Spaw et al, 1991).

The Vas Deferens

It is the long duct of the testis, it leaves the spermatic cord at

the deep inguinal ring and hooks around the lateral side of the

inferior epigastric artery and interfoveolar ligament, then it runs

backwards and downwards on the side of the wall of the pelvis

crossing the external iliac vessels, lateral umbilical ligament till it

reaches the ischial spine, where it turns medially across the terminal

part of the ureter then on the posterior surface of the urinary bladder

where it ends by joining the seminal vesicle to form the ejaculatory

duct. It is a subperitoneal structure along its whole abdominal course

(McMinn, 1990).

The Endoabdominal Fascia Transversalis

It is a fascial lining behind the abdominal muscles and in front

of the parietal peritoneum. It is the most important layer in

peritoneum of groin hernias (Nyhus et al, 1991).

The name of transversalis fascia, formerly applied to the deep

fascia covering the internal surface of the transversus abdominis

muscle, is now applied to the entire connective tissue sheet. Lining

the musculature of the abdominal cavity. In some areas, this fascial

layer is given a specific name, such as iliacus or psoas fascia, where

it covers these muscles (Skandalakis et al, 2000).

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Transversalis Fascia Analogues

In several locations in the endoabdominal fascial sac, there are

thickenings or condensations of the fascia, which are continuous with

and integrated to the sac itself. These condensations are termed the

transversalis fascia analogues, usually are formed at points of

insertion of various muscle groups, or at points of attachment of other

fascial or aponeurotic structures into the fascial sac itself. Five

important fascia analogues are transversalis fascial sling, transversus

abdominis aponeurotic arch, the iliopubic tract, iliopectineal ligament

and the interfoveolar ligament (Nyhus et al, 1991).

Interfoveolar Ligament

This is not a true ligament. It is a thickening of the transversalis

fascia at the medial side of the internal ring. It lies anterior to the

inferior epigastric vessels (Skandalakis et al, 2000).

Figure (9) Inguinal anatomy without peritoneal covering

(Rosenberger et al 2000)

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The Hasselbach Triangle

As described by Hasselbach in 1814, the bases of the triangle

were formed by the pubic pectin and the pectineal ligament. The

boundaries of this triangle as usually described today are:

• Superolaterally: the inferior epigastric vessels

• Medial: the rectus sheath

• Inferior: the inguinal ligament This is smaller than that

described by Hasselbach in 1814. Most direct inguinal hernias occur

in this area (Skandalakis et al, 2000).

Preperitoneal Fascia

The preperitoneal fascia of the groin is a specialized local

development of ordinary connective tissue framework on which

serosal layer of peritoneal cells depends on its support. Part of this

fascia is loose areolar tissue, the more superficial of which presents a

definite membranous layer, and this membranous part of the

preperitoneal fascia is sometimes mistaken for transversalis fascia

(Bendavid, 1992).

Between the two lies a variable quantity of the extraperitoneal

fat (Fowler, 1978).

This plane of preperitoneal fascia is the most important in

laparoscopic inguinal hernia repair as it is the place where the mesh

is applied and fixed (Klein, 1991).

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Peritoneal Folds

The most striking lower abdominal features are two or three

vertical folds; each is directed cranially towards the umbilicus. The

midline fold is the least constant of these and when present, is the

median umbilical or embryological urachal fold. It arises from the

dome of the bladder, reaching towards the umbilicus but more

usually disappearing at about half this distance. More consistent are

folds arching from each lateral pelvic wall and containing ligaments.

These ligaments are called medial umbilical folds and are formed by

the obliterated umbilical artery, which is the terminal branch of the

anterior division of the internal iliac artery and extends to the

umbilicus. The obliterated umbilical arteries, when divided, usually

have a degree of patency. They form the inferomedial walls of the

iliac fossae. Inguinal and femoral hernias usually lie lateral to these

folds whereas obturator hernias are inferomedial (Desmond, 1997).

The Lateral Umbilical Ligament

The lateral umbilical ligament is an insignificant structure in

relation to conventional approaches to the groin hernias, but does

interfere with visualization of the inguinal region, when viewed

laparoscopically (Charles et al, 1992).

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Figure (10) Peritoneal covering with deep ring (Tim Bax et al, 2007)

Preperitoneal Anatomy

The peritoneum may be separated from underlying structures

by preperitoneal blunt dissection (extraperitoneal approach) or by

incision and mobilization of peritoneal flaps (transperitoneal

approach). When the peritoneum is incised it is found to have two

distinct layers. There is a glistening and fragile superficial layer

which is relatively avascular. The deeper adherent layer is thicker and

stronger and contains a network of seemingly haphazard blood

vessels supplying the peritoneum. Although the two are separable,

they should be incised as one layer. It is also important with a staple

or suture closure of peritoneum to ensure both layers are present in

the closure. Once the peritoneum and preperitoneal fascia have been

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traversed the proper preperitoneal space of Bogros, which joins the

prevesical space of Retzius in the pelvis, is entered. This well-defined

space is the correct plane of dissection. The area is relatively

avascular with only an occasional perforating vessel connecting the

transversalis fascia and the preperitoneal fascia. The blood vessels

superficial to this space originate from the epigastric and external

iliac vessels. The blood supply deep to this space originates from the

deep internal iliac vessels (Arregui etal, 1993)

Iliopubic Tract

While the epigastric artery is the beacon of laparoscopic

surface anatomy in the inguinal area, the iliopubic tract can be called

the pivot of preperitoneal anatomy. Fascia encases the entire

peritoneal cavity as a continuous sheet. It is an embryonal structure

given different names in different areas. The fascia applied to the

transversus abdominis muscle is transversalis fascia, while that

covering the psoas and iliacus is the fascia iliacus. While these two

muscle groups do not join, their relevant fascial sheets meet in a

straight line posterior to, but parallel with the inguinal ligament. This

pale fascial condensation is the iliopubic tract (Page et al, 1996).

It has also been given other names, which have caused some

confusion, e.g. the deep crural arch, the deep femoral arch and

Thompson's ligament. It extends from the anterior superior iliac spine

medially to form the lower border of the internal inguinal ring,

crossing the femoral vessels to form the anterior margin of the

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femoral sheath. The tract curves around the medial surface of the

femoral sheath to inserts just lateral to Cooper's ligament. The fascia

and tract do not merge with the inguinal ligament and this can easily

be demonstrated during an anterior abdominal wall dissection where

an instrument can be passed horizontally between the two structures

Figure (11) Site of direct and indirect hernia (Tim Bax et al, 2007)

Perhaps the most prominent and most easily located areas of

the iliopubic tract are medially where it forms the roof of the femoral

canal and immediately lateral to the epigastric artery where it forms

the floor of the internal ring. The presence of the iliopubic tract as

such a distinct structure redefines the base of Hesselbach's triangle,

so that, from a laparoscopic view point, the iliopubic tract replaces

the inguinal ligament as the floor of that triangle. Inguinal hernias are

located above the iliopubic tract and femoral hernias below it. Direct

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hernias occur within Hesselbach's triangle and indirect hernias are

lateral to the epigastric artery (Desmond, 1997).

The Deep Inguinal Ring

Is situated in the transversalis fascia, midway between the

anterior superior iliac spine and the symphysis pubis, about 1, 25 cm

above the inguinal ligament. It is related above to the arched lower

margin of transversus abdominis, and medially to the inferior

epigastric vessels and the interfoveolar ligament, when present

(McMinn, 1990)

.

Figure (12) The transversals fascia (Tim Bax et al, 2007)

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It is inverted u-shaped ring, composed of thickened

transversalis fascia, suspended by two pillars, medial and lateral to

the posterior aspect of the transversus abdominis muscle. It lays

opposite a point one finger breadth above the mid point of inguinal

ligament (McMinn, 1990).

Floor Of Inguinal Canal

Between the iliopubic tract and the arching edge of the

transversalis is the floor or posterior wall of the inguinal canal. The

internal ring perforates the transversalis fascia laterally. The medial

edge of the deep ring has a prominent crescentic shape concave

laterally and is called the interfoveolar ligament, formed by the

transversalis fascia, which splits to encompass the epigastric vessels

near this free edge. The lateral aspect of the iliopubic tract can then

be seen to join with the transversus abdominis muscle to form the

lateral boundaries of the internal ring. The musculoaponeurotic

transversus abdominis then arches over the internal ring and

Hasselbach's triangle to insert medially into the pubis anterior to the

rectus abdominis muscle. The floor of the inguinal canal is formed in

most patients by the transversus abdominis aponeurosis, which

extends to insert onto Cooper's ligament but can be quite variably

attenuated, sometimes leaving only the thin, transparent, and weak

transversalis fascia intervening between the intra-abdominal Forces

and the non supporting external oblique (Arregui et at, 1993).

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Below the medial part of the iliopubic tract lies a triangular

area also bounded laterally by the external iliac vein and inferiorly by

Cooper's ligament, which is a glistening white structure running

along the anterosuperior border of the superior pubic ramus. It is

always easy to locate and is even more prominent than the medial

end of the iliopubic tract. The femoral ring is the upper end of the

femoral canal and lies medial to the external iliac vein. It is bounded

medially by fascia iliacus and the underlying reflected portion of

inguinal ligament, with Cooper's ligament on the pectineal line as the

inferior margin and the iliopubic tract as the upper margin. A discrete

pad of adipose tissue and sometimes a lymph node forms a plug in

the femoral ring when there is no femoral hernia (Desmond, 1997).

Vessels of the Inguinal Area

1. Epigastric vessels

The epigastric artery and vein are the largest of these and are

easily located. The artery lies lateral to the vein as both precede

superomedially toward the rectus muscle, which is reached well

below the level of the arcuate ligament which marks the lower end of

the posterior rectus sheath. The first epigastric branch is a

communicating obturator branch which drops down over the superior

pubic ramus to anastomose with the obturator vessels immediately

beneath this bone. The communicating obturator artery is usually less

obvious than the vein but when large, is called an aberrant obturator

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artery. A pubic branch passes horizontally below the iliopubic tract

towards the pubic tubercle and cave of Retzius. The cremasteric

vessels branch forwards and immediately enter the inguinal canal

which is only seen if the epigastric vessels are mobilized. The

rectusial branches given off when the lateral edge of the rectus is

reached are the last visualized branches of the epigastrics, between

these and the cremastric branches the epigastric artery in particular is

very elastic and easily manipulated. A small artery to the vas is

usually visible and can easily be damaged during mobilization of an

indirect hernial sac. It is a branch of the internal iliac artery.

2. Gonadal vessels

Testicular arteries are solitary and always difficult to separate

from the accompanying gonadal veins. Proximally, the number of

testicular veins is reduced, so that just one or two prominent gonadal

veins are evident several centimeters proximal to the deep ring

(Desmond, 1997).

3. External iliac vessels

The external iliac artery runs along the pelvic brim on the psoas

muscle (retro-peritoneal) and passes beneath the inguinal ligament to

enter the femoral sheath. Its two branches are given just above the

inguinal ligament, the inferior epigastric artery and the deep

circumflex iliac artery.

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Figure (13) Spermatic vessels and vas and inferior epigastric vessels

(Tim Bax et al, 2007)

The external iliac vein enters the abdomen on the medial side

of the artery. Over the sacroiliac joint each is joined by the internal

iliac vein to form the common iliac vein (Skandalakis et al., 2004).

Nerves In The Inguinal Area

The nerves in this area include the femoral nerve which lies in

a groove between psoas and iliacus muscles and is not seen during

normal dissection in this region. The nerves assume great importance

in a laparoscopic hernia repair, mainly because they are not easily

seen but are readily traumatized by dissection, staple or suture. Even

the edge of a mesh can cause sensory nerve irritation. The two most

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relevant of these nerves are the genitofemoral and the lateral

cutaneous nerve of the thigh. The lateral cutaneous nerve lies on the

iliacus muscle and is found approximately midway between the

anterior superior iliac spine and epigastric vessels as it passes deep to

the fascia iliacus and below the iliopubic tract. It has the thickness of

a match and is only visualized after dissecting away fascia iliacus.

Injury to this nerve results in either a sensory deficit in the

posterolateral thigh or pain in this area on movement (MacFadyen,

1992).

The genitofemoral nerve is located beneath the fascia iliacus

between the spermatic vessels and the external iliac artery. It

bifurcates close to the deep inguinal ring, the femoral branch enter

the femoral sheath to supply sensation to a small area below the

inguinal ligament. The genital branch passes from the anterior

surface of the external iliac artery to pierce fascia iliacus and enter

the inguinal canal where it lies on the posteroinferior aspect of the

spermatic cord. It supplies sensation to lateral scrotal skin or labium

majus. Both branches are most vulnerable near the dorsal margin of

the deep inguinal ring lateral to or beneath the spermatic cord

(Kraus, 1994).

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Figure (14) Inside of the inguinal area is traversed by several lumber nerves.

(Tim Bax et al, 2007)

Il = Ilioinguinal nerve

GF = Genitofemoral nerve

LFC= Lateral cutaneous femoral nerve

Triangle of Doom

The vas deferns enters the internal ring from an inferiomedial

direction, while the testicular vessels enter from the superior path.

This gap between the two has been termed the "triangle of Doom".

An area where no staples or sutures should be placed in order to

Avoid any major vascular injuries, where in this triangle the iliac

vessels are situated (Skandalakis et al, 2000).

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Square of Doom

Katkhouda and Mouiel (1993), stated that; the triangle of

doom should be extended laterally to the psoas muscle where two

nerves of great importance are found: the lateral femorocutaneous

and the genitofemoral nerve; these two nerves should be kept in mind

when placing sutures or staples laterally on the psoas in order to

avoid neuromas or hyposthesia of the groin. This area described as

the "square of doom" is located between the vas medially and the

iliopubic tract superiorly.

Triangle of Pain

It is bounded by:

• Lateral border: reflected peritoneum

• Inferolateral border: iliopubic tract

• Superomedial border: gonadal vessels It contains the

following nerves:

• Lateral femoral cutaneous nerve

• Ant femoral cutaneous nerve

• Femoral branch of genitofemoral nerve

• Femoral nerves (Skandalakis et al, 2000)

Circle of Death

Formed of anastomosis between following arteries

• Common iliac artery and its two terminal divisions

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• Internal iliac artery and obturator artery which gives

aberrant obturator artery.

. External Iliac Artery which gives rise to inferior epigastric

artery

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Laparoscopic anatomy of inguinal canal

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