Surface Markings of the Abdomen

8. Surface Markings of the Abdomen

FIG. 1220– Surface lines of the front of the thorax and abdomen.

Bony Landmarks.—Above, the chief bony markings are the xiphoid process, the lower six costal cartilages, and the anterior ends of the lower six ribs. The junction between the body of the sternum and the xiphoid process is on the level of the tenth thoracic vertebra. Below, the main landmarks are the symphysis pubis and the pubic crest and tubercle, the anterior superior iliac spine, and the iliac crest.

Muscles (Fig. 1227).—The Rectus lies between the linea alba and the linea semilunaris; the former is indicated by the middle line, the latter by a curved line, convex lateralward, from the tip of the cartilage of the ninth rib to the public tubercle; at the level of the umbilicus the linea semilunaris is about 7 cm. from the middle line. The line indicating the junction of the muscular fibers of Obliquus externus with its aponeurosis extends from the tip of the ninth costal cartilage to a point just medial to the anterior superior iliac spine.

The umbilicus is at the level of the fibrocartilage between the third and fourth lumbar vertebræ.

The subcutaneous inguinal ring is situated 1 cm. above and lateral to the public tubercle; the abdominal inguinal ring lies 1 to 2 cm. above the middle of the inguinal ligament. The position of the inguinal canal is indicated by a line joining these two points.

Surface Lines.—For convenience of description of the viscera and of reference to morbid conditions of the contained parts, the abdomen is divided into nine regions, by imaginary planes, two horizontal and two sagittal, the edges of the planes being indicated by lines drawn on the surface of the body (Fig. 1220). In the older method the upper, or subcostal, horizontal line encircles the body at the level of the lowest points of the tenth costal cartilages; the lower, or intertubercular, is a line carried through the highest points of the iliac crests seen from the front, i. e., through the tubercles on the iliac crests about 5 cm. behind the anterior superior spines. An alternative method is that of Addison, who adopts the following lines:

(1) An upper transverse, the transpyloric, halfway between the jugular notch and the upper border of the symphysis pubis; this indicates the margin of the transpyloric plane, which in most cases cuts through the pylorus, the tips of the ninth costal cartilages and the lower border of the first lumbar vertebra; (2) a lower transverse line midway between the upper transverse and the upper border of the symphysis pubis; this is termed the transtubercular, since it practically corresponds to that passing through the iliac tubercles; behind, its plane cuts the body of the fifth lumbar vertebra.

By means of these horizontal planes the abdomen is divided into three zones named from above, the subcostal, umbilical, and hypogastric zones. Each of these is further subdivided into three regions by the two sagittal planes, which are indicated on the surface by a right and a left lateral line drawn vertically through points halfway between the anterior superior iliac spines and the middle line. The middle region of the upper zone is called the epigastric, and the two lateral regions the right and left hypochondriac. The central region of the middle zone is the umbilical, and the two lateral regions the right and left lumbar. The middle region of the lower zone is the hypogastric or pubic, and the lateral are the right and left iliac or inguinal. The middle regions, viz., epigastric, umbilical, and pubic, can each be divided into right and left portions by the middle line. In the following description of the viscera the regions marked out by Addison’s lines are those referred to.

Stomach (Fig. 1223).—The shape of the stomach is constantly undergoing alteration; it is affected by the particular phase of the process of gastric digestion, by the state of the surrounding viscera, and by the amount and character of its contents. Its position also varies with that of the body (Figs. 1221, 1222), so that it is impossible to indicate it on the surface with any degree of accuracy. The measurements given refer to a moderately filled stomach with the body in the supine position.

FIG. 1221– With the patient in the erect posture.

FIG. 1222– With the patient lying down.

FIG. 1223– Front of abdomen, showing surface markings for liver, stomach, and great intestine.

The cardiac orifice is opposite the seventh left costal cartilage about 2.5 cm. from the side of the sternum; it corresponds to the level of the tenth thoracic vertebra. The pyloric orifice is on the transpyloric line about 1 cm. to the right of the middle line, or alternately 5 cm. below the seventh right sternocostal articulation; it is at the level of the first lumbar vertebra. A curved line, convex downward and to the left, joining these points indicates the lesser curvature. In the left lateral line the fundus of the stomach reaches as high as the fifth interspace or the sixth costal cartilage, a little below the apex of the heart. To indicate the greater curvature a curved line is drawn from the cardiac orifice to the summit of the fundus, thence downward and to the left, finally turning medialward to the pyloric orifice, but passing, on its way, through the intersection of the left lateral with the transpyloric line. The portion of the stomach which is in contact with the abdominal wall can be represented roughly by a triangular area the base of which is formed by a line drawn from the tip of the tenth left costal cartilage to the tip of the ninth right cartilage, and the sides by two lines drawn from the end of the eighth left costal cartilage to the ends of the base line.

FIG. 1224– Topography of thoracic and abdominal viscera.

A space of some clinical importance—the space of Traube—overlies the stomach and may be thus indicated. It is semilunar in outline and lies within the following boundaries: the lower edge of the left lung, the anterior border of the spleen, the left costal margin and the inferior margin of the left lobe of the liver.

Duodenum (Fig. 1225).—The superior part is horizontal and extends from the pylorus to the right lateral line; the descending part is situated medial to the right lateral line, from the transpyloric line to a point midway between the transpyloric and transtubercular lines. The horizontal part runs with a slight upward slope from the end of the descending part to the left of the middle line; the ascending part is vertical, and reaches the transpyloric line, where it ends in the duodenojejunal flexure, about 2.5 cm. to the left of the middle line.

FIG. 1225– Front of abdomen, showing surface markings for duodenum, pancreas, and kidneys. A A’. Plane through joint between body and xiphoid process of sternum. B B’. Plane midway between A A’ and transpyloric plane. C C’. Plane midway between transpyloric and transtubercular planes.

Small Intestine.—The coils of small intestine occupy the front of the abdomen. For the most part the coils of the jejunum are situated on the left side, i.e., in the left lumbar and iliac regions, and in the left half of the umbilical region. The coils of the ileum lie toward the right in the right lumbar and iliac regions, in the right half of the umbilical region, and in the hypogastric region; a portion of the ileum is within the pelvis. The end of the ileum, i.e., the ileocolic junction, is slightly below and medial to the intersection of the right lateral and transtubercular lines.

Cecum and Vermiform Process.—The cecum is in the right iliac and hypogastric regions; its position varies with its degree of distension, but the midpoint of a line drawn from the right anterior superior iliac spine to the upper margin of the symphysis pubis will mark approximately the middle of its lower border.

The position of the base of the vermiform process is indicated by a point on the lateral line on a level with the anterior superior iliac spine.

Ascending Colon.—The ascending colon passes upward through the right lumbar region, lateral to the right lateral line. The right colic flexure is situated in the upper and right angle of intersection of the subcostal and right lateral lines.

Transverse Colon.—The transverse colon crosses the abdomen on the confines of the umbilical and epigastric regions, its lower border being on a level slightly above the umbilicus, its upper border just below the greater curvature of the stomach.

Descending Colon.—The left colic flexure is situated in the upper left angle of the intersection between the left lateral and transpyloric lines. The descending colon courses down through the left lumbar region, lateral to the left lateral line, as far as the iliac crest (see footnote p. 1181).

Iliac Colon.—The line of the iliac colon is from the end of the descending colon to the left lateral line at the level of the anterior superior iliac spine.

Liver (Fig. 1223).—The upper limit of the right lobe of the liver, in the middle line, is at the level of the junction between the body of the sternum and the xiphoid process; on the right side the line must be carried upward as far as the fifth costal cartilage in the mammary line, and then downward to reach the seventh rib at the side of the thorax. The upper limit of the left lobe can be defined by continuing this line downward and to the left to the sixth costal cartilage, 5 cm. from the middle line. The lower limit can be indicated by a line drawn 1 cm. below the lower margin of the thorax on the right side as far as the ninth costal cartilage, thence obliquely upward to the eighth left costal cartilage, crossing the middle line just above the transpyloric plane and finally, with a slight left convexity, to the end of the line indicating the upper limit.

According to Birmingham the limits of the normal liver may be marked out on the surface of the body in the following manner. Take three points: (a) 1.25 cm. below the right nipple; (b) 1.25 cm. below the tip of the tenth rib; (c) 2.5 cm. below the left nipple. Join (a) and (c) by a line slightly convex upward; (a) and (b) by a line slightly convex lateralward; and (b) and (c) by a line slightly convex downward.

The fundus of the gall-bladder approaches the surface behind the anterior end of the ninth right costal cartilage close to the lateral margin of the Rectus abdominis.

Pancreas (Fig. 1225).—The pancreas lies in front of the second lumbar vertebra. Its head occupies the curve of the duodenum and is therefore indicated by the same lines as that viscus; its neck corresponds to the pylorus. Its body extends along the transpyloric line, the bulk of it lying above this line to the tail which is in the left hypochondriac region slightly to the left of the lateral line and above the transpyloric.

Spleen (Figs. 1217, 1226).—To map out the spleen the tenth rib is taken as representing its long axis; vertically it is situated between the upper border of the ninth and the lower border of the eleventh ribs. The highest point is 4 cm. from the middle line of the back at the level of the tip of the ninth thoracic spinous process; the lowest point is in the midaxillary line at the level of the first lumbar spinous process.

Kidneys (Figs. 1225, 1226).—The right kidney usually lies about 1 cm. lower than the left, but for practical purposes similar surface markings are taken for each.

On the front of the abdomen the upper pole lies midway between the plane of the lower end of the body of the sternum and the transpyloric plane, 5 cm. from the middle line. The lower pole is situated midway between the transpyloric and intertubercular planes, 7 cm. from the middle line. The hilum is on the transpyloric plane, 5 cm. from the middle line. Round these three points a kidney-shaped figure 4 cm. to 5 cm. broad is drawn, two-thirds of which lies medial to the lateral line. To indicate the position of the kidney from the back, the parallellogram of Morris is used; two vertical lines are drawn, the first 2.5 cm., the second 9.5 cm. from the middle line; the parallelogram is completed by two horizontal lines drawn respectively at the levels of the tips of the spinous process of the eleventh thoracic and the lower border of the spinous process of the third lumbar vertebra. The hilum is 5 cm. from the middle line at the level of the spinous process of the first lumbar vertebra.

Ureters.—On the front of the abdomen, the line of the ureter runs from the hilum of the kidney to the pubic tubercle; on the back, from the hilum vertically downward, passing practically through the posterior superior iliac spine (Fig. 1226).

FIG. 1226– Back of lumbar region, showing surface markings for kidneys, ureters, and spleen. The lower portions of the lung and pleura are shown on the right side.

FIG. 1227– Front of abdomen, showing surface markings for arteries and inguinal canal.

Vessels (Fig. 1227).—The inferior epigastric artery can be marked out by a line from a point midway between the anterior superior iliac spine and the pubic symphysis to the umbilicus. This line also indicates the lateral boundary of Hesselbach’s triangle—an area of importance in connection with inguinal hernia; the other boundaries are the lateral edge of Rectus abdominis, and the medial half of the inguinal ligament. The line of the abdominal aorta begins in the middle line about 4 cm. above the transpyloric line and extends to a point 2 cm. below and to the left of the umbilicus—or more accurately to a point 2 cm. to the left of the middle line on a line which passes through the highest points of the iliac crests (A A’, Fig. 1227). The point of termination of the abdominal aorta corresponds to the level of the fourth lumbar vertebra; a line drawn from it to a point midway between the anterior superior iliac spine and the symphysis pubis indicates the common and external iliac arteries. The common iliac is represented by the upper third of this line, the external iliac by the remaining two-thirds.

Of the larger branches of the abdominal aorta, the celiac artery is 4 cm., the superior mesenteric 2 cm. above the transpyloric line; the renal arteries are 2 cm. below the same line. The inferior mesenteric artery is 4 cm. above the bifurcation of the abdominal aorta.

Nerves.—The thoracic nerves on the anterior abdominal wall are represented by lines continuing those of the bony ribs. The termination of the seventh nerve is at the level of the xiphoid process, the tenth reaches the vicinity of the umbilicus, the twelfth ends about midway between the umbilicus and the upper border of the symphysis pubis. The first lumbar is parallel to the thoracic nerves; its iliohypogastric branch becomes cutaneous above the subcutaneous inguinal ring; its ilioinguinal branch at the ring.