Ascending colon
Colon ascendens
The ascending colon runs up the right flank from the caecum to the underside of the liver, where it turns left at the right colic (hepatic) flexure. It is secondarily retroperitoneal.
Overview
The ascending colon is about 12–20 cm long. It is narrower than the caecum and lies on the posterior abdominal wall, covered by peritoneum only on its front and sides. Lateral to it, the right paracolic gutter connects the hepatorenal pouch above with the pelvis below. This is a route by which fluid, blood or pus can track, for example from a perforated appendix or ulcer.
At the inferior surface of the right lobe of the liver, close to the gallbladder and right kidney, the colon bends forward and to the left at the right colic (hepatic) flexure and continues as the transverse colon. Its contents are still semi-liquid, and fermentation and water absorption are most active here. Antiperistaltic activity in the proximal colon prolongs the time contents spend here.
- Location
Right lumbar region and right flank, from the right iliac fossa to the hepatic flexure under the right lobe of the liver.
Anatomy
- Innervation
Superior mesenteric plexus: vagus (parasympathetic) and lesser splanchnic nerves, T10–T12 (sympathetic).
- Arterial supply
Ileocolic and right colic arteries (SMA), linked through the marginal artery.
- Venous drainage
Ileocolic and right colic veins → superior mesenteric vein.
- Lymphatic drainage
Epicolic and paracolic → ileocolic and right colic nodes → superior mesenteric nodes.
- Relations
Posterior: iliacus, quadratus lumborum, transversus abdominis aponeurosis, the lower pole of the right kidney, and the iliohypogastric and ilioinguinal nerves. Anterior: coils of small intestine, greater omentum and the anterior abdominal wall.
Function
- Absorbs water and electrolytes.
- Bacterial fermentation (highest SCFA production).
- Mixes and moves contents onward (haustral contractions, antiperistalsis).
Clinical significance
Right-sided colon cancer
Usually exophytic tumours in a wide lumen with liquid stool. They present with iron-deficiency anaemia, fatigue, weight loss or a mass, and rarely with obstruction. Treatment is a right hemicolectomy that removes the ileocolic and right colic pedicles with their lymph nodes.
Compiled from standard anatomy and physiology references — see the Digestive System sources. For education only; not medical advice.