What are the boundaries of the inguinal canal?
■ Anterior wall: skin, superficial fascia, external oblique (for whole length); internal oblique for lateral one-third
■ Posterior wall: transversalis fascia (for whole length); conjoint tendon and pectineal (Cooper’s) ligament medially
■ Floor: inguinal ligament (Poupart’s ligament)
■ Roof: arching fibres of internal oblique and transversus abdominis which fuse to form the conjoint tendon on the posteromedial aspect of the canal.
The deep inguinal ring is a hole in the transversalis fascia and lies a finger-breadth above the mid-inguinal point (i.e. half way between the anterior superior iliac spine and pubic tubercle). The superficial inguinal ring is a hole in the external oblique aponeurosis.
Abdomen and pelvis
What is a hernia?
A hernia is a protrusion of a viscus, or part of a viscus, outwith its normal position.
How can you distinguish a femoral from an inguinal hernia?
An inguinal hernia lies above and medial to the pubic tubercle, while a femoral hernia lies below and lateral to the pubic tubercle.
What is the difference between a direct and an indirect inguinal hernia?
A direct hernia passes straight through a weakness in the anterior abdominal wall and passes through the superficial ring only. An indirect hernia passes through both the deep and superficial inguinal rings and thereby passes along the entire length of the inguinal canal. They can be distinguished clinically by placing your hand over the deep ring and asking the patient to cough (deep ring occlusion test). An indirect hernia is controlled at the deep ring, whereas a direct inguinal hernia is not.
At surgery, the neck of an indirect inguinal hernia lies lateral to the inferior epigastric artery, whereas the neck of a direct inguinal hernia lies medial to the inferior epigastric artery. Occasionally a pantaloon hernia may occur (with both direct and indirect components).
What is Hasselbach’s triangle, and what is its surgical importance?
The boundaries of Hasselbach’s triangle are:
■ medial half of inguinal ligament
■ linea semilunaris (lateral border of rectus abdominis)
■ inferior epigastric artery.
Its surgical importance lies in the fact that the triangle is a potentially weak area in the anterior abdominal wall since it is not reinforced by the conjoint tendon. It is responsible for causing direct inguinal hernias.
What are the contents of the spermatic cord?
Apply the ‘rule of 3s’ (Table 1.2).
➜ Testis
What is the blood supply to the testis?
The testis is supplied by the testicular artery which arises directly from the descending abdominal aorta approximately at the level of L2. The explanation lies in the fact that the testis develops high up on the posterior abdominal wall early in embryonic life. As it descends into the scrotum during development, the testis carries with it the same blood supply that it received whence it was positioned on the posterior abdominal wall (i.e. from the aorta).
What is the venous drainage of the testis?
There is asymmetry between the two sides. On the right side, the testis
Section 1: Anatomy
drains by way of the pampiniform plexus into the inferior vena cava, but the left testis drains into the left renal vein. This may explain why varicoceles are more common on the left side.
What is the lymphatic drainage of the testis?
As a general rule regarding lymphatic drainage, superficial lymphatics (i.e. in subcutaneous tissues) tend to run with superficial veins, whereas deep lymphatics run with arteries. The testis thus drains lymph to the para-aortic set of lymph nodes, since the testicular artery arises from the aorta. The scrotum on the other hand drains to the inguinal group of lymph nodes. The testis, unlike the scrotum, never drains to the inguinal lymph nodes.
The clinical consequence of this is that a testicular carcinoma
metastasises to the para-aortic group of lymph nodes and never results in inguinal lymphadenopathy, unless the scrotum is also involved. A scrotal carcinoma, on the other hand, causes inguinal lymphadenopathy.
What is the innervation of the testis?
The testis is supplied by T10 sympathetic nerves. The consequences of this are two-fold. First, it results in testicular pain (trauma, testicular torsion etc.) being referred to the umbilicus (T10 dermatome). Second, the ureters are also supplied by T10 sympathetics. Thus a renal calculus may refer pain down to the testis, as is seen in classical renal colic.
What layers does the surgeon traverse when operating on a testis?
■ Skin
■ Subcutaneous tissue (containing dartos muscle)
■ Colles’ fascia
■ External spermatic fascia (external oblique)
Abdomen and pelvis
Table 1.2
Contents of the spermatic cord: the rule of 3s
Three constituents: vas deferens (the round ligament is the female equivalent); lymphatics; obliterated processus vaginalis
Three nerves: genital branch of the genitofemoral nerve (motor to cremaster, sensory to cord); ilioinguinal nerve (within the inguinal canal but outside the spermatic cord); autonomics
Three arteries: testicular artery; artery to the vas (from the superior or inferior vesical artery); cremasteric artery (from the inferior epigastric artery).
Three veins: pampiniform plexus; vein from vas; cremasteric vein Three fascial coverings: external spermatic fascia (derived from external oblique); cremasteric muscle and fascia (derived from internal oblique and transversus abdominis); internal spermatic fascia (derived from transversalis fascia)
■ Cremaster muscle and fascia (internal oblique/transversus abdominis)
■ Internal spermatic fascia (transversalis)
■ Parietal layer of tunica vaginalis
■ Visceral layer of tunica vaginalis
■ Tunica albuginea of testis.
➜ Ureters
What type of muscle do the ureters consist of?
The ureters are segmental muscular tubes, 25 cm long, composed of smooth (involuntary) muscle throughout their entire length.
What type of epithelium lines the ureters?
The ureters are lined by transitional epithelium (urothelium) throughout their length. Transitional epithelium is almost exclusively confined to the urinary tract of mammals where it is highly specialised to accommodate stretch and to withstand the toxicity of the urine.
How may the ureters be identified at surgery so as to prevent inadvertent ligation?
The ureter is characteristically a whitish, non-pulsatile cord, which shows peristaltic activity when gently pinched with forceps (i.e. it vermiculates).
What is the blood supply to the ureters?
Blood supply to the ureters, like the oesophagus, is segmental. The upper one-third is supplied by the renal arteries, the middle third from branches given off from the descending abdominal aorta, and the lower one-third is supplied by the superior and inferior vesical arteries. Blood supply to the middle third is the most tenuous. Consequently the middle third of the ureter is most vulnerable to postoperative ischaemia and stricture formation if blood supply to it is endangered by stripping the ureter clean of its surrounding tissue at surgery.
Where do the ureteric constrictions take place?
Along the course of the ureter are three narrowings that often form the site of obstruction in ureteric calculus disease:
■ pelvi-ureteric junction
■ where the ureter crosses the pelvic brim in the region of the bifurcation of the common iliac artery
■ vesico-ureteric junction.
The vesico-ureteric junction is the point of narrowest calibre.
What is special about the way in which the ureters enter into the bladder?
In both sexes the ureters run obliquely through the bladder wall for 1–2 cm before reaching their orifices at the upper lateral angles of the trigone. This forms a flap valve preventing reflux of urine retrogradely back up the ureters. If this flap valve is congenitally deficient, vesico-ureteric reflux results.
Section 1: Anatomy