Inguinal region

Boundaries

• ASIS
• Pubic tubercle

Functions (of inguinal region in general)

• Anchors lower abdominal musculature to pelvis
• Conduit for spermatic cord in men/round ligament in women
• Femoral vessels pass inferiorly

Embryology

• Testes and ovary appear during weeks 7 and 10 respectively
• Gubernaculum attaches caudal ends of gonads to labioscrotal swellings
• Testes - originate in posterior abdo wall, then descend into pelvic cavity. Invaginated by processus vaginalis, the testes and cord pass into scrotum. This invagination is obliterated.
• Ovaries - descend into pelvis, and gubernaculum forms the ovarian and round ligaments. Persistence of processus vaginalis can form a protrusion into the labia majora called canal of Nuck.

Layers at inguinal region

• Skin
• Subcutaneous fat
  • Superficial epigastric vein
  • Anterior circumflex iliac vein (drains to external iliac)
• Camper's
• Scarpa's
• External oblique
  • Entirely aponeurotic below ASIS - no muscle within inguinal region
  • Inguinal ligament ('Poupart's ligament') - in-rolled lower edge of the external oblique aponeurosis, which runs between ASIS and pubic tubercle, as it rolls posteriorly to form a shelving edge.
    • Not free-lying - attached to iliopsoas laterally and fascia lata of the thigh medially
• Internal oblique
  • Predominately muscular as it passes through the inguinal region - these fibres are not adequate to hold sutures
  • Fibres directed medially and inferiorly in the inguinal region
  • Conjoint tendon is traditionally described as forming from the fused fibres of IO and TA. Apparently only present in 5-10% of patients, and is most evident at the insertion of these muscles on the pubic tubercle. Probably not a useful term.
  • Cremaster arises from IO.
• Transversus abdominis
  • Muscular fibres laterally in inguinal region, with aponeurotic fibres starting medial to internal ring. Therefore, it is durable enough to use for hernia repair in this region.
  • Forms the transversus abdominus arch (along with IO), which comprises the superior edge of the internal inguinal ring, and inserts into the superior pubic ramus or pubic tubercle
  • A small number of aponeurotic fibres continue inferior to internal ring
    • Iliopectineal arch - the strong fascia which lies over the iliopsoas muscle
      • Divides the space deep to inguinal ligament in two, at a point lateral to the femoral vessels
      • Blends with inguinal ligament in front and pectineal ligament/pectineus fascia behind - the only way through the inguinal ligament here is beneath the iliopsoas fascia
    • Iliopubic tract is the free lower edge of TA/transversalis fascia
      • Forms as a small group of aponeurotic fibres from TA and some transversalis fascia, which runs deep and parallel to the inguinal ligament.
      • It courses over the femoral vessels, defining the anterior border of the femoral sheath, and eventually inserting at the iliopectineal arch on superior ramus of pubis, near AIIS.
      • Blends to some extent with pectineal ligament
      • It also contributes to the posterior wall of the inguinal canal, along with the anterior and medial walls of the femoral sheath
      • This is also described in some sources as 'the internal view of the inguinal ligament'
    • Falx inguinales - the purported fibres of transversus aponeurosis inserting to the pubic tubercle - not clinically significant.
  • In between the iliopubic tract and transversus abdominis arch, there is a weak spot just covered by transversalis fascia, which is the site where direct inguinal hernias develop.
• Transversalis fascia
  • The connective tissue layer that underlies the abdominal wall musculature
  • Although denser than usual in the inguinal region, it is still relatively thin.
  • No clear distinction between lower border of TA aponeurosis and transversalis fascia
  • Nyhus: 'it possess little intrinsic strength and, by itself, is a worthless material as far as the construction of a sound hernia repair is concerned.'
    • However, the aponeurosis of TA certainly is capable of holding sutures, so the distinction is academic since the two structures are quite blended

• Preperitoneal space
  • Adipose tissue
  • Lymphatics
  • Blood vessels
    • Inferior epigastric vessels
    • Deep circumflex iliac vessels - below lateral portion of iliopubic tract
  • Nerves
    • Lateral femoral cutaneous nerve
    • Genitofemoral nerve
  • Vas deferens
• Peritoneum

Important structures near inguinal region

• Inguinal ligament - see above under EO
• Lacunar ligament (Gimbernat's ligament): occurs as the inguinal ligament fans out medially. This fanning allows it to have a broader insertion onto the pectineal ligament. The lacunar ligament is also the medial border of the femoral space.
  • In its lateral border, may contain an aberrant branch between obturator artery and EIA/DIEA (25% of patients) which can be difficult to control if injured. Also known as corona mortis artery, or if it is quite small, as the 'pubic branch' of IEA. Can be accompanied by veins. See 'femoral hernia' topic.
  • Named for the vascular 'lacuna' or opening, for which it forms the medial border
• Pectineal ligament (Cooper's ligament) is formed with contributions from lacunar ligament, IO, TA and pectineus. It inserts onto the pectineal line of the pubic bone, overlying the pectineus muscle. It is usually about 6cm long. It is the posterior border of the femoral space.
  • Both lacunar and pectineal ligaments are robust anchoring points for hernia repairs - very thick, tough, fibrous band.
• Conjoint tendon - see above under IO
• Iliopectineal arch and iliopubic tract - see above under TA
• Interfoveolar ligament (Hesselbach's ligament) - thickening at lateral edge of internal ring, made up of fibres derived from the transversus abdominis muscle
  • This ligament pulls the inguinal canal closed when transversalis fascia contracts, by functioning as a sling around the internal ring

Myopectineal orifice

• A general descriptor for the space through which groin hernias occur
• First described by Fruchaud in 1956
• Bounded medially by rectus abdominis, inferiorly by pectineal ligament, laterally by psoas, and superiorly by transversus abdominis/internal oblique muscles (transverse arch)
• The below triangles has been described as the 'critical view of safety' for laparoscopic inguinal hernia repairs

• The five triangles:
  • Pain
    • The triangle is bounded medially by spermatic vessels, and superiorly by iliopubic tract (or maybe even up to 2cm above it)
    • Lateral femoral cutaneous nerve of the thigh - lies on ilacus, midway between ASIS and DIEA, then passing deep to fascia iliacus and below the iliopubic tract
    • Femoral nerve - lies in a groove between psoas and iliacus muscles, approximately midway between psoas and iliacus
    • Femoral branch of genitofemoral nerve - main trunk is beneath fascia iliacus, between spermatic vessels and the iliac artery, and bordering the psoas - bifurcates close to deep ring - genital branch into canal, and femoral branch into femoral sheath
    • Ilioinguinal nerve is not usually seen laparoscopically but can still be injured by fixation

• Doom
  • Contains external iliac vessels
  • Bounded by vas def medially and spermatic vessels laterally
• Indirect hernias
• Direct hernias
• Femoral hernias

Innervation

• Iliohypogastric (see below under 'inguinal canal')
• Ilioinguinal (see below)
• Genitofemoral (see below)
• Lateral femoral cutaneous nerve
  • Lumbar plexus branch from L2 and L3
  • Exits from lateral border of psoas muscle and crosses iliacus
  • Runs in pre-peritoneal plane under the inguinal ligament near its lateral attachment to ASIS, about 1cm medial to ASIS. Then passes through or superficial to sartorius and pierces the investing fascia about 4cm below the lateral end of the inguinal ligament.
    • Cadaveric study showed the nerve can course anywhere from 6.5cm medial to ASIS to 6cm lateral
  • Divides into anterior and posterior divisions
  • Can cause meralgia paraesthetica - see separate topic
• See also - ilioinguinal/iliohypogastric nerve block under 'anaesthetics' - 'regional blocks'

Vascular supply

• Deep inferior epigastric artery - arises from external iliac, just superior to inguinal ligament, travels along the medial border of the internal ring, and goes upwards to supply rectus abdominis
• Three branches of femoral artery supply the superficial tissues
  • Superficial epigastric - close to internal ring
  • Superficial circumflex iliac - laterally
  • Superficial external pudendal - medially

Lymphatics

• Discussed separately under 'lower limb'
• Superficial inguinal nodes - adjacent to termination of great saphenous vein. Receive lymphatics from lower limb, infra-umbilical abdo wall, buttock, perineum, anal canal, penis and scrotum/labia and vagina external to hymen
• Deep inguinal nodes - beneath the fascia lata along the femoral vein. Receives lymph from glans penis/clitoris
  • Includes node of Cloquet
• Testes drain to para-aortic/renal nodes
• To biopsy - incise over palpable node. Tributaries of great saphenous vein may need to be ligated. Ligate lymphatic vessels.

Inguinal canal:

• Relations
  • Inguinal ligament inferiorly, with medial contributions from lacunar ligament
  • Conjoint tendon superiorly (transversus abdominis and internal oblique - although it is disputed in anatomical literature as to whether these fibres are actually fused), which curves from in front of the cord laterally to behind the cord medially, and then it inserts into the pubic crest and pectineal line of the pubic bone
  • Transversalis fascia posteriorly, fused with iliopubic tract
  • External oblique anteriorly
  • Internal ring laterally - point of entry of spermatic cord structures into the inguinal canal
    • This is best conceptualised as a defect in transversalis fascia, with fibres from IO and TA curving superiorly
    • Midway between ASIS and pubic symphysis - mid-inguinal point
    • Inferior border formed/reinforced by iliopubic tract (see above under TA)
    • Lateral border reinforced by the interfoveolar ligament (Hesselbach's ligament) - see separate topic above under 'structures'
    • External ring medially
    • Triangular opening in EO aponeurosis, superior and 1.5cm laterally to the pubic tubercle
  • Superficial ring medially
  • Hesselbach's triangle:
    • The margins of the floor of the inguinal canal
    • Inferior epigastric vessels, rectus sheath, inguinal/pectineal ligament
    • Direct hernias occur through this triangle
• Strength
  • Laterally: EO aponeurosis
  • Medially: conjoint tendon
• Contents (spermatic cord/round ligament, genital branch of genitofemoral nerve, and ilioinguinal nerve)
  • Men:
    • Spermatic cord - (3 arteries, 3 fasciae, 3 nerves, 3 other things)
      • 3 arteries (testicular, deferential, cremasteric)
        • Testicular - largest artery in the cord. Originates from aorta. Gives off a branch to the epididymis, then divides to medial and lateral branches at the back of the testis. There is an anastomosis between testicular, cremasteric and ductal arteries in the region of the epididymis, but atrophy will probably still occur if the main testicular artery is divided (frank necrosis is actually unlikely according to Last's).
        • Cremasteric artery: originates from inferior epigastric at level of deep ring. Supplies cremasteric muscle and coverings of the cord. Enter inguinal canal through their own foramen in the posterior wall.
        • Artery to the vas or 'deferential artery' - from the superior or inferior vesical
      • 3 fasciae (external, cremasteric, internal spermatic fascia)
        • External spermatic fascia - acquired from EO aponeurosis as the cord passes through the superficial ring
        • Cremaster muscle/cremasteric fascia - striated muscle bundles united by areolar tissue. Arises laterally from the inguinal ligament, IO and TA muscles. The longest fibres reach as far down as tunica vaginalis of the testis, and loop back to attach to pubic tubercle. Functions to reflexively elevate the testis towards the inguinal canal.
        • Internal spermatic fascia is derived from transversalis fascia. It projects along the canal like a sleeve, containing everything that passes through deep ring.
      • 3 nerves (genital branch of genitofemoral nerve, ilioinguinal, sympathetic)
        • Genital branch of genitofemoral - see below.
        • Ilio-inguinal - see below. Outside cord.
        • Sympathetic twigs accompany the arteries
      • 3 other (ductus deferens, pampiniform plexus, lymphatics)
        • Ductus deferens - usually lies in medial or posterior part of the cord. Direct continuation of the canal of the epididymis. Leaves the canal via the deep ring, passes medially just under the peritoneum, pierces the prostate and opens into the prostatic urethra.
        • Pampiniform plexus - mass of intercommunicating veins from testis, which surround the testicular artery. Separates out into about four veins in the inguinal canal, and becomes one on the surface of psoas. Left vein to left renal vein and right vein directly to IVC.
          • Jamieson's says there are also cremasteric vein (to IEV) and deferential veins (to IIV)
        • Lymphatics - those from the testis draining to para-aortic nodes, and those from the coverings draining to external iliac nodes
      • Processus vaginalis
        • When patent it forms the sac of an indirect inguinal hernia
      • Arrangement (from external to internal)
        • External fascia
          • Ilioinguinal nerve
          • Lymphatics from cord coverings
        • Cremasteric fascia
          • Cremasteric artery and vein and nerve (genital branch of genitofemoral nerve)
        • Internal fascia
          • Testicle, testicular artery, pampiniform plexus, lymphatics
          • Ductus deferens and deferential artery/vein
          • Sympathetic twigs

• Women:
  • Obliterated processus vaginalis
  • Round ligament
  • Lymphatics from uterus
• Nerves
  • Iliohypogastric - Originates L1. Bifurcates into lateral and anterior cutaneous branches above the iliac crest. First pierces IO 3cm medial/superior to ASIS to travel between IO and EO. The anterior cutaneous branch does not traverse internal ring, but enters on superior border between transversis abdominis and internal oblique, running 2cm superior to cord. Supplies skin of pubic region. Not usually seen during IHR.
    • Lateral cutaneous branch peels off above iliac crest, supplying posterolateral gluteal skin
  • Ilioinguinal - Usually from L1. First pierces IO 2cm medial/superior to ASIS to travel between IO and EO. Does not traverse internal ring, enters on superior border between transversus abdominis and internal oblique. Found anterior to the cord within the inguinal canal. Exits the superficial ring along with the cord, and then travels in between external and internal spermatic fascia. Sensory nerve - base of penis, upper medial thigh.
  • Genital branch of genitofemoral - Originates L1 (femoral) and L2 (genital) and courses inferiorly along psoas.
    • Genital branch enters canal via the inferior aspect of the deep ring and lies posterior in the cord. Supplies cremaster muscle and the skin of lateral scrotum/labia.
    • Femoral branch passes through the femoral sheath beneath inguinal ligament, lateral to femoral artery, and supplies skin of thigh over femoral triangle.
• Any indirect hernia would reside anterior to these structures in the inguinal canal

• Structures deep to the posterior wall:
  • Inferior epigastric artery. Gives off cremasteric branch at the deep ring.

Femoral sheath

• A thickening of the deep fascia of the thigh to encase the major vessels
• Derived from:
  • Iliopsoas fascia laterally
  • Pectineus fascia posteriorly
  • Transversalis fascia anteromedially
• Extends for about 4cm then fuses with adventitia of femoral vessels
• Perforated by small arterial vessels and GSV
• Boundaries
  • Iliopectineal arch laterally
  • Iliopsoas inferiorly
  • Iliopubic tract superficially
  • Lacunar ligament medially
  • Pectineal ligament deep, with pectineus fascia under that
• Compartments - divided by septal fascia
  • Lateral - femoral artery
  • Intermediate - femoral vein
  • Medial - femoral canal

Femoral canal

• Boundaries
  • Superficial - liiopubic tract of transversalis fascia, then superficially again is inguinal ligament
  • Deep - pectineal/Cooper ligament, then pectineus fascia
  • Medial - lacunar ligament
  • Lateral - femoral vein
  • Cranial - femoral ring (larger in females hence more femoral herniae)
  • Caudal - 1-2cm - terminates at foramen ovalis
• Contents
  • Lymphatics - Cloquet's node
  • Fat
• Function
  • Permits passage of lymph into abdomen
  • Permits expansion of femoral vein