Anatomy - Right hemicolectomy, laparoscopically assisted

The colon frames 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 through the absorption of water. The total length of the colon averages 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 mesocolon
• Taenia libera: free on the surface, facing the abdominal wall
• Taenia omentalis: connected with the greater omentum
• Appendices epiploicae are fat appendages from the tela subserosa in the area of the free taeniae.
• Plicae semilunares are indentations of all wall layers intraluminally, whereas haustra are the outward bulges between them.

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

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

• Definition: blind-ending initial part of the ascending colon, corresponding to an outpouching 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 converge

• Definition: Section of the large intestine 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 position – designations 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 through 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: Ileocolic artery
  • Ascending colon:
  • Ileocolic artery and right colic artery
  • The right colic artery is inconsistent and present in only 60% of cases. It originates either from the superior mesenteric artery (70.8%), the middle colic artery (15.4%), or the ileocolic artery (13.8%). A "true" right colic artery is found in dissection after transection of the ileocolic artery in significantly less than half of the cases.
  • Transverse colon: Middle colic artery 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 (middle colic artery) and the inferior mesenteric artery (left colic artery) near the left colic flexure distally (Riolan's anastomosis), not or insufficiently developed in 20% of cases.

• Venous Drainage:
  • Venous drainage via the ileocolic vein, right colic vein, superior right colic vein, middle colic vein 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: right gastroepiploic vein, pancreaticoduodenal veins, right colic vein, superior right colic vein, and in 10% also the middle colic vein. 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:
  • Ileocolic lymph nodes
  • Right colic lymph nodes
  • Middle colic lymph nodes
  • Mesocolic lymph nodes

• Supply via the enteric nervous system (Autonomic)
• Consists of sympathetic and parasympathetic supply
• Parasympathetic: Supply by branches of the vagus nerve: Truncus vagalis posterior
• Sympathetic: Nn. Splanchnici major, minor, and lumbales, Ganglion mesenterium sup.
• Cannon-Böhm point: in the area of the left flexure: from here, parasympathetic innervation is taken over by the pelvic splanchnic nerves.