The anterior abdominal wall and safe laparoscopic ports

1. Rectus abdominis and the linea alba

Two straight muscles run from the costal margin to the pubis on either side of the midline, separated by the linea alba, a band of fused aponeuroses. The umbilicus sits in the linea alba.

Surgeon’s corner: A midline laparotomy through the linea alba is fast and almost bloodless, and the umbilicus is the thinnest point of the wall: the classic site for the open (Hasson) camera port.

2. The three flat muscles: the outer two

Lateral to the rectus, three flat muscles form the flank. On the patient’s right side you see the outermost, the external oblique: its fibres run down and forwards, like hands in your pockets. On the patient’s left side it has been removed to show the internal oblique beneath, with fibres at right angles to it.

Surgeon’s corner: Muscle-splitting incisions (e.g. the gridiron incision for open appendicectomy) separate each layer along its fibres instead of cutting them: less pain, fewer hernias.

3. The deepest flat muscle: transversus abdominis

Remove the internal oblique too and the transversus abdominis appears: the deepest of the three, with fibres running horizontally round the flank like a corset. Behind it lie the transversalis fascia and the peritoneum.

Surgeon’s corner: The nerves of the abdominal wall (T7 to L1) run between the internal oblique and the transversus: this plane is where the TAP block puts the local anaesthetic.

4. The epigastric vessels

Behind each rectus muscle the inferior epigastric artery (from the external iliac artery) runs up to meet the superior epigastric artery (from the internal thoracic artery). They run roughly along the lateral third of the rectus.

Surgeon’s corner: Lateral laparoscopic ports go lateral to the rectus sheath (or are placed under vision, transilluminating the wall) to avoid these vessels; an injured epigastric artery bleeds into the wall and the port site.

5. Nerves of the lower wall

The lower intercostal, iliohypogastric and genitofemoral nerves run between the muscle layers and supply the skin, muscles and groin.

Surgeon’s corner: Nerve entrapment by a suture or a mesh tack causes chronic groin pain after hernia repair: tack above the iliopubic tract and away from the nerves.