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muscular fibres of the external oblique, is another slight triangular depression, ing which corresponds to the inferior and narrow part of the aponeurosis of the external the t oblique muscle.
Close above, and almost parallel to, the medial half of the inguinal ligament is the inguinal canal, traversed by the spermatic funiculus (Fig. 1101); the latter can be felt to emerge at the subcutaneous inguinal ring immediately above the pubic tubercle. The abdominal and subcutaneous inguinal rings have been fullythy described elsewhere; the former is triangular in shape, with its apex directed superiorly and laterally, and its base immediately above the pubic crest. By invaginating the skin of the scrotum the little finger may be passed through the ring into the canal. It is to be noted that the neck of an inguinal hernia lies above the pubic tubercle, whereas the neck of a femoral hernia emerges below the medial end of the inguinal ligament, lateral to the pubic tubercle. The abdominale inguinal ring, an opening in the fascia transversalis, lies half an inch above a
FIG. 1101.-- THE GROIN. The structures seen on reflection of part of the obliquus internus abdominis (A. M. Paterson).
point a little medial to the middle of the inguinal ligament. The inferior epigastric artery may be mapped out by drawing a line from a point midway between the superior anterior iliac spine and the symphysis pubis towards the umbilicus. The vessel, together with the medial third of the inguinal ligament and the inferior part of the lateral border of the rectus, bounds a triangle known as Hesselbach's triangle. As the inferior epigastric artery passes superiorly and medially to disappear behind the falx aponeurotica inguinalis and the lateral border of the rectus, it lies behind the spermatic funiculus immediately medial to, and below, the abdominal inguinal ring. The floor of Hesselbach's triangle is formed throughout by the fascia transversalis, superficial to which, over the inedial half or so of the triangle, is the falx aponeurotica inguinalis. An oblique inguinal hernia leaves the abdomen at the abdominal inguinal ring and traverses the whole length of the inguinal canal; its coverings are therefore the same as those of the spermatic funiculus, and the neck of the sac lies lateral to the inferior epigastric artery, hence this variety of hernia is also termed lateral inguinal hernia. A direct inguinal hernia, on the other hand, instead of traversing the whole length of the inguinal canal, pushes before it that part of its posterior wall which is formed by the floor of Hesselbach's triangle. The neck of the sac, therefore, lies medial to the inferior epigastric artery, and this variety of hernis may be termed a medial inguinal hernia. If a direct hernia makes its way through the medial part of Hesselbach's triangle, it derives a covering from the
falx inguinalis, as well as from the fascia transversalis; if through the lateral part of the triangle, the lateral edge of the falx inguinalis curves round the medial side of the neck of the sac. To relieve the constriction at the neck of the sac, in the case of an oblique inguinal hernia, the edge of the knife is directed superiorly and laterally to avoid the inferior epigastric artery, while in a direct hernia the artery is avoided by dividing the constriction in a superior and medial direction. In an oblique inguinal hernia the sac lies within the internal spermatic fascia (fascia propria of the hernia), whereas in a direct hernia the fascia propria is derived from the fascia transversalis of Hesselbach's triangle. The extraperitoneal fat which covers the outer surface of the hernial sac is sometimes hypertrophied to such an extent as to amount to a fatty tumour.
In a large proportion of children, at birth, the vaginal process of peritoneum, which connects the tunica vaginalis testis with the abdominal peritoneum, is still patent, especially on the right side. Should the bowel force its way along the patent process a congenital inguinal hernia arises. In the majority of the cases of congenital inguinal hernia it will be found that the tunica vaginalis testis has been shut off by closure of the lower part of the vaginal process, only the superior part remaining patent and forming the sac of the hernia.
In the child the persistence of a patent vaginal process can almost invariably be detected by rolling the cord between the finger and thumb; after the ductus deferens and spermatic vessels have slipped away from one's grasp the edge of the sac can be felt to follow them. In regard to the operation for the cure of inguinal hernia, it should be borne in mind that in the acquired form the hernia produces the sac, whereas in the congenital variety the sac is the cause of the hernia; it follows, therefore, that in the operation for acquired hernia the closure of the canal is as important as the removal or obliteration of the sac, while in a congenital hernia the most essential part of the operation is the closure of the neck of the sac, and as the muscular and fascial apparatus forming the walls of the canal are often well developed (especially in children), they should be interfered with as little as possible. A patent vaginal process may persist during adult life without any bowel descending into it; on the other hand, years after birth, bowel may suddenly enter it. In practically all oblique inguinal hernia, which develop suddenly in children as well as in adolescents and young adults, the sac is of congenital origin.
In the ordinary form of hydrocele the fluid is confined to the tunica vaginalis testis, but when the vaginal portion of the processus vaginalis remains patent, the hydrocele may extend upwards into the inguinal canal, and may or may not communicate with the general peritoneal cavity. In the condition known as encysted hydrocele of the cord the patent funicular process is shut off both from the tunica vaginalis testis and from the peritoneal cavity.
Before proceeding to deal with the abdominal cavity reference must be made. to some anatomical points connected with the more typical incisions made by surgeons in opening the abdomen.
Incisions in the Median Plane.-Median line incisions through the linea alba have the advantage of being comparatively bloodless and rapid of execution, of dividing no motor nerves, and of enabling the surgeon to expose a wide area of the abdomen. Unless special precautions are taken, however, they are more liable to be followed by a ventral hernia.
Above the umbilicus the linea alba is comparatively broad, so that the edges of the recti are separated by a distinct interval, which may be of considerable width in obese subjects and multiparous women. Deep to the linea alba is the transversalis fascia, which is so thin and adherent that the two structures form practically a single layer. The extraperitoneal fat, which forms a comparatively thick stratum, must not be mistaken for omentum. The peritoneum presents itself as a thin, bluish, semi-transparent membrane. If it is necessary to prolong the incision. downwards below the level of the umbilicus, it should skirt its left margin so as to
avoid the round ligament of the liver. If, in closing a median supra-umbilical laparotomy wound, the surgeon merely sutures the edges of the stretched lines alba without opening into the rectal sheaths, a hernia may result. To ensure against it the medial borders of the recti are exposed by opening into their sheaths along each edge of the wound. In closing the wound, the deepestow suture (continuous) includes on each side the posterior layer of the rectal sheath along with the split linea alba, the transversalis fascia and the peritoneum. This gives a substantial "first line of defence." The next suture takes up some of the fibres of the medial edges of the recti, along with the anterior layer of their sheaths The skin is sutured separately. By the above procedure the edges of the recti are brought into actual contact and a double-layered linea alba is fashioned, one layer behind the margins of the recti and the other in front of them.
Below the umbilicus the medial edges of the recti are practically in contact, so that an incision between them opens into the rectal sheath on both sides.
The nearer the opening into the abdomen approaches the symphysis pubisti the more likely is the bladder to be encountered; this applies more especially in th children in whom the bladder extends higher up out of the pelvis. Before opening the abdomen, therefore, by a low median incision, the bladder should be emptied in supra-pubic cystotomy, on the other hand, it is intentionally filled so as to elevate the peritoneum (superior false ligament of the bladder) well above the symphysis. Below this peritoneal layer is the space of Retzius, occupied by a pad of extra-peritoneal fat which must be separated by blunt dissection before the bladder wall is actually exposed. In opening the bladder the pre-vesical veins, which ramify on its surface, are avoided as far as possible. Above the pubes the fascia transversalis recedes somewhat from the posterior surface of the recti, leaving behind it a cellular interval which must not be mistaken for the space of Retzius.
If a transverse incision is added to the inferior end of a supra-umbilical median incision, free access may be obtained to the hypochondriac as well as to the epigastric region. Before dividing the fibres of the rectus, however, the anterio layer of the sheath is stitched to them to prevent their retraction. In dividing the posterior layer of its sheath the terminal portions of the ninth and tenth inter costal nerves need not be injured as they run in a transverse direction.
Incisions through the Recti. In opening the abdomen by longitudinal incisions through the recti, the superior epigastric artery will be encountered above the umbilicus, and the inferior epigastric below it. The nearer the opening approaches the lateral border of the rectus, the more will its nerve-supply injured. Above the level of the umbilicus, the posterior layer of the rectal sheath well developed; and in closing the wound it is included in the same suture as the transversalis fascia and the peritoneum, the three together forming a most efficient "first line of defence." The higher up and further lateral the incision is made through the rectus, the more will the posterior layer of the sheath be found to b made up of transverse muscular fibres prolonged inwards from the transvers abdominis muscle. Below the level of the umbilicus, the posterior layer of the rectal sheath is much thinner, and where it ceases, namely, about midway betwee the umbilicus and the pubes, it constitutes what is known as the linea semicirculars (semilunar fold of Douglas). Below this level, therefore, the "deep closure" of laparotomy wound through the rectus is less secure than is the case at a highe level. It is all the more important, therefore, to see that the edges of the anteri layer of the sheath are accurately sutured.
Incisions Lateral to the Rectus.-Longitudinal incisions lateral and parall to the lateral border of the rectus are as far as possible to be avoided, first because they divide the motor nerves, and, secondly, because the abdominal wall almost entirely aponeurotic, and, therefore, a hernia is liable to result.
Incisions lateral to the rectus, above the level of the umbilicus, are generall made more or less parallel to the costal margin. Such incisions give excelle access to the gall-bladder and bile-ducts. The fibres of the external obliqu! muscles are divided transversely; but, fortunately, those of the internal oblig and transversus muscles may be divided more or less parallel to the fibres. T abdominal portions of the eighth, ninth, and tenth thoracic nerves which cours
between the two deep muscles, run in a medial and slightly downward direction, so that it is practically impossible to avoid dividing one or other of them.
In the iliac regions, to reach the cæcum and vermiform process on the right side, and the pelvic colon on the left side (colostomy), it is customary, by using what is known as the "gridiron incision," to split the three abdominal muscles in the direction of their fibres. The external oblique is split in the direction of the skin incision, which is made obliquely from above downwards and medially. After retracting the edges of this muscle the fibres of the internal oblique and transversalis muscles are split horizontally. The abdomen is then opened by dividing the transversalis fascia and peritoneum. If a comparatively large opening is required the branch of the deep circumflex iliac artery, which ascends between the internal oblique and transversus muscles, a little medial to the anterior superior iliac spine, is divided and ligatured, while the ilio-hypogastric and ilio-inguinal nerves are to be avoided. If it is necessary to extend the incision in a medial direction, the lateral part of the anterior layer of the sheath of the rectus is opened and the rectus muscle retracted medially; while the inferior epigastric artery, now exposed, is pushed aside or ligatured before the opening in the fascia transversalis and peritoneum is enlarged.
DISTRIBUTION OF SENSORY NERVES IN ANTERIOR ABDOMINAL WALL.
A knowledge of the segmental distribution of the sensory fibres of the anterior rami of the lower intercostal nerves enables us to appreciate the significance of the so-called girdle pain often associated with lesions of the spinal medulla and its nerve-roots. In tuberculous disease of the vertebral column, for example, the girdle pain may be an early symptom of the disease, and when present it affords a valuable guide to the situation of the disease in the vertebral column. The seventh thoracic nerve supplies the skin at the level of the epigastric triangle, the eighth and ninth, that between it and the umbilicus, the tenth that at the level of the umbilicus, the eleventh and twelfth that between the umbilicus and groin.
THE ABDOMINAL CAVITY.
Subdivisions of the Abdominal Cavity. To simplify the topography of the abdominal viscera the abdomen is arbitrarily divided into nine regions by two horizontal and two vertical planes. Of the two horizontal planes, the superior or infracostal plane is at the level of the lowest part of the tenth costal cartilages; the inferior or intertubercular plane is at the level of the tubercles of the iliac crests. The two vertical planes correspond upon the surface to a line, drawn vertically upwards on each side from a point midway between the anterior superior iliac spine and the pubic symphysis. Superiorly, these vertical planes generally strike the tip of the ninth costal cartilages. The subdivisions of the superior zone are termed the epigastric and right and left hypochondriac regions, of the middle zone the umbilical and right and left lumbar regions, of the inferior zone the hypogastric and right and left iliac regions. The epigastric, umbilical, and hypogastric regions may be further divided into right and left halves by the median plane. The xiphisternal junction is on a level with the fibro-cartilage between the ninth and tenth thoracic vertebræ. The infracostal plane passes through the superior part of the third lumbar vertebra; the intertubercular plane through the fifth lumbar vertebra, about one inch above the sacral promontory. The umbilicus is situated usually from one to two inches above the intertubercular line.
In the method of surface topography employed by Addison the plane of separation between the superior and middle abdominal zones is placed midway between the superior border of the manubrium sterni and the superior border of the pubic symphysis. It will be found to lie at or near the mid-point between the xiphisternal junction and the umbilicus. Posteriorly, this plane strikes the inferior border of the first lumbar vertebra, and it passes so constantly through the pylorus that it may with advantage be termed the transpyloric plane.
The peritoneal cavity may be regarded as a large and complicated lymph sac which is intimately related to the abdominal viscera, and more especially to the
gastro-intestinal canal. Inflammatory infections of the peritoneum are therefore almost always secondary to lesions of the viscera. The peritoneal lymph sac is brought into direct communication with the subperitoneal lymph vessels of the diaphragm through stomata which open upon the peritoneum covering the abdominal surface of that muscle. With the object, therefore, of diminishing septic absorption after operations for peritonitis, the patient is kept in the half-sitting posture, and pelvic drainage is established. The healthy peritoneum, in virtue of the vital action of its endothelial cells, is endowed with great absorptive properties, and, when irritated,
has the power of throwing out an abundant exudation, the cellelements of which are actively phagocytic.
FIG. 1102.-LATERAL ASPECT OF TRUNK, SHOWING SURFACE
R.L. Right lung.
R.K. Right kidney.
The reflection of the peritoneum and its relations to the various organs have been fully described in the section on the Digestive System.
The attachment of the transverse mesocolon to the posterior abdominal wall is at the level of the first lumbar vertebra, and lies, therefore, a little above the infracostal plane. The attachment, which ascends slightly as it passes from right to left, crosses the right kidney, the descending part of the duodenum, and the head of the pancreas, after which its attachment follows the anterior border of the pancreas. The peritoneal subdivision above this attachment is roofed in by the diaphragm, and includes the superior part of the great sac, and, behind it, the larger portion of the omental bursa. The organs related to this area of the peritoneum are the liver, along with the bile-ducts and gallbladder, the stomach and part of the duodenum, the spleen, the pancreas, the upper parts of the kidneys, and the suprarenal glands. Suppuration connected with any of these organs is liable to spread upwards under the cupola of the diaphragm, producing what is known as subphrenic abscess.
The attachment of the mesentery of the small intestine extends from the left side of the second lumbar vertebra downwards to the right be iliac fossa. The attachment may mapped out on the surface by drawing a line from a point on the transpyloric line. one inch to the left of the median plane, to the mid-point of a line drawn horizontally between the right anterior superior iliac spine and the median plane.
Subdivisions of the Peritoneal Cavity. From the surgical point of view the peritoneal cavity may be arbitrarily divided into four great subdivisions: namely a supracolic, a right infracolic, a left infracolic, and a pelvic. All these subdivisions communicate freely with one another behind the anterior abdominal wall, as well as on each side, along the gutter-like channels in the loins. It is along these gutters that pus readily makes its way from the upper part of