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Vertebral levels (Fig. 22.1)
muscle. It crosses the costal margin at the tip of the 9th costal cartilage.
(In each case the lower border is referred to.)
• T9: xiphoid process.
Inguinal herniae (Figs 22.3 and 52.1)
• L1: the transpyloric plane (of Addison). This horizontal plane passes • The linea semilunaris is the lateral edge of the rectus abdominis
approximately through the tip of the 9th costal cartilage, the pylorus, • Indirect inguinal herniae: arise as a result of persistence of the pro-
pancreatic neck, duodenojejunal flexure, the gall-bladder fundus and cessus vaginalis of the embryo. Abdominal contents bulge through the
the hila of the kidneys. This plane also corresponds to the level at which deep inguinal ring, into the canal, and eventually into the scrotum. This
the spinal cord terminates and the lateral edge of rectus abdominis hernia can be controlled by digital pressure over the deep ring.
crosses the costal margin. • Direct inguinal herniae: arise as a result of weakness in the poster-
• L2: the subcostal plane. This plane corresponds to a line joining the ior wall of the inguinal canal. This hernia cannot be controlled by
lowest points of the thoracic cageathe lower margin of the 10th rib digital pressure over the deep ring and only rarely does the hernia pass
laterally. into the scrotum.
• L3: the level of the umbilicus (in a young slim person). The clinical distinction between direct and indirect inguinal hernias
• L4: the transtubercular plane. This corresponds to a line which joins can be difficult. At operation, however, the relation of the hernial neck
the tubercles of the iliac crests. to the inferior epigastric artery defines the hernia type, i.e. the neck of
the sac of an indirect hernia lies lateral to the artery whereas that of a
Lines of orientation direct type always lies medial to it.
Vertical lines: these are imaginary and most often used with the sub-
costal and intertubercular planes, for purposes of description, to subdi- Surface markings of the abdominal viscera (Fig. 22.2)
vide the abdomen into nine regions (Fig. 22.1). They pass vertically, on • Liver: the lower border of the liver is usually just palpable on deep
either side, through the point halfway between the anterior superior inspiration in slim individuals. The upper border follows the undersur-
iliac spine and the pubic tubercle. More commonly used, for descrip- face of the diaphragm and reaches a level just below the nipple on each
tion of pain location, are quadrants. The latter are imaginary lines aris- side.
ing by the bisection of the umbilicus by vertical and horizontal lines. • Spleen: this organ lies below the left hemidiaphragm deep to the 9th,
10th and 11th ribs posteriorly. The anterior notch reaches the mid-
Surface markings of the abdominal wall axillary line anteriorly.
• The costal margin (Fig. 22.1) is the inferior margin of the thoracic • Gall-bladder: the fundus of the gall-bladder lies in the transpyloric
cage. It includes the costal cartilages anteriorly, the 7th–10th ribs later- plane (L1). The surface marking corresponds to a point where the lat-
ally and the cartilages of the 11th and 12th ribs posteriorly. eral border of rectus abdominis (linea semilunaris) crosses the costal
• The symphysis pubis is an easily palpable secondary cartilaginous margin.
joint which lies between the pubic bones in the midline. The pubic • Pancreas: the pancreatic neck lies on the level of the transpyloric
tubercle is an important landmark and is identifiable on the superior plane (L1). The pancreatic head lies to the right and below the neck
surface of the pubis. whereas the body and tail pass upwards and to the left.
• The inguinal ligament (Figs 11.1 and 22.2) is attached laterally to the • Aorta: the aorta bifurcates to the left of the midline at the level of L4.
anterior superior iliac spine and medially to the pubic tubercle. • Kidneys: the kidney hila lie on the level of the transpyloric plane
• The superficial inguinal ring (see Fig. 11.1) is a triangular-shaped (L1). The lower pole of the right kidney usually extends 3 cm below the
defect in the external oblique aponeurosis. It is situated above and level of the left and is often palpable in slim subjects.
medial to the pubic tubercle. • Appendix: McBurney’s point represents the surface marking for the
• The spermatic cord can be felt passing medial to the pubic tubercle base of the appendix. This point lies one third of the way along a line
and descending into the scrotum. joining the anterior superior iliac spine and the umbilicus. McBurney’s
• The deep inguinal ring (Fig. 22.3) lies halfway along a line from the point is important surgically as it represents the usual site of maximal
anterior superior iliac spine to the pubic tubercle. tenderness in appendicitis and also serves as the central point for the
• The linea alba (see Fig. 11.1) is formed by the fusion of the aponeu- incision made when performing an appendicectomy.
roses of the muscles of the anterior abdominal wall. It extends as a de- • Bladder: in adults the bladder is a pelvic organ and can be palpated
pression in the midline from the xiphoid process to the symphysis pubis. above the symphysis pubis only when full or enlarged.

Surface anatomy of the abdomen 53