Inspired by the beautiful anatomical lithograph drawings from Gray’s Anatomy, this Daily Doodle illustrates the difference between direct and indirect inguinal hernias.

The perspective of this drawing is looking at the transversalis fascia from inside the abdomen. Try to imagine that you have been miniaturized and are hanging out with the appendix, looking at the anterior abdominal wall…

There are two main types of inguinal hernias: direct and indirect.

Direct inguinal hernias are “true” hernias in that they protudes through the abdominal wall via a weakness or defect in the transverse fascia. The area of fascia affected by direct inguinal hernias is colored green in this Daily Doodle. This green area is known as Hesselbach’s triangle, which is formed by the inguinal ligament inferiorly, the rectus abdominus muscle medially and the inferior epigastric vessels laterally.

Unlike direct inguinal hernias which protrude directly through the abdominal wall, indirect inguinal hernias slip down the inguinal canal through a patent processus vaginalis, which is normally obliterated after 38 to 48 weeks gestational age. To remember this, indirect inguinal hernias indirectly pass through the abdominal wall, unlike direct hernias that protrude directly through the fascia. The orange area of the doodle represents the entrance of the inguinal canal which is lateral to Hesselbach’s traingle. In indirect inguinal hernias, the hernia sac enters the internal ring of the inguinal canal and travels down towards the external ring and upon exiting, the hernia sac may enter the scrotum.

When direct and indirect inguinal hernias occur at the same time on the same side, it is referred to as a Pantaloon hernia, which is quite rare.

Quick Summary!

Indirect Inguinal Hernia (orange)

• Most common type of hernia in males and females
• More frequent on the right side
• Failure of obliteration of procesus vaginalis
• Lateral to inferior epigastric vessels
• Hernia sac passes through internal inguinal ring
• Increased risk of incarciration
• Can enter scrotum

Direct Inguinal Hernia (Green)

• Weakness/defect of Hasselbach’s Triangle
• Medial to inferior epigastric vessels
• Usually aquired
• More so in elderly

Get ready for being quizzed!

What are the contents of the spermatic cord in men?

1. Cremasteric muscle fibers
2. Vas deferens
3. Testicular artery
4. Testicular pampiniform venous plexus
5. Genital branch of the genitofemoral nerve
6. +/- hernia sac

Which nerve emerges lateral to the internal ring and travels toward the external ring ? What happens when it is cut? The ilioinguinal nerve. Numbness of inner thigh or lateral scrotum

What structure is found in the inguinal canal in women in replacement of the vas deferens? Round Ligament

What are the layers of the abdominal wall from superficial to deep?

1. Skin
2. Subcutaneous fat
3. Camper’s fascia
4. Scarpa’s fascia
5. External oblique
6. Internal Oblique
7. Transversus abdominus
8. Transversalis fascia
9. Preperitoneal fat
10. Peritoneum

References:

1. David C Brooks, Ayman Obeid and Mary Hawn. “Classification, clinical features and diagnosis of inguinal and femoral hernias in adults”. February 15, 2014. www.uptodate.com
2. Grey’s Anatomy Illustration “Inguinal Hernia” http://upload.wikimedia.org/wikipedia/commons/6/6f/Gray547.png
3. “Inguinal Hernias” Toronto Notes