Incisions

Midline

Linea alba most easily found above the umbilicus, where it is wider
Forceful lateral retraction of skin edges leads to splitting of the subcutaneous tissues, generally leading to linea alba
Hard to find linea alba below umbilicus
May see pyrimidalis fibres inferiorly
Careful of bladder which lies between rectus and peritoneum
Patent urachus can be divided with impunity

Paramedian incision

Incise anterior rectus sheath vertically along entire incision
Free rectus abdominis from sheath (dividing any tendinous intersections) and retract laterally (to preserve nerve supply, which enters laterally)
Beware of deep IE artery
Incise tough posterior sheath and transversalis fascia and peritoneum

Rectus split incision

Same as paramedian, but rectus is not retracted, which means the section of it medial to the incision is denervated

Pararectus

Vertical incision along lateral border of rectus, which is retracted medially

Transrectus

Splits rectus fibres vertically

Transverse upper and lower incisions

Option in children, as you maximise the length of the incision, since their abdomens are shorter
Transecting the rectus sheath and muscle transversely causes little damage to its innervation since innervation is segmental - usually only get one or two nerves
Lateral abdo wall muscles usually heal without weakness

Pfannenstiel

Gently curving, 2-5cm superior to pubis
Through fascia - incise
Anterior rectus sheath are exposed and transected, dissecting away the sheath from adherent rectus superiorly and inferiorly
Retract muscles laterally to reveal transversalis fascia
Open peritoneum in midline, aware of bladder
Iliohypogastric nerve is also at risk

Lanz

Sometimes described for open appendicectomy, but can be transposed to left side for colonic resections

Kocher

From 2-5cm inferior to xiphoid process, approximately 3cm inferior and parallel to costal margin (don't go too close or will need to include periosteum in closure)
Can be extended bilaterally to form a chevron/rooftop/double Kocher (probably will need to take down falciform ligament and ligamentum teres)
Divide anterior rectus sheath (beware superior epigastric artery, which should be ligated), rectus muscle, lateral abdo wall muscles are all divided along the same oblique line
Peritoneum incised and opened
Beware larger 9th thoracic nerve laterally - should be preserved. Smaller 8th thoracic nerve can be sacrificed.

McBurney

Perpendicular to a line that connects ASIS to umbilicus
If transverse, it is a Rockey-Davis incision
If extended laterally for more exposure of caecum, called Rutherford Morrison incision
Layers
- Scarpa's fascia - can be well-developed in young people and masquerade as EO
- EO: split obliquely. No muscle fibres should be seen
- IO with muscle fibres crossing at right angles to the split EO aponeurosis.
- Transversus: transversely-running fibres (can masquerade as peritoneum)
- Peritoneum
Avoid injury to rectus and innervation
Beware of iliohypogastric nerve which should be protected

In super-obese patients, a lower midline incision can be prone to infection due to apron. Sometimes the upper midline incision gives reasonable access to lower abdominal structures, due to the degree of drape in these patients.