Anatomy - Right hemicolectomy

The colon encircles the inner abdominal wall and runs below the liver and stomach, surrounding the loops of the small intestine. The position of the colon is intra- or secondarily retroperitoneal. Its primary function is the thickening of the chyme by absorbing water. The total length of the colon is on average 120-150 cm. The colon begins at the ileocecal valve and ends at the rectosigmoid junction, where it transitions into the rectum.

The colon is divided into the following sections:

• Cecum with the appendix
• Ascending colon
• Transverse colon
• Descending colon
• Sigmoid colon

• The longitudinal muscle layers of the colon form three band-like muscle strips that are visible from the outside and are referred to as taeniae. They are distinguished as follows:
• Taenia mesocolica: located towards the mesentery
• Taenia libera: free on the surface, facing the abdominal wall
• Taenia omentalis: connected with the greater omentum
• Fat appendages from the tela subserosa in the area of the free taeniae are referred to as appendices epiploicae.
• Plicae semilunares are indentations of all wall layers intraluminally, whereas haustra are the outward bulges in between.

For right hemicolectomy, the following intestinal segments are relevant from oral to aboral:

• Right flexure and right lateral hemicolon
• Ascending colon
• Cecum with vermiform appendix

• Definition: blind initial part of the ascending colon, corresponding to a bulge of the same; lat.: caecus = blind
• Length 5-7 cm
• Synonyms: cecum, blind gut
• Location: intraperitoneal or also secondarily retroperitoneal, below the ileocecal valve, the Valva Bauhini
• Identification: by the taeniae and the vermiform appendix
• Vermiform appendix: intraperitoneal, in the area of the converging taeniae at the cecal pole, length: 6-20 cm, on average 8 cm, at the origin of the appendix the 3 taeniae unite

• Definition: Large intestine section between the ileocecal valve, the entry of the small intestine (ileum), and the right colic flexure
• Synonyms: ascending colon, or simply Ascendens
• Location: [secondarily] retroperitoneal, extends from the right lower abdomen to the right flexure – peritoneal fixation to the posterior abdominal wall by the so-called Toldt's fascia
• Length: 12-20 cm
• Identification: by the longitudinal muscle fiber bundles – the taeniae, which retain their positional names from the transverse colon; the transverse diameter is significantly larger than that of the descending colon!

• Synonyms: transverse colon or simply Transversum.
• Location: intraperitoneal; mobile fixation by its own mesentery – mesocolon transversum, runs transversely ascending through the abdominal cavity from the right to the left flexure
• Length: 30-45 cm
• Identification: by the three taeniae and the greater omentum attached to the taenia omentalis
• The left flexure is always higher than the right flexure due to its fixation by the phrenicocolic ligament

• Arterial Supply:
  • The arterial supply of the right hemicolon is provided by branches of the superior mesenteric artery.
  • Cecum: A. ileocolica
  • Ascending colon:
  • A. Ileocolica and A. colica dextra
  • The A. colica dextra is inconsistent and present in only 60%. It originates either from the superior mesenteric artery (70.8%), the middle colic artery (15.4%), or the ileocolic artery (13.8%). A "true" A. colica dextra is found in preparation after transection of the ileocolic artery in significantly less than half of the cases.
  • Transverse colon: A. colica media with a right and a left branch, the bifurcation usually occurs after a short common trunk.
  • Left colonic flexure: Watershed between the supply area of the superior mesenteric artery and the inferior mesenteric artery, anastomosis between the superior mesenteric artery (A. colica media) and the inferior mesenteric artery (A. colica sinistra) near the left colonic flexure distally (Riolan's anastomosis), not or insufficiently developed in 20% of cases.

• Venous Drainage:
  • Venous drainage via V. ileocolica, V. colica dextra, V. colica dextra superior, V. colica media into the superior mesenteric vein. This forms the portal vein in conjunction with the splenic vein and other visceral veins behind the pancreatic head.
  • Henle's Trunk (syn.: Gastropancreatic trunk):
  • important landmark
  • located in the middle (cranio-caudally viewed) of the pancreatic head and receives the following veins: V. gastroomentalis dextra, Vv. Pancreaticoduodenales, V. colica dextra, V. colica dextra sup., and in 10% also the V. colica media. Henle's trunk thus drains blood from the stomach, duodenum, pancreatic head, ascending colon, and partially from the transverse colon.
  • Drains into the superior mesenteric vein.

• Lymphatic Drainage:
  • Important lymph nodes for the right hemicolon are:
  • Nll. ileocolici
  • Nll. colici dextri
  • Nll. colici medii
  • Nll. mesocolici

• Supply via the enteric nervous system (Autonomic)
• Consists of sympathetic and parasympathetic supply
• Parasympathetic: Supply by branches of the vagus nerve: Posterior vagal trunk
• Sympathetic: Greater, lesser, and lumbar splanchnic nerves, superior mesenteric ganglion
• Cannon-Böhm point: in the area of the left flexure: from here, parasympathetic innervation is taken over by the pelvic splanchnic nerves.