This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
These are made through all portions of the abdominal walls according to the organs it is desired to gain access to. They should be so planned as to avoid unnecessarily wounding the muscles, arteries, and nerves. It having been found that incisions through fascia alone are more liable to be followed by hernia than those through muscles, incisions through the linea alba and lineae semilunares are to be avoided. Incisions through the recti muscles are best made near their inner edge. If made in the outer edge the nerves supplying the muscle will be divided, causing subsequent paralysis and weakness. If made through the middle, only the nerves supplying the inner half will be divided, but the main trunks of the deep and superior epigastric arteries will be cut and cause troublesome bleeding. There is least harm done by making the incision through the inner edge of the muscle. If the method of Battles is resorted to, of dividing the outer edge of the sheath of the rectus longitudinally and displacing the muscle inward, or of dividing the muscle itself longitudinally, then not only are large branches of the deep epigastric arteries met but in dividing the posterior layer of the sheath the nerves are divided. If the rectus is divided transversely (as Kocher advises in operations on the gall-bladder) care must be taken to avoid wounding the nerves; he claims that the scar acts only as an additional linea transversa and does not injure the functions of the muscle. Injury to the nerves and rectus muscle both can be avoided by incising the sheath transversely and then pulling the rectus to one side (Weir), or by dissecting up the sheaths of both recti transversely and separating the muscles in the median line (Pfannenstiel and Stimson).
Fig. 393. - Incisions for abdominal operations.
Incisions through the transverse muscles if made in the same direction through all three muscles are bound to cut some in a direction more or less transverse to their fibres. The incision of McBurney - for appendicitis - avoids wounding the muscles. He separated the external oblique in the direction of its fibres downward and inward, crossing a line from the anterior superior spine to the umbilicus, 4 to 5 cm. (1 1/2 to 2 in.) to the inner side of the spine. The internal oblique and transversalis are then separated in the direction of the fibres and drawn in the opposite direction. This method is applicable where small openings suffice; but when large incisions are essential, as in bad suppurating cases of appendicitis and in operations to expose the kidney and ureter, it is customary with many to incise all the muscles in the line of the fibres of the external oblique. Should nerves be encountered they are if possible to be drawn aside. In this incision the internal oblique and transversalis are incised nearly transversely, and bleeding from the deep circumflex iliac artery which runs between them will be encountered.
Edebohls exposes the kidney by incising alongside of the outer edge of the erector spinae muscle. The latissimus dorsi is separated in the direction of its fibres, the lumbar aponeurosis is incised and kidney exposed. A normal kidney can be delivered through this incision, but not one much enlarged. When the kidney is much enlarged the incision is to be prolonged anteriorly along the crest of the ilium (see page 396). The relation of the pleura is to be borne in mind: it crosses the twelfth rib about its middle to reach its lower edge posteriorly. Hence the upper end of the incision should always be kept anterior to it (see section on Pleura).