4. The inguinal canal & hernias

Question 1

what are the boundaries of the inguinal canal

Answer 1

• floor: inguinal ligament (thickened medially by lacunar ligament)
• roof: muscular arches and aponeuroses of internal oblique and transverse abdominis
• posterior wall: transversalis fascia (reinforced medially by inguinal falx - conjoint tendon of internal oblique and transversus abdominis, inserting on pubic tubercle)
• anterior wall: external oblique aponeurosis

Question 2

describe the openings of the inguinal canal

Answer 2

1. deep inguinal ring: pierces transversalis fascia, 3 cm superior to midpoint of inguinal ligament, lateral to inferior epigastric vessels
2. superficial inguinal ring: pierces external oblique aponeurosis, superolateral to pubic tubercle (margins of ring = lateral and medial crura)

Question 3

describe the contents of the inguinal canal in males and females

Answer 3

• blood and lymphatic vessels
• ilio-inguinal n.
• spermatic cord (males) or round ligament of uterus (females)

Question 4

what is the inguinal ligament and what are the 2 mid points associated with it

Answer 4

Inferior margin of external oblique aponeurosis, extends from ASIS of ileum to pubic tubercle.

Mid-point of inguinal ligament = 1/2 way between ASIS and pubic tubercle. Location of deep inguinal ring.

Mid-inguinal point = 1/2 way between ASIS and pubic symphysis. Femoral a. crosses into lower limb at this point.

Question 5

Describe the descent of the male gonads during dev.

Answer 5

During male dev., testes establish in posterior abdominal wall, but descend into scrotum, guided by GUBERNACULUM- fibrous tissue cord attaching caudal pole of testes to future scrotum.

Testes leave abdominal cavity and enter scrotum via INGUINAL CANAL, flanked anteriorly by PROCESSUS VAGINALIS (out-pocketing of peritoneum).

Upper part of processus degenrates, leaving only lower portion which forms TUNICA VAGINALIS.

Question 6

Why do ovaries not descend as far as testes

Answer 6

Foetal ovaries establish in posterior abdominal wall, bud descend into pelvis, guided by GUBERNACULUM.

Gubernaculum runs from ovaries to labia majora, but attaches en route to uterus, preventing ovaries from descending as far as testes.

Question 7

which structures does the gubernaculum form in the mature female

Answer 7

Part from ovary to uterus = ovarian ligament

Part from uterus to labia majora (running through inguinal canal) = round ligament of uterus

Question 8

name 3 features that normally prevent inguinal herniation during increases in abdominal pressure

Answer 8

1. oblique path of canal: means that deep and superficial rings don’t overlap, and that increased intr-abdominal pressure forces post. wall of canal against anterior wall, closing passage
2. simultaneous contraction of external oblique: approximates anterial canal wall to post. wall, and increases tension on crura - resists dilation of superficial ring
3. contraction of internal oblique and transversus abdominis: descends roof and constricts canal

Question 9

what is an abdominal hernia and what are the different types

Answer 9

Hernia = protrusion of viscera from abdominal cavity. Has 3 parts:

• contents: commonly loops of bowel or omenta
• sac: pouch of parietal peritoneum
• coverings of sac: layers of abdominal wall

Types: inguinal (75%), umbilical (10%), incisional (10%) and femoral (3-5%)

Question 10

describe the causes of direct and indirect inguinal hernias

Answer 10

Direct: weakness of anterior abdominal wall in inguinal triangle (eg distended superficial ring, narrow inguinal falx) - males >40yrs

Indirect: patency of processus vaginalis (complete or superior part) - younger males

Question 11

contrast the courses of direct and indirect inguinal hernia

Answer 11

Direct - medial to inferior epigastric vessels:

i) bulges through Hesselbach’s triangle, generally in vicinity of superficial inguinal ring (traverses only medial 1/3 of canal)…
ii) exits anterior abdominal wall via superficial ring, lateral to spermatic cord
iii) rarely enters scrotum

Indirect - lateral to inferior epigastric vessels:

i) passes through deep inguinal ring…
ii) traverses entire canal within processus vaginalis…
iii) exits anterior abdominal wall via superficial ring, remaining within spermatic cord…
iv) commonly passes into scrotum

Question 12

describe the course of a femoral hernia

Answer 12

Protrusion of viscera through femoral ring into femoral canal (due to weakness of lower abdominal wall).

Can enlarge by passing through saphenous opening into subcutaneous tissue of thigh.

Question 13

what do the terms ‘incarcerated’ and ‘strangulated’ mean in relation to hernias

Answer 13

incarcerated = stuck, irreducible

strangulated = disruption to blood supply, leading to tissue necrosis

Question 14

what is the difference between an infantile umbilical hernia and omphalocoeles

Answer 14

Acquired infantile hernia = content herniates through weakness in umbilical scar but is still covered by skin

Omphalocoele = persistence of physiological herniation - intestinal loops remain in umbilical cord. Only has peritoneal/amnion covering