Inguinal region:
Anterior wall: external oblique aponeurosis; inguinal ligament more anteriorly
Posterior wall: transverse abdominus and part of internal oblique
Deep/internal inguinal ring:
Defect in transversalis fascia
Lateral to inferior epigastric artery
Above inguinal ligament
Superficial/external inguinal ring:
Defect in external oblique aponeurosis and inguinal ligament, immediately superior and lateral to pubic tubercle
Inferior epigastric artery:
Originates from EIA proximal to inguinal ligament
Passes medial to deep inguinal ring
Within the investing fascia of rectus abdominis, deep to rectus abdominis
Inferior epigastric artery and inguinal ligament divide inguinal region into 3 anatomic areas:
1. Hesselbach's triangle or inguinal canal: inferiorly by inguinal ligament, medially by lateral margin of rectus abdominis, and superolaterally by inferior epigastric artery
2. Femoral region: inferior to medial aspect of inguinal ligament
3. Region lateral to inferior epigastric artery and just above the inguinal ligament
Conjoint tendon:
Condensation of internal oblique and transversus abdominis aponeuroses
Lacunar ligament:
Reflection of the inguinal ligament
Four weak areas = 4 hernias:
1. Deep inguinal ring = indirect inguinal hernia
2. Inferior aspect of Hasselbach’s triangle = direct inguinal hernia; situated just lateral to conjoint tendon and medial to the inferior epigastric artery
3. Inferior to inguinal ligament and lateral to lacunar ligament = femoral hernia, medial to femoral vessels
4. Lateral margin of rectus abdominis muscle, superior to inferior epigastric artery as it crosses linea semilunaris = spigelian hernia
Relationship of hernia to inferior epigastric artery:
Hernia arising lateral to inferior epigastric vessel = indirect = passing thru inginal canal
Hernia arising medial to inferior epigastric vessel = direct = bulging thru posterior wall
Technique:
Don’t apply pressure.
Slow valsalva = slow strain. No coughing.
Transverse oblique plane:
Identifying deep inguinal ring:
1. Transverse oblique scan of rectus abdominis – identify inferior epigastric vessels deep to rectus within investing fascia
2. Transverse oblique scan of femoral vessels - move cranially to see origin of inferior epigastric vessels
Deep inguinal ring lies lateral to inferior epigastric vessels.
Medially symphisis pubis and laterally inferior epigastric vessels.
Short axis = sagittal plane:
Identify femoral artery in longitunal plane – move medially to identify inferior epigastric vessel – as they pass superiorly towards rectus abdominis, move more medially.
Inguinal canal is seen as ill-defined oval shaped area with hypoechogenic tubular structures.
In men, spermatic cord (heterogeneous hyperechoic structure with hypoechoic tubules and vascularity) is seen originating from the internal inguinal ring
Valsalva leads to narrowing of inguinal canal, distension of the femoral and inferior epigastric vessels, distension of vessels within the inguinal canal
Indirect inguinal hernia:
Thru inguinal canal
Persistent processus vaginalis seen in 30% adults
Can be extensive and protrude thru external ring
Superior to inguinal ligament
Transverse plane:
Lateral to inferior epigastric vessels
Extends thru the long axis of inguinal canal
Sagittal plane:
Distends canal in valsalva, effacing the contents
Direct inguinal hernia:
Usually in the inferior aspect of Hesselbach's triangle (H)
Protrude from posterior inguinal wall within transverse abdominis fascia
More localized
Transverse plane:
Medial to inferior epigastric vessels
Sagittal plane:
Comes from posterosuperior aspect into the canal
Femoral hernia:
Lateral to lacunar ligament, inferior to inguinal ligament
Transverse scan thru femoral vessels, valsalva leads to distension of femoral vein. Hernia, if any, will be seen, and may prevent normal expansion of the femoral vein
Spigelian hernia:
Along the linea semilunaris, just superior to inferior epigastric artery as it passes deep to lateral border of rectus abdominis muscle
Reference:
1. Jamadar DA et al. Sonography of inguinal region hernias. AJR 2006; 187: 185-190
2. McNally EG. Practical musculoskeletal ultrasound. Elsevier publication. 2005
