Embryologic Development of the IC
A basic understanding of the embryologic development and detailed anatomy of the processus vaginalis in its formation of the inguinal canal,
plays an essential role in establishing the diagnosis.
The inguinal canal develop in the female embryo as well as in the male.
There are two structures that have major roles in the development of the IC: processus vaginalis (PV),
an evagination of the parietal peritoneum,
and the gubernaculum,
a fibromascular ligament.
The gubernaculum arises in the course of the 7th week of the embryonic development which extend down both sides of the abdomen.
The superior aspect is attached to the inferior pole of the developing gonad,
testis in males ,
the uterus and ovaries in females.
In females,
the cranial section of the gubernaculum becomes the ovarian ligament,
and the caudal section becomes the round ligament of the uterus.
The round ligament,
attaches to the internal aspect of the labioscrotal folds,
the future scrotum or labia majora.
The gubernaculum allows the gonads to descend.
As the gonads are descending,
an evagination of the parietal peritoneum herniated through the anterior abdominal wall ventral to the gubernaculum,
forming the processus vaginalis.
Extensions of the layers of the abdominal wall accompany the PV and form the walls of the IC.
The craneal portion of the PV usually closes at or just before birth,
and obliteration proceeds gradually in a downward direction.
Normal Anatomy of the IC
The IC is a tubular,
narrow,
diagonal passage in the lower anterior abdominal wall measuring approximately 4cm in length.
The posterior wall of the canal is formed by the muscle,
aponeurosis and fascia of transversus abdominis and also part of the internal oblique.
The anterior wall is formed from the fascia of the external oblique muscle.
The IC has two openings: the deep and superficial inguinal rings.
The deep inguinal ring is an oval gap in the transversalis fascia and lies 1cm superior to the inguinal ligament and lateral to the inferior epigastric vessels.
The superficial inguinal ring is a triangular opening in the aponeurosis of the external oblique muscle.
Imaging of the IC
US
B-mode and color Doppler ultrasound (US) remains the initial imaging modality of choice.
US is the most practical and rapid method of obtaining images and provides an excellent opportunity of real-time dynamic examination,
important in the diagnosis of hernias and varicocele.
We usually perform the US exploration with high-frequency transducers (10-12 MHz),
comparing with the contralateral side.
CT and MRI
Occasionally,
we will have to complete with computed tomography (CT) or magnetic resonance imaging (MRI),
specially in imaging of deeper structures and to evaluate a larger area or the abdominal extension.